Hi everyone,
I have a Motor control center which is feeding at the same time a VFD for a 150 kW motor (460V, 3 phase, 60Hz) and 4 voltage regulator transformers(5kVA, 480:120 VAC), these transformers are feeding the I/O racks with all the PLC´s.
When the drive is turned on but the motor is not running all the signals in the PLC´s are ok, but when starting the motor with drive and it is running, most of the signals get flashing and some of them get out.
In the other hand, when the drive is getting fed trhough a different MCC everything runs ok, the drive has its own line reactor, how can I solve this problem?? what coud be the possible cause??

 

If it works OK with a different MCC than you may be having problems with connection points on the MCC you are using. mesure the 460 volt line when it is under load, make shure it is stedy. Look at the equipment bonding and grounding.