24.06.2025 by Viktor Siebert
Initial Situation: Three Failed Robot Servo Motors in Automotive Supply SGMGH-55A2A-OY15 Yaskawa Servo Motor
A well-established Belgian company in the automotive supply sector was facing a critical challenge. Their production line relied on specialized industrial robots equipped with Yaskawa SGMGH-55A2A-OY15 servo motors, featuring custom UTSAH-B17CL-E encoders and integrated RNB7.4K-06 DC-90V brakes. These motors had been failing regularly—approximately every three months—and the manufacturer Yaskawa no longer offered replacement units or repair services.
The Dilemma: Replace the Entire Robot System or Find an External Solution?
For the company, a full replacement of the robotic systems would have meant a multimillion-euro investment. At the same time, they had enough spare motors for short-term needs, but knew that more failures were inevitable. Since sustainability and resource-consciousness are central to their values, they began searching for an external service provider capable of offering a long-term repair solution.
The Challenge: Custom-Programmed Encoders with No Known Repair Option
The root cause of the failures was quickly identified: in all three cases, the Yaskawa UTSAH-B17CL-E encoder was defective. This encoder was specifically programmed for the robotic application and had no known replacement or repair process. While we were familiar with similar motors from other projects, this particular encoder was new territory for us.
Our Approach: In-House Repair Development and Customer-Centered Testing
After a technical evaluation, we jointly decided with the customer to develop a dedicated repair process for the encoder. Since the motors were not urgently needed, we had enough time to plan and carry out the repair meticulously.
The first motor was completed within three weeks and sent to the customer for real-world testing in their robotic system. After successful operation, we received approval to proceed with the repair of the other two motors, which were then restored and delivered accordingly.
Work Performed in Detail
All three motors underwent a complete overhaul in our facility, including:
- Encoder Repair: Development and execution of a repair method for the UTSAH-B17CL-E encoder
- Bearing Replacement: Renewal of all rolling-element bearings according to manufacturer specifications
- Brake Replacement: Installation of new RNB7.4K-06 DC-90V brake units
- Mechanical Restoration: Sandblasting, full cleaning, and repainting
- Seal Replacement: All seals replaced to ensure operational reliability
- Function Testing: Final testing on our motor test bench under mechanical and electrical load
Result: A Sustainable, Reliable, and Future-Proof Solution
This solution combined sustainability with technical and economic efficiency. The customer was able to continue operating their robotic systems without the need for expensive replacements or redesigns. By successfully developing a repair solution for an encoder previously considered unrepairable, we significantly extended the lifecycle of their existing machines.
Information about the mentioned Servomotor:
SGMGH-55A2A-OY15 Yaskawa Servo Motor
More information about our Yaskawa repairs can be found here.
📞 Feel free to contact us if you have any questions regarding your Yaskawa drive tech
Device Specifications
| Parameter | Value |
|---|
| Motor Type | SGMGH-55A2A-OY15 |
| Rated Power | 5500 W (5.5 kW) |
| Rated Torque | 35 Nm |
| Rated Speed | 1500 rpm |
| Rated Current | 42.1 A |
| Voltage | 200 V (3-phase) |
| Insulation Class | F |
| Encoder | UTSAH-B17CL (absolute serial) |
| Brake | RNB7.4K-06, DC 90V |
| Protection Class | IP67 |
| Estimated Weight | approx. 35 kg (varies by options) |
Application Environment
The motor is part of Yaskawa’s Sigma II Series, commonly used in industrial robots—especially in automotive manufacturing lines. It is designed for:
- High-precision positioning
- Continuous-duty operations
- Reliable holding force (via brake)
It operates in enclosed electrical cabinets under controlled ambient temperatures (preferably < 40°C). The built-in brake suggests vertical axis usage or safety-relevant motion applications.
Functional Description
The SGMGH-55A2A-OY15 is a 1500 rpm AC servo motor equipped with a serial absolute encoder (UTSAH-B17CL), capable of delivering accurate position feedback even after power loss. The motor integrates into Yaskawa Sigma II drive systems and typically operates with a SGDH amplifier. Key features include:
- Precise and dynamic position control
- High torque capacity
- Encoder with multi-turn absolute feedback
- Brake system for holding and safety functions
- Environmental sealing (IP67) for industrial conditions
Alarm Codes and Troubleshooting
| Alarm Code | Description | Suggested Action |
|---|
| A.03 | Main Circuit Encoder Error | Check encoder wiring and power supply |
| A.10 | Overcurrent or Heat Sink Overheated | Inspect load and motor for blockage or excessive torque |
| A.30 / A.32 | Regeneration Error / Overload | Check braking resistor and motion profile |
| A.40 / A.41 | Overvoltage / Undervoltage | Inspect power source and input voltage |
| A.51 | Overspeed | Verify command values and adjust parameters |
| A.81 – A.86 | Absolute Encoder Errors / Battery Issues | Replace battery, inspect encoder and connections |
| A.C9 / A.CA | Encoder Communication / Parameter Errors | Recheck encoder settings and communication lines |
| A.d0 | Excessive Position Error | Verify mechanics, re-tune position control loop |
| A.F1 | Power Line Phase Loss | Check power connections and 3-phase supply integrity |
