VFD trips GFI

[InverterDuty]

I am trying to run a 1hp, 3p motor with a vfd. I need the motor to run on a gfi. I have tried several different brand of motors as well as drives. Every configuration has caused the gfi to trip. With some testing we determined the trip was caused by current leakage from the motor. I contacted marathon motor and they had a solution. They have made a special motor that has one extra lead that you connect the the negative side of the DC brake output. Since the DC output is isolated, the result was almost a complete elimination of leakage current. Since it is a special motor, lead times can be long and it is only offered in a few frame sizes. My question is... What attributes of a motor contribute to motor leakage and has anyone found an off the shelf motor that will work in conjunction with a vfd on a gfci circuit? The odd thing is a competitor of mine makes a machine that uses a standard motor with a vfd that does work on a gfi. I tried there control circuit on my motor with no luck, so I know it is a motor issue. The problem is that the motor they use is made in china and does not have certification on its own to be imported into the us. In addition the equipment I would like to use USA sourced parts as much as possible. Are there any filters or devices that can help with the leakage current of a motor.

Thank you in advance.

 

[rhatcher]

InverterDuty,
If the Chinese motor does not have the 'extra lead' and therefore does not have the capacitive shield of the Marathon motor, then one is left to assume that the difference is in the rotor as suggested by you on 1 Oct 12 12:12. If so, could the leakage be through the rotor, into the driven equipment, and then back to the GFCI through the equipment safety ground? Some questions to consider:

- Have you isolated the leakage to determine if it is coming from the stator or the rotor?
- Does the GFCI trip if the motor is run solo and sitting on an isolation mount?
- Does the Chinese motor have a grounding brush/grounding ring installed on the shaft?