Hi all,

I have a technical question regarding calculating the active power and consumption of a 3 phase motor using an Iotawatt.

My mains supply is 3 phase + neutral, with 230V between each phase and neutral and 400V between any two phases.

The motor is a 3 phase motor and doesn’t use the neutral, and I have no reason to assume that it isn’t balanced with an identical power factor on all phases.

The Iotawatt is set up un 3-phase derived mode, and I am measuring 420W on one of the phases going to the motor.

I am trying to calculate the actual total power consumed by the motor, and I have some doubts about my approach. I have been using

420W / 230V (assumed by Iotawatt) * 400 (actual between 2 phases) * 3 phases

… but that yields over 2kW, when the motor spec says 1.02kW.

UI cos(phi) gives 420 * sqrt(3) = 727W which may be correct?

Or is it rather 420 / 240 * 400 * sqrt(3) ??

Where is the truth?

Thanks!