In power plant auxiliary equipment, electric motors serve as the primary power source to ensure the normal operation of the unit. Therefore, the losses caused by motor failures are substantial, especially for medium-sized motors, which can seriously affect the safe operation of the unit. Our statistics on motor failures show that bearing damage, or failures caused by bearing damage, account for over 60% of all motor failures. Therefore, addressing bearing damage is a crucial aspect of motor troubleshooting. Analysis indicates that most medium-sized motors use either an "end-cover sliding bearing" or "end-cover rolling bearing" structure. Based on our experience in overhauling various medium-sized motors, we identify the following problems: End-cover sliding bearing type: These motors often experience bearing overheating and oil leakage, leading to corrosion of the stator coils and excessive oil and dust accumulation inside the motor, resulting in poor ventilation and overheating, ultimately causing damage. Box-type high-voltage motors: These are a new type of motor produced in China in recent years, with superior performance and appearance compared to the "JS series" motors. However, some manufacturers produce these motors with deficiencies in bearing design, resulting in a higher incidence of bearing failures during operation. These motors have an oil baffle mounted on the outside of the bearing with a small clearance from the bearing. This seems to keep the grease inside the bearing sufficient, but this structure has the following disadvantages: (1) It is not conducive to the heat dissipation of the bearing and the circulation of the grease, causing the bearing temperature to rise during operation, reducing the performance of the grease, and then causing a vicious cycle of further temperature rise, resulting in bearing damage. (2) Due to the presence of the bearing oil baffle, it is impossible to inspect the bearing when the bearing cover is opened during minor repairs, and it is impossible to clean and inspect the bearing without removing the oil baffle during major repairs, resulting in replacement and unnecessary waste. (3) Because the oil baffle and bearing need to be disassembled and replaced during multiple repairs, the fit between the inner hole of the oil baffle and the shaft becomes loose, causing the oil baffle to fall off the shaft during operation and causing failure. Double bearing motor: Some medium-sized motors currently produced in China use a double bearing structure on the load side. Although this increases the radial load capacity on the load side, it also brings difficulties to maintenance. During major motor overhauls, bearings cannot be cleaned and inspected, necessitating replacement; otherwise, the quality of maintenance cannot be guaranteed, leading to increased maintenance costs. Furthermore, in motors with this structure, most bearings operate at relatively high temperatures, reducing their lifespan and causing damage. Bearing accessory structure issues: Currently, most bearing accessories in Chinese motors use an inner and outer oil cap structure. The disadvantages of this structure are poor sealing, allowing dust from both inside and outside the motor to easily be drawn into the bearing, accelerating wear and damage. Additionally, the structure of these accessories offers little benefit to heat dissipation, cooling, and grease circulation, resulting in higher operating temperatures, reduced lifespan, and bearing failure before the motor reaches its scheduled maintenance cycle. Our analysis of imported medium-sized motor structures reveals two key features: first, sealing devices are installed on both sides of the bearing, ensuring internal cleanliness; second, positioning and cooling devices are installed on the outer side of the bearing, and the oil chamber space is larger, significantly reducing operating temperature and providing good lubrication, thus extending bearing life. Bearing selection issues: Based on our analysis and calculations of motor bearings, we believe that bearing failure is closely related to the selection of the bearing. Comparing domestically produced motors with imported ones, the load-side bearings of domestically made medium-sized motors generally use "medium-sized roller bearings." The radial load capacity of these bearings far exceeds the calculated value, but the allowable speed is only slightly different from the actual motor speed, resulting in the bearings not reaching their rated service life. However, imported medium-sized motors typically use larger "light-duty ball bearings" on the load side, while using smaller "light-duty roller bearings" on the unloaded side. This not only ensures the bearing's load capacity but also allows the bearing's allowable speed to far exceed the actual motor speed, thus achieving or exceeding the bearing's service life. Modification Process and Methods: Based on our analysis of the various motors mentioned above, we have modified the motor bearings in our factory over the years with excellent results. Our factory, established in 1958, began modifying bearings for "end-cover sliding bearing type" motors in the early 1970s, accumulating considerable experience. In the 1980s, our factory introduced and put into operation imported boilers and all auxiliary equipment. After years of operation and several overhauls, we identified the advantages of the imported medium-sized electric motor's structural design and further modified it by combining it with the actual structure of our domestically produced motors. In the modification of the motor bearings, we first evaluated the bearing selection and discovered the aforementioned problems, thus requiring recalculation, design, and selection of the bearings. The modification plan was based on the actual structural dimensions of the motor, using imported motor bearings and accessories as much as possible in the design. Statistical analysis of the motor's operation after the modification showed that the service life of most bearings more than doubled, solving the problem of frequent bearing failure in most medium-sized electric motors and providing a reliable guarantee for the safe operation of the unit. The above is our discussion of the modification of some electric motor bearings at Huangtai Power Plant. Although we have achieved good results in the modification work, there are still many shortcomings. In the future, we will further explore and strive to apply advanced technologies more widely in our practical work, making a greater contribution to the development of the power industry.