What is a servo press?

A servo press uses servo motors for precise force and position control during forming operations.

How do I calculate servo press tonnage?

Use our free tonnage calculator at servopress.club/tonnage-calculator.html

ABB ACS880 Drive on Servo Press: 7081 and 7082 Thermal Fault Diagnosis

admin

ABB ACS880 drives are increasingly used on servo press retrofits and new installations. The 7081 and 7082 fault codes relate to motor thermal protection.

## Fault 7081: Motor Overtemperature (Estimated)

The ACS880 uses a thermal model to estimate motor temperature. Fault 7081 triggers when the estimated temperature exceeds the motor thermal limit.

This is a model-based fault - the drive does not have a direct temperature measurement, it calculates temperature based on current history and the motor thermal time constant (parameter 35.50).

Common causes in press applications:
- Running above rated continuous SPM for extended periods
- Thermal time constant (35.50) set incorrectly for the actual motor
- Ambient temperature higher than the 40C design point
- Motor cooling fan failed or blocked

Fix:
1. Check parameter 35.50 (motor thermal time constant): should match the motor datasheet value
2. Check parameter 35.51 (motor load curve): verify the curve matches the motor nameplate
3. If the motor has a PTC thermistor, connect it to the drive and use direct temperature measurement instead of the model
4. Reduce SPM or add a duty cycle (run 45 minutes, rest 15 minutes)

## Fault 7082: Motor Overtemperature (Measured)

This fault uses a direct temperature measurement from a PTC thermistor or PT100 sensor in the motor winding.

If you get 7082, the motor is actually hot - do not reset and continue.

Diagnosis:
1. Let the motor cool for 30 minutes
2. Check motor cooling: is the fan running? Are the fins clean?
3. Check the duty cycle: what is the actual SPM and forming load?
4. Check the thermistor connection: a broken thermistor wire reads as maximum resistance, which the drive interprets as overtemperature

## ACS880 Data Logger for Press Diagnostics

The ACS880 has a built-in data logger accessible via ABB Drive Composer software. For press fault diagnosis, configure the logger to capture:
- Motor current (01.06)
- Motor torque (01.10)
- Motor temperature (35.01)
- DC bus voltage (01.11)

Log at 1ms intervals for 10 seconds triggered on the fault. This gives you the complete picture of what happened before the fault.

## ACS880 Parameter Backup Before Maintenance

Always back up parameters before any maintenance that might reset the drive:
1. Connect Drive Composer
2. File > Backup > Save to PC
3. Store the backup file with the press serial number and date

Restoring a parameter backup after a drive replacement takes 10 minutes and avoids re-commissioning from scratch.

anna_controls

7081 is estimated motor temperature (calculated from current and thermal model). 7082 is measured motor temperature (from PTC or PT100 sensor). If you get 7081 but not 7082, the thermal model parameters are wrong —update motor thermal time constant in parameter 06.15. If you get 7082, the motor is actually hot and you have a real cooling problem.

raj_maintenance

We had recurring 7081 faults on a retrofit press. Turned out the motor nameplate data entered in the drive was wrong —someone entered the old motor's parameters instead of the new one. The thermal model was calculating based on a smaller motor and tripping early. Took us 3 weeks to figure out. Always double-check motor parameters after a retrofit.

mike_chen_eng

The wrong motor data story is painfully common on retrofits. We had a similar one - but our issue was subtler. The ACS880 thermal model uses parameter 06.15 (motor thermal time constant) which defaults to something like 150s. Our servo motor had a much shorter thermal time constant (~45s) because it was a compact high-torque design with less thermal mass. So the drive was UNDER-protecting the motor - it thought the motor could handle sustained current longer than it actually could. We only caught it when the PT100 sensor (7082) started tripping but the estimated temp (7081) was still showing safe. If you're commissioning an ACS880 on a servo press, my checklist: 1) Enter exact motor nameplate data including stall current and thermal time constant from the motor datasheet, not the generic defaults. 2) If the motor has a PT100/PTC sensor, wire it and enable 7082 - don't rely solely on the thermal model. 3) Run a thermal test: hold 80% rated torque at zero speed for the motor's rated stall time and compare drive estimated temp vs actual sensor temp. They should track within 10%. If they diverge, your model parameters are wrong.