Hi:
I saw the motor yesterday. It is vertically installed. The lower ring looks good. The arcing occurred between the two upper rings. The middle one is all blacked out and there are grooves in it up to 1/8" deep. 60 degrees clockwise from the brushes there is a black spot on the middle...
Hi:
Humidity and environmental dust are definetly not the root cause.
I learned that similar motors are designed for 200% rotor voltage plus 1000 volts. In my case that means 3.2 KV isolation.
Normally the motor is powered off by opening the HV breaker.
This cuts the power to both stator and...
Hi:
The drive people confirm the rotor voltage went up around 1500-1600 V. However, I am now concerned by something else:
They apparently did the same test a couple of times for short durations of 4-5 sec before the last 10 sec test that leaded to the flashover.
Given that the rotor current...
Thanks for the replies.
The motor is an indoor installation where dust and humidity are not a problem. I know there was preventive maintenance done in the past but cannot tell precisely when it was done last.
The motor is rated at 600 RPM. From past observation I do not think it went above...
Hi UKpete:
The variable speed mode is implemented with a slip energy recovery drive that feeds the energy back into the 4 KV primary.
Arcing occurred in the general area of the rings. I did not see the damage myself but arcing between the rings is most probable.
Those who witness the failure...
Hi:
Actually I have more information. The pump pushes liquid into a vertical pipe and there is no check valve. IE when the motor stops it starts to spin in the other direction for a few seconds (long enough to empty the vertical pipe).
The motor is about 20 years old.
So I figure the rotor...
Hi:
We had a wound rotor failure while commissionning a new
slip energy recovery drive. Arcing occured in the brush
slip ring area. I wonder if anyone could explain what might
have happened. Here is the story:
The 500HP/4KV motor drives a pump. It can be run either
with the drive in variable...
