Motor Overload Trip (Electronic Thermal Relay Function)

What does E.THM mean?

The inverter's electronic thermal O/L relay function detects when the motor is overheating due to excessive load or insufficient cooling, especially during low-speed operation. A pre-alarm (TH) is issued at 85% of the Pr.9 setting, and the inverter output stops when the accumulated heat reaches the trip level. This protection may be insufficient for multiple or special motors, requiring an external thermal relay. Overheating can severely damage the motor windings.

Complete Troubleshooting Guide

1. 1

   Reduce the mechanical load applied to the motor to decrease current draw.

2. 2

   Verify that Pr.71 (Applied motor) is correctly set for the specific motor type, especially if it's a constant-torque motor.

3. 3

   Adjust the stall prevention operation level in the inverter parameters to prevent nuisance trips during high load.

4. 4

   If driving multiple motors or a dedicated, multi-pole motor, install an external thermal relay on the inverter output side for accurate motor protection.