Yaskawa Sigma-7 A.710 after motor change, motor growls: what to check?
I just replaced a servomotor on my Yaskawa Sigma-7 SERVOPACK, and now it's throwing an A.710 alarm. The motor growls and moves erratically right after servo ON. What should I check first?
Alarm A.710 on a Yaskawa Sigma-7 SERVOPACK indicates an instantaneous overload, meaning the servomotor operated under a torque significantly exceeding its rating for a short period. This is a Gr.2 alarm and can be reset once the underlying cause is resolved. Given the symptoms of a recent motor change and erratic motor behavior, the issue likely points to incorrect motor or encoder wiring.
Likely causes and checks
1Motor or encoder wiring wrong or a poor connection
- Points to it
- The servomotor power wiring (U, V, W) or encoder connection is incorrect or loose, preventing the motor from producing useful torque. This often occurs after a motor or cable change and manifests as the motor growling or moving erratically.
- Check
- Verify that the Servomotor power wiring (U, V, W) and encoder are correctly wired according to the manual and that all connections are tight.
2Mechanical problem: the load cannot be driven
- Points to it
- The machine mechanism is jammed, a brake is not released, or there is binding, preventing the motor from moving the load as commanded. This results in high current at low speed and the motor not following its reference.
- Check
- Compare the operation reference with the actual motor speed. Then, with power isolated and the brake released, attempt to turn the mechanism by hand to check for jams or binding.
3Operation beyond the overload protection characteristics
- Points to it
- The commanded acceleration, deceleration, or peak torque exceeds the motor's overload protection limits. This can happen during the heaviest moves or after a reduction in cycle time.
- Check
- Compare the run command (acceleration/deceleration and peak torque) with the motor's overload characteristics. Reconsider the load and operating conditions, or consider using a larger motor if the current operating conditions are necessary.
4Load on the motor shaft above the allowable value
- Points to it
- External factors like an over-tensioned belt, a misaligned coupling, or a side load on the motor shaft are imposing excessive stress on the motor.
- Check
- Inspect the machine for any loads on the motor shaft that exceed the allowable value, such as belt tension or coupling alignment, and correct the mechanism as needed.
Next check: Given that the alarm appeared right after a motor change and the motor growls and moves erratically, the first step should be to meticulously check the Servomotor power wiring (U, V, W) and the encoder connections for correctness and tightness.
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