DC motor field & armature wiring

Discussion in 'General Electronics Chat' started by strantor, Mar 29, 2011.

  1. strantor

    Thread Starter AAC Fanatic!

    Oct 3, 2010
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    I had a 5hp DC motor (setup with old DC drive) burn up a few weeks back. I sent it off to get rewound and when it came back another guy installed it. When I started it up, it ran backwards so I swapped the leads to the armature. It goes the right direction now but it runs really hot. Should I swap the field voltage wiring also?
     
  2. t_n_k

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    Mar 6, 2009
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    Presumably just swapping the field leads without re-swapping the armature leads will leave you with the motor running the wrong direction again. I can't see why that would lead to overheating anyway.

    I would investigate the overheating problem further. Why did the motor burn out originally? Has the load changed in some way to cause a much higher loading? Is there a problem with the DC drive control? Ask an electrician to check the motor DC amps under load to make sure the value is within the armature current rating. Also check the field winding DC voltage / current as a precaution.
     
  3. strantor

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    It's the other way around; I swapped the armature leads and left the field leads alone.
    It was assumed the old motor burned up from aged insulation - it was >30yrs old, as is the drive. I suppose the load could have changed mechanically; I'll look into that. I'll check the current draw. thanks
     
  4. strantor

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    Armature drawing 7A, rated @ 14. Can't check voltage while it's running. The operator says before he started it, mechanically it (the entire machine, it's just a winder that reels up wire onto a spool) was a little stiffer to operate; but that is probably due to new belts (there's a dozen belts) throughout.
     
  5. strantor

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    Good reading:http://zone.ni.com/devzone/cda/ph/p/id/54

    "Notice that the shunt field is connected across the armature and it is not reversed when the armature is reversed. ......If the motor operates but draws excessive current or heats up, the motor should be tested for loose or shorting coils. Field coils may tend to come loose and cause the motor to vibrate and overheat, or the armature coils may come loose from their slots and cause problems. If the motor continues to overheat or operate roughly, the motor should be removed and sent to a motor rebuilding shop so that a more in-depth test may be performed to find the problem before the motor is permanently damaged by the heat. "
     
    Last edited: Mar 29, 2011
  6. GetDeviceInfo

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    Jun 7, 2009
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    So, what did you find?
     
  7. strantor

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    Well my semi-pro diagnosis was that they rewound it wrong. I called up the rewind shop and they sent a guy out to look at it. they are going to give us another motor to try out while they take our motor back and inspect it.
     
  8. GetDeviceInfo

    Senior Member

    Jun 7, 2009
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    So, what's happening.

    I believe in the concept that it's as important to give as it is to recieve. Some of us have put time into trying to help, and it would only be reasonable to hope that you carry through with some feedback.
     
  9. strantor

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    I whole-heartedly agree. You continue to recieve information as I get it. I just got the motor back from the rewind shop last night; my supervisor, who is a mechanic, is the one who recieved it & the night shift electrician installed it. I asked my supervisor what the rewind shop guy said and all I got was "mmm, something about dipped and baked and nothing wrong with the insulation but probably the internal wiring but it's supposed to work now." Night shift guy said it's not running hot anymore so I guess you get about as much closure & understanding from that as I do. I continue to assume that they rewound it wrong.
     
  10. PackratKing

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    Jul 13, 2008
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    From above...........

    "" I asked my supervisor what the rewind shop guy said and all I got was "mmm, something about dipped and baked and nothing wrong with the insulation but probably the internal wiring but it's supposed to work now.""

    Odds are the rewind shop didn't "dip and bake" first time around. Their oversight, intentional or no, came back to bite them.
     
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