Trouble shooting three phase motor- where to start.
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  1. #1
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    Default Trouble shooting three phase motor- where to start.

    I have a five hp three phase motor on a machine which won’t run.
    It surges briefly- like a 1/8 turn when I connect to power and makes a deep hum but won’t run.

    Where to start troubleshooting?

    The motor is spins perfectly free.

    Thanks all

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    Step one.... make sure all wires are carrying current. If not , proceed. If so, then there is another issue, possibly with the connection of coils.

    Step 2 make sure all 3 are properly connected

    Step 3 check resistance of all 3.

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    Sounds like you have lost a phase. As above, check what is getting to the motor.

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    Ok- I checked supply- all is good.
    This is a large belt sander and the 5 hp is the primary belt motor.

    The machine also has a three phase oscillating motor which works fine.

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    You guys were right on it and that helped sort it out- the service disconnect for the main motor had punky contacts and were dropping a leg.

    Thanks
    Last edited by Trboatworks; 08-20-2021 at 12:29 PM.


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