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FAQ02195 of Solid-state Relays FAQ

FAQ No. FAQ02195

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What is the difference between Solid-state Relays and Contact Relays?


Solid State Relays use semiconductors for no-contact operation. Solid-state Relays are not very different in operation from Contact Relays (Electromagnetic Relays). Solid-state Relays, however, consist of electronic parts with no mechanical contacts. Therefore, Solid-state Relays have a variety of features that Contact Relays do not incorporate.

Use both Relays in accordance with the intended use.

Main features of the Solid State Relay and the Contact Relay

Input characteristics

SubjectMeritSolid State RelayMeritContact Relay (Electromagnetic Relay)
Noise & SurgeYesNothingReverse-surge happen when input signal stopped

Output characteristics

SubjectMeritSolid State RelayMeritContact Relay
(Electromagnetic Relay)
Number of
contact poles
Normally 1a contactYesMultiple contact available
Load currentAllow a few times higherrash current.
And have no operation zone as small
Need some treatment, contact reliability at
small current operation at high current
TransitHave a destruction or malfunction
risks at high voltage or transit voltage
Bounce/chatterYesNo bounce or chatteringHave some bounce or chattering
Leak currentA fewμA and a few mAYesZero
Noise/SurgeNoise occurred during
theloss time operation
Surge noise occurred when the inductive
load used
ArcYesNothingArc happen at middle and large load
YesAvailableNot available
LifeYesNo limitationApprox a few million times

Environmental characteristics

SubjectMeritSolid State RelayMeritContact Relay
(Electromagnetic Relay)
TemperatureRequired the heat-sink design as
self-heating of semicon device
Required the body material and change of
operation mode.
Operation soundYesNothingContact sound occurred

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