DC Power Supply Dynamics

[babambu]

Can you help with this unit.

A DC Power Supply should be ON during normal running of the process plant. On Emergency Generator power it should switch-OFF and is PLC controlled. It should remain OFF even after the mains power return. This DC power supply should only be mannualy turned ON after this incident.

What puzzeles me this partially works as it turns OFF on Emergency Power but once the mains return it turns ON for about 2sec and then OFF again. Please help.

 

[powerjunx]

Simply, TIMING DEVICE works unsatisfactorily. It flickers to the extent whenever the main power is restored. Try to troubleshoot..

What kind of DC power supply unit you have?

 

[waross]

It sounds as if, somewhere in the circuit, the supply is being switched by a set of normaly closed relay contacts. The contacts supply power until the PLC initializes and energises the relay, opening the contacts.
PLCs are great, but if an application is so simple that you can use a push button and a relay to control the power, it may be overkill to add a PLC for this function particularly when it is causing issues which would not exist with a button and relay circuit.
yours