3 Phase Supply Problem

[Theredfox]

During a maintenance check on an electrical supply panel supplying a copeland compressor, the supply voltage on one of the three phases was significantly lower than the other two. What is the most likely cause of this problem?
Cheers.

[taz24]

During a maintenance check on an electrical supply panel supplying a copeland compressor, the supply voltage on one of the three phases was significantly lower than the other two. What is the most likely cause of this problem?
Cheers.


Assuming the supply to the building is ok (check it first)
I would suggest looking at either the breaker or contactor supplying the power.

If there is a bad conection accros the switch gear it will cause the voltage to drop.

Cheers taz.

.

[Yuri B.]

Inbalance in loads on other el equipment (the line of the phase with lowered V overloaded), wrong connectiion of bridges on power transformer.

[sedgy]

hi thredfox,
hope you dont mind me going back to basics, but , have you tested each phase to earth 240 vac in the uk it would be then test across each pair of red to blue , red to yellow, blue to yellow, in the uk this would give 415 vac hope this shows where the fault is hopefully one fuse down , all the best,