04.06.2026 by Viktor Siebert
Repair of a Yaskawa SGDV-260D01A Servopack After Power Stage Failure and Alarm A.720
A customer sent us a Yaskawa SGDV-260D01A Servopack from the Sigma V series that was completely non-functional. During machine operation, the axis had suddenly stopped. According to the customer, an abrupt standstill occurred immediately before the failure.
During the initial analysis, it became clear that this was not a simple electronic fault. The damage indicated a severe overload condition within the drive system. Particularly interesting was the fault memory evaluation performed later, which provided important clues regarding the actual root cause.
The technical specifications of the unit were taken directly from the nameplate. The SGDV-260D01A is a powerful 400 V Sigma V Servopack with an output power of 7.5 kW.
Initial Diagnosis
After opening the Servopack, several severe failures were identified.
The following assemblies were damaged:
• Power stage damaged
• Power transistor modules destroyed
• Both regenerative braking resistors defective
• Significant thermal stress within the power section
The extent of the damage indicated that the output stage had been exposed to excessive current over an extended period.
After repairing the power board and replacing the defective components, the unit could be powered up again. The internal fault memory was then evaluated.
Alarm A.720 was found in the fault history.
According to the Yaskawa documentation, Alarm A.720 means “Overload: Low Load”. The servomotor was operated continuously with a torque exceeding its rated value.
Actual Root Cause
The combination of destroyed power transistors, failed braking resistors and the stored A.720 alarm resulted in a clear technical conclusion.
Probable cause:
• Mechanical blockage of the servomotor
• Defective or seized motor bearings
• Excessive axis friction
• Mechanical stiffness within the machine
• Continuous motor overload
According to the Yaskawa manual, Alarm A.720 can occur when the servomotor cannot run properly because of mechanical problems and is therefore continuously overloaded.
The customer also confirmed that the original motor had suddenly stopped shortly before the failure.
The motor was therefore already replaced by the customer before the repaired Servopack was put back into service.
Repair Measures
The following work was performed:
| Measure | Description |
|---|
| Incoming inspection | Fault analysis and damage assessment |
| Disassembly | Complete Servopack disassembly |
| Cleaning | Removal of dust and contamination |
| Power stage repair | Repair of the output stage |
| Transistor module replacement | Replacement of damaged power modules |
| Braking resistor replacement | Replacement of both resistors |
| Control board inspection | Verification of control circuitry |
| Fault memory analysis | Evaluation of stored alarms |
| Load testing | Long-term testing under load |
| Final inspection | Approval for shipment |
Final Testing and Return Shipment
After completion of the repair, the SGDV-260D01A was tested on our test bench.
The following functions were verified:
• Startup behavior
• DC bus voltage
• Current consumption
• Regeneration function
• Braking function
• Communication
• Operation under load
• Long-term stability
No additional faults were detected during the endurance test.
The Servopack operated reliably and was released for return shipment.
Customer Feedback
“Thank you for the fast analysis. The information regarding the possible mechanical root cause helped us replace the motor in time and prevent further damage.”
Information about the mentioned Servopack: Yaskawa Servopack SGDV-260D01A
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.
Technical Specifications
| Parameter | Value |
|---|
| Manufacturer | Yaskawa Electric Corporation |
| Model | SGDV-260D01A |
| Series | Sigma V |
| Device Type | AC Servopack |
| Main Supply | 3PH 380–480 VAC |
| Frequency | 50/60 Hz |
| Input Current | 21.7 A |
| Control Supply | 24 VDC ±15 % |
| Control Current | 1.5 A |
| Output Voltage | 3PH 0–480 V |
| Output Frequency | 0–300 Hz |
| Output Current | 25.7 A |
| Output Power | 7.5 kW |
| Protection Class | IP10 |
| Ambient Temperature | 0 to 55 °C |
| Production Date | 09.10.2010 |
Operating Environment and Compatible Equipment
Typical applications:
| Industry | Application |
|---|
| Machine tools | Feed axes |
| Machining centers | X, Y and Z axes |
| Packaging machines | Positioning drives |
| Robotics | Motion axes |
| Handling systems | High dynamic axes |
| Special machinery | Precision drive systems |
Functional Description
The Yaskawa SGDV-260D01A belongs to the Sigma V Servopack family and provides precise control of servomotors.
Its main functions include:
• Speed control
• Position control
• Torque control
• Encoder evaluation
• Overload monitoring
• Regeneration control
• Protection functions against overcurrent and overvoltage
The integrated braking resistors and power stage process regenerative energy safely during braking operations. In the event of mechanical blockage or overload, several monitoring functions protect the drive system.
Components
| Assembly | Designation |
|---|
| Control Board | SGDV-IFA01B |
| Capacitor Board | SGDV-CC260DAA / 400-005-576-A0Y |
| Power Board | SGDV-CB260DAA / 400-005-575-B0Y |
| Power Module | Power Stage |
| Braking Resistors | Internally installed |
Alarms and Troubleshooting
| Alarm | Description | Cause | Remedy |
|---|
| A.100 | Overcurrent or Heatsink Overtemperature | Excessive IGBT current or overheating | Check power stage |
| A.300 | Regeneration Error | Braking resistor or braking circuit defective | Check resistors |
| A.320 | Regenerative Overload | Excessive regenerative energy | Review braking resistor sizing |
| A.330 | Power Supply Wiring Error | Wiring fault | Check wiring |
| A.400 | Overvoltage | DC bus voltage too high | Check power supply |
| A.410 | Undervoltage | DC bus voltage too low | Check supply voltage |
| A.510 | Overspeed | Motor speed too high | Check control loop |
| A.710 | Overload High Load | Short-term severe overload | Reduce load |
| A.720 | Overload Low Load | Continuous overload condition | Inspect mechanics |
| A.7A0 | Heatsink Overtemperature | Temperature above 100 °C | Check cooling system |
| A.7AB | Fan Fault | Cooling fan stopped | Replace fan |
| A.C90 | Encoder Communication Error | Communication fault | Check encoder cable |
Preventive Measures for the Customer
This repair case once again demonstrated that the root cause is not always located within the Servopack itself.
Recommended preventive actions:
• Regular inspection of motor bearings
• Monitoring unusual axis noises
• Temperature monitoring of motors
• Inspection of braking resistors
• Cleaning cooling passages
• Monitoring motor current consumption
• Preventive overhaul of older servomotors
A blocked or mechanically overloaded motor can destroy a power stage within a very short time.
Conclusion
The repair of this Yaskawa SGDV-260D01A clearly demonstrated how closely mechanical systems and power electronics are connected. The stored Alarm A.720 provided valuable evidence of a long-term motor overload condition. Through repair of the power stage, replacement of the transistor modules and braking resistors, and the timely replacement of the motor, the complete drive system could be returned to reliable operation.