# EEVblog Electronics Community Forum

## Electronics => Beginners => Topic started by: electronics man on May 22, 2015, 03:01:35 pm

Title: high voltage across relay contacts?
Post by: electronics man on May 22, 2015, 03:01:35 pm
i have an application where there may be a hight voltage across the contacts of a relay however it will never be switching that high voltage. most relays are only rated to switch about 30V however i won't be witching that voltage . my question is is it ok to have this voltage across contacts without switching it even though the relay is rated to switch a lower voltage and can i increase the breakdown voltage across contacts by putting relay contacts in series (increased gap = increased breakdown voltage)  O0 O0 O0 O0
Title: Re: high voltage across relay contacts?
Post by: Pillager on May 22, 2015, 03:32:45 pm
... can i increase the breakdown voltage across contacts by putting relay contacts in series (increased gap = increased breakdown voltage)

I wouldn't do that. Yes, it is theoretically possible, but not recommended. Buy a suitable relay for the voltage you're expecting, it's your safest bet.

BTW, how high is High Voltage?
Title: Re: high voltage across relay contacts?
Post by: electronics man on May 22, 2015, 03:51:36 pm
... can i increase the breakdown voltage across contacts by putting relay contacts in series (increased gap = increased breakdown voltage)

I wouldn't do that. Yes, it is theoretically possible, but not recommended. Buy a suitable relay for the voltage you're expecting, it's your safest bet.

BTW, how high is High Voltage?
i meant to put in 1KV MAX
Title: Re: high voltage across relay contacts?
Post by: PSR B1257 on May 22, 2015, 04:18:25 pm
Quote
most relays are only rated to switch about 30V
Depends on the relay.
The nominal switching voltage is here not determining, since this is the voltage where the relay is able to switch it's rated nominal current.

Take a closer look in the datasheet. You will find a figure called Dielectric strength for the contacts.
Here is an (random) example: http://www.omron.com/ecb/products/pdf/en-g5le.pdf (http://www.omron.com/ecb/products/pdf/en-g5le.pdf)
Title: Re: high voltage across relay contacts?
Post by: Asmyldof on May 22, 2015, 09:01:42 pm
And for the general question of "Can I do this with a relay" always take the lowest dielectric withstand/strength you can find, unless you know which one to pick for your exact situation.