Applicable Systems
Street Crane Overhead Crane
Symptoms
The Street Crane system displays alarm ST005, indicating a variable frequency drive fault. The VFD controlling the hoist or travel motor has reported an internal fault, stopping the motor.
Possible Causes
- VFD has detected an output phase-to-phase short or ground fault in the motor cable or the motor winding
- VFD DC bus voltage is too high due to regenerative braking energy not being dissipated by the braking resistor
- VFD internal IGBT module has failed or the control board has a communication error with the power stage
Troubleshooting Steps
- Step 1: Check the VFD fault code on the drive display and cross-reference the manual
Fault code is identified and the root cause is understood from the drive manual fault code table - Step 2: Inspect the motor cable and motor winding insulation with a megohmmeter at 500V
Insulation resistance is above 100 megohms, confirming no phase-to-phase or ground fault - Step 3: Verify the braking resistor continuity and the VFD DC bus voltage during deceleration
Resistor is continuous and the DC bus voltage stays below the overvoltage trip threshold during braking
How to Reset
To reset: 1) Repair the motor cable or winding. 2. Replace the braking resistor. 3. Replace the VFD if the IGBT is failed. 4. Power cycle and press RESET. 5. Verify the motor runs without VFD faults.
Source: Street Crane Manual, Street Crane Company Limited
Category: Crane