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Thermal inspection, current analysis, ventilation check and insulation degradation: motor overheating diagnostic guide

Technical analysis: Troubleshooting electric motor overheating: thermal imaging, current analysis, ventilation check, an

Thermal inspection, current analysis, ventilation check and insulation degradation: motor overheating diagnostic guide

1. Problem Description and Area of Application

This guide is intended for diagnosing overheating of electric motors, which may occur due to various reasons, including ventilation failure, winding insulation degradation, high current or incorrect settings. The problem is critical, as overheating may lead to winding wear, insulation loss, explosion or even motor failure. This guide covers electric motors used in industrial installations, including mining, chemical, energy and agricultural sectors.

2. Safety during diagnostics

Disconnect the engine power supply before starting the diagnostics.

Use personal protective equipment (protective gloves, goggles, safety equipment). Before working, perform the lockout/tagout (LOTO) procedure to prevent accidental engine startup. Before performing diagnostics, check whether the engine contains residual energy, for example, through energy accumulation in capacitors or windings.

3. Required diagnostic tools

Tool Name Model/Specification Measurement range Objective
Thermal camera Flir T620 –10°C to 1200°C Detection of thermal anomalies on the engine surface
Multimeter Fluke 87V 0–2000 mA, 0–2000 V, 0–200 Ω Current, Voltage and Resistance Measurement
Vibration Analyzer TECHNOSCOPE VIBRA 3 0–10000 Hz Vibration anomaly detection
Thermometer Testo 825 –50°C to 600°C Additional temperature measurement of critical points

4. Initial Assessment (Checklist)

Step Action
1 Check whether the engine temperature meets the set limit (not more than 90°C under load).
2 Record the current and voltage values.
3 Check the condition of the ventilation openings and fans.
4 Record the engine usage duration history and changes in the system.
5 Check whether any alarms have occurred in the condition monitoring system.

5. Systematic Diagnostic Flow

  1. Symptom: Engine overheats during operation.
    1. Apply a thermal camera to detect thermal anomalies.
    2. If the temperature exceeds 90°C, perform additional diagnostic actions.
    3. Measure the current at the motor terminals.
    4. If the current exceeds the nominal value (for example, 120% nominal), perform a load volume check.
    5. Check the ventilation status.
    6. If ventilation is blocked, perform cleaning and restore operation.
  2. Symptom: Incorrect ventilation operation.
    1. Check the ventilation filters and clean them.
    2. Check the fan operation.
    3. If the fan is not working, perform the replacement.
  3. Symptom: High motor current.
    1. Measure the current at the input terminals.
    2. If the current exceeds 120% nominal, check the current in the network.
    3. If the current in the network is normal, check the motor windings.

6. Cause Matrix of Defects

Symptom Possible causes (by probability) Diagnostic test Expected result, if the cause is confirmed
Engine Overheating
  1. Incorrect Ventilation (100%)
  2. Insulation degradation (80%)
  3. High current (70%)
  4. Incorrect loading (60%)
  1. Perform a thermal inspection.
  2. Measure current and voltage.
  3. Check the condition of the filters and fans.
  1. Temperature exceeds 90°C.
  2. Current above 120% nominal.
  3. Filters are blocked or the fan is not working.

7. Diagnosis of the main causes of the defect

7.1. Incorrect Ventilation

Cause: Blocked ventilation may lead to engine overheating due to insufficient cooling. This usually occurs due to dust accumulation, moisture or mechanical failures of the fan. If ventilation is not working, the engine cannot dissipate heat, resulting in increased temperature.

Diagnosis: Perform a thermal inspection to determine if there is an abnormal temperature on the engine surface. Measure the temperature of the ventilation openings. Check the operation of the fan. If the fan is not working, perform replacement.

Reconditioning: Clean the filters and ventilation openings. Check the fan condition. If the fan is not working, perform replacement.

7.2. Insulation Degradation

Cause: Degradation of winding insulation may occur due to continuous overheating, moisture, electrical overvoltages or physical damage. This leads to a reduction in insulation resistance, which may cause short circuits, increased current and, finally, motor overheating.

Diagnosis: Measure the insulation resistance of the windings using a multimeter. The normal insulation resistance value should be no less than 10 MOhm. If the resistance is lower, this indicates insulation degradation.

Reconditioning: Replace the windings or insulation. Check the motor condition and perform the resistance measurement again.

7.3. High Current

Cause: High current may occur due to incorrect loading, measurement errors or exceptional conditions in the electrical network. High current leads to an increase in motor temperature, which may result in overheating.

Diagnosis: Measure the current at the motor terminals. The normal current value should not exceed 120% of the nominal. If the current is higher, check the electrical network.

Return to normal: Perform electrical network diagnostics. Correct incorrect settings or change the load.

8. Step-by-step correction procedure

8.1. Incorrect Ventilation

  1. Clean the ventilation filters and ventilation openings.
  2. Check the fan operation.
  3. If the fan is not working, perform the replacement.
  4. Check the engine temperature after restoring the ventilation.

8.2. Insulation Degradation

  1. Measure the insulation resistance of the windings.
  2. If the resistance is less than 10 MOhm, perform the winding replacement.
  3. Check the engine condition and perform the resistance measurement again.

8.3. High Current

  1. Measure the current at the motor terminals.
  2. If the current exceeds 120% nominal, check the electrical network.
  3. Correct incorrect settings or change the load.
  4. Check the engine temperature after correction.

9. Prevention

Main Cause Preventive strategy Visual method Recommended interval
Incorrect ventilation Regular cleaning of filters and ventilation openings Thermal inspections Monthly
Insulation Degradation Periodic measurement of insulation resistance Resistance Measurement Quarterly
High current Check electrical network settings Current Measurement Monthly

10. Parts and Components

Part Description Specification When to replace Category UNITEC-D
Ventilation filter Material: polypropylene; size: 200x200 mm After contamination UNITEC-D: Category 300
Fan Material: aluminium; power: 0.5 kW After failure UNITEC-D: Category 200
Motor windings Material: copper; insulation resistance: 10 MOhm After degradation UNITEC-D: Category 100

Відвідайте наш e-каталог на https://www.unitecd.com/e-catalog/ для отримання деталів про запчастини.

11. References

  • DSTU 2583: Electrical Equipment. Execution Standards
  • EN 60034-1: Requirements for electric motors
  • ISO 14692: Motor Diagnostics
  • UNITEC-D: Technical Maintenance Guide for Electric Motors

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