Charging Switch Malfunction

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The internal charging switch is commanded to close, but its feedback indicates it is still open, suggesting an operational malfunction or a defective component. This prevents the DC link from being properly charged, inhibiting drive startup or operation. If ignored, the drive will not function.

• Defective pre-charge resistor (e.g., R_charge) in the charging circuit, preventing proper DC link voltage build-up.
• Failure of the pre-charge contactor or relay (e.g., K1), where the contacts are welded open or the coil is faulty.
• Control board feedback circuit malfunction, misinterpreting the state of the charging switch.
• Low auxiliary power supply (e.g., 24VDC) to the control board or charging circuit components.
• High inrush current demand on the DC bus during power-up, potentially due to a large capacitive load, stressing the charging circuit.

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1. 1

   With input power off and DC link discharged (measure DC+ and DC- for 0V), visually inspect the pre-charge resistor and contactor/relay for physical damage or signs of overheating.

2. 2

   Measure the resistance of the pre-charge resistor (if accessible and not shorted by a contactor) to verify its integrity.

3. 3

   Verify the auxiliary power supply voltage (e.g., 24VDC at control board terminals) is within the specified tolerance.

4. 4

   Cycle the main input power to the drive, carefully observing (if safe and visible) the operation of the pre-charge contactor.

5. 5

   Perform a component-level diagnostics test (if available via HMI or diagnostic software) for internal power board relays and sensors.