Shnubber Kweshtyun

[captainkirksdog]

Hey, Are snubbers needed across relay contacts carrying AC line voltage? If so, what mght be a good choice for 300 watts (resistive)? Better yet, what might be the formula or equation? Thanks.

 

[Optikon]

Hey, Are snubbers needed across relay contacts carrying AC line voltage? If so, what mght be a good choice for 300 watts (resistive)? Better yet, what might be the formula or equation? Thanks.

Captain,

If you make/break an AC path delivering 300W there could be problems.
300W into resistive but is the load inductive? If it is arcing you are wishing to extinguish for longer life of relay can you consider MOV?

For snubbers, there is not one simple equation that fits all situations. Choose which kind of snubber is most appropriate.

RC?
RCD?
RC-zener? etc..

The general idea is to convert this transient energy (that is getting snubbed) into heat in the resistive part of the snubber. Also things like clamping voltage etc.. come into consideration. I'm sure there are examples on the web for switchmode power supply snubber calculations. You can start there. I've only done RC & RCD snubbers for SMPS before and each time the calculations were different.

If you want a collection of app notes on MOV's (how to select & use with relay example) PM me with an email address that can accept Mb of files.