Heatsink sensor fault

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The frequency converter is not receiving a temperature signal from the heatsink sensor, specifically the IGBT thermal sensor on the power card. This loss of feedback means the drive cannot monitor critical internal temperatures, posing a significant risk of overheating and damage to the power semiconductors if not resolved.

• Open circuit in the heatsink temperature sensor (e.g., NTC thermistor) wiring due to mechanical stress, vibration, or faulty crimps.
• Degraded or failed heatsink temperature sensor component itself, causing an inaccurate or missing resistance signal.
• Faulty input channel on the control board responsible for reading the heatsink sensor signal.
• Loose or corroded electrical connection between the heatsink sensor leads and the power card or control board input terminals.

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1. 1

   1. Completely de-energize the frequency converter and wait for the DC bus capacitors to discharge to a safe voltage level (<50V). Verify with a multimeter.

2. 2

   2. Locate the heatsink temperature sensor on the power card, typically in close proximity to the IGBT modules.

3. 3

   3. Disconnect the sensor's wiring from the control board or power card's input terminals.

4. 4

   4. Using a multimeter, measure the resistance of the heatsink temperature sensor across its terminals. Compare the measured value to the manufacturer's specified resistance curve for the ambient temperature. An open circuit (infinite resistance) or an abnormally high resistance indicates a faulty sensor.

5. 5

   5. Check the continuity of the sensor wiring from the sensor terminals back to the control board's input terminals using a multimeter. Look for breaks or high resistance in the cable path.

6. 6

   6. If the sensor and its wiring are confirmed to be functional and within specification, the fault may lie with the control board's input circuitry, necessitating a control board replacement.