Stator Faults

Classification

• open-phase (open circuit) fault
• turn to turn short circuit (shorted turn, Inter-turn Short Circuit Fault), (ITSF) within a coil
• coil to coil short circuit (shorted coil) within same phase
• phase to phase short circuit fault (including three-phase fault)
• coil to ground fault
• supply imbalance (unbalanced voltage)
• voltage surge
• overload
• iron core related

Causes

• Mechanical stresses (due to movement of stator coil and rotor striking the stator)
• Electrical stresses (supply voltage transient due to different faults (like line-to-line, line-to-ground, or three-phase fault), due to lightning, opening, or closing of circuit breakers or due to variable frequency drives)
• Thermal stresses (due to thermal overloading, due to over current flowing due to sustained overload or fault, higher ambient temperature, obstructed ventilation, unbalanced supply voltage, etc.)
• Environmental stresses (too hot or too cold or too humid environment, presence of foreign material)

Effects

Effects of winding failures

• High temperature (core, winding)
• Electrical discharges
• Environmental pollution
• Short circuit

Causes of winding failures

• breakdown of the winding’s insulation
• high temperature,
• too many starts,
• contamination,
• too much current,
• excessive voltage
• physical damage.

Visualization

• Open-phase fault
  

• Turn to turn fault within a coil
  

• Coil to coil fault within a phase
  

• Phase to phase fault
  

• Coil to ground fault
  

Inter-turn short circuit of the stator winding in three-phase induction motors. (a) Short circuits in one phase due to motor overload (b) Short circuits in one phase due to blocked rotor. (c) Inter-turn short circuits are due to voltage transients. (d) Short circuits in one phase due to a phase loss in a Y-connected motor. (e) Short circuits in one phase due to a phase loss in a delta-connected motor. (f) Short circuits in one phase due to an unbalanced stator voltage

References

• cardosoDiagnosisFaultTolerance2018
• saadConditionMonitoringFaults2018
• karmakarInductionMotorFault2016

References

• Failures in Three-Phase Stator Windings