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Sizing RC Network for Contactor
Sizing a RC snubber circuit for a size 1 contactor.

I want to put a RC network across both of the coils of two mechanically interlocked size one 120 vac contactors.

Can you help me size this network? Looking at different networks they can have varying resistance and capacitive values. The contactors in question change state a couple times a month if that matters at all.

Thanks in advance for your reply.

By W.L. Mostia on 21 August, 2018 - 2:23 pm
1 out of 1 members thought this post was helpful...

You might find the following websites useful:

http://www.hiquel.com/fileadmin/userfiles/AppNotes/Englisch/HIQUEL_Snubber_AppNote_EN_0100.pdf

http://www.ee.bgu.ac.il/~pel/links/DESIGN_OF_SNUBBERS_FOR_POWER_CIRCUITS.pdf

https://www.illinoiscapacitor.com/pdf/Papers/RC_snubber.pdf

William (Bill) L. Mostia, Jr. PE
ISA Fellow
Sr. Functional Safety Consultant
SIS-SILverstone, LLC.
http://www.sissilverstone.com

"No trees were killed to send this message, but a large number of electrons were terribly inconvenienced." Neil deGrasse Tyson

Any information is provided on a Caveat Emptor basis.

are you driving the coils with solid-state devices switching direct current on/off?

No solid state devices, standard 120 60hz.

Generally you do not need the snubbers to handle the inductive kick-back with ac coils. Only where solid state switching of DC coils, in which case diodes are typically used to protect the switching devices.