Improvement of medium-sized motor bearings

　　In power plant auxiliary equipment, motor as the main source of power to complete and ensure the normal operation of the unit, so the damage failure occurs when the motor is also quite big, medium-sized motor, in particular, can seriously affects the safe operation of the unit. According to our statistics found that the failure of motor bearing damage or because of the bearing damage caused by the motor fault, account for more than 60% of all motor fault, so solve the motor bearing damage is also solve the problem of the importance of motor fault. According to the analysis, most medium-sized motor is "end cover sliding bearing type" structure and "rolling bearing type" structure. After we summary and analysis of the various medium-sized motor repair experience, think that there are the following questions:

　　1, sliding bearing end cover: most of this kind of Structure Of Bearings heating and oil leakage phenomenon, caused the corrosion of motor stator winding, and make the motor internal oil pollution and dust too much, caused the poor ventilation, make the motor temperature is too high and damage.
　　2, box type high voltage motor: the motor is a new type of motor production in China in recent years, its performance, appearance is superior to "JS series motor. But some of the factory produced this kind of motor, for there are some deficiencies in the design of the bearing, causing the motor bearing fault happened more in the running. Structure of the motor is equipped with a distance outside of the bearing oil baffle plate bearing clearance is small, it can keep up the inside of the bearing grease is enough, but exist in the structure the following disadvantages:

　　(1), is not conducive to bearing cooling and lubricating grease of circulation, make the bearing temperature rise in the operation, the performance of the grease is reduced, which in turn cause a vicious cycle of temperature rises, the bearing damage.
　　(2), because of the existence of bearing oil baffle plate, and makes the motor when minor repair, open the bearing cover cannot check, and when the motor overhaul, do not remove the oil baffle plate is also unable to check the bearing cleaning, only change, causing unnecessary waste.
　　(3), for many times maintenance need to remove the oil pan and the replacement of the bearings, the oil baffle disc hole and shaft with loose, make oil baffle plate in the run emerge from the axis, cause of failure.
　　3, double bearing type machine: now the part of the production in our country medium-sized motor, load side adopted double bearing structure. It increases the load side of the radial bearing capacity, but also brought difficult to repair. During the overhaul of motor, bearing to cleaning and checking and must be replaced, otherwise can't guarantee the quality of maintenance, caused the rise in the cost of maintenance. In addition, the structure of the motor, most of the bearing in the operation temperature is higher, reduce the service life of bearing and damage.

　　4, the structure of the bearing accessories question: at present our country most motor bearing accessories is with the internal and external oil cover structure. This kind of structure defects are the sealing effect is poorer, the motor internal and external dust easily inhaled into the bearing, speed bearing wear and damage; Is its bearing structure of the attachment of bearing cooling, cooling and lubricating grease of cycling doesn't work, so the bearing running at higher temperature, reduce the service life, reach a repair cycle caused by motor bearing is damaged. According to our analysis found that imports of medium-sized motor structure is a sealing devices are installed on the both sides of the bearing all, ensured the cleanness of bearing internal; 2 it is on the outer edge of the bearing is equipped with positioning, cooling device, and the bearing oil chamber space is larger, which greatly reduce the temperature of bearing operation, and get good lubrication, prolong the service life of bearing.
　　5, bearing selection problem: according to our analysis and calculation of motor bearing, bearing fault has a lot to do with the selection of bearing. Imports from China's motor and motor comparison, domestic medium-sized motor load side bearing, general is to choose "medium roller bearing". The radial load capacity of the bearing is significantly more than the calculated value, but allows the speed and the actual motor speed differs little, caused the service life of bearing can not reach the rated. But imports of medium-sized motor load side bearings are generally choose larger "light ball bearing", and the light side is choose smaller than lateral load roller bearings "light", such not only to ensure the bearing capacity of bearing, and bearing allows speed considerably more than the actual speed of the motor, so can achieve or exceed the bearing service life.
　　Transformation process and methods:
　　Through our analysis of the above all kinds of motor, the transformation of motor bearing is for many years in our factory and has received the good effect. Old factory, our factory is completed and put into operation in 1958 in the early seventy s we went to "end cover sliding bearing type" problem of the motor bearing of transformation, and accumulated a lot of experience. In the eighty s, the factory after all the import boilers and ancillary equipment. After years of operation and after several times of maintenance, we find out the advantages of the imported medium on the motor structure design and combines the actual conditions of our domestic motor structure, further the reform.
We are in the recovery of motor bearing, first of all, the selection of bearing, found that the above problems, namely, the design and selection of bearing calculation. The retrofit scheme is based on the actual structure size of the motor, as far as possible to design the structure of the imported motor bearing and accessories (see chart) imported motor bearing structure. After the modification of the motor running, the service life of the bearing are mostly more than doubled, solved the problem of the most frequent medium-sized motor bearing damage, which provide a reliable guarantee of safe operation of the unit.