Fairy nuff...............
DC Overvoltage fault
- Thread starter ptonsparky
- Start date
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ptonsparky
Tom
- Occupation
- EC - retired
New motor went on today. Not a rebuilt this time. Bearing protection and the whole bit.
We did not remove the load reactor that had been installed for the original motor.
Is there any reason that we should have removed it?
We did not remove the load reactor that had been installed for the original motor.
Is there any reason that we should have removed it?
petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- engineer
It is not going to hurt anything, and might help.
synchro
Senior Member
- Location
- Chicago, IL
- Occupation
- EE
See pages 5 and 6 of the document below from Rockwell. If you use a load reactor they recommend that it be used close to the drive. The reactor will limit the peak current output from the drive when the the IGBTs switch and cause the output voltage to change quickly. However, the paper mentions the possibility of a resonance of the reactor's inductance with the cable capacitance that might increase the peak voltage at the motor. The only way to tell for sure would be to measure it with an oscilloscope.
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ptonsparky
Tom
- Occupation
- EC - retired
Interesting.
Now, how do I measure the peak voltage at the motor? It is about 200' down.
synchro
Senior Member
- Location
- Chicago, IL
- Occupation
- EE
Now that would be a problem.
You could measure the voltage at a junction box near the well if there is one. But definitely somewhere on the motor side of the reactor, preferably as close as you can reaonably get to the motor. And even the output terminals of the reactor should show indications of a resonance if there is one.
Why would you need to?
ptonsparky
Tom
- Occupation
- EC - retired
I should have said ‘if…’. Brain malfunction.
Either way I don't think you would or should have a need to do so.
- Location
- San Francisco Bay Area, CA, USA
- Occupation
- Electrical Engineer
I would insist on someone inspecting the type of damage on the old motor. If it's related to reflected wave damage to the insulation, I would replace that load reactor with a DV/DT filter. However if the new motor is actually a good quality "Inverter Duty" motor (meaning it meets NEMA MG-1 Part 31 specs), then it should be fine up to a certain distance (Yaskawa should be able to tell you what that distance is).
Side note: I have seen even Inverter Duty motors (good Reliance ones) suffer from reflected wave spike damage because the Input and Output conductors were in the same cable tray right next to each other with no shielding, so make sure you don't have anything like that going on.
As to why the DC bus OV trip? When you get damage to the motor windings it's usually a race to see which trip happens first. GF trip in VFDs is done by summing the 3 output phase currents and looking for a non-zero value exceeding some preset level (sometimes up to 30%), so often times something else will trip first.
Side note: I have seen even Inverter Duty motors (good Reliance ones) suffer from reflected wave spike damage because the Input and Output conductors were in the same cable tray right next to each other with no shielding, so make sure you don't have anything like that going on.
As to why the DC bus OV trip? When you get damage to the motor windings it's usually a race to see which trip happens first. GF trip in VFDs is done by summing the 3 output phase currents and looking for a non-zero value exceeding some preset level (sometimes up to 30%), so often times something else will trip first.
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