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Thread: Two speed one winding motor troubleshooting advice

  1. #41
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    Quote Originally Posted by phineascage View Post
    We have no instrumentation to measure air flow. Good idea though.
    Are the motors TEFC? If there was a cooling issue shouldn't the motor shop have picked that up?
    Si hoc legere scis nimium eruditionis habes.

  2. #42
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    Quote Originally Posted by Besoeker View Post
    Are the motors TEFC? If there was a cooling issue shouldn't the motor shop have picked that up?
    Yes as stamped on the nameplate: TEFC.

  3. #43
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    are the fan blades adjustable pitch?

  4. #44
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    Quote Originally Posted by phineascage View Post
    Yes as stamped on the nameplate: TEFC.
    Unless the fan is damaged or the fins are unusually dirty, the shaft mounted fan should provide rated cooling. But that doesn't address the excessive current.
    I'm still with it being a motor fault. And I'm still of the opinion that 152A no-load current is excessive despite what the motor shop claims.
    Si hoc legere scis nimium eruditionis habes.

  5. #45
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    Quote Originally Posted by Ingenieur View Post
    are the fan blades adjustable pitch?
    No they are fixed.

  6. #46
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    Quote Originally Posted by phineascage View Post
    I have not measured actual voltage on our two other normally functioning fan motors. I tend to believe though that the voltage at each of their respective output contactors is roughly 480 on all phases since they are fed from the same MCC as our problem motor.

    I wish I could find a voltage drop, I could stop scratching my head.
    I think voltage at motor end of the circuit is important to know

    Quote Originally Posted by Besoeker View Post
    Not on a TEFC.
    I think he meant the driven load....

    Quote Originally Posted by Besoeker View Post
    Thought we had put than one to bed.
    The current difference is seen uncoupled.
    But we keep getting posts that ignore that fact.
    I live for today, I'm just a day behind.

  7. #47
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    Quote Originally Posted by kwired View Post
    I think voltage at motor end of the circuit is important to know

    I think he meant the driven load....

    But we keep getting posts that ignore that fact.
    And that's not very helpful.
    Si hoc legere scis nimium eruditionis habes.

  8. #48
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    Quote Originally Posted by kwired View Post
    I think voltage at motor end of the circuit is important to know

    I think he meant the driven load....

    But we keep getting posts that ignore that fact.
    Voltage at the motor end on the problem motor was measured. It was roughly 476VAC. All balanced.

  9. #49
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    Quote Originally Posted by Besoeker View Post
    Whilst true, the OP has observed a 45A current difference with the motor uncoupled so unrelated to the gearbox.
    In my world, electrohydraulics, a flat mounting surface and uniform proper torque (yeah, torque, I know) are necessary. A non-planar surface or significantly uneven torque will affect internal clearances to the point that sticking will occur.

    On the test bench, all is fine. Installed, current is high and at least one bearing has failed.

    Given all the great postings here, I'd check that the mounting surface is in a plane. The motor frame COULD be so distorted that abnormal bearing loads impose additional friction/loads.

  10. #50
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    Quote Originally Posted by GeorgeB View Post
    In my world, electrohydraulics, a flat mounting surface and uniform proper torque (yeah, torque, I know) are necessary. A non-planar surface or significantly uneven torque will affect internal clearances to the point that sticking will occur.

    On the test bench, all is fine. Installed, current is high and at least one bearing has failed.

    Given all the great postings here, I'd check that the mounting surface is in a plane. The motor frame COULD be so distorted that abnormal bearing loads impose additional friction/loads.
    Good points if I may say so, sir....
    I wouldn't rule out a distorted motor frame causing a problem and, as you rightly point out, there has been a bearing failure in the past. That, if I recall correctly, is what got the motor to the repair shop in the first place. But I'm inclined to think that the amount of force to distort the frame might snap the feet off especially if it is a cast iron frame which is often the case.

    And that still leaves the 152A measured on the shop test. Interesting problem, not that it helps the OP. It will be interesting to see what is concluded/discovered when the motor goes back to the shop.
    Si hoc legere scis nimium eruditionis habes.

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