Three phase motor current verification

brushless-dc-motorcurrent measurementthree phase

I want to verify that the quadrature current through a permanent magnet synchronous motor (PMSM) is actually the same amount as I commanded the field-oriented control (FOC) motor controller to push it through.

I have only one current clamp so I can only measure one phase at a time. Is the actual motor current just 3 times the RMS current through one phase?

Best Answer

Essencially yes.

To determine the power flowing into or out of a 3phase system you can make use of

  1. 1wattmeter method
  2. 2wattmeter method
  3. 3wattmeter method

In this instance you could take advantage of this and assume the 3 currents are the same (bar phaseshift) to derive the currents of the 3phase system.

HOWEVER... you are interested in Iq which means you really need to know all 3 currents and equally the present angular position to then apply park&clark transformations correctly.

Any slight disturbance in the other 2 current waveforms would influence the actual Iq used by your FOC, something you would not be able to see.

For a CRUDE 1st approximation, yes you could take the one and phaseshift it to produce the other 2 waveforms

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