What the A.100 alarm means

An overcurrent flowed through the IGBT power stage or the SERVOPACK heat sink overheated; the servo pack cuts motor power to protect itself. On YRC1000/DX200 this surfaces as a major servo alarm for the affected axis. This is a routine repair in our workshop for Yaskawa DX100 / DX200 / YRC1000 systems, and we normally pin it down during the first site check.

Most common causes

  • Short circuit or ground fault in the motor power cable (U/V/W)
  • Motor winding short to ground
  • Damaged SERVOPACK power stage (IGBT failure)
  • Ambient temperature above 55 degC or clogged cabinet cooling
  • Excessive load inertia or repeated hard acceleration
Field note: Begin with the first item in the list; it has a far higher on-machine occurrence rate than the others.

Step-by-step field fix

  1. Power off, discharge the DC bus, then measure motor cable phases U/V/W to ground for a short
  2. Disconnect the motor and power up the SERVOPACK alone — if A.100 returns with no motor, the power stage is dead
  3. Check cabinet cooling: fans, filters, ambient temperature
  4. Review the application duty cycle; soften acceleration if inertia is high
  5. Replace the SERVOPACK and re-verify with a test jog; back up CMOS.BIN before any board swap
Safety first: For YASKAWA a-100, this alarm family involves the DC bus, which sits at several hundred volts and stays charged for minutes after power-off - touching terminals is a shock hazard. On site you may not carry out the first step yourself: Power off, discharge the DC bus, then measure motor cable phases U/V/W to ground for a short. Beyond that it is the DC bus and power stage work - leave it to a professional. On YASKAWA a-100: checking incoming voltage at the disconnect and looking at breakers and fuses is fine to do yourself; opening the cabinet to touch bus terminals or pulling power modules needs a qualified electrician.

How we diagnose drive alarms on site

YASKAWA a-100 belongs to the drive & power stage family. On YASKAWA a-100 the failing stage is Yaskawa Sigma-series servo drives (servo packs) assigned per axis in the cabinet on the DX100 / DX200 / YRC1000 / YRC1000micro - the fault sits on the energy chain: mains input, rectification, DC bus, braking resistor, inverter power devices and the drive board. We start reading YASKAWA a-100 at the pendant alarm list (A / E / 4xxx segments) together with the servo drive's digit display.

The chain involved in YASKAWA a-100 runs: three-phase mains -> rectifier -> DC bus (bus capacitors) -> brake chopper / braking resistor -> inverter (IGBT) -> motor.

Short circuit or ground fault in the motor power cable (U/V/W) is common on YASKAWA a-100, but look at the duty cycle: Cells with high-inertia loads or frequent start-stop cycles return far more regenerative energy than a plain transfer cell, and the braking resistor lives in a hot cycle that shortens its life. When we suspect this family we ask what changed: if the takt was raised recently or a heavier fixture went on, the alarm cluster usually lines up with that process change. Replacing the resistor alone will not fix it - the chopper rating and resistor wattage have to be re-checked against the new duty.

Field notes on this page cover YASKAWA a-100 (Overcurrent or Heat Sink Overheated (SERVOPACK)); written by the Henghuan repair team, updated 2026-10-01.

Stalled on the diagnosis? Let an engineer help remotely

Share the alarm code, machine model and the operating condition at the moment of the alarm. Our engineers are highly experienced with YASKAWA a-100, and remote diagnosis (phone/video) is completely free.

Get a Free Remote Diagnosis See Repair Services

Hotline: +86-20-39029800 · WhatsApp: +86-188-1886-2860

Related Drive & Power Stage alarms

A.320 — Regenerative Overload A.400 — Overvoltage — Main Circuit DC Voltage Too High A.410 — Undervoltage — Main Circuit DC Voltage Too Low A.710 — Overload — High Load (Stall-level Torque) A.720 — Overload — Low Load (Continuous Over-torque) A.7A0 — Heat Sink Overheated (>100 degC)
Same family: this code belongs to the Drive & power stage alarms family - the page collects all Drive & power stage-family codes we have handled, with the common inspection order and spares.
Other brands: we also keep field-fix libraries for Universal Robots · Kawasaki · Staubli and more — see the complete alarm code hub.

Frequently asked questions

QWhat does the YASKAWA a-100 alarm mean?

An overcurrent flowed through the IGBT power stage or the SERVOPACK heat sink overheated; the servo pack cuts motor power to protect itself. On YRC1000/DX200 this surfaces as a major servo alarm for the affected axis. This is a routine repair in our workshop for Yaskawa DX100 / DX200 / YRC1000 systems, and we normally pin it down during the first site check. YASKAWA a-100 sits in the drive & power stage family; on our work orders the highest-frequency trigger for this code is "Short circuit or ground fault in the motor power cable (U/V/W)".

QCan I clear a YASKAWA a-100 alarm myself?

Whether YASKAWA a-100 clears on its own depends on the outcome of "Power off, discharge the DC bus, then measure motor cable phases U/V/W to ground for a short". Finish the flow with "Replace the SERVOPACK and re-verify with a test jog; back up CMOS.BIN before any board swap" to confirm YASKAWA a-100 - do not skip it. If that step is clean, the second most frequent cause on YASKAWA a-100 is "Motor winding short to ground". After clearing YASKAWA a-100, watch it for one shift. A second trip means stop and let an engineer arrive with the right test gear for the DC bus and power stage.

QFor drive/power alarms like YASKAWA a-100, what spares do you bring on site?

The commonest causes we see on YASKAWA a-100 are "Short circuit or ground fault in the motor power cable (U/V/W), Motor winding short to ground, Damaged SERVOPACK power stage (IGBT failure)", so we stock the van against those. For YASKAWA a-100 specifically, we stock the van along the energy chain: braking resistors, bus capacitors, input fuses, drive-board supply parts and the common power modules for the brand. For YASKAWA a-100, drive alarms usually stop the whole line, so they sit at the front of our dispatch queue. Before we roll, tell us what YASKAWA a-100 shows on the pendant alarm list (A / E / 4xxx segments) together with the servo drive's digit display and what the machine was doing - phone or video triage is free.

This page on YASKAWA a-100 is based on the field experience of the Henghuan Robotics repair team. Alarm explanations are our own summary for troubleshooting reference and may differ across controller and software versions — if unsure, verify against Yaskawa documentation or reach out to us. Henghuan is an independent service provider with no affiliation or endorsement by Yaskawa.