F0021 CURRENT MEASUREMENT Fault in ABB ACS550 Drive
F0021 – CURRENT MEASUREMENT in the ABB ACS550 Drive VFD indicates an internal hardware fault. The drive has detected that the current measurement signal is outside the allowable range, meaning it cannot accurately measure the output current required for motor control and protection.
This fault is typically caused by a defective IGBT module, current transformer (CT), current measurement circuit, or control board.
Possible Causes
- Internal current measurement circuit failure.
- Defective IGBT module.
- Faulty current transformer (CT).
- Damaged CT circuit.
- Failed control board.
- Internal analog measurement circuit fault.
- PCB component failure.
- Electrical surge or component damage.
Solutions
1. Check the Drive IGBT
- Test the IGBT module using a multimeter.
- Replace the power module if an IGBT short circuit or open circuit is found.
2. Check the Current Transformer (CT)
- Inspect the current transformer (CT).
- Check the CT circuit for loose connections, damaged wiring, or failed components.
3. Check the Control Board
- Replace the control card if necessary.
- After replacement, verify whether the fault has been cleared.
4. Inspect Internal Hardware
- Check the current measurement circuitry for damaged components.
- Repair or replace the drive if an internal hardware failure is confirmed.
Additional Information
The ABB ACS550 continuously monitors motor output current using internal current transformers (CTs) and current sensing electronics. If the measured current falls outside the valid operating range, the drive generates F0021 – CURRENT MEASUREMENT and prevents operation to protect the inverter and motor.
Typical causes include:
- Failed IGBT module.
- Faulty CT.
- Damaged current sensing circuit.
- Defective control board.
Because this is an internal hardware fault, parameter changes will generally not resolve the problem.
Common Symptoms
- Drive displays F0021 – CURRENT MEASUREMENT.
- Drive will not start.
- Fault appears immediately after power-up or during startup.
- Output current cannot be measured correctly.
- Drive remains in a fault condition after reset.
- Motor does not run.
Recommended Troubleshooting Sequence
- Verify that the displayed fault is F0021.
- Disconnect power and follow lockout/tagout procedures.
- Test the IGBT module using a multimeter.
- Inspect the current transformer (CT).
- Check the CT circuit for damaged wiring or loose connections.
- Inspect the control board for visible damage.
- Replace the control board if necessary.
- Repair or replace any defective hardware.
- Reset the fault.
- Confirm normal drive operation.
F0021 CURRENT MEASUREMENT Check Table
| Check Point | Action |
|---|---|
| IGBT module | Test using a multimeter |
| Current transformer (CT) | Inspect for damage |
| CT circuit | Check wiring and connections |
| Control board | Replace if faulty |
| Current measurement circuit | Inspect for internal damage |
| PCB components | Check for burned or damaged parts |
| Internal hardware | Repair or replace if required |
| Drive operation | Verify normal operation after repair |
Preventive Maintenance Tips
- Periodically inspect the drive for signs of overheating or electrical damage.
- Check power terminals and internal connections during scheduled maintenance.
- Keep the drive clean and free from dust accumulation.
- Ensure adequate cooling to prevent damage to the power module.
- Protect the drive from voltage surges and electrical disturbances.
- Inspect the IGBT module if repeated current-related faults occur.
- Record recurring F0021 faults to identify developing hardware issues.
- Follow ABB preventive maintenance recommendations for the ACS550 Drive VFD.
Proper inspection of the IGBT module, current transformer (CT), CT circuit, current measurement electronics, and control board will help diagnose and correct F0021 – CURRENT MEASUREMENT faults in ABB ACS550 drives, ensuring reliable motor current measurement and safe drive operation.
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