What causes Yaskawa Σ-7 (Sigma-7) SERVOPACK alarm A.720?

1. Duty cycle beyond the motor overload characteristics: Compare effective (RMS) torque over the cycle with the motor rating and overload characteristics; reconsider the operating conditions or increase motor capacity. 2. Mechanical friction or binding: Compare the operation reference and motor speed, then check lubrication, alignment and the shaft load against the allowable value. 3. Holding load at standstill (vertical axis, counterbalance problem): Check the holding torque at standstill and the counterbalance or brake arrangement. 4. Wiring or parameter fault (U/V/W, encoder, Pn282, Pn080): Check the motor and encoder wiring and the settings of Pn282 and Pn080 = n.□□X□. 5. SERVOPACK failure: Yaskawa’s listed action is to replace the SERVOPACK.

Yaskawa Sigma-7 A.720: Continuous Overload Causes

Technical review pending. This guide is based on the cited manufacturer documentation; check it against the manual for your exact model and firmware before acting.

Alarm A.720 on a Yaskawa Σ-7 SERVOPACK is Continuous Overload: the servomotor was operating continuously under a torque that exceeded the rating. It is a Gr.1 alarm and can be reset once the cause is removed and the motor has cooled.

Diagnose this with AI

Upload a keypad photo, the fault history or a parameter export from your Yaskawa Σ-7 (Sigma-7) SERVOPACK. InduQT compares the evidence and suggests the next useful checks.

Try Free Servo Diagnostic

When it happens

At constant speed with high friction or a heavy process load
At standstill while holding a vertical or out-of-balance load against gravity
Late in a shift or after a cycle-time change, as heat builds up

Likely causes and checks

1Duty cycle beyond the motor overload characteristics

Points to it: Alarm appears after running for a while; A.910 warnings before it; worse in hot ambient.
Check: Compare effective (RMS) torque over the cycle with the motor rating and overload characteristics; reconsider the operating conditions or increase motor capacity.

2Mechanical friction or binding

Points to it: Torque at constant speed has crept up over weeks; dry ways or a failing bearing.
Check: Compare the operation reference and motor speed, then check lubrication, alignment and the shaft load against the allowable value.

3Holding load at standstill (vertical axis, counterbalance problem)

Points to it: Alarm while the axis sits still in servo-lock.
Check: Check the holding torque at standstill and the counterbalance or brake arrangement.

4Wiring or parameter fault (U/V/W, encoder, Pn282, Pn080)

Points to it: After commissioning or a motor change.
Check: Check the motor and encoder wiring and the settings of Pn282 and Pn080 = n.□□X□.

5SERVOPACK failure

Points to it: Load, wiring and settings check out.
Check: Yaskawa’s listed action is to replace the SERVOPACK.

Telling it apart

A.720 builds up over time at moderate overload; A.710 trips quickly at very high torque. A sudden A.720 with no change in the process is often friction or a brake that is dragging.
An A.720 at standstill with the motor warm points to holding torque, not to motion.

Evidence to collect

Alarm history including A.910 warnings and their timing
Torque trend over a full cycle
Ambient temperature near the motor
Lubrication and maintenance records
Whether the axis is vertical or counterbalanced

Work on fuel trains, burners, pressure vessels and electrical equipment must be done by qualified personnel following the manufacturer’s documentation and local codes. Never bypass a safety device or interlock.

Yaskawa Σ-7 (Sigma-7) SERVOPACK alarm A.720: Continuous Overload