Initial Situation and Background.

The two Yaskawa AC servo motors SGMAH-04AAA21 and SGMAH-04AAA61D-OY equipped with the TRD-FWAG13 encoder were deliberately ordered from us as fully overhauled exchange motors by a machine manufacturer. Not because these motors are difficult to obtain on the market, but precisely because they are widely available.

Over an extended period, the customer had attempted to source servo motors of this power class via online platforms such as Ebay and Asian marketplaces. At first glance, this approach appeared attractive. Availability, fast delivery, and low prices seemed convincing. In practice, however, a very different picture emerged.

Several of the supplied motors already showed abnormalities during commissioning. Unstable running, rising temperatures, and sporadic encoder faults occurred. In other cases, the motors initially functioned but failed again after a short operating time. Detailed analysis revealed that some units were relabelled motors, incompatible variants, or even devices with manipulated nameplates. Particularly critical were cases where a 200-volt motor was declared as a 400-volt version. Such motors may start briefly but quickly reach their thermal and electrical limits.

Another major issue was the lack of proper overhaul. Bearings, seals, and encoders were not replaced. In many cases, the motors had only been visually refurbished or repainted. Technically, they remained in a worn condition.

After several failed attempts and repeated machine downtime, the customer consciously chose a different path and approached us with a clear requirement: secure origin, genuine devices, complete general overhaul, and a transparent and verifiable test process.

Preventive Overhaul Process at industrypart

For both SGMAH motors, no partial repair was performed. Instead, a complete preventive overhaul was carried out, regardless of whether individual components still appeared functional.

After incoming inspection and documentation of the nameplates, the motors were completely dismantled. All assemblies were individually inspected, cleaned, and evaluated. The objective was not only to restore functionality, but to return the motors to a technically reliable condition, as close as possible to a new unit.

The overhaul process included the following measures:

• Replacement of all ball bearings regardless of visible wear
• Renewal of all seals to ensure proper protection
• Inspection and replacement of the TRD-FWAG13 encoder at the slightest irregularity
• Cleaning of windings and housings to remove deposits and residues
• Verification of insulation and electrical characteristics
• Mechanical inspection of shaft, fits, and bearing seats

Particular emphasis was placed on authenticity verification. Nameplates, serial numbers, mechanical design, electrical ratings, and encoder variants were cross-checked. Only clearly original and fully compatible components were used.

Test Setup and Functional Verification

After completion of the mechanical and electrical overhaul, both motors were tested on our in-house test bench. A Yaskawa SGDH-04AE-OY servopack was used, fully compatible with the 200-volt SGMAH motor series.

Commissioning and parameterization were carried out using SigmaWin, allowing realistic operating conditions to be simulated. Each motor underwent multiple test phases:

• No-load testing across the entire speed range
• Thermal endurance testing under continuous operation
• Encoder signal verification and position feedback analysis
• Current consumption and torque behavior monitoring
• Noise and vibration assessment

Only after stable and reproducible operation over an extended period were the motors approved for shipment. All test results were documented and remain internally traceable.

Why Customers Deliberately Avoid Marketplace Products

The decisive factor for the customer was not the price, but predictability. Machine manufacturers require motors that operate reliably without unexpected issues. A seemingly inexpensive purchase can quickly become costly if machines stop, faults are difficult to diagnose, or secondary damage occurs.

The SGMAH motors overhauled by us originate from verifiable sources, are fully reconditioned from a technical standpoint, and are tested under real operating conditions, not merely inspected. This is precisely why further inquiries from the same customer followed, both for stock replenishment and for rapid exchange solutions in service cases.

nformation about the mentioned Servopack and Servomotor:

• Yaskawa SGMAH-04AAA21 Servo Motor
• Yaskawa SGMAH-04AAA61D-OY Servo Motor
• Encoder Yaskawa TRD-FWAG13
• Yaskawa Servopack SGDH-04AE-OY

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

Technical Specifications

Operating Environment and Compatible Equipment

Functional Description

The SGMAH servo motors of the Sigma-II generation are brushless AC motors with integrated encoder feedback. They are designed for precise positioning tasks and deliver constant torque over a wide speed range. The TRD-FWAG13 encoder provides position data to the servopack, which controls current and torque accordingly.

Typical Fault Patterns and Causes

Components

Conclusion

These two SGMAH motors clearly demonstrate why more and more machine manufacturers deliberately turn away from seemingly inexpensive marketplace solutions. A genuine general overhaul, combined with authenticity verification, preventive replacement, and real operational testing, provides reliability, availability, and long-term stability. This is exactly what professional users expect and precisely what we stand for at industrypart.