Power plant auxiliary equipment, electric motor as the main power source to complete and to ensure the normal operation of the unit, so when the motor failed, the loss is quite large, especially medium-sized motor, can seriously affect the safety of the unit operation. According to our statistics on motor fault found, bearing damage or cause motor failure, accounting for more than 60% of all the fault of the motor bearing damage and solve the motor bearing damage is also an important problem to solve motor fault. According to the analysis, most of the medium-sized motor cover sliding bearing type structure and end caps rolling bearing structure. After a summary and analysis on a variety of medium-sized motor repair experience, that there are the following questions:
    Cover sliding bearing type: such motor Most with of bush fever and oil spill phenomenon, caused by corrosion stator coil, and internal motor oil and the fouling too much, resulting in a poorly ventilated, so that motor temperature damage.
    2, box-type high-voltage motors: The motor is produced in China in recent years new motor, its performance, appearance superior to JS series motor. However, some manufacturers produce such motor, due to the existence of certain deficiencies in the design of the bearing, resulting in a motor bearing failure occurs in the operation of more. The structure of these motors is fitted in the outside of the bearing to a small oil baffle plate away from the bearing gap, so to see inside the bearing grease can maintain adequate, but this structure is the existence of the following disadvantages:
    (1), not conducive to the cooling of the bearing and the circulation of the grease, so that the bearing temperature rise in operation, lower the performance of the grease, and then causing the vicious cycle of temperature rises, so that the bearing is damaged.
    (2), due to the presence of the bearing block oil pan, making minor repairs, the motor open bearing cap can not check in the overhaul of the motor, do not remove the block oil pan can not be cleaned checks bearing only replacement, causing unnecessary waste.
    (3), due to the many overhaul is required to remove the oil baffle plate and the bearing replacement, resulting in the internal bore and the shaft in the oil baffle plate with the loose, so that the oil baffle plate is disengaged from the shaft in operation, resulting in failure.
    3, double-bearing motor: China is now a part of the production of medium-sized motor, the load side with a double-bearing structure. This is despite an increase in the load side of the radial load capacity, but also brought to overhaul the difficulty. Overhaul of the motor, the bearings can not be cleaning and inspection and must be replaced, otherwise it can not ensure the quality of the overhaul, resulting in an increase in maintenance costs. Further, the motor of such a structure, most of the temperature of the bearing in operation is relatively high, so that the service life of the bearing reduces damaged.
    4, bearing Accessories structural problems: most of motor bearing attachments within and outside the oil cap structure. The disadvantage of such a structure is poor sealing effect, the motor, the dust from the outside easily be sucked into the interior of the bearing, accelerated wear of bearings and damage; longer cycle of its bearing attachment structure of the heat dissipation, cooling, and grease of the bearing basic does not work, so the higher operating temperature of the bearing life decreased, causing the motor to reach a maintenance cycle bearings that damage. According to our analysis imported medium motor structure discovery, all on both sides of the bearing mounted sealing means to ensure that the cleaning of the interior of the bearing; second is in the outside of the bearing is equipped with positioning, the cooling device, and the bearing oil chamber space This greatly reduces the bearing running temperature, and obtain a good lubrication, extended bearing life.
    5, bearing selection problem: According to our analysis and calculation of the motor bearings that bearing failure bearing selection has a great relationship. Compare motor with imported motor from our point of view, the domestic medium load side of the motor bearings, generally is the choice of "medium-sized roller bearings. The radial load carrying capacity of the bearing is much higher than the calculated value, but the permissible speed is very little difference to the actual motor speed, causing the life of the bearing is less than the rated. But imports of medium-sized motor load side bearings generally use larger light ball bearing, the no-load side is chosen smaller than the load side of the "light roller bearings." This will not only ensure the carrying capacity of the bearing and bearing permissible speed greatly exceeds the actual rotation speed of the motor it is possible to meet or exceed the life of the bearing.


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