They are GE Fuji Electric G11 drives.
I looked through a PQM on the bus and found that the phase voltage THD was proportional to the voltage across the grounding resistor. At a ground voltage of ~45V, the voltage THD reached ~21%. Both of these would increase and decrease simultaneously. The...
Actually, I apologize again. My previous statement more accurately represents what I mean. I do not expect that there is a ground fault, so the voltage across the HRG resistor tells me that the phase-to-phase voltages are imbalanced.
I agree that you are correct, but I do not feel that it is...
You are correct.
Sorry, I wrote the relevant sentence incorrectly. I meant that the voltage across the HRG resistor indicates imbalanced phase-to-ground voltage magnitudes.
Some cable runs from the drive to the motor load are over 150 meters. There are line reactors for each of the VFDs, but I am not sure what their %Z is.
The phase-to-ground voltage tells me that that the phase voltages are imbalanced. The somewhat periodic and smooth shift between 5V and 45V...
From looking at the drive instruction manuals, I do not believe any VFD filters are grounded. The only grounding points are for the ground terminal on the VFD and for external braking resistors.
I will look into what you said and follow up. Thanks, jraef!
It seems like you are saying that there may be a separate issue that is causing the voltage across the HRG resistor to reach 45V, correct? Or are you saying that the deteriorating filter may be causing the increased voltage?
Sorry, the voltmeter is measuring the voltage across the high-resistance ground resistor. The high-resistance grounding unit is connected to the neutral point of a 480V wye transformer secondary.
I was not the one that installed the VFDs, but I am responsible for maintaining electrical...
Hi all,
Today I noticed that a voltmeter measuring the voltage across a high-resistance ground off of a 480V bus is fluctuating between 5V-45V, with about 10 seconds between each low and high point. The bus feeds several small VSD-powered motors (30 hp or less). Is there any reason to be...
Hi all,
I have several 13800/480 V, 1000 kVA transformers at my site. What is your opinion on bypassing the low-pressure alarms on these transformers? They are in a non-corrosive environment, and there are monthly operator rounds to inspect each transformer's pressure level.
I do not really...
