Add New Drive to an Existing PLC

Atish09,

ABB drives, like virtually all others, supply their own internal power to operate their control terminals. That means that any switches or other controls that are attached to them must not impose an external source of power on these terminals. This is a fairly low voltage DC, which means that it must be kept away from electrically-noisy and line-voltage wires also, as well as be insulated for the maximum voltage on any wire within the cabinet (or box or raceway) these control wires are in. This is basic stuff that any industrial electrician should know and do.

You say that the drive can "run in local mode"--I interpret this to be that it can run from the keypad. Therefore, the drive's input and output sections are still good. You probably have a damaged control board.

Two steps to take:

1. Check and ensure that the drive's control wiring to the PLC and all other controls does not interconnect with any source of power other than the drive. While doing this, also check the ABB wiring diagram to make sure the control inputs are correctly wired, so they are receiving their voltage from the proper terminal of the ABB drive. Use a decent multimeter set on DC ranges to do this.
2. Contact a qualified person to then service/repair the drive.

Always, remember to properly protect yourself from any shock or arc flash hazard while doing this work. You are near live terminals, and depending on the supply circuit there usually is a potentially fatal amount of power present. Use tools that are insulated for the voltage present, use voltage-rated gloves, use a meter rated for at least 600V (and with a recognized testing agency's listing). Depending on the overcurrent protection on the input circuit and the other characteristics of this circuit, there can be enough energy present on the input terminals to do anything from making a bright light and loud noise to physically blowing you backward and sending you to the hospital for 2 months IF YOU ARE NOT WEARING PROPER PROTECTIVE CLOTHING.

-John M.