Initial Situation and Customer Report.

When the Yaskawa SGDS-15A12A Servopack arrived at our facility the customer reported recurring disturbances on one of his axes. During operation alarm A.810 appeared which indicates a problem in the encoder communication. The customer initially assumed that the motor itself was the cause and replaced it with an identical unit taken from a neighboring machine. Since the error continued to appear the Servopack was sent to us for diagnosis.

Initial Diagnosis on the Test Bench

On our test bench we tested the device with a fully functional reference motor. The same alarm A.810 appeared immediately at power on. This behavior is typical when the problem originates inside the Servopack and is not related to the motor or cabling. In encoder faults of this type the cause is usually a disturbance in the signal path between encoder and controller. This includes insufficient signal processing, unstable supply conditions or incorrect feedback levels. The exact manifestation may vary but the principle remains the same: the Servopack cannot detect valid or stable encoder data.

Internal Analysis of the Unit

During further analysis it became clear that several internal functional areas were no longer operating within their intended parameters. Such deviations usually result from long term thermal load, vibration, ageing effects or external influences that accumulate over time. For us it was therefore evident that a complete refurbishment of all relevant signal and control paths was necessary. The goal is to restore the unit to a state that meets the original specifications and ensures long term operational reliability.

Comprehensive Overhaul

We carried out a comprehensive overhaul. This included the systematic verification and restoration of signal stability, the renewal of critical functional sections, the reworking of sensitive feedback paths and the optimization of the internal supply levels. In addition the entire device was thoroughly cleaned so that it is free from deposits and contamination which could affect thermal or electrical stability. This ensures that all subsequent tests are carried out under optimal conditions.

Extended Test Run and Quality Control

In the following test run the Servopack went through a wide range of functional, load and temperature tests. The encoder communication was monitored over several hours both in dynamic operation and at constant speed. All values remained stable and not a single error occurred. Rapid direction changes, high acceleration values and extended load phases also showed no abnormalities. The behavior fully matched that of a new device.

Return to the Customer and Preventive Advice

We were able to return the Servopack to the customer with full functional approval. In addition he received the recommendation to check the encoder cables in the machine regularly for mechanical stress, bends or contact issues. Many faults do not occur suddenly but develop gradually over years alongside the natural ageing of the electrical infrastructure. If these points are identified and addressed early failures can often be prevented entirely.

Conclusion and Insights

With the repair of the SGDS-15A12A the machine became fully operational again. This case once again demonstrated that systematic diagnosis and a structured approach are essential to identify faults correctly. An unverified motor replacement would not have solved the issue. The combination of experience, test bench technology and well defined repair procedures ensures that the devices operate reliably in the long term and downtime is minimized.

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Technical Profile:

Operating Environment and Compatible Equipment

The SGDS-15A12A is a 1.5-kW Servopack of the Sigma III generation. Typical fields of application include CNC lathes, handling portals, tool changer systems, axes in machining centers, packaging systems and high-speed automation equipment.
Compatible motors include Sigma-III AC servo motors with absolute or incremental encoder systems.

The device is used in control architectures where high dynamics and fast control cycles are required. The integrated encoder evaluation is highly sensitive to disturbances, wiring problems and unstable supply conditions.

Functional Description

The SGDS-15A12A controls a 1.5-kW servo motor in torque, speed and position mode. It continuously monitors the encoder, the DC bus, the power stage, thermal states and all communication paths.

Special characteristics of Sigma-III Servopacks
• Increased processing performance compared to Sigma II
• Enhanced encoder evaluation and diagnostic capabilities
• Independent monitoring of absolute backup supply, positional data integrity and communication states
• Improved protection of IGBT stage, DC bus section and thermal detection circuits

Alarm A.810 indicates an Encoder Backup Error, which occurs when the encoder feedback system cannot provide stable or valid data. Common reasons include:
• interrupted encoder wiring
• unstable supply voltage
• internal disturbances in the encoder input section
• ageing effects or temperature stress
• communication errors in the feedback path

Alarm Messages and Troubleshooting (Extract Sigma II / Sigma III)

Components