Yaskawa Σ-7 (Sigma-7) SERVOPACK alarm A.100: Overcurrent Detected
Alarm A.100 on a Yaskawa Σ-7 SERVOPACK is Overcurrent Detected: an overcurrent flowed through the power transistor or the heat sink overheated. It is a Gr.1 alarm and cannot be cleared with an alarm reset.
Diagnose this with AI
Try Free Servo Diagnostic 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.
When it happens
- Immediately at servo ON (short or ground fault in cable, motor or SERVOPACK)
- During heavy acceleration or deceleration
- With a heavy load at standstill or very low speed
Likely causes and checks
1Main circuit cable miswired, loose, short-circuited or ground-faulted
- Points to it
- Trips the instant servo turns ON, even unloaded.
- Check
- With power isolated and the bus discharged, check the wiring, then check for shorts between U, V, W and between each phase and ground on the cable.
2Short circuit or ground fault inside the Servomotor
- Points to it
- Cable tests good; coolant ingress at the motor.
- Check
- Test U, V, W phase-to-phase and phase-to-ground at the motor with it disconnected from the SERVOPACK; replace the motor if faulty.
3Short circuit or ground fault inside the SERVOPACK
- Points to it
- Alarm with the motor disconnected.
- Check
- Check for shorts across the SERVOPACK U, V, W terminals and to ground; replace the SERVOPACK if faulty.
4Regenerative resistor wiring, capacity or resistance problem
- Points to it
- Trips on deceleration of large loads.
- Check
- Check the regenerative resistor wiring and the regenerative load ratio in SigmaWin+; use a resistance not below the SERVOPACK minimum allowable value.
5Frequent dynamic brake stops (A.730/A.731 history)
- Points to it
- Repeated emergency stops with the dynamic brake.
- Check
- Check how often the DB is used and whether A.730 or A.731 occurred.
6Heavy load at standstill or low speed, or noise
- Points to it
- Trips while holding or crawling; or random trips with poor FG wiring.
- Check
- Compare the operating conditions with the specifications; improve FG wiring (FG wire size equal to the main circuit wire size).
Telling it apart
- A.100 covers the power transistor and heat sink; A.101 means motor current exceeded the allowable current. The cable, motor and SERVOPACK short checks are the same for both.
- Trip at servo ON points to a short or ground fault; trip only on large moves points to regeneration, load or the dynamic brake.
Evidence to collect
- Alarm history and the moment of the trip
- Insulation test results for motor and cable (motor disconnected)
- Regenerative load ratio from SigmaWin+
- Whether A.730/A.731 occurred
- FG wiring and cable routing
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