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Servo motor overheating is one of the most common causes of unplanned downtime. Here's how to diagnose and fix it.
## Temperature Limits
Most servo motors are rated for continuous operation at 40°C ambient with winding temperature rise of 80°C (Class B) or 105°C (Class F). Sustained operation above rated temperature **reduces insulation life by 50% for every 10°C excess**.
## Common Causes
**1. Duty Cycle Exceeds Rating**
Calculate actual duty cycle: (on-time / cycle-time) × 100%. Compare to motor's rated duty cycle.
**2. Cooling Fan Failure**
Check fan rotation direction — reverse rotation gives only ~30% of rated airflow. Clean fan blades regularly.
**3. Ambient Temperature Too High**
Derate motor by 3% per °C above 40°C. Consider adding forced air cooling for hot environments.
**4. Servo Gain Tuning Issues**
Poorly tuned gains cause the motor to hunt (oscillate), generating heat without useful work. Check for oscillation with a servo analyzer.
**5. Mechanical Binding**
Increased mechanical resistance forces the motor to work harder. A 10% increase in mechanical load can cause 20% increase in motor heating.
## Solutions
- Install motor temperature monitoring with alarm at 100°C and shutdown at 120°C
- Add thermal imaging to monthly maintenance routine
- Consider motor with higher thermal class (Class H) for demanding applications
- Optimize speed profile to reduce RMS current — slower approach, faster return