Question

Is it true you need to add some form of protection when using relay outputs to turn on solenoids or motor contactors

Answer

Yes, it is true. Devices with coils (inductive loads) driven by a PLC relay output will generate a voltage spike when it is turned off. You should install some form of surge suppression, such as TVS, MOV or Diode, at the coil or as close to the coil of the solenoid (or other device) as possible.

App Note AN-MISC-032 covers surge suppression in more detail

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FAQ Subcategory: Power, I/O, and Wiring

This item was last updated on 2021-01-20
Document ID: 1171

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