0

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, in that case the total current is then double the amount measured, so I could calculate Irms for a single phase and double it to get the Irms for the motor, and monitor Vrms between 2 phases and get the power consumption? Or is that not true?

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?