The customer contacted us in an urgent production situation. A machine that plays an important role for special orders began to fail sporadically. The SGDB-02VN servopack reported A.10 Overcurrent, but not consistently. Production was interrupted and deadlines were approaching. The customer brought the drive personally and also supplied the associated motor SGMG-05A2AB, since the cause could be either motor or drive. The customer had experienced both scenarios in the past: seized bearings causing load spikes and encoder issues leading to false overcurrent detection.

During initial functional checks on our test bench the unit ran normally. The fault only appeared during dynamic operation with rapid load changes, strong acceleration profiles and thermal fluctuations. As soon as these conditions were reproduced, the drive suddenly switched off with overcurrent alarm. Such sporadic behavior typically indicates a borderline condition in the power stage or current detection circuitry.

The unit was completely disassembled for a detailed inspection. Inside we found subtle oxidation marks and thermal signatures near one of the gate driver components. Further analysis revealed that a driver IC became unstable within a narrow temperature window, causing incorrect current readings. Under demanding load transitions the controller interpreted these distorted measurements as a real overcurrent event and initiated an emergency shutdown. Additionally, several electrolytic capacitors in the DC link had noticeably increased ESR values, which degrade response stability.

To exclude the motor as a possible source, the SGMG-05A2AB was opened and inspected. The insulation values were stable, no oil or coolant ingress was found and the ball bearings were still running cleanly. The encoder operated without dropout. This confirmed that the error originated solely from the drive.

We rebuilt the entire power stage. Critical semiconductors, gate driver elements, resistors and isolation components were replaced. The DC link received new high-temperature capacitors to restore long-term stability. The control PCB underwent detailed cleaning, optical inspection and verification of all signal paths.

Following these repairs the drive was subjected to extended tests. On our load simulation bench the servopack operated through high-stress profiles significantly beyond those of typical machine operation. The unit was cycled through temperature ranges, rapid load changes and voltage variations. The error did not reappear.

Because this machine is crucial for the customer and the motor series has long been discontinued, the customer decided to order a fully refurbished replacement motor from us to keep as spare stock. This ensures operational continuity because SGMG-series motors are increasingly difficult to obtain in reliable condition on the open market.

The repaired drive was returned and the customer completed his production order on time. The machine has since operated flawlessly. This repair demonstrates that even older drive systems can remain dependable when professionally overhauled and maintained with foresight.

Preventive measures for the customer

• Regular cabinet cleaning and ventilation checks
• Inspection of all connectors and encoder cables
• Bearing replacement in aging motors
• Periodic insulation measurements
• Preventive replacement of DC link capacitors after long service life
• Avoiding cable stress or bending radii violations
• Monitoring machine load and vibration patterns

Conclusion

The SGDB-02VN remains a robust and serviceable drive. Proper refurbishment of the power stage and control circuitry significantly extends the life of the machine. This case highlights the importance of preventive maintenance, especially for discontinued drive generations.

Information about the mentioned Servopack: Yaskawa SGDB-02VN AC Servopack

Mentioned Motor: Yaskawa SGMG-05A2AB AC servo Motor

Further details on our Yaskawa repairs can be found here: Yaskawa Sigma 1 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

Operating environment and compatible equipment

The SGDB-02VN is used in machine tools, industrial robots, production systems and machining platforms.
Typical environments include:

• CNC machining centers of earlier generations
• Pick-and-place systems
• Tool changer axes
• Feed axes of small milling machines

Compatible motors:

• SGMG-05A2AB (0.5 kW, 200 V)
• SGMG-05A2xx series
• Other suitable SGM/SGMG motors depending on parameterization

Functional description

The Yaskawa SGDB-02VN is a servodrive from the predecessor series of Sigma drives. Its key tasks include:

• Providing a stable output for the motor
• Reading encoder feedback for precise regulation
• Monitoring the DC link
• Protecting the system through internal diagnostics
• Communicating with the controller via analog or MECHATROLINK interfaces

The unit operates in a closed control loop consisting of current, speed and position regulation.
The drive continuously monitors temperature, load, overcurrent, encoder data and supply voltage.

Alarm messages and troubleshooting (excerpt SGDB series)

Components of the SGDB-02VN