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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