Understanding ABB Alarm A783: Motor Control Optimization Blocked

A guide to resolving the A783 alarm in ABB ACS880 and ACS580 drives. Learn why the drive blocks motor optimization and how to complete the ID run successfully.

ABB Drive Guide: Alarm A783

Alarm A783
Meaning: Motor control optimization blocked

The A783 alarm is a warning message typically found in ABB's all-compatible drive family (ACS880, ACS580, etc.). It indicates that the drive's internal motor control algorithm is attempting to optimize or identify motor parameters, but a specific condition is preventing it from completing the process.

Important: A783 is an alarm, not a fault. The drive will likely still run, but motor performance (torque accuracy and efficiency) may not be optimal until the optimization is completed.

Common Causes

• Pending ID Run: A motor Identification Run (ID Run) has been requested but not yet performed.
• Autophasing Required: For Permanent Magnet (PM) motors, the drive needs to determine the rotor position (autophasing) but is blocked.
• Motor is Rotating: The drive cannot perform certain optimizations if the motor is already spinning (e.g., due to a fan back-draft or a spinning load).
• Control Mode Conflict: Switching between Scalar and Vector control without re-tuning.

How to Resolve A783

1. Perform a Motor ID Run
Navigate to Parameter 99.13 (ID run requested). Select the appropriate mode (usually Normal or Standstill). Press the Start button on the control panel to begin the process. The A783 alarm should disappear once the ID Run status changes to "Done".

2. Stop the Motor Completely
Ensure the motor shaft is completely stationary before starting the optimization. If the load is causing the motor to spin (like a windmilling fan), you may need to mechanically lock the shaft or use the "Flystart" settings if applicable.

3. Check Parameter 99.04
Verify the Motor Control Mode. If you have recently changed this from Scalar to Vector, the drive requires a new optimization to map the motor characteristics.

Summary Checklist

• Is the motor data in Group 99 entered correctly?
• Is the motor safe to rotate for a few seconds?
• Are there any other active interlocks preventing the drive from starting the ID Run?