Hey out there... here's what we have. A Siemens ED63B080 80 amp 3 phase CB is tripping randomly when our elevator pump motor starts up. The motor is a 40hp 3 phase motor by Magnetek. Pretty normal setup and has been reliable for many years. What we see is when the contactors shift from start contactor to run contactor the incoming power wires "jump" (sort of like stiffening up). The amps are about 130 amps start and 50 amps run. Motor has been completely checked without finding problems, new contactors have been installed, new circuit breakers and even the wires have been upgraded to 6 awg from 8 awg.
Sooooo, what would cause an 80 amp CB that is supposed to trip at 25k amps/480 randomly trip when this motor switches from start to run?
We did a check on the building power with a Powersight 3000 unit and found that the building power rises and falls from typically 460 vac to 510 vac over a 3 hour period. We have seen sags down to 330 vac and peaks at 510 vac (phase to phase). The sags seem to happen on all phases at random times (about every 45 minutes one of the phases will sag). We also see current on leg A is below B and C legs (example, when the large air comp. kicks in we see 210 amps on B and C legs but only 110 amps on A leg). The A leg seems to always be 10 to 100 amps lower than the other legs. The "high voltage" guys say nothings wrong with building power and that it's the elevator... see our problem? Any extra "2 cents" out there would be appreciated!
Sooooo, what would cause an 80 amp CB that is supposed to trip at 25k amps/480 randomly trip when this motor switches from start to run?
We did a check on the building power with a Powersight 3000 unit and found that the building power rises and falls from typically 460 vac to 510 vac over a 3 hour period. We have seen sags down to 330 vac and peaks at 510 vac (phase to phase). The sags seem to happen on all phases at random times (about every 45 minutes one of the phases will sag). We also see current on leg A is below B and C legs (example, when the large air comp. kicks in we see 210 amps on B and C legs but only 110 amps on A leg). The A leg seems to always be 10 to 100 amps lower than the other legs. The "high voltage" guys say nothings wrong with building power and that it's the elevator... see our problem? Any extra "2 cents" out there would be appreciated!