Problem with a transformer

Discussion in 'General Electronics Chat' started by Maintenance Man, Mar 9, 2011.

  1. Maintenance Man

    Thread Starter New Member

    May 12, 2010
    Hi to all,
    Last week we had a frequency drive that runs a conveyor belt keep tripping out with a loss phase fault. The frequency drive is 3 phase for a 480 v motor with a gear box. The problem would occur when the line ran for a while then would trip the frequency drive with a phase loss error. The frequency drive, motor and wires were changed by the other crew in which it did not solve the problem. I changed the transformer used to drop the 480v to 120v for the control circuit. The 3 phase comes off the bus bars in the MCC panel and goes to the main breaker then from the bottom of the main breaker; it goes to the top of the frequency drive in which 2 of the leads goes to the transformer for the control circuit. Because the problem would occur after the belt was running for a while made me think there was a problem with the transformer shorting across the windings when it got heated up causing the frequency drive to think it had lost a phase in which it would shut down with the phase loss error. My question is ,if the way I am thinking about this it correct about the transformer causing the phase loss or was there something else going on with the transformer. All I know is that the problem went away when I had put in the new transformer. Any feedback would be greatly appreciated. Thank you very much for you help.
    Maintenance Man
  2. Kermit2

    AAC Fanatic!

    Feb 5, 2010
    Put a megohm meter on it(one lead to the metal of the structure) and see what happens to the resistance when you warm it up. IF the wife will let you use her kitchen and oven, then it would be easy to test it. If SWMBO doesn't like you doing that - then settle for 2nd place prize of "YOU FIXED IT"