How to Check Why Induction motor Heat and Draws Over Current

When an induction motor draws overcurrent and gets overheated more than its rated values, it usually indicates a problem in the motor or its operating conditions. Here are the main reasons:

🔌 1. Overloading

Reason: 

The motor is driving a mechanical load heavier than its rated capacity.

Effect: Excess torque demand → More current drawn → Heating of windings.

Example: A motor rated for 5 HP is running a load requiring 7 HP.

⚠️ 2. Low Voltage Supply

Reason:

 Supply voltage is lower than the rated voltage.

Effect: Motor draws more current to maintain torque → Heating increases.

Example: A 415V motor running at 380V.

🌀 3. Phase Imbalance or Single Phasing

Reason: 

One phase may have low voltage or is disconnected.

Effect: Causes unbalanced current and overheating in one or more windings.

Example: One fuse blown in a three-phase system.

🧲 4. Rotor or Bearing Issues

Reason: 

Bearing damage, rotor misalignment, or air gap issues.

Effect: Increases mechanical friction or magnetic unbalance → More current drawn → Overheating.

🪛 5. Blocked Rotor or Jammed Load

Reason: 

The motor shaft is jammed, seized, or mechanically obstructed.

Effect: No rotation → Locked rotor current flows → Immediate overheating.

📉 6. Poor Ventilation or Cooling

Reason: 

Fan is broken or vents are blocked.

Effect: Heat generated in the motor doesn’t dissipate → Overheating.

Example: Dust-clogged cooling fins or fan cover.

🛠️ 7. Wrong Motor Connection or Wrong Size

Reason: 

Motor connected in star instead of delta (or vice versa), or undersized motor used.

Effect: Reduced power output or higher current drawn → Overheating.

⚡ 8. Harmonics or Voltage Unbalance

Reason: 

Non-linear loads or poor power quality.

Effect: Causes negative torque components → Extra current → Heat loss.

✅ Solutions:

1. Check load – ensure motor is not overloaded.

2. Measure supply voltage and balance across phases.

3. Inspect motor bearings, shaft, and cooling fan.

4. Use proper protection: overload relay, thermistor, MCB, MCCB, etc.

5. Perform insulation resistance (IR) test and winding resistance check.

6. Consider derating in poor ventilation areas or high ambient temperatures.

If you want, I can help you prepare a maintenance checklist or test procedure for this issue.