Cause : Overcurrent comes when the power unit has detected an overcurrent condition. If you're experiencing an overcurrent fault with a Siemens SINAMICS G120 drive, it indicates that the current flowing through the motor exceeds the permissible limit set by the drive's protection settings.

- closed-loop control is incorrectly parameterized.
- motor has a short-circuit or fault to ground (frame).
- U/f operation: Up ramp set too low.
- U/f operation: rated current of motor much greater than that of power unit.
- High discharge and post-charging current for line supply voltage interruptions.
- High post-charging currents for overload when motoring and DC link voltage dip.
- Short-circuit currents at power-on due to the missing line reactor.
- power cables are not correctly connected.
- power cables exceed the maximum permissible length.
- power unit defective.
- line phase interrupted.

Fault value (r0949, interpret bitwise binary):
Bit 0: Phase U.
Bit 1: Phase V.
Bit 2: Phase W.
Bit 3: Overcurrent in the DC link.

Solutions :

- check the motor data - if required, carry out commissioning.
- check the motor circuit configuration (star/delta).
- U/f operation: Increase up ramp.
- U/f operation: Check assignment of rated currents of motor and power unit.
- check the line supply quality.
- Reduce motor load.
- Correct connection of line reactor.
- check the power cable connections.
- check the power cables for short-circuit or ground fault.
- check the length of the power cables.
- replace power unit.
- check the line supply phases.

Here's how to address this issue:

1. Identify the Cause: Determine the reason for the overcurrent fault. Common causes include:

   • Mechanical overload on the motor shaft.
   • Electrical issues such as short circuits, phase imbalances, or ground faults.
   • Excessive acceleration or deceleration rates.
   • Incorrect motor parameters or configuration settings in the drive.
   • Motor bearing failure or mechanical binding.

2. Inspect Motor and Mechanical System: Check the motor and associated mechanical components for any signs of damage, wear, or obstruction. Ensure that the load on the motor is within its rated capacity and that there are no mechanical issues causing excessive resistance or friction.

3. Review Drive Parameters: Verify the motor parameters and configuration settings in the SINAMICS G120 drive. Pay attention to parameters related to current limits, acceleration/deceleration rates, and protection settings. Adjust these parameters if necessary to ensure they align with the motor specifications and application requirements.

4. Check Power Supply and Wiring: Examine the power supply voltage and wiring connections to the drive and motor. Ensure that the voltage levels are within the acceptable range and that all connections are secure and properly tightened. Look for any signs of loose connections, damaged cables, or overheating.

5. Monitor Current Levels: Use the diagnostic tools provided by the SINAMICS G120 drive to monitor the current levels during operation. Analyze the current waveform and trends to identify any irregularities or spikes that could indicate an underlying issue.

6. Implement Protective Measures: Consider implementing additional protective measures such as current-limiting devices, surge suppressors, or soft-starters to mitigate the risk of overcurrent faults and protect the motor and drive system.

7. Perform Test Runs: Conduct test runs with the motor and drive system under different operating conditions to verify that the overcurrent issue has been resolved. Monitor the system closely for any recurring faults or abnormalities.