Today is...
Wednesday, June 26, 2019
Welcome to Control.com, the global online
community of automation professionals.
Featured Video...
Featured Video
Watch an animation of a conveyor stacking operation demonstrating the use of a move on a gear command.
Our Advertisers
Help keep our servers running...
Patronize our advertisers!
Visit our Post Archive
Relay Maximum Switching Voltage
Getting 240 VAC from a 3 wire 3 phase system to avoid overloading a relay maximum switching voltage.

I have a shore power relay with an output contact maximum switching voltage of 250 V AC. This is a Schneider Electric RM22TA33.

The input to the relay is 3 phases @ 415 V (this is within spec).
The relay senses symmetry, and when conditions are met, it closes the N/O output contact to energise a 415 V coil (5 W steady power, 30 W inrush power).

My issue is that this relay is on a ship which has generators connected as a 3 phase, 4 wire system (eg there is a neutral). However the relay is only utilised to provide shore power to the ship.

The shore power is a 3 phase 3 wire system. There is no neutral.

In essence the schematic goes as such:


L3--------relay N/O contact-------contactor coil-----L1

Therefore, under normal circumstances there is 415 V of potential across the open contact...

Is there anyway to overcome this? It is obviously exceeding the spec of the contact rating. However, I don't have a neutral available to install an interposing relay...

Would a Delta-Wye transformer work? I also have a snapshot of the schematic here if that can be attached at all...excuse me as I am new here.

Kind Regards,