Undervoltage 3 (Soft-Charge Bypass Circuit Fault)

What does Uv3 mean?

The soft-charge bypass circuit has failed, typically due to a damaged relay or contactor within this circuit. This failure can prevent proper charging of the DC bus, leading to the drive being unable to start or operate correctly.

• Soft-charge bypass relay or contactor failure (e.g., stuck open, coil fault, damaged contacts).
• Pre-charge resistor has an open-circuit, preventing DC bus charging.
• Control circuit failing to energize the soft-charge bypass contactor during power-up sequence.
• Damaged or severely degraded DC bus capacitors preventing them from fully charging.
• Auxiliary power supply failure to the soft-charge bypass control circuit.

Click steps to track your progress.

1. 1

   1. With power off and discharged, use an ohmmeter to check the resistance of the pre-charge resistor; it should be finite and not an open circuit.

2. 2

   2. Visually inspect the soft-charge bypass relay/contactor for signs of arcing, physical damage, or improper operation.

3. 3

   3. Check the control voltage output from the drive's internal circuit that energizes the soft-charge relay coil during the power-up sequence.

4. 4

   4. Verify the DC bus capacitors for any physical swelling, leakage, or signs of overheating, which could indicate a failure.

5. 5

   5. Confirm that the drive's internal diagnostics correctly detect the state of the soft-charge circuit components (if accessible).

6. 6

   6. If external components are functional, the internal soft-charge control circuit on the drive's power board may be faulty; replace the drive.