Yaskawa Σ-7 (Sigma-7) SERVOPACK alarm A.710: Instantaneous Overload
Alarm A.710 on a Yaskawa Σ-7 SERVOPACK is Instantaneous Overload: the servomotor was operating for several seconds to several tens of seconds under a torque that largely exceeded the rating. It is a Gr.2 alarm and can be reset once the cause is removed.
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When it happens
- During acceleration or deceleration of a high-inertia load
- When the axis jams, hits a hard stop or drags against a brake
- Right after servo ON if the motor wiring or phase order is wrong (the motor cannot produce useful torque)
Likely causes and checks
1Motor or encoder wiring wrong or a poor connection
- Points to it
- Alarm soon after a motor or cable change; motor growls or moves erratically.
- Check
- Check that the Servomotor power wiring (U, V, W) and encoder are correctly wired and the connections are tight.
2Mechanical problem: the load cannot be driven (jam, brake not released, binding)
- Points to it
- Motor speed does not follow the reference; current is high at low speed.
- Check
- Compare the operation reference with the actual motor speed, then turn the mechanism by hand with power isolated and the brake released.
3Operation beyond the overload protection characteristics
- Points to it
- Alarm appears on the heaviest move or after a cycle-time reduction.
- Check
- Compare the run command (accel/decel and peak torque) with the motor overload characteristics; reconsider the load and operating conditions or use a larger motor.
4Load on the motor shaft above the allowable value
- Points to it
- Belt over-tensioned, misaligned coupling or side load on the shaft.
- Check
- Check the machine for loads on the motor shaft above the allowable value and correct the mechanism.
5Wrong Pn282 (linear encoder scale pitch) or Pn080 phase sequence setting
- Points to it
- Linear motor or newly commissioned axis.
- Check
- Check Pn282 and Pn080 = n.□□X□ against the motor and encoder.
Telling it apart
- A.710 is short-time, very high torque (seconds to tens of seconds); A.720 is torque somewhat above the rating held continuously. A.710 points to jams, collisions and aggressive moves; A.720 to a duty cycle or friction problem.
- Warning A.910 is output before A.710 or A.720. If you see A.910 in the history, the overload built up over time rather than from a single jam.
- If the motor turns poorly from the first move after a rewire, check the phase order before blaming the load.
Evidence to collect
- Alarm history including any A.910 warnings
- Torque and speed trend (SigmaWin+ trace) for the move that tripped
- Motor model and load inertia
- Brake release confirmation
- Recent mechanical or wiring work
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