Motor Overheat

What does oH3 mean?

The motor overheat signal, typically from a PTC thermistor input to a multi-function analog terminal (H3-02, H3-06, or H3-10 = E), has exceeded its alarm level. Possible causes include faulty motor thermostat wiring, a locked-up machine, or the motor itself overheating due to excessive load or an inappropriate V/f pattern. Continued operation with an overheated motor risks winding insulation breakdown and costly motor failure.

• Actual motor overheating due to sustained overload, insufficient cooling, or high ambient temperature.
• Faulty PTC thermistor inside the motor providing an erroneous high resistance signal.
• Wiring fault (e.g., open circuit, high resistance) in the thermistor cable to H3-02, H3-06, or H3-10.
• Incorrect configuration of the multi-function analog input parameter (H3-02, H3-06, or H3-10 = E).
• Inadequate sizing of the motor for the mechanical load requirements.

Click steps to track your progress.

1. 1

   Measure the resistance of the motor's PTC thermistor directly at the motor terminal box.

2. 2

   Measure the resistance of the thermistor feedback cable at the drive's input terminal (H3-02, H3-06, or H3-10).

3. 3

   Verify parameter H3-XX (Multi-Function Analog Input) is correctly set to 'E' (PTC Thermistor Input).

4. 4

   Check the motor's surface temperature using an infrared thermometer; compare to its rated operating temperature.

5. 5

   Inspect the motor for proper ventilation and clear cooling fins, removing any accumulated dust or debris.

6. 6

   Monitor drive output current and motor speed during operation to identify sustained overload conditions.