Power Co. Capacitors Cause VFD's to Kick Out

What do you mean by "go out"? Surely there is some sort of trip code isn't there? Also describe your power system, i.e wye, delta, open delta, corner grounded etc. Depending on these answers it could be very simple.

I had the exact problem only the voltage was 12.46 kv. The capacitors were on a timer and when they came on line the customers drives would trip off. I had the utility take out the timer so that the capacitors remained on line all the time and no more trouble. The capacitors cause a voltage rise then they are energized and the substation regulator can not lower the voltage quick enough to keep the drives from tripping off. Another solution is to install a 480/460 volt transformer and the voltage rise will not be enough to trip the drives.

Similar problem a few years back. VSD's being left on "stop" all weekend. Monday morning they were toast. After a lot of head scratching we found that one of our on load tap changers had tripped on O/L. Reset, end of problem.

A quick fix could be to isolate the drives on the Friday and power up ready for Monday morning.

It may be that your line reactors are undersized or too far away. It is hard to tell from here. Ideally, they should be within every cabinet that contains VFD's. One set for the whole power distribution system will not compensate for ringing on the power network very well.

Frequently, when the VFD's are on standby, the DC power supply is fully charged so that the slightest impulse above nominal voltage also gets added and an over-voltage will cause trips. A line reactor will suppress a fast (high frequency) change in voltage but a slower change in voltage level (greater than 50 mSec) may be long enough to over charge the DC supply in the VFD's.

You may be able to simply change the tap on your substation so that you are running at 460 instead of 480. This is certainly within tolerance and may be the easiest solution. If you can monitor the voltage during switching of the capacitor bank, you may have a clearer understanding of the problem.

The most likely reason is that your DC bus is experiencing an overvoltage fault, but you should check your fault log to be sure. If you can't change the power feed, you may be able to stop the fault by adding a breaking resistor to the VFD (assuming of course, that it is an overvoltage problem, and your VFD can accept a resistor).