Initial situation and fault description.

The Yaskawa AC Servo Motor SGMAH-01A1A2S was sent to us with an encoder fault. According to the customer, the machining center stopped suddenly during operation. There were no warning signs or gradual performance loss, but an abrupt standstill. The motor was operated with an SGDH-01AE or SGDH-02AE servopack from the Sigma II series.

Over the years, the customer had several identical motors in stock and replaced them one after another. For a long time, this approach worked well. Over time, however, it became clear that no new replacement motors were available anymore. Yaskawa no longer supplies this motor type, and the machine manufacturer does not provide replacements either. When the last operational motor failed, production came to a complete halt.

Decision to repair

A retrofit to a modern drive system would have required replacing the motor, servo drive, cables, and in some cases parts of the control system. The effort, cost, and risk were completely disproportionate to the condition of the machine, which was still mechanically and control-wise in very good shape.

Internet offers turned out to be unreliable. Many motors offered are neither new nor properly tested, and in some cases relabeled or technically non-original units are circulating. For the customer, it was clear that repairing the existing motor was the only reasonable option.

Diagnosis and express repair

The motor was delivered as an express job. Immediately after receipt, technical inspection was started. The encoder no longer provided a stable signal. Electrically, the motor itself was basically intact, while mechanically it showed age-related wear.

Due to acute production pressure, the repair was prioritized. Within 24 hours, the motor was repaired and returned to service. A few days later, the customer sent three additional identical motors for repair, this time without time pressure, in order to refurbish the entire stock preventively.

Repair scope and procedure

As part of the repair, the encoder was replaced. Depending on the version, a compatible encoder of type UTSIH-B13DC, UTSIH-B13DC-E, or TRD-WBG13 was installed. In addition, typical wear parts were replaced that regularly cause issues on these motors after many years of operation.

The motor was completely disassembled, cleaned, re-sealed, and mechanically inspected. Bearings and connectors were evaluated and replaced where necessary. After reassembly, the encoder was adjusted and a full functional test was performed on a suitable test bench using an SGDH servopack.

Test results and quality assurance

The motor was tested under realistic operating conditions. Speed, feedback signals, current consumption, and thermal behavior were all within specification. The encoder delivered a stable and clean signal without dropouts.

After successful testing, the customer received a fully functional motor that could be integrated back into the existing machine without any changes to control system or cabling.

Why repair makes sense

Especially with small servo axes, their importance is often underestimated. If such a motor fails, the entire machine often comes to a standstill. Since replacement units are no longer available and retrofits are economically unreasonable, professional repair is often the only sustainable solution.

We have the necessary know-how, suitable spare parts, and testing equipment to reliably repair discontinued Yaskawa motors such as the SGMAH-01A1A2S.

rmation about the mentioned Servopack and Servomotor:

• Yaskawa SGMAH-01A1A2S Servo Motor
• Encoder Yaskawa TRD-FWAG13, UTSIH-B13DC-E
• Yaskawa Servopack SGDH-01AE-OY

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.

Model designation

Technical specifications

Encoder

Compatible servo drives

Typical alarm messages SGDH Sigma II

Repair measures

Typical applications