PTC thermistor operation

What does E.PTC mean?

This fault indicates that the resistance of the PTC thermistor, connected between inverter terminals 2 and 10, has exceeded the threshold set in Pr. 561 (PTC thermistor protection level), causing the inverter to trip. This typically signals motor overheating due to overload. This protective function is active only when Pr. 561 is set to a value other than '9999'. Continued overload and overheating can severely damage the motor.

• Motor winding temperature exceeding the activation threshold of the embedded PTC thermistor.
• Open circuit in the PTC thermistor wiring (e.g., between inverter terminals 2 and 10) due to damage or loose connection.
• Incorrect PTC thermistor type or resistance range installed for the application, causing premature tripping.
• Parameter Pr. 561 (PTC thermistor protection level) set too low, triggering the fault at normal operating temperatures.
• High ambient temperature around the motor causing the PTC thermistor to reach its trip resistance.

Click steps to track your progress.

1. 1

   Disconnect main power supply to the inverter and wait for DC bus discharge (measure terminal V+/V- for 0VDC).

2. 2

   Allow the motor to cool down completely, ensuring its surface temperature is below operating limits.

3. 3

   Disconnect the PTC thermistor leads from inverter terminals 2 and 10.

4. 4

   Using an ohmmeter, measure the resistance of the PTC thermistor at the motor connection points.

5. 5

   Verify the measured PTC resistance is within the expected range for a cold PTC thermistor (typically 20-250 ohms depending on type).

6. 6

   Check parameter Pr. 561 (PTC thermistor protection level) to ensure it is set correctly according to the PTC thermistor and motor specifications.