Definition Relay Terminology COIL (also referred primary inp
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Relay Technical Information
Definition Relay Terminology
COIL
(also referred primary input) Nominal Coil Voltage (Rated Coil Voltage) single value narrow range) source voltage intended design applied coil input. Pick-Up Voltage (Pull-In Voltage Must Operate Voltage) voltage unoperated relay increased, value below which contacts must function (transfer). Drop-Out Voltage (Release Must Release Voltage) voltage operated relay decreased, value above which contacts must revert their unoperated position. Maximum Continuous Voltage maximum voltage that applied continuously coil without causing damage. Short duration spikes Coil Designation
Single side stable type Non-polarized Polarized coil latching type
higher voltage tolerable, this should assumed without first checking with manufacturer. Nominal Operating Current value current flow coil when nominal voltage impressed coil Nominal Operating Power value power used coil nominal voltage. coils expressed watts; expressed volt amperes. Nominal Power Nominal Voltage Nominal Current. Coil Resistance This resistance coil type relays temperature conditions listed catalog. (Note that certain types relays, resistance temperatures other than standard 20°C 68°F.)
coil latching type 4-terminal 3-terminal
black coil represents energized state. latching relays, schematic diagrams generally show coil reset state. Therefore, coil symbol also shown reset coil reset state.
CONTACTS (secondary output)
Contact Forms Denotes contact mechanism number contacts contact circuit. Contact Symbols
Form contacts (normally open contacts)
Form contacts also called N.O. contacts make contacts. Form contacts also called N.C. contacts break contacts. Form contacts also called changeover contacts transfer contacts. Contacts Abbreviation make-before-break contacts. Contact mechanism where Form contacts (normally open contacts) close before Form contacts open (normally closed contacts). Rated Switching Power design value watts (DC) volt amperes (AC) which safely switched contacts. This value product switching voltage switching current, will lower than maximum voltage maximum current product.
Maximum Switching Voltage maximum open circuit voltage which safely switched contacts. voltage maximums will differ most cases. Maximum Switching Current maximum current which safely switched contacts. current maximums differ. Maximum Switching Power upper limit power which switched contacts. Care should taken exceed this value. Maximum Carrying Current maximum current which after closing prior opening, contacts safely pass without being subject temperature rise excess their design limit, design limit other temperature sensitive components relay (coil, springs, insulation, etc.). This value usually excess maximum switching current. Maximum Switching Capability minimum value voltage current which reliably switched contacts. These numbers will vary from device type device type. Factors affecting minimums include contact material, contact pressure, wipe, ambient conditions type relay enclosure (sealed non-sealed). Maximum Switching Capacity This listed data column each type relay maximum value contact capacity interrelationship maximum switching power, maximum switching voltage, maximum switching current. switching current switching voltage obtained from this graph. example, switching voltage fixed certain application, maximum switching current obtained from intersection between voltage axis maximum switching power. Maximum Switching Capacity relay) Example: Using relay switching voltage maximum switching current Maximum switching capacity given resistive load. sure carefully check actual load before use.
Form contacts (normally closed contacts)
Form contacts (changeover contacts)
Definition Relay Terminology
1,000V
100V
Maximum switching capacity
10mV 10µA
100mA
current
Breakdown Voltage (Hi-Pot Dielectric Strength) maximum voltage which tolerated relay without damage specified period time, usually measured same points insulation resistance. Usually stated value (RMS) minute duration. Surge Withstand Voltage ability device withstand abnormal externally produced power surge, lightning strike, other phenomenon. impulse test waveform usually specified, indicating rise time, peak value fall time. (Fig.
Surge voltage
Contact Resistance This value combined resistance resistance when contacts touching each other resistance terminals contact spring. contact resistance measured using voltage-drop method shown below. measuring currents designated Fig.
Wave peak value
Time(µs)
Measured contact
FIG.
Power source
Ammeter
Voltmeter Variable resister
FIG.
Test Currents
Rated Contact Current Test Current Switching Current (mA) Less than 0.01 0.01 more less than more less than more 1,000
resistance measured with reasonable accuracy 4328A milliohmmeter. general, relays with contact rating more, measure using voltage-drop method Capacitance This value measured between terminals 1kHz 20°C 68°F.
PERFORMANCE
Insulation Resistance resistance value between mutually isolated conducting sections relay, i.e. between coil contacts, across open contacts between coil contacts core frame ground potential. This value usually expressed "initial insulation resistance" decrease with time, material degradation accumulation contaminants.
Operate Time (Pull-In Pick-Up Time) elapsed time from initial application power coil, until closure normally open contacts. (With multiple pole devices time until last contact closes.) This time does include bounce time. Operate Bounce Time time period immediately following operate time during which contacts still dynamic, ending once bounce ceased. Release Time (Drop-Out Time) elapsed time from initial removal coil power until reclosure normally closed contacts (last contact with multi-pole) this time does include bounce. Release Bounce Time time period immediately following release time during which contacts still dynamic, ending when bounce ceased. Time Term used describe operate time bi-stable latching relay. Reset Time Term used describe release time bi-stable latching relay. With w-coil magnetic latching relay time from first application power reset coil until reclosure reset contacts. With single coil latching relay, time measured from first applica-
tion reverse coil voltage until reclosure reset contact. Shock Resistance, Destructive acceleration which withstood relay during shipping installation without suffering damage, without causing change operating characteristics. Usually expressed "G"s. Shock Resistance, Functional acceleration which tolerated relay during service without causing closed contacts open more than specified time. Vibration Resistance, Destructive vibration which withstood relay during shipping, installation without suffering damage, without causing change operating characteristics. Expressed acceleration displacement, frequency range. Vibration Resistance, Functional vibration which tolerated relay during service, without causing closed contacts open more than specified time. Mechanical Life minimum number times relay operated under nominal conditions (coil voltage, temperature, humidity, etc.) with load contacts. Electrical Life minimum number times relay operated under nominal conditions with specific load being switched contacts. Contact Bounce (Time) Generally expressed time (msec.), this refers intermittent switching phenomenon contacts which occurs collision between movable metal parts contacts, when relay operated released. Maximum Switching Frequency This refers maximum switching frequency which satisfies mechanical life electrical life under repeated operations applying pulse train rated voltage operating coil. Life Curve This listed data column each type relay. life (number operations) estimated from switching voltage switching current. example, relay operating Switching voltage 125V Switching current 0.6A life expectancy 300,000 operations. However, this value resistive load. sure carefully check actual load before use.
voltage
Definition Relay Terminology
Life Curve
1,000
HIGH FREQUENCY CHARACTERISTICS
resistance load
125V resistance load
Current
Isolation High frequency signals leak through stray capacitance across contacts even contacts separated. This leak called isolation symbol (decibel) used express magnitude leak signal. This expressed logarithm magnitude ratio signal generated leak with respect input signal. larger magnitude, better isolation. Insertion Loss high frequency region, signal disturbance occurs from self-induction, resistance, dielectric loss well from reflection impedance mismatching circuits. Loss these types disturbances called insertion loss. Therefore, this refers magnitude loss input signal. relay from large particulate contamination, also protect user personnel from shock hazard. Flux-Resistant Type this type construction, solder flux penetration curtailed either insert molding terminals with header, simple sealing operation during manufacturing. Sealed Type This type sealed relay totally excludes ingress contaminants sealing compound being applied header/cover interface. constituent components annealed physical chemical stability. This annealing
smaller magnitude, better relay. V.S.W.R. (Voltage Standing Wave Ratio) High frequency resonance generated from interference between input signal reflected (wave) signal. V.S.W.R. refers ratio maximum value minimum value waveform. V.S.W.R. when there reflected wave. usually becomes greater than Notes: Except where otherwise specified, tests above conducted under standard temperature humidity (5°C 35°C 41°F 95°F, 60±15%). coil impressed voltage switching tests rectangular wave rated voltage. phase load operation random. process drives residual volatiles plastics, insuring contaminant free environment inside sealed relay, resulting more stable contact resistance over life. Hermetic Seal plastic sealed type true hermetic seal, there exchange molecules through plastic cover over time. only true hermetic seals metal metal glass metal relay. entire device purged with nitrogen prior sealing, improving reliability.
PROTECTIVE CONSTRUCTION
Several different degrees protection provided different relay types, resistance dust, flux, contaminating environments, automatic cleaning, etc. Open Type reasons cost, some devices provided with enclosure. usually assumed that application will overall enclosure protective environment. Dust Cover Type Most standard relays provided with dust cover some type. This protects
CONSTRUCTION CHARACTERISTIC
Type Construction
Life
;;;;
Characteristics Automatic Soldering Dust Cover Type Most basic construction where case base body) fitted together. Terminals sealed molded simultaneously. joint between case base higher than surface board. Terminals, case, base filled with sealing resin.
Base
Yes,
Automatic Cleaning
Harmful Resistance
Flux-Resistant Type
Base
Sealed Type
Sealing resin
Metal case
Metallic Hermetic Seal Type
Hermetically sealed with metal case metal base. Terminals sealed with glass.
Glass
Metal base
Cleaning solvent Although absorption plastic does occur, insignificant actual practice. metallic hermetic seal type explosion-proof requirements.
Definition Relay Terminology
OPERATIONAL FUNCTION
Single Side Stable Type Relay which turns when coil energized turns when deenergized. (Fig.
Coil Latching Type Relay with latching construction composed coils: coil reset coil. relay reset alternately applying pulse signals same polarity. (Fig.
Fig. Fig.
(Typical schematic relay)
(Typical schematic relay)
Coil Latching Type Relay with latching construction that maintain state with pulse input. With coil, relay reset applying signals opposite polarities. (Fig.
Operation Indication Indicates reset states either electrically mechanically easy maintenance. wired type (LED wired relay), lamp type (lamp wired relay) available. (Fig.
wired relay
Fig.
Fig.
(Typical schematic relay)
TERMINAL CONFIGURATION
Type board through hole terminal board clinching terminal board surface-mount terminal Plug-in terminal Quick connect terminal Screw terminal
Typical relay type
Terminal configuration
TX-D TX-S relay, relay, DS-BT relay, relay, relay, relay, relay, relay, relay, relay
Typical relay type
TX-SMD, TQ-SMD, TX-D, TX-S relay relay, type
relay relay relay relay
relay relay relay
relay relay relay
MOUNTING METHOD
Type Insertion mount
Mounting configuration
Typical relay type
Notes: Sockets available certain board relays. relay, relay, relay, etc.) type (solder type) direct screw mounting case also available. relay, relay)
Surface mount Socket mount Terminal socket mount type type
Terminal Socket
TX-D, TX-S relay, relay, DS-BT relay, relay, relay, relay
TX-SMD,TQ-SMD, relay, type
relay relay relay
relay relay relay
relay relay relay
relay relay relay JT-N relay
General Application Guidelines
relay encounter variety ambient conditions during actual resulting unexpected failure. Therefore, testing over practical range under actual operating conditions necessary. Application considerations should reviewed determined proper relay.
METHOD DETERMINING SPECIFICATIONS
order relays properly, characteristics selected relay should well known, conditions
Specification item Rating Pick-up voltage (current) Drop-out voltage (current) Maximum continuous impressed voltage (current) Coil resistance Impedance Temperature rise Input frequency type Contact arrangement Contact rating Contact material Life Contact pressure Contact resistance Operate time Release time Bounce time Switching frequency Vibration resistance Shock resistance Ambient temperature Life Mounting method Cover Size
relay should investigated determine whether they matched environmental conditions, same time, coil conditions, contact conditions, ambient conditions relay that actually used must sufficiently known advance.
table below, summary been made points consideration relay selection. used reference investigation items points caution.
Consideration points regarding selection
Coil
Select relay with consideration power source ripple. Give sufficient consideration ambient temperature coil temperature rise. When used conjunction with semiconductors, additional attention application should taken.
Contacts
desirable standard product with more than required number contacts. beneficial have relay life balanced with life device used contact material matched type load? necessary take care particularly with level usage.
Operate time
beneficial have bounce time short sound circuits similar applications.
Mechanical characteristics
Give consideration performance under vibration shock location. particular, when used high temperature applications, relay with class class coil insulation required. Selection made connection method with plug-in type, printed circuit board type, soldering, terminals, screw fastening type. adverse atmosphere, sealed construction type should selected. there special conditions?
Other items
BASICS RELAY HANDLING
maintain initial performance, care should taken avoid dropping hitting relay. Under normal use, relay designed that case will detach. maintain initial performance, case should removed. Relay characteristics cannot guaranteed case removed. relay atmosphere standard temperature humidity with minimal amounts dust, SO2, H2S, organic gases recommended. Also note that silicon-based resins near relay result contact failure. installation adverse environments, sealed types (plastic sealed type, etc.) should considered. Care should taken observe correct coil polarity polarized relays. Proper usage requires that rated voltage impressed coil. rectangular waves coils sine waves coils. sure coil impressed voltage does continuously exceed maximum allowable voltage. Absolutely avoid using switching voltages currents that exceed designated values. rated switching power life given only guides. physical phenomena contacts contact life greatly vary depending type load operating conditions. Therefore, sure carefully check type load operating conditions before use. exceed usable ambient temperature values listed catalog. flux-resistant type sealed type automatic soldering used. alcohol based cleaning solvents when cleaning performed using sealed type relay. Avoid ultrasonic cleaning types relays. Avoid bending terminals, because cause malfunction. guide, Faston mounting pressure kgf} relays with terminals. proper use, read main text details.
General Application Guidelines
PROBLEM POINTS WITH REGARD
actual relays, various ambient conditions encountered, because unforeseen events occur which thought drawing board, with regard such conditions, tests necessary under possible range operation. example, consideration must always given variation performance when relay characteristics being reviewed. relay mass production item, matter principle, must recognized that relay used extent such variations without need adjustment.
RELAY COIL
operation type operation relays, power source almost always commercial frequency 60Hz) with standard voltages 115, 240V Because this, when voltage other than standard voltage, product special order item, factors price, delivery, stability characteristics create conveniences. extent that possible, standard voltages should selected. Also, type, shading coil resistance loss, magnetic circuit eddy current loss, hysteresis loss exit, because lower coil efficiency, normal temperature rise greater than that type. Furthermore, because humming occurs below level pick-up voltage (minimum operating voltage), care required with regard power source voltage fluctuations. example, case motor starting, power source voltage drops, during humming relay, reverts restored condition, contacts suffer burn damage welding, with occurrence false operation self-maintaining condition. type, there inrush current during operation time (for separated condition armature, impedance current greater than rated current flows; adhered condition armature, impedance high rated value current flows), because this, case several relays being used parallel connection, necessary give consideration power consumption. operation type operation relays, standards exist power source voltage current, with voltage standards 100V, with regard current, values expressed catalogs milliamperes pick-up current. However, because this value pick-up current nothing more than guarantee just barely moving armature, variation impressed voltage resistance values, increase coil resistance temperature rise, must given consideration worst possible condition relay operation, making
necessary consider current value times pick-up current. Also, because extensive relays limit devices place meters both voltage current, because gradual increase decrease current impressed coil causing possible delay movement contacts, there possibility that designated control capacity satisfied. Thus necessary exercise care. type relay coil resistance varies ambient temperature well heat generation extent about 0.4%/°C, accordingly, temperature increases, because increase pick-up drop-out voltages, care required. Impressed voltage coil order have stable operation relay, impressed voltage should basically within range rated voltage. However, necessary +10% that waveform voltage -15% impressed coil sine wave. There problem power source commercially provided power, when stabilized power source used, there waveform distortion that equipment, there possibility abnormal overheating. means shading coil coil, humming stopped, with distorted waveform, that function displayed. Fig. below shows example waveform distortion. power source relay operating
Fig. Distortion stabilized power source
circuit connected same line motors, solenoids, transformers, other loads, when these loads operate, line voltage drops, because this relay contacts suffer effect vibration subsequent burn damage. particular, small type transformer used capacity margin safety, when there long wiring, case household used small sales shop where wiring slender, necessary take precautions because normal voltage fluctuations combined with these other factors. When trouble develops, survey voltage situation should made using synchroscope similar means, necessary counter-measures should taken, together with this determine whether special relay with suitable excitation characteristics should used, make change circuit shown Fig. which capacitor inserted absorb voltage fluctuations. particular, when magnetic switch being used, because load becomes like that motor, depending upon application, separation operating circuit power circuit should tried investigated.
Sine wave
Approximate keystone wave
Waveform with this harmonic included
Fig. Voltage fluctuation absorbing circuit using condenser
Switch 100V Relay coil
General Application Guidelines
Power source input power source type relay, battery either half wave full wave rectifier circuit with smoothing capacitor used. This characteristics with regard excitation voltage relay will change depending upon type power source, because this, order display stable characteristics, most desirable method perfect case ripple included power source, particularly case half wave rectifier circuit with smoothing capacitor, capacity capacitor small, influence ripple, humming develops unsatisfactory condition produced. With actual circuit used, absolutely necessary confirm characteristics. (Fig. With regard T-Series (TQ, TX-D, TX-S, TQ-SMD), NF,S, relays, necessary give consideration power source with less than ripple, series, relays, there hindrance operation. Coil temperature rise Proper usage requires that rated voltage impressed coil. Note, however, that voltage greater than equal maximum continuous impressed voltage impressed coil, coil burn layers short temperature rise. Furthermore, exceed usable ambient temperature range listed catalog. Temperature rise pulse voltage When pulse voltage with time less than minutes used, coil temperature rise bares relationship time. This varies with ratio time time, compared with continuous current passage, rather small. various relays essentially same this respect. (Fig.
Current passage time
continuous passage
Relay Smoothing capacitor Ripple portion
Emax. Emin.
Emean.
portion
Ripple percentage
Emax.-Emin Emean.
Emax. Maximum value ripple portion Emin. Minimum value ripple portion Emean.= Average value ripple portion
Fig.
pull-up force becomes somewhat weakened, necessary take care since resistance vibration shock reduced. Also ordinarily following must given thought. desirable have less than ripple reed type relay (including relay also). hinge type relay, half wave rectifier only cannot used, with Pick-up voltage change coil temperature rise (hot start) relays, after continuous passage current coil, current turned OFF, then immediately turned again, temperature rise coil, pick-up voltage will become somewhat higher. Also, will same using higher temperature atmosphere. resistance/temperature relationship copper wire about 0.4% 1°C, with this ratio coil resistance increases. That order cause operation relay, current necessary becomes higher than pickup current, accompanying rise resistance value. Operate time case operation, there extensive variation operate time depending upon point phase which switch turned coil excitation, expressed certain range, miniature types most part cycle (about 10msec.). However, somewhat large type relay where bounce large, operate time 16msec., with release time order 18msec. Also, case operation, extent large coil input, operating time rapid, rapid, contact bounce time extended. Stray circuits (bypass circuits) case sequence circuit construction, because bypass flow alternate routing, necessary take care
addition smoothing capacitor, used. However, ripple characteristics must investigated. hinge type relay, there types which cannot full wave rectifier alone other types which full wave rectifier alone, necessary discuss this with maker determine which possible.
Temperature rise value 100% About About About
have erroneous operation abnormal operation. understand this condition while preparing sequence circuits, shown Fig. with lines written power source lines, upper line always lower line (when circuit same thinking applies). Accordingly side necessarily side making contact connections (contacts relays, timers, limit switches, etc.), side load cir- cuit side (relay coil, timer coil, magnet coil, solenoid coil, motor, lamp, etc.). Fig. shows example stray circuits. Fig. (a), with contacts closed, after relays operate, contacts open, there series circuit through relays will sometimes restored drop condition. connections shown Fig. correctly made. addition, with regard circuit, because simple means diode prevent stray circuits, proper application should made.
Voltage
Upper side line Contact circuit Power source lines Load circuit Lower side line
Time
Fig.
Fig. Example vertically written sequence circuit
General Application Guidelines
good example
Correct example
Fig. Stray circuits
Gradual increase coil impressed voltage suicide circuit When voltage impressed coil increased slowly, relay transferring operation unstable, contact pressure drops, contact bounce increases, unstable condition contact occurs. This method applying voltage coil should used, consideration should given method impressing voltage coil (use switching circuit). Also, case latching relays, using self contacts "B," method self coil circuit complete interruption used, because possibility trouble developing, care
should taken. circuit shown Fig. causes timing sequential operation using reed type relay, this good example with mixture gradual increase impressed voltage coil sucide circuit. timing portion relay when timing times out, chattering occurs causing trouble. initial test (trial production), shows favorable operation, number operations increases, contact blackening (carbonization) plus chattering relay creates instability performance.
Instability point Switch
Reed relay Reed relay
Capacitor Variable resistance (for time adjustment)
R1a: Form relay R1b: Form relay
Fig. timing sequential operation using reed type relay
Phase synchronization load switching switching relay contacts synchronized with phase power, reduced electrical life, welded contacts, locking phenomenon
(incomplete release) contact material transfer occur. Therefore, check relay while operating actual system. However, problems develop, control relay using appropriate phase. (Fig.
Vin.
Load
Load voltage Vin.
Fig.
Erroneous operation inductive interference situations where both control load wiring close proximity, thought should given separating shielding conductors order prevent false relay operation. This becomes increasingly important with long wiring runs, achieved using separate conduit load control conductors. Inductive coupling also minimized maintaining large physical separation load control wiring. Influence external magnetic fields Many modern electro-mechanical relays polarized, high sensitivity design. Care should exercised placement these devices when strong, external magnetic fields present, such proximity power transformers permanent magnets (speakers, etc.). Operational characteristics change under external magnetic influence. Long term current carrying applications which involve lengthy duty cycles, preferred configuration would form N.C. contacts long term duty. those instances where form contact held closed extensive time periods, coil heating will increase contact rise result shorter than optimum life. Alternately, latching types considered these applications, using storage capacitor "Reset" relay powerdown. Regarding electrolytic corrosion coils case comparatively high voltage coil circuits particular above DC), when such relays used high temperature high humidity atmospheres with continuous passage current, corrosion said result occurrence electrolytic corrosion. Because possibility open circuits occurring, attention should given following points. side power source should connected chassis. (Refer Fig. (Common relays) case where unavoidably side grounded, case where grounding possible. Insert contacts switch) side power source, connect start coil winding side. (Refer Fig. (Common relays) When grounding required, connect ground terminal side coil. (Refer Fig. with ground terminal) When side power source grounded, always avoid interting
General Application Guidelines
contacts (and switches) side. (Refer Fig. (Common relays) case relays provided with ground terminal, when ground terminal considered effective, making connection ground plays
Judgment: Good (Fig.
important role method preventing electrolytic corrosion. Note: designation drawing indicates insertion insulation between iron core chassis. relays where ground terminal providJudgment: Good (Fig.
Switch Bobbin Switch
iron core grounded directly chassis, consideration electrolytic corrosion, more expedient make connection.
Judgment: Good (Fig.
Judgment: good (Fig.
Bobbin
Bobbin
Relay coil
Iron core
Relay coil
Iron core
Relay coil
Iron core
Switch
(Insulation resistance)
Start coil winding
(Insulation resistance)
Bobbin
Switch
CONTACT
contacts most important elements relay construction. Contact performance conspicuously influenced contact material, voltage current values applied contacts particular, voltage current Contact circuit voltage, current, load [Voltage, When there inductance included circuit, rather high counter generated contact circuit voltage, since, extent value that voltage, energy applied contacts causes damage with consequent wear contacts, transfer contacts, necessary exercise care with regard control capacity. case there zero current point such there with accordingly, once cathode been generated, because difficult quench that arc, extended time major cause. addition,
waveforms time application release), type load, frequency switching, ambient atmosphere, form contact, contact switching speed, bounce. Because contact transfer, welding,
abnormal wear, increase contact resistance, various other damages which bring about unsuitable operation, following items require full investigation.
direction current being fixed, phenomenon contact shift, noted separately below, occurs relation contact wear. Ordinarily, approximate control capacity mentioned catalogues similar data sheets, this alone sufficient. With special contact circuits, individual case, maker either estimates from past experience makes test each occasion. Also, catalogues similar data sheets, control capacity that mentioned limited resistive load, there broad meaning indicated that class relay, ordinarily
proper think current capacity that 125V circuits. [Current] current both closing opening time contact circuit exerts important influence. example, when load either motor lamp, extent inrush current time closing circuit, wear contacts, amount contact transfer increase, contact welding contact transfer make contact separation impossible.
Relay coil
coil winding
Iron core
(Insulation resistance)
General Application Guidelines
Characteristics Common Contact Materials Characteristics contact materials given below. Refer when selecting relay.
(silver) AgCd (silver-cadmium) (silver-tungsten) AgNi (silver-nickel) AgPd (silver-palladium) alloy (platinum, gold,silver) plating (rhodium) clad (gold clad) plating (gold plating) flash plating (gold thin-film plating) Electrical conductivity thermal conductivity highest metals. Exhibits contact resistance, inexpensive widely used. disadvantage easily develops sulfide film sulfide atmosphere. Care required voltage current levels. Exhibits conductivity contact resistance silver well excellent resistance welding. Like silver, easily develops sulfide film sulfide atmosphere. Hardness melting point high, resistance excellent, highly resistant material transfer. However, high contact pressure required. Furthermore, contact resistance relatively high resistance corrosion poor. Also, there constraints processing mounting contact springs. Equals electrical conductivity silver. Excellent resistance. standard temperature, good corrosion resistance good sulfidation resistance. However, circuits, organic gases adhere easily develops polymer. Gold clad used prevent polymer buildup. Expensive. Excellent corrosion resistance. Mainly used current circuits. Combines perfect corrosion resistance hardness. plated contacts, used relatively light loads. organic atmosphere, care required polymers develop. Therefore, used hermetic seal relays (reed relays, etc.) Expensive. with excellent corrosion resistance pressure welded onto base metal. Special characteristics uniform thickness nonexistence pinholes. Greatly effective especially level loads under relatively adverse atmospheres. Often difficult implement clad contacts existing relays design installation. Similar effect cladding. Depending plating process used, supervision important there possibility pinholes cracks. Relatively easy implement gold plating existing relays. Purpose protect contact base metal during storage switch device with built-in switch. However, certain degree contact stability obtained even when switching loads.
Contact Material
Surface Finish
Contact Protection Counter When switching inductive loads with relay such relay sequence circuits, motors, clutches, solenoids, always important absorb surges (e.g. with diode) protect contacts. When these inductive loads switched off, counter several hundred several thousand volts develops which severely damage contacts greatly shorten life. current these loads relatively small around less, counter will cause ignition glow discharge. discharge decomposes organic matter contained causes black deposits (oxides, carbides) develop contacts. This result contact failure. Fig. (a), with steep waveform generated across coil with polarity shown Fig.
instant inductive load switched off. counter passes through power supply line reaches both contacts. Generally, critical dielectric breakdown voltage standard temperature pressure about volts. Therefore, counter exceeds this, discharge occurs contacts dissipate energy (1/2Li2) stored coil. this reason, desirable absorb counter that 200V less. memory oscilloscope, digital memory, peak hold meter, etc., used measure counter emf. However, since waveform extremely steep, considerable discrepancies result depending precision equipment used. table shows counter various relays measured high precision peak hold meter. Actual measurement counter peak hold meter
Nominal Coil Voltage Relay Type relay (single side stable) relay 144V 410V 165V 470V
develop such those shown Fig. After while, uneven contacts lock they were welded together. This often occurs circuits where sparks produced moment contacts "make" such when current large inductive capacitive loads when inrush current large (several amperes several tens amperes). Contact protection circuits contact materials resistant material transfer such AgCu used countermeasures. Generally, concave formation appears cathode convex formation appears anode. capacitive loads (several amperes several tens amperes), always necessary conduct actual confirmation tests.
Meterial transfer contacts 188V 510V
Peak voltage meter Several hundred several thousand volts
Fig.
Fig. Example counter actual measurement peak hold meter.
Material Transfer Phenomenon Material transfer contacts occurs when contact melts boils contact material transfers other contact. number switching operations increases, uneven contact surfaces
9-10
General Application Guidelines
Contact Protection Circuit contact protective devices protection circuits suppress counter
Circuit
Contact Inductive load
level. However, note that incorrect will result adverse
Application
effect. Typical contact protection circuits given table below.
Good Good)
Circuit
load timer, leakage current flows through circuit causing faulty operation.
Circuit
used with voltage, sure impedance load sufficiently smaller than that circuit
circuit
Contact Inductive load
load relay solenoid, release time lengthens. Effective when connected both contacts power supply voltage voltage across load 200V.
guide selecting contact voltage contact current Values vary depending properties load variations relay characteristics. Capacitor acts suppress discharge moment contacts open. Resistor acts limit current when power turned next time. Test confirm. capacitor with breakdown voltage 300V. type capacitors (non-polarized) circuits.
Contact Inductive load
Diode circuit
Diode
diode connected parallel causes energy stored coil flow coil form current dissipates joule heat resistance component inductive load. This circuit further delays release time compared circuit. times release time listed catalog)
diode with reverse breakdown voltage least times circuit voltage forward current least large load current. electronic circuits where circuit voltages high, diode used with reverse breakdown voltage about times power supply voltage.
Contact
Diode zener diode circuit
Inductive load
Effective when release time diode circuit long.
zener diode with zener voltage about same power supply voltage.
Contact Inductive load
Varistor circuit
Varistor
Using stable voltage characteristics varistor, this circuit prevents excessively high voltages from being applied across contacts. This circuit also slightly delays release time. Effective when connected both contacts power supply voltage voltage across load 200V.
Avoid using protection circuits shown figures right. Although inductive loads usually more difficult switch than resistive loads, proper protection circuit will raise characteristics that resistive loads. (Fig.
Fig.
Contact
Contact
Load
good
good
Although extremely effective suppression contacts open, contacts susceptible welding since energy stored when contacts open discharge current flows from when contacts close.
Although extremely effective suppression contacts open, contacts susceptible welding since charging current flows when contacts close.
Mounting Protective Device actual circuit, necessary locate protective device (diode, resistor, capacitor, varistor, etc.) immediate vicinity load contact. located away, effectiveness protective device diminish. guide, distance should within 50cm. Abnormal Corrosion During High Frequency Switching Loads (spark generation) example, valve clutch switched high frequency, bluegreen corrosion develop. This occurs from reaction with nitrogen when sparks (arc discharge) generated during switching. relays
with case, case must removed holes drilled case. similar phenomenon occurs presence ammonia-based gas. Therefore, care required circuits where sparks generated high frequency. Type Load Inrush Current type load inrush current characteristics, together with switching frequency important factors which cause contact welding. Particularly loads with inrush currents, measure steady state current inrush current select relay which provides ample margin safety. table right shows relationship between typical loads their inrush currents.
Type load Resistive load Solenoid load Motor load Incandescent lamp load Mercury lamp load Sodium vapor lamp load Capacitive load Transformer load
Inrush current Steady state current times steady state current times steady state current times steady state current Approx. times steady state current times steady state current times steady state current times steady state current
Load
Power supply
Power supply
9-11
General Application Guidelines
Load Inrush Current Wave Time
Incandescent Lamp Load Mercury Lamp Load i/io times
Contacts
Fluorescent Lamp Load i/io times
(for high power factor type) minutes discharge tube, transformer, choke coil, capacitor, etc., combined common discharge lamp circuits. Note that inrush current times, especially power supply impedance high power factor type. seconds less
Incandescent lamp
Approx. second Inrush current/rated current =i/io times
Motor Load i/io times
Solenoid Load i/io times
Electromagnetic Contact Load i/io times
Capacitive Load i/io times
0.07 second second Conditions become harsher plugging inching performed since state transitions repeated. cycles (1/60 1/30 seconds)
cycles (1/120 1/30 seconds)
When Using Long Wires long wires (100 300m) used relay contact circuit, inrush current become problem stray capacitance existing between wires. resistor (approx. series with contacts. (Fig.
Equivalent circuit
Contacts Added resistor Wire (100 300m) Stray capacitance wire
Fig.
Phase Synchronization Switching Loads switching relay contacts synchronized with phase power, reduced electrical life, welded contacts, locking phenomenon (incomplete release) contact material transfer occur. Therefore, check relay while operating actual system. However, problems develop, control relay using appropriate phase. (Fig. Cautions Related Contacts Connection load contacts Connect load side power supply shown Fig. (a). Connect contacts other side. This prevents high voltages from developing between contacts. contacts connected both side power supply shown (b), there risk shorting power supply when relatively close contacts short.
9-12
Load
Load voltage Load voltage
Fig.
Fig.
Good example
example
General Application Guidelines
Dummy Resistor Since voltage levels contacts used current circuits (dry circuits) low, poor conduction often result. method increase reliability dummy resistor parallel with load intentionally raise load current reaching contacts. Care required especially low-level switching circuits (0.1V less, 0.2mA less). Contact material and, course, bifurcated contacts must also taken into consideration.
Avoid Circuits Where Shorts Occur Between Form Contacts (Fig. clearance between form contacts compact control components small. occurrence shorts arcing must assumed. Even three N.C., contacts connected that they short, circuit must never designed allow possibility burning generating Contacts overcurrent. Double pole relay forward reverse motor rotation Fig. example form circuit using switching form contacts must never designed.
Commercial power Home generator Load
N.C. N.O. Load Relay coil Contacts Double pole relay Push-botton switch
Shorts Between Different Electrodes Although there tendency select miniature control components because trend toward miniaturizing electrical control units, care must taken when selecting type relay circuits where different voltages applied
between electrodes multi-pole relay, especially when switching different power supply circuits. This problem that determined from sequence circuit diagrams. construction control component itself must coils reset coils connected together parallel, connect diode series each coil. Fig. Also, coil relay reset coil another relay connected parallel, connect diode coils series. coil reset coil connected parallel with inductive load (e.g. another electromagnetic relay coil, motor, transformer, etc.), connect diode coil reset coil series.
examined sufficient margin safety must provided especially creepage between electrodes, space distance, presence barrier, etc.
LATCHING RELAYS
Latching relays shipped from factory reset state. shock relay during shipping installation cause change state. Therefore, recommended that relay used circuit which initializes relay required state (set reset) whenever power turned Avoid impressing voltages coil reset coil same time. Connect diode shown since latching compromised when relay used following circuits.
Parallel connection coils
diode having ample margin safety repeated reverse voltage peak reverse voltage applications having average rectified current greater than equal coil current. Avoid applications which conditions include frequent surges power supply. Avoid using following circuit since self-excitation contacts will inhibit normal keep state. (Fig.
Parallel connection coils
Reset coil coil coil Reset coil coil Reset coil coil Reset coil
Load
Latching relay Form contacts Form contacts
example
Fig.
Diode connection Diode connection Diode connection Diode connection
Parallel connection coils reset coils
Circuit with inductive load parallel with coil reset coil
Reset coil coil coil
Reset coil
reset coil
Motor Common relay coil
Diode connection Diode connection Diode connection
Four-Terminal Latching Relay coil latching type circuit Fig. terminal coil terminal reset coil connected common voltages same polarity applied other side reset operations. this type circuit, short terminals relay noted next table. This helps keep insulation high between winding.
Fig.
9-13
General Application Guidelines
switch Reset coil
coil
Reset switch
Fig.
Relay Type Flat Slim
Terminal Nos.
Notes: *DS4c relays constructed that coil reset coil separated high insulation resistance. DSP, TQ-SMD, series, relays applicable polarity.
HANDLING CAUTIONS TUBE PACKAGING
Some types relays supplied tube packaging. remove relays from tube packaging, sure slide stop plug hold remaining relays firmly together they would move tube. Failing this lead appearance and/or performance being damaged.
Slide plug.
Stop plug
AMBIENT ENVIRONMENT
Ambient Temperature Atmosphere sure ambient temperature installation does exceed value listed catalog. Furthermore, environmentally sealed types (plastic sealed type, metallic hermetic seal type) should considered applications atmosphere with dust, sulfur gases (SO2, H2S), organic gases. Silicon Atmosphere Silicon-based substances (silicon rubber, silicon oil, silicon-based coating material, silicon caulking compound, etc.) emit volatile silicon gas. Note that when silicon used near relay, switching contacts presence causes
9-14
silicon adhere contacts result contact failure. this case, substitute that silicon-based. Vibration Shock relay magnetic switch mounted next each other single plate, relay contacts separate momentarily from shock produced when magnetic switch operated result faulty operation. Countermeasures include mounting them separate plates, using rubber sheet absorb shock, changing direction shock perpendicular angle. Influence External Magnetic Fields Permanent magnets used reed relays polarized relays (including relays), their movable parts constructed ferrous materials. this reason, when magnet permanent magnet other large relay, transformer, speaker located nearby, relay characteristics change faulty operations result. influence depends strength magnetic field should checked installation. Usage, storage, transport conditions During usage, storage, transportation, avoid locations subject direct sunlight maintain normal temperature, humidity, pressure conditions. allowable specifications environments suitable usage, storage, transportation given below. Temperature: allowable temperature range differs each relay, refer relay's individual specifications. addition, when transporting storing relays while they tube packaged, there cases when temperature differ from allowable range. this situation, sure consult individual specifications. Humidity: R.H.
perature. within range indicated graph below. Condensation Condensation forms when there sudden change temperature under high temperature, high humidity conditions Condensation will cause deterioration relay insulation. Freezing Condensation other moisture freeze relay when temperatures lower than 32°F. This causes problems such sticking movable parts operational time lags. temperature, humidity environments plastic becomes brittle relay exposesd temperature, humidity environment long periods time.
ENVIRONMENTALLY SEALED TYPE RELAYS
Sealed type relays such plastic sealed type available. They effective when problems arise during board mounting (e.g. automatic soldering cleaning). They also, course, feature excellent corrosion resistance. Note cautions below regarding features environmentally sealed type relays avoid problems when using them applications. Operating Environment Plastic sealed type relays especially suited environments which require airtight relays. Although there problem they used level, avoid atmospheric pressures beyond 96±10kPa. Also avoid using them atmosphere containing flammable explosive gases. metallic hermetic seal types these applications. Operating Environment Sealed Type Relays (generation NOX) Environmentally sealed type relays include metallic hermetic seal type relay plastic sealed type relay. When plastic sealed type relay used atmosphere high humidity switch load which easily produces arc, created water absorbed from outside relay combine produce nitric acid. This corrodes internal metal parts adversely affects operation. Avoid ambient humidity 85%RH higher 20°C 68°F). high humidity unavoidable, consult
;;;;;;;;;;;;;;;;; ;;;;;;;;;;;;;;;;; ;;;;; ;;;;;;;;;;;;;;;;; ;;;;;;;;;;;;;;;;; ;;;;;; ;;;;;;;;;;;;;;;;; ;;;;;;;;;;;;;;;;; ;;;;;;;;;;;;;;;;; ;;;;;;;;;;;;;;;;; ;;;;;;;;;;;;;;;;; ;;;;;;;;;;;;;;;;;
Tolerance range (Avoid freezing when (Avoid used temperatures condensation when lower than 0°C32°F) used temperatures higher than 0°C32°F) Temperature, +158
Humidity, %R.H.
Pressure: humidity range varies with temperature. within range indicated graph below.
General Application Guidelines
PROCESSING CONSIDERATIONS
Handling State relays precision mechanical devices such sensitive abusive handling practices. Every attempt made during their manufacture preclude anomalies. Relays packed variety ways best protect them during shipment subsequent handling. These include "Egg Crate" type inserts which support relay prevent damage terminals, foam trays which prevent shock damage, tubes similar those used semiconductor manu-facturers machine dispensing assembly. During incoming inspection subsequent customer handling operations, care should taken degrade device which been supplied prime condition. Some areas concern: Terminals should handled order prevent contamination surface finish. This could lead solderability problems. Terminal layout P.C. board hole pattern should match. misalignment caused mis-registered P.C. board holes lead severe stress relay, compromising performance reliability (seal integrity). storage temperature specification should observed. Relays should stored handled suitably clean area. Fluxing Depending upon type relay involved, fluxing procedures should researched carefully. unsealed relay prone internal flux contamination which compromise contact performance, ideally should hand soldered. "Flux-resistant" relays available which will prevent flux migration through terminal-header interface. These "sealed" relays compatible with mist foam spray fluxing operations, however "Flux-esistant" types totally sealed which precludes washing operations, makes non-active flux almost necessity. Pre-heating board assembly prior soldering "Flux-resistant" types will flux further help prevent flux being driven into relay during soldering operation. Soldering with fluxing, automated soldering processes can, unless controlled carefully, compromise performance unsealed relays. Flux-resistant sealed types compatible with mist wave soldering procedures. Some state-of-the-art relays suitable various reflow processes, such I.R. vapor phase maximum soldering temperatures times will vary from relay type relay type, should exceeded. I.R. reflow process with relay specifically designed withstand process, will probability degrade relay cause performance problems. safe practice would review thermal profile process case case basis with sales office. Cleaning cleaning process which involves potential contamination unsealed relay should avoided. Sealed devices immersion cleaned suitable solvent (see solvent compatibility chart). Cleaning ultrasonic bath should also avoided. harmonic bath frequency induced contacts causing friction welding subsequent contact sticking. Relays with removable "vent" should vented after cooling room temperature following cleaning drying. Mounting relay surfaces contacts (fixed contacts movable contacts) vertical prevents dirt dust well scattered contact material (produced large loads from which arcs generated) powdered metal from adhering them. Furthermore, desirable switch both large load level load with single relay. scattered contact material produced when switching large load adheres contacts when switching level load cause contact failure. Therefore, avoid mounting relay with level load contacts located below large load contacts. Adjacent Mounting When many relays mounted close together, abnormally high temperatures result from combined heat generated. Mount relays with sufficient spacing between them prevent heat buildup. This also applies when large number boards mounted with relays installed card rack. sure ambient temperature relay does exceed value listed catalog. Influence Adjacent Mounting Polarized Relays When polarized relays mounted close together, their characteristics change. Since affect adjacent mounting differs according type relay, refer data particular type. Terminals guide, quick connect mounting pressure kgf} relays with terminals.
MOUNTING CONSIDERATIONS
View Bottom View Relays used boards, especially flat type relays, have their bottom surface indicated terminal wiring diagrams. Relay with terminals viewed from bottom (terminals cannot seen from top) Relay with terminals viewed from (all terminals seen from top) Note during board pattern design (NL, Mounting Direction Mounting direction important optimum relay characteristics. Shock Resistance ideal mount relay that movement contacts movable parts perpendicular direction vibration shock. Especially note that vibration shock resistance Form contacts while coil excited greatly affected mounting direction relay. Contact Reliability
METHOD MOUNTING
direction mounting specifically designated, extent possible, direction contact movement should such that vibration shock will applied. When terminal socket used After drilling mounting holes, terminal socket should mounted making certain mounting screws loose. standard sockets available one-touch mounting rail 35mm 1.378 inch width.
Fig.
9-15
General Application Guidelines
When reversible terminal sockets used reversible terminal sockets (HC, socket) one-touch mounting. panel thickness .039 .079 inch should used.) (Fig. socket should pushed through opening mounting panel until projections side mounting bracket extend over back surface. (Fig. When terminal board uses screw fastening connections, either pressure terminals other means should used make secure fastening wire. Connections Wrapping Socket Applicable Wire Type Solid wires with diameters 0.26 0.65 .010 .026 inch applicable wrapping terminals (0.5 .020 inch type standard). Tinned copper wires most suitable this purpose. Solid bare copper, brass, nickel wires also used. Never stranded wires wrapping sockets. Winding Wire wire would wrapping terminal ways: i.e. only stripped conductor would, single turn coated wire wrapped together with stripped conductor. later type winding suitable wire diameters 0.32 .013 inch less. Unwrapping Wire When unwinding wire from wrapping terminal, commercially available unwrapping tool. wrapping conditions, bits sleeves, refer table. chassis cutout identical that existing socket. socket mounting track hold down clip also used. Relay Types Applicable Wrapping Socket (with hold down clip) wrapping socket with hold down clip used standard-type relays, relays with indication latching relays. When using standard wrapping socket relays with indication latching relays, special hold down clip supplied with socket (see table).
Fig.
When four projections visible from back side mounting panel, mounting completed socket fastened. remove socket, projections side mounting bracket should pushed inward same time body socket should pushed lightly from back side. socket then removed from panel. socket should inserted through opening mounting panel that terminal wiring side toward back side. mounting panel used units, with less than that number. (Fig.
Conductor winding
Coated wire winding
Wire Wrapping Condition, Bits Sleeves
Item Wire size dia. inch) 0.26 .010 Stripping length inch) Wrapping type Typical Pulling wrapping strength turns (kgf) type 36-A 37-A 21-A 25-A 34-A 43-A 22-A 26-A 33-A 34-A 40-A 45-A 23-A 40-A 44-A 46-A Sleeve time 22-B 22-B 20-B 20-B 20-B
Coated wire winding 1.575 1.614 Coated wire winding Conductor winding Coated wire winding Conductor winding 1.693 1.732 Conductor winding Coated wire winding Conductor winding Coated wire winding
.016
Fig.
REGARDING CONNECTION LEAD WIRES
When making connections, depending upon size load, wire crosssection should least large values shown table below.
Permissible current Cross-section (mm2) 12.5 0.75 1.25
Conditions .020
Conductor winding 1.417 1.457 Conductor winding Conductor winding Conductor winding Coated wire winding Conductor winding Coated wire winding 0.65 .026 1.614 1.654 Conductor winding Conductor winding Coated wire winding
Wrapping Sockets Applicable Relay Types
Socket type Standard wrapping socket Wrapping socket with hold down clip Applicable relays Standard relays (including amber type) relays with indication (use accessory hold down clip) latching relays (use accessory hold down clip) relays with indication latching relays
9-16
General Application Guidelines
CAUTIONS USE-Check List
Check Item
correct rated voltage applied? applied coil voltage within allowable continuous voltage limit? ripple coil voltage within allowable level? voltage applied polarized coil, polarity observed? When start required, increase coil resistance resulting from coil temperature rise taken into account setting coil voltage? coil voltage free from momentary drop caused load current? (Pay special attention self-holding relays.) supply voltage fluctuation taken into account when setting rated coil voltage? relay status become unstable coil voltage (current) gradually increased decreased. relay tested real circuit with real load? load rated within contact ratings? Does load exceed contacts' minimum switching capacity? Special attention required contact welding when load lamp, motor, solenoid, electromagnetic contractor. relay tested with real load? load cause contact lock-up large contact transfer. relay tested with real load? inductive load, surge absorber used across contacts? When inductive load causes heavy discharge across relay contacts, contacts corroded chemical reaction with nitrogen atmosphere. relay tested with real load? Platinum contacts generate brown powder catalyzer effect vibration energy. relay tested with real load? contact switching frequency below specification? When there more than sets contacts (2T) relay, metallic powder shed from contacts cause contact failure other (particularly light loads). relay tested real circuit? delay capacitor used across relay contacts cause contact welding. relay tested with real load? relay, large contact bounce cause contact welding. relay tested real circuit with real load? high voltage induced across transformer load. relay tested with real load? Does circuit design take into account electrolytic corrosion coil? transistors other circuit components protected counter electromotive force that develops across relay coil? circuit designed relay coil left deenergized while relay inactive long period time? relay operated within ratings approved relevant international standard compliance required)? circuit protected from malfunction when relay's activation and/or deactivation time varies considerably? circuit protected from malfunctions that might result from relay contact bounce? circuit protected from malfunction when high-sensitivity self-holding relay, such type, used? When there more sets contacts (2T) relay, discharges from load switching cause short circuits across more sets contacts. circuit designed suppress such discharges? Item above also requires special attention when loads supplied from separate power sources. Does post-installation insulation distance comply with requirement relevant international standard Electrical Appliance Material Control Law? circuit protected from malfunction when relay driven transistors? When used on/off control, relay activation tends synchronize with line frequency, resulting extremely shortened life. relay tested real circuit with real load? 13.Does board design take into account on-board relay? 14.RF signals leak across relay's open contacts. Check adequate contact isolation relays needed. ambient temperature allowable operating temperature range? relative humidity below percent? operating atmosphere free from organic sulfide gases? operating atmosphere free from silicon gas? Depending load type, silicon cause black substance from contacts, leading contact failure. operating atmosphere free from excessive airborne dust? relay protected from water splashes? relay protected from vibration impact which cause poor contact with socket? ambient vibration impact below level allowable relay? relay free from mechanical resonance after installed position? relay's internal pressure equivalent ambient atmospheric pressure (760 mmHg±20%)? insulation coating applied relay along with board? Depending load type, black substance form cause contact failure. relay protected from solder chips flux when manually soldered? preparations flux application automatic soldering complete? board cleaning process designed minimize adverse affects relays? adequate separations provided between polarized reed relays prevent magnetic coupling? relay terminals free from stress socket? Polarized relay's characteristics affected strong external magnetic field. relays installed away from such fields? very long leads (100 meters) used connect load, stray capacity existing across leads cause surge current. relay tested with real load? Unless otherwise specified, relay terminals should soldered 250°C 482°F within sec. 350°C 662°F within sec. badly warped board cause stress relay terminals which lead degraded relay characteristics. Glass shot should used clean board solder flux. This cause relay malfunction glass powder becoming lodged relay's internal structure. Relays should always used with their plastic shields installed, degraded relay performance result. away relay terminal stress cause degraded relay performance. 9-17
Coil Drive Input
Load (Relay contacts)
Circuit Design
Operating Environment
Installation Connection
Reliability
What Reliability? Reliability Narrow Sense Term industrial world, reliability index long particular product serves without failure. Reliability Board Sense Term Every product finite service lifetime. This means that product continue normal service infinitely. When product broken down, user throw away repair reliability repairable products recognized "reliability broad sense term. "For repairable products, their serviceability maintainability another problem. addition, reliability product design becoming serious concern manufacturing industry. short, reliability three senses: i.e. reliability product itself, serviceability product, reliability product design. Intrinsic Reliability Reliability UseReliability "built" into products. This referred intrinsic reliability which consists mainly reliability narrow sense.Product reliability user's site called "reliability use," which consists mainly reliability broad sense. relay industry, reliability significance aspects servicing.
Reliability (broad sense)
Reliability (narrow sense), durability Long life time: MTTF, B10, R(T), failure rate: Lamda MTBF Maintainability MTTR Preventive maintenance, predicted maintenance Design reliability Human factor, redundancy, fool-proof, fail-safe
Availability
Reliability Measures following list contains some most popular reliability measures:
Reliability measure Degree reliability R(T) MTBF MTTF Failure rate Safe life Sample representation 99.9% hours hours fit, 1%/hour hours
f(t) Time R(T) MTTF MTTF Safe life
Degree Reliability Degree reliability represents percentage ratio reliability. example, none light bulbs failed hours, degree reliability defined hours time 10/10 100%. only three bulbs remained alive, degree reliability 3/10 30%. Z8115 standard defines degree reliability follows: probability which system, equipment, part provides specified functions over intended duration under specified conditions. MTBF MTBF acronym mean time between failures. indicates mean time period which system, equipment, part operates normally between incidences repair. MTBF only applies repairable products. MTBF tells long product used without need repair. Sometimes MTBF used represent service lifetime before failure. MTTF MTTF acronym mean time failure. indicates mean time period until product becomes faulty MTTF normally applies unrepairable products such parts materials. relay such objective MTTF.
Failure Rate Failure rate includes mean failure rate momentary failure rate. Mean failure rate defined follows: Mean failure rate Total failure count/total operating hours general, failure rate refers momentary failure rate. This represents probability which system, equipment, part, which continued normal operation certain point time, becomes faulty subsequent specified time period. Failure rate often represented unit percent/hours. parts with failure rates, "failure unit (Fit) 109/hour" often used instead failure rate. Percent/count normally used relays. Safe Life Safe life inverse degree reliability. given value which makes following equation true: R(B) general, "B[1 R(B)] 10%" more often used. some cases this represents more practical value reliability than MTTF.
9-18
Reliability
Failure What Failure? Failure defined state system, equipment, component which part functions impaired lost. Bathtub Curve Product's failure rate throughout lifetime depicted bathtub curve, shown below. Failure rate high beginning service lifetime. Initial failure period high failure rate initial failure period derived from latent design errors, process errors, many other causes. Initial failures screened manufacturer's site through burn-in process. This process called debugging, performing aging screening. (II) Accidental failure period initial failure period followed long period with low, stable failure rate. this period, called accidental failure period, failures occurs random along time axis. While zero accidental failure rate desirable, this actually practical real world. (III) Wear-out failure period final stage product's service lifetime comes wear-out failure period, which life product expires wear fatigue. Preventive maintenance effective this type failure. timing relay's wear-out failure predicted with certain accuracy from past record uses. relay intended only accidental failure period, this period virtually represents service lifetime relay. Weibull AnalysisWeibull analysis often used classifying product's failure patterns determine lifetime. Weibull distribution expressed following equation: Weibull distribution adopted actual failure rate distribution three variables above estimated.
Failure rate
Time
where
figure parameter Measurement parameter Position parameter
Weibull probability chart simpler alternative complex calculation formulas. chart provides following advantages: Weibull distribution closest proximity actual failure rate distribution. Weibull probability chart easy use. Different types failures identified chart.
Failure rate
following describes correlation with bathtub curve. value parameter represents type failure. When Initial failures When Accidental failures When Wear-out failures
Time
9-19
Applications Relays Electronic Circuits
RELAY DRIVE MEANS TRANSISTOR
Connection method voltage impressed relay always full rated voltage, time, voltage completely zero avoidance trouble use. (Fig.
(Good) Collector connection With this most common connection, opertion stable.
Fig.
(Care) Emitter connection When circumstances make this connection unavoidable, voltage completely impressed relay, transistor does conduct completely operation uncertain.
(Care) Parallel connection When power consumed complete circuit becomes large, consideration relay voltage necessary.
Countermeasures surge voltage relay control transistor coil current suddenly interrupted, counter emf. sudden high voltage pulse develAs suitable ratings this diode, curoped coil. this voltage exceeds rent should equivalent average voltage resistance transistor, rectified current coil, transistor will degraded, this inverse blocking voltage should about will lead damage. absolutely nec3 times value power source essary connect diode circuit voltage. (Fig. means preventing damage from
Diode
Fig.
Take care ASO.
Snap action (Characteristic relay with voltage rise fall voltage) Unlike characteristic when voltage impressed slowly relay coil, this case where necessary impress rated voltage short time also drop voltage short time. (Fig.
Fig.
Non-pulse signal
Pulse signal (square wave)
Good) Without snap action (Good) Snap action
Schmitt circuit (Snap action circuit) (Wave rectifying circuit) When input signal does produce snap action, ordinarily Schmitt trigger circuit used produce safe snap action. Characteristic points common emitter resistor must have value sufficiently small compared with resistance relay coil. (The voltage impressed relay must greater than excitation voltage.) relay coil current, difference voltage point when
9-20
conducting point when conducting creates hysteresis detection capability Schmitt circuit, care must taken setting values. When there chattering input signal because waveform oscillation, time constant circuit should inserted stage before Schmitt trigger circuit. (However, response speed drops.) (Fig.
Signal
Applications Relays Electronic Circuits
Avoid Darlington circuit connections. (High amplification) This circuit trap into which easy fall when dealing with high circuit technology. This does mean that immediately connected defect, linked troubles that occur after long periods with many units operation. (Fig.
VCESAT About 0.7V
VCESAT About 0.1V
good) Darlington connection
Fig.
excessive consumption power, heat generated.) strong necessary.)
(Good) Emitter connection
conducts completely.) sufficient signal use.)
Residual Coil Voltage switching applications where semiconductor (transistor, UJT, etc.) connected coil, residual voltage retained relay coil which cause incomplete restoration faulty operation. using coils, there reduction danger incomplete restoration, contact pressure, vibration resistance. This because drop-out voltage more rated voltage, value
compared that coil, also there tendency increase life lowering drop-out voltage. When signal from transistor's collector taken used drive another circuit shown figure right, minute dark current flows relay even transistor off. This cause problems described above. (Fig.
Fig. Connection next stage through collector
dark current good)
RELAY DRIVE MEANS
Ordinary drive method drive, necessary take particular care with regard gate sensitivity erroneous operation noise. (Fig. Caution points regarding ON/OFF control circuits peak values occur only zero (When used temperature similar phase values phenomenon this type control circuits) control. (Depending upon sensitivity When relay contacts close simultaneand response speed relay) ously with single phase power Accordingly, either extremely long source, because electrical life life extremely short life results contacts suffers extreme shortening, care with wide variation, necessary necessary. (Fig. take care with initial device quality When relay turned check. using SCR, serves half wave power source there ample cases where easily Fig. restored. this manner relay operation restoration timing easily synchronized with power source frequency, timing load switching also easily synchronized. When load temperature control high current load such heater, switching occur only
Heater
There problem even with more than times rated current. ohms must connected. This prevention isolation point error sudden rise power source noise. (dv/dt countermeasure)
Fig.
RELAY DRIVE FROM EXTERNAL CONTACTS
Relays board have high sensitivity high speed response characteristics, because they respond sufficiently chattering bouncing, necessary take care their drive. When frequency low, with delay response time caused condenser, possible absorb chattering bouncing. (Fig. (However, possible only condenser. resistor should also used with capacitor.)
External contact
Fig.
9-21
Applications Relays Electronic Circuits
SERIES PARALLEL CONNECTIONS
series with relay parallel with parallel connection with relay
Power consumption: common with relay (Good) Defective LED: Relay does operate good) voltage circuit: With LED, 1.5V down good) parts: (Good)
Power consumption: common with relay (Good) Defective LED: Relay operate good) voltage circuit: With LED, 1.5V down good) parts: (Care)
Power consumption: Current limiting resistor (Care) Defective LED: Relay operate stable (Good) voltage circuit: (Good) parts: (Care)
ELECTRONIC CIRCUIT DRIVE MEANS RELAY
Chatterless electronic circuit Even though chatterless characteristic feature relays, this fullest extent chatterless electrical circuits, much same mercury relay. meet requirement such circuits input binary counter, there electronic chatterless method which chattering absolutely permissible. Even chattering develops side, either N.O. side contacts N.C. side contacts, flip flop does reverse, counter circuit pulsed without miss. (However, bouncing from N.O. side N.C. side must absolutely avoided.) (Fig. Triac drive When electronic circuit using direct drive from triac, electronic circuit will isolated from power circuit, because this, troubles erroneous operation damage develop easily. introduction relay drive most economical most effective solution. (Photo coupler pulse transformer circuits complicated.) When zero cross switching characterisNotes: lines should made short possible. necessary that there noise from coil section induced into contact section.
N.O.
N.C.
R-S-F.F
Binary Counter
Fig.
necessary, solid state relay (SSR) should used. (Fig.
Fig.
ASSURANCE POWER SOURCE RELAY ELECTRONIC CIRCUIT
Constant Voltage circuit board pattern Ordinarily, extremely undesirable have ripple voltage variation electronic circuit power source. This naturally true also relay power sources same extent electronic circuit. Accordingly, desirable have constant voltage circuit dedicated electronic circuit with sufficient margin current. Roughly speaking, this also good relay, from practical
9-22
Regular circuit (Example) Relay power supply Regular circuit Regulated power supply voltage stabilizer. Electronic circuit
Fig.
Applications Relays Electronic Circuits
viewpoint, relay should operated within standards ripple voltage variation. Similarly, circuit diagram shown Fig. means Prevention Voltage Drop Rush Current circuit shown Fig. (a), rush current flows from lamp capacitor. instant contacts close, voltage drops relay releases chatters. manner which board pattern designed, ON/OFF operation relay coil, lamp, etc., will exert influence electronic circuit. This just matter technique that necessary.
Lamp
this case necessary raise transformer's capacity smoothing circuit. shows example modified circuit. shows battery-powered version.
Lamp
Battery
Motor
Fig.
BOARD DESIGN CONSIDERATIONS
Pattern Layout Relays Since relays affect electronic circuits generating noise, following points should noted. Keep relays away from semiconductor devices. Design pattern traces shortest lengths. Place surge arrester (diode, etc.) near relay coil. Avoid routing pattern traces susceptible noise (such audio signals) underneath relay coil section. Avoid through-holes places which cannot seen from (e.g. base relay). Solder flowing through such hole cause damage such When necessary hand soldering part component after soldering been done providing narrow slot circular part foil pattern, slot will prevent hole from being plugged with solder. (Fig.
good)
Diode bridge Relay coil Diode bridge
(Good)
Constant voltage
Electronic circuit
Relay currents electronic circuit currents flow together through
Fig.
Constant Electronic circuit voltage coil currents consist only circuit currents consist only simple design consideration change safety operation.
seal. Even same circuit, pattern design considerations which minimize influence on/off opera-
tions relay coil lamp other electronic circuits necessary. (Fig.
When printed circuit board itself used connector edge should beveled. (This When only single side used prevents peeling foil when connector blade, there distortion board inserted into socket.) circuit board, contact will defective. Care should taken. (Fig.
Through hole
Fig.
0.5mm .012 .020 inch
Fig.
Bevel radius
(Care)
(Good)
(Good) Contact both surfaces
9-23
Applications Relays Electronic Circuits
BOARD REFERENCE DATA
(This data been derived from samples company's products. When carrying circuit design printed circuit board, this data will found very useful reference.)
Fig.
Copper foil 0.0018mm .0007 inch Current, .008 .020 .039 .059 .079 .098 .118 Conductor width, inch 60°C 140°F 40°C 104°F 20°C 68°F 10°C 50°F
Fig.
Copper foil .035mm .001 inch Current, .008 .020 .039 .059 .079 .098 .118 Conductor width, inch 20°C 68°F 10°C 50°F
Conductor width allowable current conductor determined from safety aspect effect performance conductor rise saturation temperature when current flowing. (The narrwer conductor width thinner copper foil, larger temperature rise.) example, high rise temperature causes degradation characteristic color changes laminate. Ingeneral, allowable current capacity conductor determined that rise temperature less than degrees necessary design conductor width from this allowable conductor current capacity. Fig. Fig. Fig. show relationship between current conductor width each rise temperature different copper foils. also necessary give consideration preventing abnormal currents from exceeding destruction current conductor. Fig. shows relationship between conductor width destruction current.
60°C 140°F 40°C 104°F
Fig.
Copper foil .070mm 60°C 140°F .003 inch 40°C 104°F 20°C 68°F 10°C 50°F .020 .039 .059 .079 .098 .118 Conductor width, inch
Fig.
Destruction current, .020 .039 .059 .079 .098 .118 Conductor width, inch Copper foil thick .070 .003
Current,
.035 .001
.018 .0007
Fig.
Copper foil .035mm .001 inch Resistance, .197 .394 .7871.1811.969 3.937 7.874 11.811 19.685 39.37 78.74 Conductor lenth inch) width=0.5 .020 .039 .079 .118
Hole land diameter hold diameter land made with hole slightly larger than lead wire that component inserted easily. Also, when soldering, solder will build eyelet condition, increasing mounting strength. standard dimensions hold diameter land shown table below.
Standard dimensions hole land diameter Standard hole diameter .031 .039 .047 .063 9-24 ±0.1 ±.039 Tolerance
inch
Remarks hole diameter made 0.5mm larger than lead diameter. However, method (wave type, type) soldering used, because fear solder passing through component side, more suitable make hold diameter equal lead diameter +0.2mm. land diameter should times hold diameter. more than lead hole.
Land diameter .079 .118 .138 .177
Applications Relays Electronic Circuits
Expansion shrinkage copperclad laminates Because copperclad laminates have longitudinal lateral direction, manner punching fabrication layout must observed with care. expansion shrinkage longitudinal direction heat 1/15 that lateral, accordingly, after punching fabrication, distortion longitudinal direction will 1/15 that lateral direction. mechanical strength longitudinal direction greater than that lateral direction. Because this difference between longitudinal lateral directions, when products having long configurations fabricated, lengthwise direction configuration should made longitudinal direction, boards having connector section should made with connector along longitudinal side. (Fig. Space between conductors Fig. shows relationship between spacing between conductors destruction voltage. This destruction voltage destruction voltage PCB; flash over voltage (insulation breakdown voltage space between circuits.) Coating surface conductor with insulating resin such solder resist increases flash over voltage, because holes solder resist, necessary consider conductor destruction voltage without solder resist. fact, necessary ample safety factor when determining spacing between conductors. Table shows example design spacing between conductors. (Taken from C5010 standards.) However, when product covered electrical products control law, standards other safety standards, necessary conform regulations.
Fig.
Example shwon drawing below, 150mm 5.906 inch direction taken longitudinal direction. Longitudinal 5.906
2.756
Longitudinal direction
Also, shown drawing below, when pattern connector section, direction taken shown arrow longitudinal direction
Longitudinal direction
Destruction Voltage (kV)
.008 .020 .039 .079 .118 Conductor width inch
.157
Fig.
Table Example conductor spacing design Maximum Minimum Conductor VoltageBetween Spacing (mm) Conductors(V) more 0.381 0.635 1.27 2.54 Calculated 1011508 mm/V
9-25
Relay Soldering Cleaning Guidelines
Mounting Relay Avoid bending terminals make relay self-clinching. Relay performance cannot guaranteed terminals bent. Self-clinching terminal types available depending type relay. Correctly drill board according given board pattern illustration. Stick packaging automatic mounting available depending type relay.
example
Flux Application
Adjust position board that flux does overflow onto This must observed especially dust-cover type relays. rosin-based non-corrosive flux. board pressed down into flux-soaked sponge shown right, flux easily penetrate dust-cover type relay. Never this method. Note that board pressed down hard enough, flux even penetrate flux-resistant type relay.
example
Preheating
sure preheat before using automatic soldering. dust-cover type relays flux-resistant type relays, preheating acts prevent penetration flux into relay when soldering. Solderability also improves. Preheat according following conditions.
Temperature Time 100°C 212°F less Within approx. minute
Note that long exposure high temperatures (e.g. malfunctioning unit) affect relay characteristics.
Soldering
Automatic Soldering Flow solder optimum method soldering. Adjust level solder that does overflow onto board. Unless otherwise specified, solder under following conditions depending type relay.
Solder Temperature Approx. 250°C 482°F
Hand Soldering Keep soldering iron clean.
Soldering Iron Iron Temperature Approx. 300°C 572°F
Soldering Time Within approx. seconds Solder Z3282
Soldering Time Within approx. seconds Solder Z3282
9-26
Relay Soldering Cleaning Guidelines
Cooling Automatic Soldering Immediate cooling recommend prevent deterioration relay surrounding parts soldering heat. Although environmentally sealed type relay (plastic sealed type, etc.) cleaned, avoid immersing relay into cold liquid (such cleaning solvent) immediately after soldering. Doing deteriorate sealing performance. Hand Soldering
Cleaning
clean dust-cover type relays flux-resistant type relays immersion. Even only bottom surface board cleaned (e.g. with brush), careless cleaning cause cleaning solvent penetrate relay. Plastic sealed type relays cleaned immersion. alcoholbased cleaning solvents. other cleaning solvents (e.g. Trichlene, chloroethene, thinner, benzyl alcohol) damage relay case. However, some types relays materials which board coated prevent insulation board from deteriorating corrosive gases high temperatures, note following. coat dust-cover type relays flux-resistant type relays, since coating material penetrate relay cause contact failure. mount relay
Type Epoxy-base Urethane-base Suitability Relays Good Care
chemical resistant. Select suitable relay solvent referring cleaning solvent compatibility chart below. Cleaning with boiling method recommended. Avoid ultrasonic cleaning relays. ultrasonic cleaning cause breaks coil slight sticking contacts ultrasonic energy.
Coating
after coating. Depending type, some coating materials have adverse affect relays. Furthermore, solvents (e.g. xylene, toluene, MEK, I.P.A.) damage case chemically dissolve epoxy break seal. Select coating materials carefully.
Features
electrical insulation. slightly difficult apply, does affect relay contacts. electrical insulation, easy apply. damage case. Check before use. electrical insulation, easy apply. becomes cause contact failure. dust-cover type relays flux-resistant type relays. used only metallic hermetic sealed type relays.
Silicon-base
Care
relay components (e.g. ICs) coated, sure carefully check flexibility coating material. solder peel from thermal stress. Cleaning Solvent Compatibility Chart Yes,
Plastic seal type Plastic seal relays other than those products listed left. Amber relay Amber relays other than those products listed left amber amber amber amber amber Metallic hermetic sealed type
Relay Type
Cleaning Solvent Cleaning solvent Trichloroethane (Chlorothene) (Trichlene) chloride 624, 1000 Terg
Aqueous Alcohol-base Others
9-27
Soldering Guidelines
CAUTIONS SURFACE MOUNT RELAY INSTALLATION
meet market demand downsizing smaller, lighter, thinner products, boards also need proceed From Insertion Mounting Surface What Surface Mount Relay? From Conventional insertion mount technology (IMT) with some years history being replaced with surface mount technology (SMT). Solid-state components such resistors, ICs, diodes withstand high heat stresses from reflow soldering because they mechanical parts. contrast, conventional electromechanical relays consisting solenoid coils, spring, armatures very sensitive thermal stress from reflow soldering. Features Effects Features Effects
high density mounting installed both sides System board downsizing boards used with automatic placement robots Overall lead holes cost reducrequired system designs tion possible high density mounting heat resistance measures High reliability
Mounting technology. meet this need, offer line surface mount relays. following describes some cautions required surface mount relay installaWe applied experience gained from advanced relay technologies produce high-performance electromagnetic Insertion Mount Technology (IMT)
tion prevent malfunction incorrect operation.
relays compatible with surface mount technologies such VPS.
Insertion Mounting Technology:
Components' leads inserted into lead holes drilled into board soldered copper pads other side board using flow-soldering techniques.
Surface Mount Technology (SMT)
Components placed copper pads precoated with paste solder board assembly heated solder components pads (reflow soldering).
Relay (Surface Mount Type)
Relay Resistor board Relay Clip resistance board volatility liquid crystal resin case High impact resistant flexible hinge spring Coil sealed formation body (High heat resistance, high insulation, volatility gas) Permanent magnet, laser welding connection iron core. Warped cross-section iron core EIAJ standard conformant High wthstand voltage between contacts
Case
Armature block
Body block
surface mount relay manufactured with following advanced technologies:
Heat-resistance encapsulation technique analysis Reliability assessment Precision molding technique heat-resistant materials
Examples Applications following describes some examples typical applications: Vapor Phase Soldering (VPS) Infrared Reflow Soldering (IRS) With technology, assemblies most popular reflow soldering carried through special inactive soltechnology available surface vent, such Fluorinate FC-70, that mounting. uses sheath heater been heated vapor state. satinfrared lamp heat source. urated vapor condenses board assemblies continuously solboard surface, resulting evaporation dered they transferred through heat provides energy reflow soltunnel furnace comprised preheatdering. ing, heating, cooling-states.
Preheat stage Heating stage Cooling stage Cooling coil Saturated vapor
Heater
Belt conveyer reflow furnace assemblies transferred thin, heat-resistant belt conveyer, they soldered heat from hotplates placed begeath conveyer belt. Double Wave Soldering (DWS) Components glued board surface. board assembly transferred through molten solder fountain (with component side facing down), components soldered board. Other Technologies Other reflow soldering technologies include those utilizing lasers, air, pulse heaters.
9-28
Soldering Guidelines
Cautions installation
Paste Soldering
Mounting pads boards must designed absorb placement errors while taking account solderability insulation. Refer suggested mounting layout application data required relay product. Paste solder applied board with screen printing dispenser techniques. either method, paste solder must coated appropriate thickness shapes achieve good solder wetting adequate insulation. small, lightweight components Such chip components, self-alignment effect expected small placement errors exist. However, this effect expected electromechanical components such relays, they require precise positioning their soldering pads. relays sustain excessive mechanical stress from placement machine's pickup head, their performance cannot guaranteed. Reflow soldering under inadequate soldering conditions result unreliable relay performance even physical damage relay (even relay surface mount type with high heat resistance). Example Recommended Soldering Condition Surface Mount Relays. technique
Screen Printing
Squeegee Paste solder (for screen printing) Mask board
Solder Dispenser
Syringe Paste solder (for dispenser)
Needle board
Relay Installation
relays supplied stick packaging compatible with automatic placement processes. also offer tape packaging customer request.
Holding Pressure Direction Less than 4.903 (less than Direction Less than 9.807 (less than 1,000 Direction Less than 9.807 (less than 1,000
Reflow
technique
100°C 212°F 200°C 392°F Less than 215°C 419°F
165°C 329°F 200°C 392°F Less than 245°C 473°F
Less than sec. Less than sec.
recommended that soldered immediately cooled prevent thermal damage relay associated components. While surface mount relays solvent washable, immerse relay cold cleaning solvent immediately after soldering.
Cleaning
Manual soldering Soldering iron temperature: 300°C 572°F Soldering iron wattage: watts Soldering time: Less than sec. Others When soldering technique other than above used (hot air, hotplate, laser, pulse heater technique), carefully investigate suitability technique.
Notes: soldering temperature profile indicates temperature. some cases, ambient temperature greatly increased. Check specific mounting condition. preheating conditions technique identical those technique.
surface mount relays solvent washable. alcohol equivalent solvent cleaning. Boiled cleaning approved surface mount relays. Ultrasonic cleaning cause coil damage light contact sticking.
;;;;
120°C Less than sec.
9-29
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