Cause : Inverter thermal trip comes when the heatsink temperature reaches the overheat fault level. The drive will display "E21" and stop operation.

1. Ambient temperature too high.
2. Fan is damaged.
3. Lower the ambient temperature.
4. Fan air duct is blocked- clear the air duct.

When the inverter internal temperature is above the threshold, the thermal sensor in the inverter module detects the excessive temperature of the power devices and trips, turning the inverter output OFF.