Why does my VFD show output voltage with no Run command?

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H20pie

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Valrico, FL USA
So I'm transitioning from a 20 year career as a residential/commercial electrician and contractor, to the service and engineering side of industrial E&I. I'm learning as quickly as I can, but there is a mountain of learning ahead of me still.
With that said, I have a small Baldor VFD, with 480v 3ph input and output. It's controlling a small motor on a chemical pump. The VFD is controlled via PLC, and speed via 4-20ma.

Question: I'm troubleshooting a high-pitched whine, coming from the motor. This whine is present when the VFD is NOT receiving a run command, and when the VFD is in "remote" mode. The motor does not spin, but over time, will heat up considerably. The ma signal is good and in-line with control room, and has no effect on motor whine; the "healthy" and "run" signals coming from VFD are also good. And the "run" command signal from PLC is not present during this whining condition.

Note worthy: When I test the output leads while the VFD is off (powered but no run command), I show 385v, with respect to ground, but "O.L." with respect to phase to phase. I am not experienced enough with VFD's yet to understand why this voltage is present while off.

Finally, when I switch the VFD from "remote" to "local" (still no run command), the whining stops, and no voltage can be metered with respect to ground.

Possibly bad VFD? But along the way, I have learned with these drives, big or small, the term "bad VFD" usually means "I just can't find the issue".

Any ideas are greatly appreciated
 
If you are using a digital meter the high impedance that is common with digital meters will show this kind of reading. Even though the semiconductors are nominally off there is a tiny amount of leakage that high impedance meters will show as voltage.
 
Sounds like constant torque mode

Sounds like constant torque mode

My guess is it is in constant torque mode. This works as holding torque so motor don't drift. Some drives have an input to put it in that mode so in remote it is doing its job, in local this is not turned on.

Unless there is allot whine and heat I would not worry about it. Also always use the screen on the drive to check output current and voltage.
 
If the motor is really heating up, it's not leakage into the meter. I'm with the others saying it's something in the programming of the drive when in remote. D.C. Braking, torque mode holding current, something like that. Record all of the parameters that are not set at factory defaults and call Baldor tech support.
 
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