Micromaster 440 burned

Discussion in 'General Electronics Chat' started by chuzkin, Oct 2, 2013.

  1. chuzkin

    Thread Starter New Member

    May 21, 2012
    Dear friends.

    Today I made a terrible mistake. I connected a MM440 220VAC input to 440VAC. After some seconds, smoke appears and I cut the circuit braker. Then, I change power supply to 220VAC (correct) and when turn on the braker, something blew up inside the VFD.
    I checked inside and it seems it was just 1 of the 3 input (line) varistor S20 K275. All the other boards look fine. I will change varistor. Capacitors look fine (how can I test them?), and rectifier diodes are ok.

    Do you think varistor can be the only damaged component?
    What else should I check, and how to test?

    Thanks a lot.

    Best regards.
  2. #12


    Nov 30, 2010
  3. MaxHeadRoom


    Jul 18, 2013
    Obviously much of the circuitry in a VFD can be harmed if inputing double the AC voltage.
    You can check the input supply to a certain extent with a meter, MOV's usually display burnt look if they are shot, the 3ph bridge and caps can also be checked with a meter.
    Once you have checked these disconnect the DC output from the CAPs and power up and check voltage on the DC, if you have access to the IGBT's, these can be checked with a meter before reconnecting.
    But it is obvious that if smoke appeared there is some thing that needs replacing and should hopefully be visible?