SGMGH-03ACA61 Yaskawa AC Servo Motor: Why Timely Maintenance is Crucial

25.04.2025 by Viktor Siebert

SGMGH-03ACA61 Yaskawa AC Servo Motor: Why Timely Maintenance is Crucial

Why do Encoders Frequently Fail?

Encoders for servo motors are often more expensive than the motors themselves. But why is that the case? There are several reasons: either the manufacturer ceases production and discontinues models to push newer technology, so they stop supplying spare parts. Generally, the older the system, the more expensive the spare parts become.

Another critical factor is that encoders are complex components requiring high mechanical and electronic precision. An encoder comprises several finely tuned mechanical and electronic components that must precisely match each other. Often, exchanging encoders between different models isn’t feasible. Especially for the Yaskawa motor SGMGH-03ACA61, it is crucial that the encoder UTSIH-B17CK (working with Yaskawa Servopack SGDH-04AE) has the programmed model designation and matching serial number.

Practical Example

This issue recently arose during a repair: a customer attempted to replace the encoder on his motor himself. He bought the used encoder for 600 Euros net from a dealer who claimed it was taken from a functioning motor. However, the supposedly suitable encoder did not work with the drive and generated only alarm messages. Since the original encoder occasionally showed errors, the customer decided to have the motor tested by industrypart.

When we asked why he didn’t come directly to us, he explained it needed to be done quickly, and the offer from his supplier appeared cheaper.

What did our inspection reveal?

We tested the motor with both encoders. Even before testing, our experienced motor technician suspected that the replacement encoder was incorrectly programmed – a suspicion that proved correct. Indeed, the type designation of the replacement encoder originated from an entirely different model (SGMGH-20ACA61 working with Yaskawa Servopack SGDH-20AE), which would never be compatible with this motor.

The used encoder exhibited clear signs of wear; notably, the integrated ball bearings did not rotate smoothly. Such worn ball bearings are common failure points in encoders, leading to incorrect signals being sent to the drive. After a 30-minute testing phase, our suspicion was confirmed definitively: the drive reported Alarm A.84 due to an encoder failure.

Risks of Buying Used Encoders

On various auction platforms and through dealers, you often find used, supposedly refurbished, or even allegedly new encoders – especially common among Chinese sellers. However, many European dealers also attempt to sell such parts. Frequently, these supposed bargains lead to extensive troubleshooting, unnecessary replacements of cables, drives, or controls, and therefore significant additional costs.

Our customer was lucky in misfortune that the incorrect encoder didn’t function at all. Otherwise, he would have been embroiled in prolonged and costly troubleshooting.

Our Repair Process

We also examined the customer’s original encoder, which had the same defect: damaged ball bearings. As replacing the ball bearings in this encoder model is not possible, we installed a genuinely new encoder precisely programmed for this motor. Additionally, the motor was fully stripped, cleaned, and fitted with new ball bearings and seals. The result: the customer received an almost like-new motor.

Why do Encoder Ball Bearings Fail?

There are clear causes for this issue as well: Motor ball bearings are designed for a specific number of operating hours. Eventually, they wear out and create debris. This fine metallic debris enters the small ball bearings of the encoder and destroys them. Additionally, the debris can scratch the delicate coding disc, preventing it from providing precise signals.

Our Appeal

We want to help you avoid unnecessary problems with this information. Ensure timely maintenance of your servo motors and trust experienced specialists to prevent downtime and high follow-up costs.

Technical Specifications: