Yaskawa SGMGH-13ACA6S AC Servo Motor Hauptansicht
06.07.2025 by Viktor Siebert
When the Encoder Fails. How We Rescued a Yaskawa SGMGH-13ACA6S Motor in Record Time

A customer personally brought in his Yaskawa SGMGH-13ACA6S servo motor. The reason? The connected Servopack kept randomly showing alarm AC.9 Encoder Communication Error.

At first, the customer suspected faulty cables and replaced them, but it didn’t help. Next, he swapped the Servopacks between axes still, the same axis showed the error. Then he exchanged the encoders between the X and Y axes (both motors were identical) and suddenly the fault followed the encoder.

That confirmed it: the encoder was the issue.

Manufacturer Support? Not Really.

The customer contacted both the machine manufacturer and Yaskawa directly. The result was disappointing:

  • The machine builder offered an overhaul but it would take over a month, as the motor had to be shipped to Japan.
  • Yaskawa simply referred back to the machine manufacturer.
  • The quoted repair cost exceeded the price of a new motor.

The customer was visibly frustrated:

“I need to keep producing. This situation is killing me. The machine kept crashing, and every time the workpiece was ruined. I can’t go on like this.”

The Solution Came Through a Recommendation.

Through a recommendation, the customer found his way to us. We received the motor the same day and began diagnostics immediately. The result: the encoder was defective and unable to provide stable feedback.

Our Repair Process Precise, Fast, Reliable

  1. Disassembly & Inspection
    The motor was fully dismantled, cleaned, and checked for further damage — especially for thermal stress or bearing wear.
  2. Encoder Replacement
    The old encoder was completely removed. We installed a brand-new original encoder (UTSIH-B17CK) exactly matched for this motor type.
  3. Encoder Programming
    This step is crucial: the encoder is not just mounted mechanically it is software-configured precisely for this specific motor. Without this step, the Servopack won’t recognize or control the motor properly.
  4. Functional Testing
    The repaired motor was tested on our in-house test bench using a Yaskawa SGDH-15AE-OY Servopack. We verified:
    • Precise positioning and zero-point accuracy
    • Temperature behavior under load
    • Current consumption
    • Encoder signal integrity
    • Insulation resistance and grounding
  5. Final Check & Documentation
    After a successful 100% test, the motor was sealed and returned only four days after drop-off.

The Result? Production Back On and Plans for More.

One week later, the customer called us back:

“Everything’s been running perfectly since reinstalling the motor. I’m now thinking about having you overhaul the servo drives too. Especially with the summer heat these drives are really under strain. I’m taking company holidays in August that’s the perfect time to get them serviced.”

Conclusion: Time is Money, Precision Builds Trust

This story is a great example of how fast, competent service can get production back on track. We not only understand the technology, we understand what our customers are going through.

Information about the mentioned Servopack and Servomotor:

More information about our Yaskawa repairs can be found here.

📞 Feel free to contact us if you have any questions regarding your Yaskawa drive technology. Our experienced team is always ready to assist you.

Technical Specifications Yaskawa SGMGH-13ACA6S

SpecificationValue
ModelSGMGH-13ACA6S
SeriesSigma II
Rated Power1.3 kW
Rated Torque8.34 Nm
Peak Torque23.3 Nm
Rated Speed1500 RPM
Maximum Speed3000 RPM
Rated Current (RMS)5.4 A
Max. Current (RMS)14 A
Voltage400 V AC
EncoderIncremental 17-bit (UTSIH-B17CC)
Insulation ClassF
Protection ClassIP67 (excluding shaft opening)
MountingFlange-mounted
Weight~13.5 kg
ShaftStraight, with key and tapped center
CoolingSelf-cooled, totally enclosed

Alarm Codes & Troubleshooting Sigma II

Alarm CodeAlarm NameDescriptionRecommended Action
A.02Parameter BreakdownEEPROM data error in servo amplifierRe-initialize amplifier or replace it
A.04Parameter Setting ErrorParameter value out of allowable rangeCheck and correct parameter settings
A.05Servo Motor / Amplifier MismatchMotor and amplifier capacity do not matchVerify compatibility (e.g. SGDH-15AE + SGMGH-13ACA6S)
A.10Overcurrent / Heat Sink OverheatedExcessive current or heat sink temperature too highCheck cooling, fan, ventilation, reduce load or replace drive
A.30Regeneration ErrorFault in regenerative circuit or resistorCheck wiring and resistor function
A.32Regenerative OverloadRegenerative energy exceeds resistor capacityOptimize cycle or use higher-rated resistor
A.40OvervoltageMain DC bus voltage too highCheck input voltage, avoid regeneration spikes
A.41UndervoltageMain DC bus voltage too lowVerify input power source
A.71Overload: High LoadShort-term torque overloadCheck mechanical load, reduce acceleration/torque
A.72Overload: Low LoadLong-term continuous torque overloadAdjust mechanical setup or use higher-rated motor
A.C1Servo OverrunMotor lost control, exceeded speed or position limitsCheck feedback loop, tuning parameters, wiring
A.C9Encoder Communication ErrorNo encoder signal received or communication errorCheck encoder, cables, and signal integrity
A.bFSystem AlarmInternal system fault in servo amplifierContact support or replace drive

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