Abnormal Operating Condition and Causes of Induction Motors

05/19/2025

Abnormal Operating Conditions and Causes of Induction Motors

Three-phase induction motors are widely used in industrial applications. Their abnormal operating conditions and causes can be summarized as follows:
Abnormal Operating Conditions and Causes of Induction Motors
The following are the abnormal operating conditions and causes of induction motors:
Mechanical Overload
  • Blockage in Pump/Gear Systems: Obstruction in mechanical systems (e.g., pumps or gears) connected to the motor.
  • Damaged Bearings or Lack of Lubrication: Worn-out bearings or insufficient lubrication leading to increased friction.
  • Locked Rotor or Prolonged Starting Time: A rotor that fails to rotate (locked rotor) or extended starting duration due to mechanical resistance.
  • Motor Stalling: Inability to start due to excessive load, requiring the motor to be disconnected from both the power supply and mechanical load before restarting to resolve the overload.

Abnormal Supply Conditions

  • Low Supply Voltage: Reduced voltage below the rated value.
  • Unbalanced Supply Voltage: Uneven voltage distribution across the three phases.
  • High Supply Voltage: Excess voltage exceeding the rated value.
  • Low Frequency: Operating frequency lower than the motor’s rated frequency.
  • Supply Circuit Faults:
    • Loss of one or more phases (single-phasing).
    • Short circuits in supply cables.
    • Damaged contactor terminals or links.
    • Blown fuses.

Internal Motor Faults

  • Phase-to-Phase Faults: Short circuits occurring between stator windings of different phases.
  • Phase-to-Earth Faults: Insulation failure leading to a short circuit between a phase winding and the motor’s grounded frame.
  • Open Circuit: Breaks in windings or electrical connections, interrupting current flow.
  • Insulation Degradation: Deterioration of winding insulation (typically tested with a megger to check continuity and resistance).

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