Relay Isolation on incommers

[NoSparks]

I have been out to an industrial job this morning where I found the incommers followed by a manual isolator followed by a three phase 150Amp relay feeding into the main DB. The relay was wired in such a way that it would automatically re-energise following resoration of power after a power failure.

Can anybody throw any light on why it would be there?

 

[johnboy6083]

could it be part of a UPS/ standby generator? was there a mechanical interlock between 2 contactors?

 

[NoSparks]

No, but I have now thought that it might be part of an emergency power cutout system, althought I would not have expected it to be self resetting in that case.

 

[Guest123]

But wouldn't the power just come back on anyway after a failiure.....

If it was a type of emergency stop then surely it shouldn't be auto resetting???

 

[davelerave]

i ssume you mean it's N/C contacts?? auto-resetting
they shouldn't be used for emergency stopping anyhow



would it be to used to switch off remotely via key-switch at closing time

 

[NoSparks]

Lenny - I agree.

davelerave - No its NO contacts but when the power comes on it powers the relay which of course closes.

Geoff

 

[davelerave]

what controls are there

i'd assume it's for switch-off?? via a key-stop