From UL standard, if I only want to measure a part of device's leakage current to another part. I can just measure the Grounding wire. So I used a clamp on meter (0-10mA range) to clamp on grounding wires. In the cases below:
- Ground the motor and driver together, and measure at driver side grounding wire to the power device. I assume this will give me the total leakage.
- Unground the motor and driver, and measure at the driver side grounding wire. I assume this will give me the leakage of driver only
- Unground the motor and driver, and connect a grounding wire from motor chassis to the power device grounding. Then use clamp on meter to measure on it. I assume this will give me the motor only leakage.
But I found the sum of leakage of motor only and driver only does not equal to the total leakage. Does anyone know why? Or it is not the sum up relationship?
I used a AC power supply to do the testing. I found it gives way less leakage current reading than I use a variac. So I think the varic has some leakages too but I don't know if it is the AV power supply has some filters?
I used below connector to connect wires to the power device. Why do I get different reading on both side of the wires? I am so confused.
I am saying additional grounding wire is because the driver's power input only has line and neutral. The grounding wire doesn't go "on board". So I clipped it on metal chassis. Hope the new picture is helpful to understand.