24.10.2025 by Viktor Siebert
Repair of a Yaskawa SGDV-120D01A AC Servopack
The Yaskawa SGDV-120D01A Servopack was received from a customer with the complaint that an A.410 fault appeared instantly when the 400 V power was switched on. The unit showed no operation and remained in alarm state.
Initial visual inspection revealed no burn marks but noticeable dust and oil contamination near the cooling fins. Input and DC bus voltages were normal, indicating that the fault originated within the power section during initialization.
The unit was disassembled completely, and each module was tested separately. Analysis showed irregularities in critical components within the drive and gate-control circuits. These were replaced with tested original parts to restore the switching integrity.
After reassembly, the Servopack underwent multiple functional and thermal tests on our dedicated Sigma-V test bench. This platform allows dynamic load simulation under real conditions, using original Yaskawa motors and encoders.
The unit successfully passed all tests: current response, communication, feedback integrity, and thermal stability.
As part of preventive maintenance, capacitors, connectors, and thermal pads were replaced, and all PCBs were cleaned and coated for improved environmental resistance. The gate-driver calibration and thermal protection functions were verified and fine-tuned to ensure consistent operation.
Upon completion, the Servopack achieved full compliance with Yaskawa factory specifications and was returned to the customer with complete test documentation.
Service and Preventive Measures
| Action | Description |
|---|
| Cleaning & Coating | Removal of dust and oil residues, protective conformal coating applied |
| Preventive Replacement | Capacitors, thermal pads, and connectors renewed |
| Electrical Testing | Isolation check, gate-signal verification, and load test |
| Functional Verification | Full test cycle under dynamic load on the Sigma-V test stand |
| Documentation | Complete measurement report archived for traceability |
Conclusion
The SGDV-120D01A repair demonstrated how sensitive Sigma-V power stages can be to voltage transients and start-up inrush currents. Through systematic diagnostics and targeted replacement of critical components, full functionality was restored.
The unit now operates reliably under full load conditions verified, documented, and ready for long-term industrial use.
Information about the mentioned Servopack: Yaskawa SGDV-120D01A AC Servopack
Further details on our Yaskawa repairs can be found here: Yaskawa Sigma V Repair
📞 Feel free to contact us if you have any questions regarding your Yaskawa drive technology. Our team will be happy to assist you.
Device Specifications
| Specification | Value |
|---|
| Model | SGDV-120D01A |
| Series | Sigma-V (Σ-V) |
| Input Voltage | 3-Phase 380–480 V AC, 50/60 Hz, 7.3 A |
| Control Power Supply | DC 24 V ± 15 %, 1.4 A |
| Output | 3-Phase 0–480 V, 0–300 Hz, 11.9 A |
| Rated Power | 3 kW |
| Ambient Temperature | 0 – 55 °C |
| Protection Class | IP10 |
| Manufacturer | Yaskawa Electric Corporation, Japan |
| Production Site | Made in U.K. |
Typical Alarms and Troubleshooting
| Code | Description | Cause | Corrective Action |
|---|
| A.410 | Overcurrent | Short circuit, defective power stage, motor insulation issue, faulty gate driver | Inspect the power module, perform motor insulation test, verify control signals and DC bus stability |
| A.710 | Encoder Error | Signal interruption, contaminated connector, defective encoder | Clean connectors, check wiring, replace encoder |
| A.EB1 | Control Board Communication Error | Communication fault between control and power boards | Verify inter-board connections, re-solder contacts, test with reference control board |
| A.– | Undefined or sporadic error | Voltage drop or thermal overload | Check temperature sensors, power supply, and cooling system |
Internal Components
| Section | PCB Reference | Quantity |
|---|
| Control Board | SGDV-IFA01B | 1 |
| Power Board | SGDV-CB120DAB | 1 |
| Capacitor Board | SGDV-CC120DAA | 1 |
| Power Module | Power Unit Assembly | 1 |
Operating Environment and Compatible Equipment
The SGDV-120D01A belongs to Yaskawa’s Sigma-V series of AC Servopacks. It is commonly used in CNC machinery, tool changers, and automated axis systems.
It drives Yaskawa SGMGV and SGMJV servo motors in the 3 kW class and is designed for installation inside well-ventilated electrical cabinets with stable temperature and low dust exposure.
Functional Description
The Servopack precisely controls torque, speed, and position of the connected servo motor. The internal control board (IFA01B) communicates with the machine controller, while the power board (CB120DAB) generates the motor phases through IGBT switching. The capacitor board (CC120DAA) stabilizes the DC bus during dynamic load transitions.
During power-on, the Servopack performs a complete self-diagnostic cycle, checking the power supply, gate-driver circuits, and internal communication. If excessive current is detected during this initialization, the A.410 Overcurrent alarm is immediately triggered, shutting down the system for protection.