When an industrial motor trips, fast and accurate diagnosis is critical to reduce costly downtime. Most induction motor problems fall into one of two categories: Mechanical (bearings, alignment) or Electrical (windings, power supply).

1. Mechanical Faults (Bearings and Alignment)

• Symptom: Excessive noise (grinding, squealing) or severe vibration.
• Cause: Bearing wear (often due to poor lubrication—wrong type, too much, or too little) or misalignment with the coupled equipment.
• Action: If audible, the motor is nearing failure and needs immediate service. Use vibration analysis for the earliest warning.

2. Electrical Faults (Winding Failure)

• Symptom: Tripped circuit breaker, burnt/acrid smell, visible scorching.
• Cause: Insulation breakdown from chronic overheating, moisture, or voltage spikes. This is the most catastrophic failure.
• Action: Use a megohmmeter (megger) to test the winding insulation resistance. If low, the motor needs a rewind or replacement. Prevention is key: control motor temperature.

3. Electrical Faults (Voltage Imbalance)

• Symptom: The motor runs hot with no obvious external cause.
• Cause: Even a small (over 1%) difference in voltage across the three phases. This severely increases winding current and temperature.
• Action: Immediately measure the line voltages. Investigate the power supply or wiring leading to the motor to balance the voltage.

4. Rotor Faults

• Symptom: Pulsating torque, high current draw, increased vibration.
• Cause: Broken or cracked bars in the squirrel cage rotor, often resulting from thermal stress due to frequent starts and stops.
• Action: These are harder to spot but are characteristic of high-stress applications.

By knowing these key mechanical and electrical signs, technicians can quickly diagnose the issue, manage the repair, and dramatically reduce industrial downtime.