VFD Problem
VFD Problem
(OP)
The Power to the 1050kW, 6kV motor is fed from VCB-->VFD-->Motor. We heard from the operator that the motor stops suddenly and starts after the 30s~1min. I feel that this might be due to the voltage fluctuations from the power supply side. The Under voltage protection at the VCB Panel has 50ms time delay but the VFD has only 30ms. Therefore the under voltage protection at the VCB panel may not have operated but the under voltage protection at the VFD may have operated and restarted again as the VCB which is feeding the VFD is still ON. The important point is to note that the VFD did not trip the VCB on the operation of under voltage function. There no other alarms/trips while this happened. I have not heard about the VFD showing any fault in it's display.
Has any experienced this type of problem? any comments?
Has any experienced this type of problem? any comments?






RE: VFD Problem
the 30s to 1min tripping sounds like it might be related to overheating. It's worth checking to see if there's a zero sequence path somewhere on the motor, which could cause heating. This could be the result of a grounding issue.
RE: VFD Problem
I set up a lathe with a VFD and thinking it would make sense to have the drive in the "catch mode" where if the drive was shut off and the motor was still spinning when the operator turned it back on it would smoothly re-accelerate the motor.
What happened though was that the drive then insisted that it know what the motor was doing before ever starting which makes sense. This caused a horrifying result that was actually deadly. When you walked up to the lathe and it was off and hit run - nothing would happen - for a while. From 1 second to a minute or more. This meant the operator could press go and nothing would happen at all, could decide he hadn't pressed start and possibly start chuck-keying the chuck and have the lathe surprisingly start spinning.
I figured it out after much head scratching. It was the "catch" parameter waiting to figure out what the motor was doing and with the motor stationary it took an extended RANDOM time to figure it out and actually start the motor. Manually turning the shaft, like to align a chuck key, would allow some sort of input to appear and the VFD then knew what was happening and would've started. Without any shaft turning the VFD cannot receive any speed information and waits until noise is seen.
Turning off the catch parameter instantly solved the issue. I think the software people who wrote the VFD SW didn't realize what trap they were setting.
Keith Cress
kcress - http://www.flaminsystems.com
RE: VFD Problem
Keith Cress
kcress - http://www.flaminsystems.com
RE: VFD Problem
Bottom line, start by looking at your command signals. Many VFDs allow you to observe and capture that data.
"You measure the size of the accomplishment by the obstacles you had to overcome to reach your goals" -- Booker T. Washington
RE: VFD Problem
We got fault indications so it was not such a mystery, after all. Everyone knew it was overvoltage. The problem was WHY? Nothing to be seen on the grid. And no OV trips on the other VFDs
All I can say is: do not speculate. Record.
Record grid, DC link (yes, you need special fuses and probes), speed (a simple inductive pick-up will do), possible fault signals. Then sit back and see what happens. And then, when it happens, draw the right conclusion and just fixt it. It aint necessarily electric.
Gunnar Englund
www.gke.org
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Half full - Half empty? I don't mind. It's what in it that counts.
RE: VFD Problem
No log of the trip means it's likely being told to stop.