Customer Inquiry – Urgency for a Solution

23.04.2025 by Viktor Siebert

Customer Inquiry – Urgency for a Solution

A customer contacted us regarding his Yaskawa AC SGMPH-08AAA41D servo motor. According to his maintenance team, the motor had a short circuit to ground and required replacement. The critical issue was that this motor type was no longer available, and an actuator attached to it would also need replacing. Furthermore, the Yaskawa Servopack, closely working with the motor, could potentially be damaged as well, as motor short circuits often cause additional damage to the servopack. The customer feared that eventually, even the entire control system would need replacement, as newer motor and drive types were involved, resulting in significant costs and long waiting times due to retrofit work. He was awaiting an offer from the machine manufacturer.

Analysis and Fault Diagnosis – Repair Feasibility

The customer anxiously asked whether a short circuit in the motor necessarily meant its end. We suggested a thorough inspection of the motor first. Our experience shows that 98% of servo motors with short circuits to ground or between windings can be repaired. Usually, the motor windings are sealed, but over time emulsifying fluid seeps through the seals, causing short circuits or low resistance in the motor. Often, corroded cables in connectors or sockets lacking adequate insulation also cause short circuits.

Repair Execution – Successful Restoration

This was precisely the issue here: the motor was filled with oil and emulsion. Not visible externally, a considerable amount of fluid only emerged upon opening. We thoroughly cleaned and dried the motor openly for 24 hours. Afterwards, the short circuit was completely eliminated – the windings showed perfect insulation with high-resistance values. Unfortunately, the fluid ingress damaged the encoder, a sensitive electronic component. The glass scanning disk was destroyed by abrasion, grease, and dirt. We provided a solution by offering an encoder replacement.

Completion and Customer Satisfaction

The customer was greatly relieved by our fast and cost-effective solution. Production resumed within just one week.

The following work was performed on the motor:

Preventive overhaul: Replacement of all defective and worn-out parts, renewal of ball bearings and seals.
Intensive cleaning including paint removal and degreasing.
Repainting.
Encoder replacement and adjustment.
Extensive final and long-term tests on test benches, including final adjustments.
Completion of documentation and checklists.

Our Appeal to You: Do not prematurely dispose of motors, even if they appear irreparable. In most cases, there is a solution significantly more cost-effective and faster than replacement.

Motor Specifications

Manufacturer: Yaskawa
Type: AC Servo Motor
Model number: SGMPH-08AAA41D
Rated power: 750 W
Rated voltage: 200 V
Speed: max. 3000 rpm
Encoder type: Absolute encoder

How Servo Motors Work:

A servo motor is a specialized electric motor that enables precise motion and accurate positioning. It operates in conjunction with a servo drive (Servopack), continuously monitoring and controlling the motor position via an encoder. This continuous feedback between motor and controller allows precise control of torque, speed, and position. Servo motors are commonly used where high dynamics, accuracy, and reliability are essential, such as in robotics, CNC machinery, and industrial automation systems.