thewirenut91
Member
- Location
- Texas
- Occupation
- Electrician
I have a head scratcher.
The setup is a nearly new part winding starter, so two NEMA 4 contactors in parallel, feeding a 200hp VHS 480V motor. The motor is three wire, probably rewound. It is not PWS, so parallel 1/0 leads are brought to the motor j-box and terminated into the same Polaris tap, two to each motor lead, x3 of course. In the control panel, as is typical, two short MTW 1/0 wires come off the load side of the panel disconnect, each leg, and feed their respective poles on the motor contactors.
The weird part is that on two legs, there is about 15 amps disparity between the parallel runs at full load. There is no voltage drop across either contactor that I detected, and no obvious hot spots or high resistance connections. What could cause this amperage disparity?
Is this not essentially a perfect parallel circuit?
The motor is slightly overloaded so the high legs were causing about a 2 hr trip time on the o-loads.
The setup is a nearly new part winding starter, so two NEMA 4 contactors in parallel, feeding a 200hp VHS 480V motor. The motor is three wire, probably rewound. It is not PWS, so parallel 1/0 leads are brought to the motor j-box and terminated into the same Polaris tap, two to each motor lead, x3 of course. In the control panel, as is typical, two short MTW 1/0 wires come off the load side of the panel disconnect, each leg, and feed their respective poles on the motor contactors.
The weird part is that on two legs, there is about 15 amps disparity between the parallel runs at full load. There is no voltage drop across either contactor that I detected, and no obvious hot spots or high resistance connections. What could cause this amperage disparity?
Is this not essentially a perfect parallel circuit?
The motor is slightly overloaded so the high legs were causing about a 2 hr trip time on the o-loads.