Yaskawa Sigma-7 A.d00 after rewiring, motor jerks: what to check?
I'm getting an A.d00 alarm on my Yaskawa Sigma-7 SERVOPACK. It happens on the first move after I rewired the motor, and the motor jerks briefly before the alarm. What should I check first?
The Yaskawa Sigma-7 SERVOPACK alarm A.d00, Position Deviation Overflow, indicates that the position deviation (following error) has exceeded the Pn520 setting. This often occurs during acceleration when the motor cannot follow the position reference, or if the axis is blocked. Given the symptoms, incorrect motor wiring is a strong possibility.
Likely causes and checks
1Servomotor U, V, W wiring incorrect or loose
- Points to it
- Incorrect or loose wiring of the servomotor's main circuit cables or encoder can cause the motor to jerk or run away, leading to a large position deviation that triggers the A.d00 alarm, especially after a rewire.
- Check
- Inspect the wiring of the Servomotor Main Circuit Cables and the encoder for any faulty contacts or incorrect connections.
2Position reference acceleration too high
- Points to it
- If the position reference demands an acceleration that the motor cannot physically achieve, the position deviation will rapidly increase, causing the A.d00 alarm during the acceleration ramp.
- Check
- Reduce the reference acceleration in your control system, or consider smoothing the acceleration profile using the position reference filter (ACCFIL) in the MECHATROLINK command.
3Position reference speed too fast
- Points to it
- When the commanded speed is too high for the motor to follow, especially at its maximum capabilities, the position deviation can exceed the Pn520 limit, triggering the A.d00 alarm.
- Check
- Reduce the reference speed and re-test the operation. Also, review and reconsider the electronic gear ratio settings if applicable.
4Pn520 (Position Deviation Overflow Alarm Level) set too low
- Points to it
- The Pn520 parameter defines the threshold for the A.d00 alarm. If this value is set too low for the normal operating conditions, even healthy motion with acceptable deviation can trigger the alarm.
- Check
- Compare your current Pn520 setting with the recommended value calculated using Yaskawa's formula: maximum speed/60 × encoder resolution/(Pn102/10) × Pn210/Pn20E × (1.2 to 2). Adjust Pn520 if it is significantly lower than recommended for your application.
Next check: Given that the fault occurred after a rewire and the motor jerks, the most critical next step is to thoroughly check the Servomotor Main Circuit Cables and encoder wiring for any incorrect connections or loose contacts.
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