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Effects of rewinding ind. motors with higher resistance that the initial?

  1. Jun 13, 2010 #1
    I wonder where I work, 3-phase ind. motor with 80 ohms resistance per phase from the manufacturer was re winded and the new resistance per phase was 89 / 90 / 94 Ohms in the 3 phases. when the motor was put back, it burnt within few hour, why was this?
     
    Last edited: Jun 13, 2010
  2. jcsd
  3. Jun 13, 2010 #2
    Infantile mortality due to shorted winding?

    Why the large disparity in resistance? Did someone loose count?
     
  4. Jun 13, 2010 #3
    So does it mean that had it been there was no short winding the motor couldn't burn although with high resistance? if so what are the effects of such higher resistance?
     
    Last edited: Jun 13, 2010
  5. Jun 15, 2010 #4
    We can think about the higher resistance in the winding as an extra resistor in series with the initial windings, so the same concept as using a rheostat in starting induction motors, thus the high resistance indicates a low motor speed, but it does not cause to burn the motor.
     
  6. Jun 16, 2010 #5
    It is very clear, Increasing of Ri2 losses and consequent unbalance core fluxes (negative sequence rotary field) due to phases emf unbalancing without any cooling system modification can be caused motor burning.

    --------------------------------
    Creative thinking is breezy, Then think about your surrounding things and other thought products. http://electrical-riddles.com
     
  7. Jun 16, 2010 #6
    There are several souces for an inbalanced reistance that I can think of:

    1) Mis-wired phases
    2) Variations in wind length, e.g.: An outer winding is longer than an inner winding
    3) Turns count variation
    4) Shorted turns
    5) Wire gauge doesn't match
     
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