18.09.2025 by Viktor Siebert
Maintenance instead of retrofit three Yaskawa SGMPH-04A1A-YR52 AC servo motors successfully overhauled!
We received three of these motors from a Yaskawa application.
The customer had been sending defective units for exchange to the OEM. But recently, he was told the motors were discontinued, and the only solution was a retrofit: replacing motors, drives, and controls, a cost comparable to replacing the entire machine.
He was not willing to accept this and turned to us.
Our analysis revealed:
- Brakes still within tolerance
- Encoders faulty, delivering unreliable signals
We performed a complete overhaul:
- Bearing replacement
- Seal and connector renewal
- Thorough cleaning incl. emulsion removal
- Oven drying for moisture elimination
- Encoder replacement (UTSAH-B16DC-E) with calibration
- Signal testing and insulation measurement
On the test bench, all motors passed under load:
- Encoder signal quality
- Torque and speed tests
- Brake holding force
- Insulation resistance
The customer could continue operating his machines without retrofit saving significant costs.
Causes of Encoder or Motor Failures
- Aging of encoder electronics
- Contamination with oil, dust, or emulsions
- Bearing wear under continuous load
- Cable and connector fatigue
- Overheating from insufficient cooling
Preventive Tips for Customers
- Inspect cables and connectors regularly
- Monitor encoder signals during maintenance cycles
- Replace bearings preventively after 20,000–30,000 hours
- Keep the environment clean from oil and dust
- Test brake performance, especially in vertical axes
Information about the mentioned Servomotor and other components:
Yaskawa SGMPH-04A1A-YR52 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 |
|---|
| Model | Yaskawa SGMPH-04A1A-YR52 AC Servo Motor |
| Voltage | 400 V AC |
| Rated Current | 2.6 A |
| Rated Power | approx. 400 W |
| Rated Torque | approx. 1.27 Nm |
| Max. Speed | 3000 rpm |
| Weight | approx. 4.5–5.0 kg (estimated, similar models) |
| Protection Class | IP65 (standard for Sigma-II motors) |
| Insulation Class | B |
| Encoder | Yaskawa UTSAH-B16DC-E (absolute, high resolution) |
| Brake | OGURA CLUTCH MCDB20Y-15 |
| Cooling | Natural convection |
| Frame Size | Medium, compact |
| Manufacturer | Yaskawa Electric Corporation, Japan |
Application Environment & Compatible Devices
This motor is used in CNC machines, automation systems, and assembly equipment.
Compatible with Yaskawa Sigma II Servopacks (SGDH series) in the 400 W range.
Typical applications: feed drives, positioning axes, and precision automation.
Functional Description
The SGMPH-04A1A-YR52 is a compact AC servo motor providing high dynamics and precise torque control.
Equipped with the UTSAH-B16DC-E absolute encoder, it delivers reliable position feedback for CNC precision.
The integrated OGURA MCDB20Y-15 brake ensures secure holding at power-off, crucial for vertical axes.
Alarm Messages & Troubleshooting
Based on Yaskawa Sigma II/SGDH manuals
| Code | Error Description | Cause | Solution |
|---|
| A.02 | Parameter Breakdown | Faulty EEPROM data | Check/replace drive |
| A.03 | Main Circuit Encoder Error | Abnormal detection in power circuit | Inspect encoder/cable |
| A.05 | Servo/Motor Combination Error | Wrong motor-drive match | Verify compatibility |
| A.10 | Overcurrent / Overheating | IGBT short or overload | Improve cooling, replace parts |
| A.30 | Regeneration Error | Faulty regen circuit | Check resistor |
| A.40 | Overvoltage | DC voltage too high | Inspect supply |
| A.41 | Undervoltage | DC voltage too low | Verify mains |
| A.51 | Overspeed | Motor speed too high | Adjust parameters |
| A.71 | Overload (short-term) | Excessive load | Check mechanics, overhaul |
| A.82 | Encoder Checksum Error | Encoder memory checksum abnormal | Replace encoder |
| A.C9 | Encoder Communication Error | No communication motor ↔ drive | Replace cable/encoder |
Components
| Component | Description |
|---|
| Rotor | Laminated core with permanent magnets |
| Stator | Three-phase windings |
| Encoder | UTSAH-B16DC-E absolute encoder |
| Brake | MCDB20Y-15 holding brake |
| Bearings | Precision ball bearings |
| Housing | Black painted aluminum |
| Seals | Shaft seals, IP65 protection |
| Connectors | Power/encoder plugs |
| Cooling | Convection |