I would like to monitor long term current consumption changes over time (and derive power if I know the voltage) on a 3 phase cooling compressor for a walk-in fridge. I am not 100% sure right now, but lets assume its a 3-phase 3-wire system without separate neutral wire.
If I measure with a CT clamp close to the compressor (so definitely no other devices are connected to the phases between the clamp and the compressor), can I safely assume the current through the conductors is roughly identical? If I understand Blondels theorem correctly, you can use 2 current and voltage sensors, and
Total power = W1+W2
If I can assume that roughly i1=i2, and the RMS phase-to-phase voltages average out to be the same over time, then I would think I can just double the Irms and multiple by Vrms phase-to-phase, to get the total power consumption. Is that correct?
Does it matter for measuring if internally in the motor's connector box, the phases are connected in Wye or Delta configuration (as long as there is no separate neutral wire)? And in case of a 4-wire 3-phase system, I could then do the same but multiply it by 3?