# Run command question. Powerflex 700



## JRaef (Mar 23, 2009)

nolabama said:


> Have a drive that trips out on over voltage fault when run command is given. 482 vac present at drive. On genset genset has ran drive before. Motor spins free by hand. Controls operate motor brake. This is an arrangement of 5 8 bourse drives. Only three drives failed one fails ever time run command is given. Water was in peckerhead. Motor is a Baldor efficient motor. Have not made Megger readings on motor yet. Motor did work one cycle. Ie start to finish.
> 
> Ideas.


5 x 8HP drives, is that right? If they have brakes, they must not be fans or pumps, but are they all feeding onto the same machine load? This isn't your Bridge still is it? 

The usual cause of OV on Accel is that either you HAVE an over voltage situation, which if that reading is correct, you don't, or the load is moving faster than the commanded speed. Why I felt I wanted to eliminate fans and pumps is because sometimes if you are feeding into a common header and there is no backflow prevention, slight differences in output capacity can make one or more motor get "pulled along" by the others at a speed higher than the VFD output speed command and it regenerates into that drive. If you have all of these motor feeding a common load, like a ring gear on a swing bridge, then the same thing can happen. There are solutions if that's what it is, but it's not worth discussing if that is totally off base.


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## nolabama (Oct 3, 2007)

Off base
Feeding multiple loads. Several different linear actuators. Its not the bridge I normally talk about here. Setup is all electric on this one
Megged conductors. Conductors failed. Motor ohmed good. Will pull new wire tomorrow am. 
Don't know why over volt fault would occur if conductors bad? 
Moved drives and problem stayed with motor and conductors did not follow drive.


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## JRaef (Mar 23, 2009)

nolabama said:


> Off base
> Feeding multiple loads. Several different linear actuators. Its not the bridge I normally talk about here. Setup is all electric on this one
> Megged conductors. Conductors failed. Motor ohmed good. Will pull new wire tomorrow am.
> Don't know why over volt fault would occur if conductors bad?
> Moved drives and problem stayed with motor and conductors did not follow drive.


Huh, that is odd. I can't think of how a bad conductor would result in an OV trip. I'll ask one of the service guys tomorrow (if I can find one on a Friday).


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## nolabama (Oct 3, 2007)

Thanks.


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## nolabama (Oct 3, 2007)

Other electrician changed motor problem went away. How can a motor that seemed to ohm good cause an ov fault then? I guess in the scheme of things I don't really care the bridge works. 

Anyway on a lighter note we smoke tested the control cabinet on the other bridge. Lol I guess a fifty horse drive is way cheaper than the coast guard fines. 

So all we lost in this storm so far was an eight horse motor, a fifty horse drive and a control board on a cummins generator. That aint bad.


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## JRaef (Mar 23, 2009)

Glad to see it worked out.

Just as an update, I spoke with one of our drive techs, his response was a little generic in that if you have something like water in the conduit, it's basically a race to see what the drive will trip on first and once it trips, it stops looking for other problems. But he couldn't explain why Over Voltage would even be in that race. He deferred it to a more experienced guy, he is going to call me back when he gets off of a project out in the middle of nowhere in a few more days (no cell service).


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