Relay and Mains question

Thread Starter

vectravanman

Joined Mar 2, 2012
12
HI all

I am looking to design a circuit which when mains power drops (power cut for example) the load will also turn off. The load is a test rack which when power drops it will run on a UPS, but i want to do a circuit using a relay, probably even a Crydom SSR which will switch off the load when there is a power cut, bypassing the UPS. So i am not switching mains, i am using it as the input, and will be looking to switch low (10V) positive DC voltage off when there is a power cut. IS there a cost effective way of doing this without buying lots of components and building a PCB.

Thanks for any assistance.
 

Alec_t

Joined Sep 17, 2013
10,746
What do you want to happen when mains power comes back? Automatic turn-on of the load, or stay off until manually turned on again?
 

Thread Starter

vectravanman

Joined Mar 2, 2012
12
Sadly not an option, the equipment is designed to stay on and because the UPS doesn't last very long if there is a power cut when it loses battery life, the equipment applies a load to what its testing which recently damaged some of the test equipment. So i need a 'hard off current limiting circuit' which will cut current to the UUT when mains power goes off.
 

crutschow

Joined Mar 14, 2008
24,130
Just use an AC relay with coil rated for the mains voltage
Connect the coil to the mains and the relay NO contact in series with the load.
 

AnalogKid

Joined Aug 1, 2013
8,259
IF we're talking about removing power from multiple AC powered devices,
AND IF all are powered from the same mains feed,
THEN why do we need more than 1 or 2 poles?

ak
 

crutschow

Joined Mar 14, 2008
24,130
IF we're talking about removing power from multiple AC powered devices,
AND IF all are powered from the same mains feed,
THEN why do we need more than 1 or 2 poles?
Because that's not what we are talking about. ;)
He needs to remove the DC loads that the test equipment is driving when the AC fails.
 
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