Purpose of the blue capacitors in the OMRONs module

[eladn]

Hi.
I noticed there are blue capacitors attached to the load terminals of the OMRON relays module (can be seen in the picture attached below).
Can you please explain what is their purpose? what they are needed for?

   

[eladn]

Maybe it could be an "R-C quench circuit" like this?
   
If so, it is explained here that it is to avoid the sparks on the load contacts of the relay:
https://electronics.stackexchange.com/qu...-of-relays

[admin]

that use for overvoltage protection.

[eladn]

So this is some kind of a Zener diode?

[admin]

it's varistor.

[eladn]

Thanks! I think now it's much more clear to me. It's very valuable we have this DIY community here to grasp a better understanding of these underlying concepts and make the best use of KinCony devices.

I read online that overvoltage occurs when the relay switches off, and it may harm the relay load contacts. I'm interested in why does this overvoltage even occur when switching off, and why the exact same effect doesn't happen for example to classic mechanical switches. Where does this overvoltage come from? Do you happen to explain it in one of your videos?

[admin]

because the "OMRON" relay work with MAX250V load voltage. so if greater then AC250V , the varistor will disconnect, let is bad to protect the relay. "overvoltage" is for load's power, sometimes maybe someone connect with AC380V load, or have mistake connect the relay with high voltage (>AC 250V) , so the varistor will work as a "fuse".

[eladn]

I found a nice explanation online: https://www.electronics-tutorials.ws/res...istor.html
It turns out that inductive consumers like AC motors induce high voltage when switched off because of the energy stored in it magnetic field.

[admin]

sure , any high voltage will be protected.