Thermistor Input Fault

What does 66 mean?

The motor temperature has increased beyond limits, as detected by a thermistor input, or there is an issue with the thermistor circuit itself. This could be due to inadequate motor cooling, excessive mechanical load on the motor, or a faulty thermistor connection. Overtemperature can lead to motor damage and reduced lifespan.

• Motor overheating due to excessive mechanical load, insufficient cooling, or prolonged operation at low speeds without external ventilation.
• Broken thermistor cable or loose connection at the drive's thermistor input terminals (e.g., X1, X2).
• Thermistor sensor failure (e.g., open circuit, short circuit) within the motor winding causing an invalid resistance reading.
• Incorrect thermistor type selected in drive parameters (e.g., P3.4.1.1 for thermistor input type, P3.4.1.2 for fault threshold) not matching the installed sensor.
• Electrical noise or interference contaminating the low-voltage thermistor signal due to improper cable routing.

Click steps to track your progress.

1. 1

   1. Check the motor casing temperature using an IR thermometer to verify actual overheating; if hot, reduce load or allow the motor to cool.

2. 2

   2. Verify the wiring connections at the drive's thermistor input terminals (e.g., X1, X2) are secure, clean, and undamaged.

3. 3

   3. Disconnect the thermistor leads from the drive and measure the resistance of the thermistor directly at the motor connection box, comparing it to datasheet values.

4. 4

   4. Ensure the thermistor input parameters (e.g., P3.4.1.1 for thermistor type, P3.4.1.2 for fault threshold) are correctly configured for the motor's thermistor.

5. 5

   5. Inspect the thermistor cable for damage along its entire length and ensure it is routed separately from power cables to minimize EMI.

6. 6

   6. If the motor is consistently running hot, review the application load, motor sizing, and cooling system efficiency.