Isolating Motors On One Phase From PLCs On Another Phase

[Haldir]

If I have a 208VAC AB phase (from a 3 phase supply) powering five 220V motors, is it best to have a step up transformer or just go ahead and use an isolation transformer rated at 208 Or 220 – between the motors and where they tap off of the supply phase. The main reason I’m doing this is to prevent motor surges, etc. from affecting PLCs on the BC phase of the source supply.

No one at other sites I have visited seems to be able to answer this.

 

[jraef]

A transformer is not going to prevent a motor surge. Are you trying to protect the PLC power supply from a low-voltage condition brought on by starting the motors, or are you trying to isolate any noise created by the motors when they start? If the later, use a power conditioner on the input to the PLC power supply. It should filter out any transients caused by the motor starting. If it is a voltage dip problem the right power conditioner might work for that too, but you may need a UPS to be sure.

"Venditori de oleum-vipera non vigere excordis populi"