Precharge Fault

What does CrF mean?

This fault indicates a problem with the drive's internal capacitor precharge circuit, typically related to the precharge relay control or a damaged precharge resistor. The precharge circuit is vital for safely charging the DC bus capacitors upon power-up. If unresolved, the drive cannot power up correctly and will remain inoperable.

• Precharge relay (internal to the drive) coil failure or welded contacts preventing main contactor engagement.
• Damaged precharge resistors (internal to the drive) due to overcurrent or prolonged precharge cycles.
• DC bus voltage feedback circuit malfunction preventing accurate precharge monitoring.
• Input line voltage fluctuations or rapid power cycling exceeding the precharge circuit's design limits.
• External main contactor (if used) failing to close after the precharge cycle completes.

Click steps to track your progress.

1. 1

   1. Disconnect input power (L1, L2, L3) and wait for the DC bus voltage (e.g., terminals DC+, DC-) to discharge safely to <50VDC.

2. 2

   2. Measure resistance of internal precharge resistors (requires drive disassembly and specific technical knowledge).

3. 3

   3. Test the precharge relay (if accessible) for coil continuity and contact operation using a multimeter.

4. 4

   4. Verify input line voltage (e.g., L1-L2, L2-L3, L3-L1) is stable and within specified limits during the power-up sequence.

5. 5

   5. Check for proper closure of the main input contactor (if external to the drive) after the precharge cycle.