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3 Phase Motor Troubleshooting?

Discussion in 'ELECTRICAL ISSUES - POWER YOUR MACHINES & SHOP' started by randyjaco, Jul 17, 2017.

  1. markba633csi

    markba633csi United States Active Member Active Member

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    Higher ohm readings than I predicted but all very similar, looks Aok to me- Randy I think your problem is something else
    Mark
     
  2. RandyWilson

    RandyWilson United States H-M Supporter - Premium Content H-M Supporter-Premium

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    Could the higher resistances be because it is wired for 480V?
     
  3. Technical Ted

    Technical Ted United States Active Member Active Member

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    Can you come up with a safe way to connect the motor (fully assembled) to your source 3-phase to eliminate any other circuitry/components? If it runs OK connected directly, then you know the motor and source are OK and the trouble is someplace else. If it doesn't run OK, it's either the motor or the source...

    Good luck,
    Ted
     
  4. randyjaco

    randyjaco Reserved Active User H-M Supporter-Premium

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    Well I got it running. I pulled the motor and cleaned everything up. There was some black crud on the rotor (like burnt grease). I put it all back together and hooked it up directly. It now runs. The downside is that it seems to have minimal start up torque. The bearings are good and everything turns super easily, almost no friction. But when I turn the motor on, I get a buzzing sound for about a second, then it spins like a turbine. I plan to use a VFD on it. Any recommendations for settings to make it start up faster and minimize the buzz?

    Thanks
    Randy
     
  5. Technical Ted

    Technical Ted United States Active Member Active Member

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    If you look at your VFD manual are there any setting you can tweak to help? Or, can you test it some how on a true 3-phase power source to see how it performs then? 3-phase motors are fairly simple devices, so you might want to verify your source of power isn't causing what you are seeing.

    Ted
     
  6. markba633csi

    markba633csi United States Active Member Active Member

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    Randy may be correct- it may have been rewound for a higher voltage, hence the low torque on your lower voltage supply. That might be the reason for the epoxy coating too.
    What I would do is collect some winding resistance information for 440/600 volt motors vs. 220 and see if that explains the 6.5 ohm readings you got. Also put a clamp-on ammeter on each leg and see if it jives with the nameplate amps.
    Mark S.
     
  7. Technical Ted

    Technical Ted United States Active Member Active Member

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    Can you contact the person you got the machine from and see what voltage it was run on when they owned it? And how they ran it, whether a VFD or true 3-phase?

    Ted
     
  8. randyjaco

    randyjaco Reserved Active User H-M Supporter-Premium

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    The motor plate said 220. The previous owner never got it running and God only knows where he got it from. Just judging from what I saw tearing it down, I believe I am the first person since the factory to see the inside of that motor, but anything could have happened.

    Thanks
    Randy
     
  9. Technical Ted

    Technical Ted United States Active Member Active Member

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    Well, you would like to think that if someone was to professionally re-wind a motor for a different voltage that they would re-mark/re-stamp the motor data plate.

    Ted
     
  10. randyjaco

    randyjaco Reserved Active User H-M Supporter-Premium

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    I would agree. I also know from taking a similar motor to a motor shop, that having a motor rewound is an expensive proposition. They wanted nearly a Grand to do mine.

    Randy
     
  11. RandyWilson

    RandyWilson United States H-M Supporter - Premium Content H-M Supporter-Premium

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    I have a mill with a very clean looking three phase rewire that retained all of the original two phase plates.
     
  12. 4gsr

    4gsr Global Moderator Staff Member H-M Supporter-Premium

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    Put the motor back together and take it to your local favorite motor shop and have them check what voltage it runs on. Lets hope it is 230 volts. If it runs on 460 volts, you will know for sure it is. They shouldn't charge just for doing that I wouldn't think.
     
  13. markba633csi

    markba633csi United States Active Member Active Member

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    Only hitch is that he'll have to bring the whole machine to them, the motor is part of the frame.
    Maybe the motor shop could just tell you based on the ohm readings what voltage it is expecting...
    Mark
     
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  14. randyjaco

    randyjaco Reserved Active User H-M Supporter-Premium

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    Mark is right. I would have to take a @500 pound 1hp to the shop. The jointer is direct drive. The motor and the cutter head are all the same assembly. Hence my concern for the motor. I can’t just toss the old motor and replace it with another. If I could I would have instantly replaced it with a single phase motor and ya'll never would have known that I had a problem ;-)
    Randy
     
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