What causes Yaskawa Σ-7 (Sigma-7) SERVOPACK alarm A.810?

1. First power-up of the absolute encoder: Confirm it is the first power-up and set up (reset) the absolute encoder with Fn008. 2. Encoder Cable disconnected and reconnected: Check the encoder connection and set up the encoder. 3. No power from either the SERVOPACK (+5 V) or the battery: Check the battery and the connector status; replace the battery with control power ON, then set up the encoder. 4. Absolute encoder failure: Set up the encoder again; if the alarm still occurs, replace the Servomotor. 5. SERVOPACK failure: Yaskawa’s listed action is to replace the SERVOPACK.

Yaskawa Sigma-7 A.810: Encoder Backup Alarm

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.810 on a Yaskawa Σ-7 SERVOPACK is Encoder Backup Alarm: the power supplies to the absolute encoder all failed and the position data was lost. It cannot be reset; the encoder must be set up again (and the machine re-referenced) after the cause is fixed.

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When it happens

At power-up, the first time an absolute encoder is powered
At power-up after the Encoder Cable was disconnected, or the battery removed, while control power was off
At power-up after a long shutdown with a flat battery

Likely causes and checks

1First power-up of the absolute encoder

Points to it: New motor or new machine.
Check: Confirm it is the first power-up and set up (reset) the absolute encoder with Fn008.

2Encoder Cable disconnected and reconnected

Points to it: Motor or cable was changed, or the connector was opened during maintenance.
Check: Check the encoder connection and set up the encoder.

3No power from either the SERVOPACK (+5 V) or the battery

Points to it: Battery old or missing; A.830 or A.930 seen before.
Check: Check the battery and the connector status; replace the battery with control power ON, then set up the encoder.

4Absolute encoder failure

Points to it: Alarm returns after a correct setup with a good battery.
Check: Set up the encoder again; if the alarm still occurs, replace the Servomotor.

5SERVOPACK failure

Points to it: Encoder and battery check good.
Check: Yaskawa’s listed action is to replace the SERVOPACK.

Telling it apart

A.830 (Encoder Battery Alarm) and warning A.930 mean the battery voltage is low (about 2.7 V or less) but the position is still held; A.810 means the backup was lost and position data is gone.
Yaskawa warns that removing the battery or disconnecting the Encoder Cable while SERVOPACK control power is OFF loses the absolute data. Change batteries with only control power ON.
After an A.810 the machine position must be re-established; do not run automatic cycles until the axis is referenced again.

Relevant parameters

Parameter	Name	Why it matters
Pn008	Low Battery Voltage Alarm/Warning Selection	n.□□□0 (default) gives alarm A.830 at power-up; n.□□□1 gives warning A.930 and monitors continuously.

Evidence to collect

Alarm history showing A.810 and any earlier A.830/A.930
Battery voltage measured with a meter
What maintenance was done while power was off
Battery location (host controller or encoder cable battery case)

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.810: Encoder Backup Alarm