DC Bus Charge Circuit Fault

What does DC Charge Circuit Fault mean?

There is a fault within the drive's internal charge circuit, which is responsible for gradually charging the DC bus capacitors upon power-up. This failure prevents the drive from safely starting, as the charge circuit protects against high inrush currents that could damage components.

• Failure of the pre-charge resistors, contactor, or SCR (Silicon Controlled Rectifier) within the DC bus charging circuit.
• Main contactor (if present) for connecting the main power to the DC bus rectifiers is stuck open or failed to close.
• Short circuit across the DC bus capacitors, preventing them from charging or causing immediate discharge.
• Control circuit for the pre-charge mechanism has failed, inhibiting the charging sequence.
• Input AC line voltage (e.g., L1, L2, L3) is too low to initiate the charging sequence, or there's a significant voltage imbalance.

Click steps to track your progress.

1. 1

   1. Power down the drive completely (wait for DC bus discharge). Measure the incoming AC line voltage (L1-L2, L2-L3, L3-L1) at the drive's input terminals to ensure it is stable and within range.

2. 2

   2. Monitor the DC bus voltage (U1-03) during power-up. It should gradually rise to approximately 1.35 times the peak AC input voltage. If it remains at 0V or charges too slowly, suspect the charge circuit.

3. 3

   3. (For qualified personnel) Visually inspect the pre-charge resistors for signs of overheating or breakage, and check the auxiliary contacts of the main contactor (if present) for proper operation.

4. 4

   4. If the drive uses a pre-charge contactor, measure the coil voltage during power-up to ensure it is being energized. Check for continuity across its main contacts when closed.

5. 5

   5. For persistent faults, this indicates a significant internal hardware failure within the drive's power section, specifically the charging path. Drive repair or replacement is typically required.