Causes and solutions of motor and bearing heating

Update:10 Oct 2020

Motor (also known as motor) is a kind of electromagnetic device which can convert or transfer electric energy according to the law of electromagnetic induction. Its main function is to produce driving torque, as a power source of electrical appliances or various machinery. Its main function is to convert mechanical energy into electrical energy. At present, the most commonly used is to use heat and water energy to drive the generator rotor to generate electricity. Generally speaking, motor bearing overheating means that the temperature rise of rolling bearing exceeds 55k and that of sliding bearing exceeds 40K.
1. The rolling bearing is not installed correctly, and the fitting tolerance is too tight or too loose
Treatment method:
The working performance of rolling bearing depends not only on the manufacturing accuracy of the bearing itself, but also on the dimensional accuracy, form and position tolerance and surface roughness of the shaft and hole matched with it, the selection of fit and the correctness of installation. In general, a well assembled rolling bearing only bears radial stress in horizontal motor. However, if the fit between bearing inner ring and shaft is too tight, or the fit between bearing outer ring and end cover is too tight, that is to say, the bearing clearance will become too small after assembly, sometimes even close to zero. In this way, the rotation will be inflexible, and it will generate heat during operation. If the fit of bearing inner ring and shaft is too loose, or bearing outer ring and end cover are too loose, relative rotation will occur between bearing inner ring and shaft, or bearing outer ring and end cover, resulting in friction heating and bearing overheating. Usually, the tolerance zone of inner diameter of bearing inner ring, which is used as the reference part, is moved below the zero line in the standard. The fit between the tolerance zone of the same shaft and the inner ring of bearing is much more tight than that formed by the inner diameter tolerance zone of the bearing inner ring and the general reference hole.

2. the bearing heat can be caused by improper selection of grease or improper use and maintenance, poor quality of grease or deterioration, or mixing with dust and impurities
Treatment method:
Too much or too little grease will also cause bearing heat. When the grease is too much, there will be a great friction between the rotating part of the bearing and the grease, while when the grease is too little, it may be caused by dry friction and heat. Therefore, the amount of grease must be adjusted to be about 1 / 2-2 / 3 of the space volume of bearing chamber. The unsuitable or deteriorated grease shall be cleaned and replaced with the proper clean grease.
3. the axial clearance between the outer bearing cover of motor and the outer circle of rolling bearing is too small
Treatment method:
Large and medium motors generally use ball bearings at non axial extension ends. Roller bearing is used at the extension end of shaft, so that when the rotor is heated and expanded, it can be extended freely. Because both ends of small motor adopt ball bearing, there should be a proper clearance between outer bearing cover and outer ring of bearing. Otherwise, bearing may be heated due to excessive axial thermal elongation. When this phenomenon occurs, the front or rear bearing cover shall be removed a little, or a thin paper pad shall be added between the bearing cover and the end cover to form a sufficient gap between the outer bearing cover and the outer bearing outer ring at one end.

4. The end covers or bearing covers on both sides of the motor are not installed properly
Treatment method:
If the end covers or bearing covers on both sides of the motor are not parallel or the stop is not close to each other, the ball will deviate from the track and rotate and heat up. The end caps or bearing caps on both sides must be installed flat again, and the bolts should be rotated and fixed evenly.
5. The ball, roller, inner and outer ring and ball frame are seriously worn or metal peeling off
Treatment method:
The bearing should be renewed at this time.

6. Poor connection with the load machine. Including: poor coupling assembly, belt tension is too large, and the axis of the load machine is not the same, the pulley diameter is too small, the pulley is too far from the bearing, the axial or radial load is too large, etc
Treatment method:
Correct incorrect connections to avoid abnormal forces on bearings.
7. The shaft is bent
Treatment method:
At this time, the bearing force is no longer pure radial force, so it causes bearing heating. Try to straighten the bent shaft or replace it with a new one.

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