F30002 Fault in Siemens SINAMICS G120 Drive

F30002 DC Link Voltage Overvoltage in the Siemens SINAMICS G120 Drive indicates that the DC link (DC bus) voltage has exceeded the maximum permissible limit. The DC link stores energy between the input rectifier and the inverter. If the DC bus voltage rises above the drive's protection threshold, the drive generates Fault F30002 to protect the power semiconductors and internal components from damage.

This fault generally indicates a problem with excess regenerative energy, insufficient braking capability, high incoming supply voltage, or deceleration settings, rather than a failure of the drive hardware itself.

Possible Causes

• Excessive regenerative energy from the motor.
• Deceleration ramp time set too short.
• Heavy overhauling or high-inertia load.
• Brake resistor not connected.
• Faulty brake resistor.
• Brake chopper malfunction.
• Incoming AC supply voltage too high.
• Sudden reduction in motor load.
• Incorrect braking parameter settings.
• Regenerative energy exceeds the drive's absorption capability.
• Incorrect drive sizing for the application.
• Supply voltage fluctuations.
• Faulty DC link voltage measurement circuit.
• Loose power connections.
• Internal inverter hardware fault.

Solutions

• Cycle power to the drive and check whether the fault clears.
• Increase the motor deceleration ramp time.
• Reduce the deceleration rate to minimize regenerative energy.
• Verify the incoming AC supply voltage is within the specified range.
• Check that the brake resistor is correctly connected.
• Inspect the brake resistor for damage or open circuits.
• Verify proper operation of the brake chopper.
• Check the braking parameter settings.
• Reduce the mechanical load during deceleration if possible.
• Verify the drive is correctly sized for the application.
• Inspect power terminals for loose or damaged connections.
• Check the DC link voltage measurement circuit if hardware faults are suspected.
• Replace defective braking components if necessary.
• Contact Siemens technical support if the fault persists after inspection.

Additional Information

The DC link is an internal energy storage circuit that supplies stable DC voltage to the inverter section of the drive.

During motor deceleration or when an overhauling load drives the motor, the motor acts as a generator, returning energy to the DC link. If this regenerative energy cannot be safely dissipated or returned to the power supply, the DC link voltage increases.

When the voltage exceeds the allowable protection level, the drive generates Fault F30002 to prevent damage to components such as:

• IGBTs
• DC link capacitors
• Brake chopper circuitry
• Power electronics

Common reasons for this fault include:

• Very short deceleration ramps.
• High-inertia loads.
• Missing or faulty brake resistor.
• Brake chopper failure.
• Excessively high mains voltage.

Unlike an undervoltage fault, F30002 specifically indicates that the DC bus voltage has become too high, typically because regenerative energy cannot be absorbed effectively.

Common Symptoms

• Drive trips with Fault F30002.
• Fault occurs during rapid deceleration.
• Motor stops unexpectedly.
• Drive trips when lowering heavy loads.
• Fault appears during regenerative operation.
• Frequent trips during high-speed stopping.
• Brake resistor remains inactive or overheats.
• High DC bus voltage displayed on diagnostics.
• Fault clears after power reset but reoccurs during braking.
• Production process is interrupted.

Recommended Troubleshooting Sequence

1. Cycle power to the drive.
2. Verify the incoming AC supply voltage.
3. Increase the deceleration ramp time.
4. Check the braking parameter settings.
5. Inspect the brake resistor.
6. Verify brake resistor wiring.
7. Check brake chopper operation.
8. Inspect the mechanical load and inertia.
9. Verify correct drive sizing.
10. Inspect power cable connections.
11. Check the DC link voltage measurement circuit.
12. Replace faulty braking components if required.
13. Test the drive under normal operating conditions.
14. Monitor the DC link voltage during deceleration.
15. Contact Siemens technical support if the fault persists.

DC Link Overvoltage Check Table

Check Point	Action
Power cycle	Restart the drive
AC supply voltage	Verify within specification
Deceleration ramp	Increase ramp time if necessary
Braking parameters	Verify configuration
Brake resistor	Inspect for proper connection and condition
Brake resistor wiring	Check for loose or damaged connections
Brake chopper	Verify correct operation
Mechanical load	Reduce regenerative energy if possible
Drive sizing	Confirm suitability for the application
Power terminals	Inspect for secure connections
DC link voltage	Monitor during deceleration
Siemens technical support	Contact if the fault remains after inspection

Preventive Maintenance Tips

• Configure deceleration ramps appropriate for the load inertia.
• Install a correctly rated brake resistor for regenerative applications.
• Periodically inspect the brake resistor and brake chopper.
• Verify incoming supply voltage remains within Siemens specifications.
• Inspect power terminals and cable connections during scheduled maintenance.
• Monitor DC link voltage trends using drive diagnostics.
• Ensure the drive is properly sized for the application.
• Minimize unnecessary rapid stopping of high-inertia loads.
• Replace worn or damaged braking components promptly.
• Record recurring overvoltage faults to assist long-term diagnostics.

Proper adjustment of the deceleration ramp, routine inspection of the brake resistor, brake chopper, and power connections, verification of the incoming supply voltage, and ensuring the drive is correctly sized for the application will help prevent recurring F30002 DC Link Voltage Overvoltage faults in Siemens SINAMICS G120 drives, ensuring reliable braking performance, effective control of regenerative energy, and dependable long-term operation of the drive system.