rjm21 (Customer) asked a question.
STP-MTRAC-34156D Ground Wiring Issue - Motor Housing Live
I have a STP-MTRAC-34156D motor wired to an STP-DRVAC-24025 drive. If I tie the motor cable shield wire into earth ground, it trips the GFCI outlet that it's plugged into. If I remove the shield wire, the motor outputs 120VAC from its housing (don't ask how I figured that out).
I actually have two of these setups. On the first one, I tied the motor cable shield to the ground terminal on the stepper drive, which is NOT tied to earth ground. That motor is fine. But this did not work on the second setup, the motor housing is still live.
Any ideas?
If one motor is functioning correctly and the other is not with the exact setup. Then there could be an issue with the motor itself. I would recommend you reach out to our technical support team by filling out a contact support form at the link top of this page.
Come to think of it, I had this issue with two STP-MTRH-34127D as well. Might be worth a QC check on these larger stepper motors.
Is there any resistance between any of the winding wires and the motor body?
Thanks for the reply. There is no continuity between the motor housing/shield wire and any of the windings.
I have one of those motors on my test bench and have not had an issue with it like you describe.
I tie the cable shield to drive ground point, and I also have a wire from earth ground to the other terminal on the drive ground. This is how I have always seen drives wired for stepper, servo and basic VFD systems.
I would make sure you have the other leads connected correctly.
A+ is white
A- is green
B+ is red
B- is black
blue and yellow twisted together
orange and brown twisted together.
the incoming line circuit's ground (which should lead back to earth ground) wired to drive ground
cable shield/motor housing wired to drive ground.
Is your testing done on a GFCI outlet? That appears to be a factor in my issue.
All the leads are correct. The motor runs as it should otherwise.
If I connect cable shield to drive ground screw and then the other ground screw to earth ground as you describe, the motor acts as though one of the phases is missing. Trying to turn but loosely locking up.
I appear to have somewhat solved the issue however. I was using the ground terminal blocks KN-G12SP that clamp and ground the DIN rail. I swapped those for insulated terminal blocks KN-T12GRN-100. I also only have the motor cable shield connected to the drive ground screw, not to earth ground. For whatever reason, this doesn't pop the GFCI and also doesn't electrify the motor housing.
"If I connect cable shield to drive ground screw and then the other ground screw to earth ground as you describe, the motor acts as though one of the phases is missing. Trying to turn but loosely locking up."
To me, it sounds like the motor is faulty and one of the phases is shorted out internally and touching the housing.