Repair of a Yaskawa SGMGH-05ACA2C with encoder malfunction, full diagnosis, overhaul and load test.

The motor was sent to us because it repeatedly caused faults at certain rotational speeds, especially above 1000 rpm, and the servo amplifier reported alarm A.84. The customer had already replaced the XtraDrive XD-04-MSD0 and all cables between the drive and the motor. Even after these replacements, the fault remained. This strongly suggested that the problem originated from within the motor or its encoder.

Upon arrival, the motor underwent a documented intake inspection. During manual rotation of the shaft, we noticed slight irregularity. It was not a mechanical blockage but a subtle ticking that could indicate a damaged encoder bearing. High resolution encoders such as the UTSIH-B17CK are highly sensitive to vibration and moisture, and even small irregularities can cause feedback distortion at higher speeds.

The next step was complete disassembly of the motor. The root cause became apparent quickly. Inside the encoder housing we found moisture residue and beginning corrosion on the signal board. This type of damage corrupts the high frequency sampling of the encoder disk and generates unstable impulses. These errors appear especially at elevated rotational speeds, where sampling rates increase and the drive expects high precision feedback. The customer’s description perfectly matched this failure mode.

The internal motor structure was cleaned and dried. Windings and bearings were inspected thoroughly. There were no core component failures, yet we executed our complete preventive overhaul process, including:

• Replacement of both precision bearings
• Cleaning and dehydration of all windings
• Insulation check
• Replacement of the shaft seal
• Cleaning of the terminal box
• Installation of a brand new UTSIH-B17CK encoder
• Programming of the correct motor model into the encoder

Programming is essential, because this encoder series must be configured exactly to the motor type. Incorrect configuration causes phase misalignment and improper feedback values.

After reassembly the motor underwent an extensive load test on our specialized servo motor test bench. This equipment allows realistic load cycles up to 4.4 kW, including thermal monitoring, encoder waveform analysis and current signature testing. The SGMGH-05ACA2C passed all test cycles without any abnormal behavior.

We document every load test and provide video proof to customers. This ensures transparency and shows that the repaired motor performs flawlessly under real operating conditions. A video was also produced for this motor.

The repair was successfully completed. All critical components were renewed or validated, and the motor has regained full operational reliability. The preventive overhaul significantly increases the service life and minimizes the likelihood of future encoder failures.

Preventive Measures for the Customer

• Regular inspection of cables and connectors
• Annual encoder health check in humid environments
• Replace seals and bearings every three to five years
• Cable routing with minimal electromagnetic exposure
• Routine drive function tests and parameter backups

Conclusion

The motor exhibited a classic encoder fault that manifested at higher speeds. Through complete overhaul, encoder replacement and documented load testing the motor was restored to stable and reliable operation. Preventive maintenance avoids future production stops and ensures long term equipment availability.

Information about the mentioned Servopack and Servomotor:

• Yaskawa SGMGH-05ACA2C AC Servo Motor
• Encoder Yaskawa UTSIH-B17CK
• Yaskawa XtraDrive XD-04-MSD0

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

Operating Environment and Compatible Devices

The SGMGH-05ACA2C is used in machine tools, automation axes, handling systems and precision positioning applications. Typical systems include Z axes, feed axes, rotary tables and dynamic industrial equipment.

Compatible servo drives include:

• Yaskawa XtraDrive XD-04-MSD0
• Yaskawa SGDH series (AE and DE versions)
• Various CNC controller integrations such as Siemens combined with Yaskawa

Functional Description

The SGMGH-05ACA2C is a synchronized servo motor equipped with a high resolution encoder that provides precise feedback signals to the servo amplifier. The UTSIH-B17CK encoder ensures accurate detection of position and speed. The motor design with permanent magnets and efficient winding layout supports high dynamic response and stable operation with low thermal load.

The connected drive continuously monitors encoder signals, current flow, thermal status and internal logic. Faults in the feedback path frequently lead to alarms such as A.84 or similar encoder feedback errors.

Alarm Messages and Troubleshooting

Components