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Causes and Treatment Methods of Motor Bearing Overheating

Bearings are the most important supporting components of the motor. Under normal circumstances, when the temperature of the rolling bearing of the motor exceeds 95°C and the temperature of the sliding bearing exceeds 80°C, the bearing is overheated. Bearing overheating is a common fault when the motor is running. The causes are various and sometimes difficult to diagnose accurately. Therefore, in many cases, if it is not dealt with in time, the result will often be greater damage to the motor and the motor will be damaged. The life span is shortened, which affects work and production. Summarize the specific conditions, causes, and treatment methods of motor bearing overheating.

1. Causes and treatment methods of motor bearing overheating

(1)The rolling bearing is installed incorrectly and the fit tolerance is too tight or too loose.

Solution: The working performance of rolling bearings not only depends on the manufacturing accuracy of the bearing itself but also on the dimensional accuracy, geometric tolerance, and surface roughness of the shaft and hole it matches, the selected fit, and the correct installation. In general horizontal motors, and well-assembled rolling bearings only bear radial stress. However, if the fit between the inner ring of the bearing and the shaft is too tight, or the fit between the outer ring of the bearing and the end cover is too tight, that is, when the tolerance is too large, the bearing will The bearing clearance will become too small, sometimes even close to zero. In this way, the rotation will be inflexible and it will generate heat during operation. If the fit between the bearing inner ring and the shaft is too loose, or the bearing outer ring and the end cover are too loose, then the bearing inner ring and the shaft, or the bearing outer ring and the end cover, will rotate relative to each other, resulting in friction and heat, resulting in bearing failure. overheat. Usually, the tolerance zone of the inner diameter of the bearing inner ring as a reference part is moved below the zero line in the standard, and the tolerance zone of the same shaft and the inner ring of the bearing form a fit that is much tighter than that formed with the general reference hole.

(2)Improper selection of grease improper use and maintenance, poor quality or deterioration of grease, or mixed dust and impurities can cause bearing heating.

Solution: Adding too much or too little grease will also cause the bearing to heat up, because when there is too much grease, there will be a lot of friction between the rotating part of the bearing and the grease, and when the grease is added too little, dryness may occur Friction and heat. Therefore, the amount of grease must be adjusted to approximately 1/2-2/3 of the space volume of the bearing chamber. Unsuitable or deteriorated grease should be cleaned and replaced with suitable clean grease.

Causes and Treatment Methods of Motor Bearing Overheating插图

(3)The axial clearance between the outer bearing cover of the motor and the outer circle of the rolling bearing is too small.

Solution: Large and medium-sized motors generally use ball bearings at the non-shaft end. Roller bearings are used at the end of the shaft extension so that when the rotor is heated and expanded, it can elongate freely. Since small motors use ball bearings at both ends, there should be an appropriate gap between the outer bearing cap and the bearing outer ring. Otherwise, the bearing may heat due to excessive axial thermal elongation. When this phenomenon occurs, the front or rear bearing cover should be removed a little or a tissue pad should be added between the bearing cover and the end cover to form a sufficient gap between the outer bearing cover at one end and the bearing outer ring.

(4)The end covers or bearing caps on both sides of the motor are not installed properly.

Solution: If the end covers or bearing covers on both sides of the motor are not installed in parallel or the seams are not tight, the balls will deviate from the track and rotate to generate heat. The end caps or bearing caps on both sides must be reinstalled flat, and evenly rotated and fixed with bolts.

Causes and Treatment Methods of Motor Bearing Overheating插图1

(5)Balls, rollers, inner and outer rings, and ball cages are severely worn or metal peeling off.

Solution: Bearings should be updated at this time

(6)Poor connection to load machinery.

The main reasons are poor coupling assembly, excessive belt tension, inconsistency with the axis of the load machine, pulley diameter too small, pulley too far from the bearing, excessive axial or radial load, etc. Solution: Correct the incorrect connection to avoid abnormal force on the bearing.

(7)The shaft is bent.

Solution: At this time, the force on the bearing is no longer a pure radial force, which causes the bearing to heat up. Try to straighten the bent shaft or replace it with a new one.

2. How to protect the motor bearing from overheating

You can consider buying a temperature-measuring element near the bearing and then protecting the bearing through a control circuit. Download Generally, motors have a temperature-measuring element (such as a thermistor) inside the motor, and then two wires come out of it and are connected to a special protector. The protector sends a constant 24V voltage, which acts as the motor bearing. When overheating exceeds the set value of the protector, it will trip and play a protective role. Currently, most motor manufacturers in the country use this protection method.

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