A491 External Temperature Alarm/Warning in ABB ACS560 Drive VFD
A491 External Temperature Alarm/Warning in the ABB ACS560 Drive indicates that the measured external temperature (Temperature 1 or Temperature 2) has exceeded the configured warning limit. The drive continuously monitors external temperature sensors, and when the measured temperature rises above the warning threshold, it generates Alarm A491 to alert the operator before a temperature fault occurs.
This is a warning, not a trip fault. The drive can normally continue operating, but corrective action should be taken to prevent the temperature from reaching the fault limit.
Possible Causes
- Measured Temperature 1 exceeds the warning limit.
- Measured Temperature 2 exceeds the warning limit.
- Motor overheating.
- Insufficient motor cooling.
- Cooling fan failure.
- High ambient temperature.
- Excessive mechanical load.
- Blocked ventilation passages.
- Faulty external temperature sensor.
- Loose or damaged temperature sensor wiring.
- Warning limits configured too low.
Solutions
-
Check the values of the following parameters:
- 35.02 – Measured Temperature 1
- 35.03 – Measured Temperature 2
- Check the cooling of the motor (or other equipment whose temperature is being measured).
- Check the warning limits for Measured Temperatures 1 and 2 in Parameter Group 35 – Motor Thermal Protection.
- Inspect the external temperature sensors and their wiring.
- Verify that the motor cooling fan and ventilation are operating correctly.
- Reduce the motor load if overheating is caused by excessive load.
- Allow the equipment to cool if necessary.
Additional Information
The ABB ACS560 supports monitoring of two external temperature inputs that can be used to supervise the temperature of the motor, bearings, gearbox, or other equipment.
Alarm A491 is generated when either Measured Temperature 1 or Measured Temperature 2 exceeds the configured warning limit, providing an early indication of overheating before a protective trip occurs.
According to ABB, the recommended corrective actions are to:
- Check Parameter 35.02 – Measured Temperature 1.
- Check Parameter 35.03 – Measured Temperature 2.
- Verify the cooling of the monitored equipment.
- Check the warning limits in Parameter Group 35 – Motor Thermal Protection.
Unlike 4981 External Temperature 1 Fault, which stops the drive when the fault limit is exceeded, A491 is an early warning that allows corrective action before a shutdown becomes necessary.
Common Symptoms
- Drive displays A491 External Temperature Alarm/Warning.
- Motor or monitored equipment becomes warmer than normal.
- Drive continues operating.
- High temperature values are shown in Parameters 35.02 or 35.03.
- Cooling fan may run continuously.
- Reduced thermal margin during heavy load operation.
- Warning may disappear after the equipment cools.
- Repeated warnings during periods of high ambient temperature.
- Possible progression to an external temperature fault if ignored.
- Increased equipment temperature without an immediate drive trip.
Recommended Troubleshooting Sequence
- Verify that the alarm is A491 External Temperature Alarm/Warning.
- Check Parameter 35.02 – Measured Temperature 1.
- Check Parameter 35.03 – Measured Temperature 2.
- Inspect the motor or monitored equipment for overheating.
- Verify proper operation of cooling fans and ventilation.
- Check the external temperature sensors and wiring.
- Review the warning limits in Parameter Group 35 – Motor Thermal Protection.
- Reduce the mechanical load if necessary.
- Allow the equipment to cool.
- Continue monitoring the temperature to ensure it remains within acceptable limits.
A491 External Temperature Alarm Check Table
| Check Point | Action |
|---|---|
| Parameter 35.02 | Check Measured Temperature 1 |
| Parameter 35.03 | Check Measured Temperature 2 |
| Motor cooling | Verify airflow and fan operation |
| Monitored equipment | Inspect for overheating |
| Temperature sensors | Check sensor condition and wiring |
| Parameter Group 35 | Verify warning limits |
| Mechanical load | Reduce if excessive |
| Ambient temperature | Ensure installation is within specification |
| Drive operation | Monitor temperatures after corrective action |
Preventive Maintenance Tips
- Regularly monitor Parameters 35.02 and 35.03.
- Inspect cooling fans and ventilation systems during scheduled maintenance.
- Keep motors and monitored equipment free of dust and debris.
- Verify the accuracy of external temperature sensors.
- Inspect sensor wiring and terminal connections periodically.
- Avoid continuous operation above the equipment's rated load.
- Ensure adequate airflow around the motor and connected equipment.
- Review the warning limits in Parameter Group 35 after commissioning or process changes.
- Record recurring A491 warnings to identify developing cooling problems.
- Follow ABB preventive maintenance recommendations for the ACS560 drive and the monitored equipment.
Proper monitoring of Parameters 35.02 – Measured Temperature 1, 35.03 – Measured Temperature 2, Parameter Group 35 – Motor Thermal Protection, external temperature sensors, and equipment cooling will help prevent recurring A491 External Temperature Alarm/Warning conditions in ABB ACS560 drives, ensuring reliable thermal monitoring, early detection of overheating, and long-term system reliability.
Comments
Post a Comment