I am using a Hall Effect Sensor (clamp) to measure motor locked rotor current fed by variable frequency drive. Obviously, as soon as the drive turns on it goes to current limit mode and the result is a large current (about 2000A) at 1 to 2Hz.
For various reasons, I am having difficulties to measure a stable current and what I read fluctuates by about 200A. Below are the reasons I can think of:
I can only do something about number 3. I am thinking of placing a conductive sheet between the phase I am not measuring and current clamp. what do you all think? Dumb, genius, or ...?
For various reasons, I am having difficulties to measure a stable current and what I read fluctuates by about 200A. Below are the reasons I can think of:
- VFD PWM which is about 1.5kHz.
- Shaft being locked which results in VFD error signal being fed back to PID control resulting in fluctuating current: basically, drive ramps up voltage because speed feedback never gets above zero but then decreases voltage because the current limit is exceeded and so on...
- Interference from other phases.
I can only do something about number 3. I am thinking of placing a conductive sheet between the phase I am not measuring and current clamp. what do you all think? Dumb, genius, or ...?