What are surge countermeasures in coil relays?

ID: FAQE10041E



The back electromotive force generated by the coil when it’s turned off may cause damage to the semiconductor or device malfunction. As a countermeasure, add a surge-absorbing circuit to both ends of the coil.
If a surge-absorbing circuit is added, the relay release time will be longer. Check the circuit before use.


Surge countermeasure

  • Driving DC coil relay: Diodes are typically attached to the relay coil.
  • Driving AC coil relay: Varistors/CR elements are typically attached to the relay coil.

Examples of Surge Suppressors

Examples of Surge Suppressors

For more information, see Safty Precautions for All Relays: 2-2-5 Preventing Surges When the Coil Is Turned OFF.

Quick tips

We have prepared a technical support page dedicated to high-capacity relays that explains in detail "I don't know" when using high-current, high-voltage PCB power relays, such as back EMF voltage (Zener diode and varistor) of the coil, holding voltage application circuit, recommended conditions for high-current substrate flow solder, the influence of magnetic fields, and precautions when connecting in series and parallel. Please also use this as well.
Click here for the high-capacity power relay technical support page.

Product category Relays Signal Relays Power Relays
Classification Usage, Applications
Related keywords
  • Signal Relays
  • Power Relays
  • Back Electromotive Force
  • Transistor Drive
  • Surge-Absorbing Circuit
  • DC Coil
  • AC Coil

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