I have a 1500 ton water chiller at 480 VAC. It is an open transition wye start, delta run motor. Each of the three phases is replicated to produce six phases which are connected across the motor coils in such a way that each coil (in the run state) will have a set of conductors that brings the current in and out of the coil. Different than a standard delta connection where each coil current is mixed in the delta-corner connected conductors (i.e. phase current does not equal line current in a normal delta connection, but on the open transition delta they are equal). Each of the six phase connections has three conductors (3 x 500 MCM). Two of the conductors on the day of measurement read about 60-75 amps, where the third conductor measured 100-115 amps. Here is the difficult part, one of the conductor's currents is of opposite polarity of the other conductors on the same phase. I need to measure power, but am unable to really understand how one conductor in a phase could have a negative power while the other two would be positive. Any thoughts?
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