Inverter Thermal Trip

What does E21 mean?

This fault indicates that the inverter's internal temperature has exceeded its safe operating threshold. The thermal sensor within the inverter module detects overheating of the power devices (IGBTs), causing the inverter to trip and shut down its output to prevent damage.

• Insufficient cooling due to clogged heatsink fins or non-functional cooling fan.
• Ambient temperature exceeding the inverter's specified operating range (e.g., >40°C or 104°F).
• Continuous motor overload condition, causing excessive current and heat dissipation in the inverter's IGBTs.
• Improper electrical enclosure sizing or ventilation leading to heat buildup around the inverter.
• Internal thermal sensor malfunction providing erroneous high-temperature readings.

Click steps to track your progress.

1. 1

   1. Verify ambient temperature around the inverter using a calibrated thermometer; ensure it is within specified limits (e.g., 0-40°C).

2. 2

   2. Power down the inverter, wait 15 minutes for DC bus discharge, then inspect heatsink fins for dust/debris accumulation and clean thoroughly with compressed air.

3. 3

   3. Check inverter cooling fan operation by observing rotation after power-up; measure fan current if possible (typically <0.5A for standard units).

4. 4

   4. Review motor load profile; if consistently operating above 100% rated current (A), reduce load or consider upsizing the motor/inverter.

5. 5

   5. Measure output current (A) to the motor during operation and compare to inverter nominal current rating; adjust Parameter P1-03 (Current Limit) if necessary.