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Thread: need a motor

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  1. #1
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    need a motor

    Hello to everyone,
    I got a hold of this Comet milling maching that looks just like a brigeport, for some reason the motor is just not turning on it just makes a humming sound, but when I spin the spindle it starts only on low gear, does anyone know what can be the problem, or should I just get a new 1.5hp motor.

    Thank you

  2. #2
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    Re: need a motor

    Hi,
    is this a single phase induction motor?

    If so it sounds like the start winding is not operating at start-up, possibly the centrifugal switch or start capacitor.

    Craig

  3. #3
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    Re: need a motor

    its a 3 phase induction motor.
    I dont see any capacitors so maybe like you mention it might be the centrifugal switch
    I'll try checking that next.
    thank you for the quick reply

  4. #4
    Community Moderator Jim Dawson's Avatar
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    Re: need a motor

    A 3 phase motor does not have a centrifugal switch. Are you operating on 3 phase power? And if so is it wired for the correct voltage? The symptoms you describe sound like you are running on 230V but the motor is wired for 460V
    Jim Dawson
    Sandy, Oregon, USA

  5. #5
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    Re: need a motor

    Hi,
    its only single phase motors that have the centrifugal switch.

    Have you measured the voltage of all three phases, if you lose one phase the motor will most likely not start and hums like hell.

    Craig

  6. #6
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    Quote Originally Posted by joeavaerage View Post
    Hi,
    its only single phase motors that have the centrifugal switch.

    Have you measured the voltage of all three phases, if you lose one phase the motor will most likely not start and hums like hell.

    Craig
    So if I loose one phase does that mean i need a new motor.
    Sorry for asking this dum question ????

  7. #7
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    Re: need a motor

    you don't need a new motor. Check with multimeter if any of windings is not burned. Better- go to the motor repair ( rewind service ) workshop and ask to test the motor. They have a special stands for 3 phase motor check.
    The burned winding makes stable specific smell.

  8. #8
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    Re: need a motor

    Hi,
    lets assume you have lost a phase, it could be simply one blown use (out of three), or a fault in the wiring and/or isolator that causes the loss of a phase.
    Another possibility, and not an uncommon fault, is for one of the three contact pairs in the contactor (effectively a big relay to turn the motor on and off) has failed.

    Its also possible that there is a fault in the motor. There could be a failure to earth of one of the windings which will take out a fuse or fuses in short order. Another less common
    fault is for one winding to develop shorted turns. When this happens the winding still draws current, maybe even more than normal, but does not produce the magnetic field
    it would if it did not have shorted turns.

    If you are unfamiliar with three phase motors I would recommend assistance from an electrician, getting a reliable and credible diagnosis of the fault is the first step. Thereafter
    repair/replacement options will be clear.

    Craig

  9. #9
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    Re: need a motor

    Greetings,

    I had a similar issue with my three phase mill motor.

    Turns out the forward/reverse switch was dirty.

    Fortunately, the motor repair shop did not charge me to test the motor.

    Cheers,

    Dave

  10. #10

    Re: need a motor

    Quote Originally Posted by cob View Post
    Hello to everyone,
    I got a hold of this Comet milling maching that looks just like a brigeport, for some reason the motor is just not turning on it just makes a humming sound, but when I spin the spindle it starts only on low gear, does anyone know what can be the problem, or should I just get a new 1.5hp motor.

    Thank you
    Is the mechanical parts stuck?
    http://cncmakers.com/cnc/controllers/CNC_Controller_System/CNC_Retrofit_Package.html

  11. #11
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    Re: need a motor

    thank you guys
    finaly figure the problem , and yes it was the forward/and reverse switch that was the problem, thank you very much,
    on another note i will be adding a VFD to this mill it has a 2 hp motor does any one have any sudjestion on what type of VFD is good?
    thans again

  12. #12
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    Re: need a motor

    We used a WEG on our Bridgeport, which has a similar-sized motor. It worked okay.
    Andrew Werby
    Website

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