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About Winding Faults

There are four basic types of winding faults

  • - Between turns in a coil
  • - Between coils in a phase
  • - Between coils in different phases
  • - Between a coil or phase and ground

Only about 17% of electrical faults begin as a conductor to ground fault. The other three fault types may or may not propagate into a ground fault as the failure becomes advanced. The short-term result of these faults is reduced efficiency (and higher operating costs). Symptoms include higher operating temperatures, perhaps nuisance tripping, and reduced motor life. As faults advance, the ability of the motor to drive the load may decrease. The longer-term result is always motor failure.

More Facts about Winding Faults


  • - Usually start in the end turns of windings
  • - Greatest stresses
  • - Insulation is weakest
  • - They start small and escalate over time
  • - They always end in failure
  • - Contributing factors to failure
  • - Overloading
  • - Frequent start/stop cycling
  • - Vibration
  • - Contamination
  • - Age, Heat, & Motor Drives