12.08.2025 by Viktor Siebert
A Real Case from Our Workshop Yaskawa SGMAH-04A1A21D AC Servo Motor mit Encoder UTSAH-B16EC-E
The Yaskawa SGMAH-04A1A21D AC Servo Motor with encoder UTSAH-B16EC-E operates reliably in many applications together with the Yaskawa XtraDrive XD-04-MSD0 Servopack. In this particular case, we received the XtraDrive XD-04-MSD0 for repair. During inspection, the unit showed no active fault, but the fault memory was completely filled with Alarm A.84.
We advised the customer to also check the motor. While there are several known weak points in the XtraDrive itself that can cause this alarm, we still recommended a preventive overhaul of the Servopack. This ensures that all critical components are replaced and the device can operate trouble-free for many years.
Repeat Failure After Installation
As sometimes happens, the customer reported a fault shortly after reinstalling the Servopack. Alarm A.84 reappeared. Our office manager contacted the customer directly to go over the case again in detail. Already during the first repair, we had pointed out that the fault source could also be in the motor, particularly in the UTSAH-B16EC-E encoder.
For documentation purposes, we had recorded a test video after the first repair, completed our checklists in full, and sent them to the customer by email. After the fault reoccurred, the customer sent us both the motor and the Servopack for inspection.
Clear Diagnosis and Repair Decision
Upon receiving the units, our suspicion was confirmed: the encoder of the Yaskawa SGMAH-04A1A21D AC Servo Motor was causing sporadic A.84 error messages. We informed the customer immediately and received approval to carry out the motor repair.
Overhaul and Quality Assurance
Within three working days, the motor was completely overhauled. The encoder was replaced and programmed, the motor was mechanically serviced, all critical components were replaced, it was repainted, and then tested under load together with the customer’s Servopack. The encoder alignment was performed precisely according to the manufacturer’s specifications.
Finally, the customer once again received a detailed test video and updated checklists. Both units were carefully packed and returned to the customer.
Result and Customer Feedback
After receiving the units, the customer contacted us to express his appreciation for the professional handling of the case. He highlighted the transparent communication, thorough repair, and complete documentation, and stated that he would gladly recommend our services to others.
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 experie
Device Data (Technical Specifications)
| Parameter | Value |
|---|
| Motor type | SGMAH-04A1A21D |
| Manufacturer | Yaskawa Electric Corporation, Japan |
| Rated output | 400 W |
| Rated voltage | 200 V AC |
| Rated current | 2.8 A |
| Rated torque | 1.27 Nm |
| Rated speed | 3000 min⁻¹ |
| Maximum speed | 5000 min⁻¹ |
| Peak torque | 3.82 Nm |
| Insulation class | B |
| Mounting type | Flange mount |
| Enclosure protection class | IP55 (excluding shaft opening) |
| Rotor inertia | 0.0000173 kg·m² |
| Encoder | UTSAH-B16EC-E (absolute, 16-bit) |
| Weight (without brake) | approx. 1.7 kg |
| Weight (with brake) | approx. 2.2 kg |
| Cooling method | Totally enclosed, self-cooled |
| Optional brake | Holding torque 0.14 Nm |
Operating Environment and Compatible Devices
The SGMAH-04A1A21D is typically used in CNC machines, packaging equipment, pick-and-place machines, printing presses, and other precision applications.
It often operates together with Yaskawa XtraDrive series Servopacks (e.g., XD-04-MSD0) or Sigma-II Servopacks (SGDH-04AE-OY).
Recommended operating environment:
- Ambient temperature: 0 to +40 °C
- Humidity: 20% to 80% (non-condensing)
- Vibration resistance: 49 m/s²
Functional Description
The SGMAH-04A1A21D is a compact, high-precision AC servo motor with 16-bit encoder resolution, designed for accurate positioning and speed control.
In combination with a suitable Servopack, it performs dynamic motion control tasks found in manufacturing processes with high accuracy demands.
Its UTSAH-B16EC-E absolute encoder provides position data without the need for homing after power restoration. The compact design allows for installation even in confined machine spaces.
Alarm Messages and Troubleshooting (Selection)
| Alarm Code | Description | Possible Cause | Solution |
|---|
| A.02 | Parameter Breakdown | EEPROM data in servo amplifier faulty | Reset parameters, reinitialize amplifier |
| A.05 | Servo Motor and Amplifier Combination Error | Incorrect motor type connected | Ensure correct motor-amplifier pairing |
| A.10 | Overcurrent / Heat Sink Overheated | Overcurrent through IGBT or overheating | Check load, improve cooling |
| A.30 | Regeneration Error | Faulty regeneration circuit or resistor | Inspect resistor and regeneration circuit |
| A.40 | Overvoltage | Input voltage too high | Check supply voltage, install surge protection |
| A.41 | Undervoltage | Input voltage too low | Check power supply |
| A.71 | Overload (High Load) | Load torque exceeded rating for extended time | Reduce load, check gearing |
| A.81 | Absolute Encoder Backup Error | Encoder power supply interrupted | Inspect encoder power supply |
| A.83 | Absolute Encoder Battery Error | Battery voltage too low | Replace battery |
| A.84 | Absolute Encoder Data Error | Invalid or faulty encoder data | Check encoder, replace if necessary |
Component List
| Component | Description |
|---|
| Stator | Multi-phase winding for torque generation |
| Rotor | Permanent magnet rotor |
| Encoder UTSAH-B16EC-E | 16-bit absolute encoder |
| Shaft bearings | Precision ball bearings |
| Housing | Totally enclosed, self-cooled construction |
| Connectors | Hypertac encoder and power connectors |
| Optional holding brake | Electromagnetic brake |