3 phase converter - need help identifying circuit part

Discussion in 'General Electronics Chat' started by Trueblueglue, Oct 16, 2015.

  1. Trueblueglue

    Thread Starter New Member

    Oct 16, 2015
    4
    0
    Hello Forum,

    I'm hoping I can find some help here with identifying a faulty component on a circuit board. My step-father is very handy and he has a metal mill that runs off of 3 phase. He uses a 3 phase converter since he has residential electric.

    The converter recently broke. He pulled out the circuit board that controls it and found that one piece was sparking and beginning to catch fire / melt.

    On the board, it is marked MOV101. The physical part looks like a ceramic capacitor, but there is no writing on the part itself. Either nothing was printed on it, or it melted off due to the malfunction.

    I did some googling and this site is the only site that had a decent hit, someone was trying to identify a part marked MOV101 on a projector.
    Using info from that thread, and the fact that the part was only $0.14, I bought Panasonic part # ERZ-V07D431. It arrived today but they are a bit smaller than the original piece. I'm afraid it is incorrect.

    I'm not very proficient with electronics but I'm hoping someone can point me in the right direction to identify the part. If I can identify the part, I'm hoping I can buy it from Newark electronics and try to salvage this converter for a song and a dance instead of having to purchase a new one.

    Any help is greatly appreciated.
     
  2. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,564
    2,379
    MOV101 may be a circuit identifier, not a part No.
    You need to establish the working voltage and energy rating,.
    Is this a rotary or static convertor, Phase perfect for e.g.?
    Max.
     
  3. Trueblueglue

    Thread Starter New Member

    Oct 16, 2015
    4
    0
    MaxHeadRoom,

    Thank you for your reply. I'm afraid I've wasted your time, apologies. I misunderstood the part my step-father is trying to fix. It's actually the traveling arm that moves the work piece under the spinning drill bit.

    I think I may have found a manual for the machine online that references the schematics.

    Once again, I apologize for the confusion. Thank you for the kindness of this forum.
     
  4. Trueblueglue

    Thread Starter New Member

    Oct 16, 2015
    4
    0
    I've hit a dead end and turn once again to the kindness of this forum.

    Here are the facts, this time with pictures. Any help is greatly appreciated.

    The part is a power feed from Servo Products Company. 20151017_094725.jpg

    In the picture of the circuit board, the part in question is identical to the large red circle on the right side. It attaches just above that one in the slot marked MOV101 on the board (just to the left of the white connection piece). 20151017_094404.jpg

    so far, I've determined it some sort of metal oxide varistor. I'm not sure of the exact part though.

    The power feed works off of 120v, 50/60 HZ 3.0 amps. So, basic United States residential electric as far as I understand.

    Any help is greatly appreciated. Thank you once again forum.
     
  5. umphrey

    Member

    Dec 1, 2012
    39
    1
    One common application for varistors is transient voltage suppression. Perhaps that part is being used to protect the circuit from high voltages. I also thought they were typically high reliability parts. It is possible that one of the transistors failed or there is a short circuit somewhere which melted the varistor. You could try replacing it but be careful that the circuit may still be damaged.

    Here is a wikipedia copy and paste:

    Varistors are used as control or compensation elements in circuits either to provide optimal operating conditions or to protect against excessive transient voltages. When used as protection devices, they shunt the current created by the excessive voltage away from sensitive components when triggered.

    It is likely that your MOV is being used as a protection device and melted because it saw high voltage and thus high current.
     
  6. GS3

    Senior Member

    Sep 21, 2007
    408
    35
    Yep, that looks like a protective varistor and you can find them on PC power supplies. If you are very lucky you can just replace it but my guess is that most likely it has failed because of some other failure and replacing it will only lead to another burnt device. You probably need someone qualified to repair it.

    I would replace it and use the old technique of power up with a protective light-bulb in series.

    Good luck.
     
  7. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,564
    2,379
    MOV's are OK but they are often one time savers, IOW if a spike larger than the Joule rating appears it can save the circuit, but gets destroyed in the process.
    If the device is concealed, the destruction often goes unnoticed, so when a subsequent spike appears, it goes through to the circuit it is supposed to protect.
    I tend to use an R/C snubber as they are very indestructible.
    You can also replace with a higher energy (joule) rating.
    Max.
     
  8. Trueblueglue

    Thread Starter New Member

    Oct 16, 2015
    4
    0
    Thank you everyone for your kindness and generosity with your knowledge to a complete stranger.

    After reviewing the comments, I've decided to just order a new board. Oh well, it was worth a shot at it being a $0.50 fix :)

    Thanks again.
     
  9. GS3

    Senior Member

    Sep 21, 2007
    408
    35
    Which you can use to repair the broken one by comparison and keep it as a spare.
     
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