Other Factors Affecting Motor Bearing System Issues

(1) Uneven air gap between the stator and rotor of the motor

For the air gap between the stator and rotor of the motor. We have discussed many topics, such as the impact of air gap between the stator and rotor on efficiency, vibration and noise, and temperature rise. When the air gap between the stator and rotor of a motor is uneven, the most direct manifestation after the motor is powered on is low-frequency electromagnetic noise. The impact on the bearing system comes from the radial roller pulling force, which causes the bearings to always be in an eccentric state during motor operation, resulting in bearing heating and damage.

(2) Axial alignment of stator and rotor cores

This issue has a significant impact on motors with relatively long iron lengths and radial ventilation ducts. In actual production and processing, due to errors in the positioning dimensions of the stator or rotor iron core, as well as thermal processing during rotor manufacturing, the rotor iron core may become bent, resulting in the generation of axial force during motor operation. In this state, the motor bearings may operate abnormally due to the effect of axial force.

(3) Axis current issue

This issue has a significant impact on variable frequency motors, low-voltage high-power motors, and high-voltage motors. For the issue of shaft current, which is also an old topic we have talked about many times, the reason for the generation of shaft current is the effect of shaft voltage. There are two measures to avoid this problem, namely, effectively reducing the shaft voltage from the design and manufacturing process, or cutting off the current circuit.

If effective measures are not taken, the shaft current will have a devastating impact on the bearing. When it is not severe, the bearing system will exhibit noise, which will then increase; When the shaft current is severe, the noise in the bearing system changes rapidly, and upon disassembly and inspection, there will be obvious washboard like marks on the bearing ring; The issue of shaft current is accompanied by a significant problem of degradation and failure of lubricating grease, which can cause the bearing system to heat up and burn out in a short period of time.

(4) Rotor slot inclination

Most motor rotors have straight slots, but in order to meet one of the performance indicators of the motor, it may be necessary to make the rotor into a skewed slot. When the slope of the rotor slot is large, the axial magnetic pulling force component of the motor stator and rotor will increase, causing the shaft to bear abnormal axial force and generate heat.

Special Factors Affecting Motor Bearing System Issues

(1) Poor heat dissipation conditions

For most small motors, the end cover may not necessarily have heat dissipation ribs, while for large-sized motors, the heat dissipation ribs on the end cover are particularly important for controlling the bearing temperature; For some small motors with increased capacity, the heat dissipation of the end cover is also improved to further improve the temperature of the bearing system.

(2) Control of Bearing System for Vertical Motor

We have discussed the assembly control requirements for vertical motor bearings before. If there are dimensional deviations or incorrect assembly directions, the motor bearings will not be able to operate normally, which will inevitably lead to bearing noise and heating.

(3) Bearing heating under high-speed and heavy load conditions

For high-speed motors with large loads, bearings with relatively high accuracy should be selected to avoid problems caused by insufficient bearing accuracy. If the consistency of the rolling element size of the bearing is not good, under the load operation of the motor, due to the uneven force on each rolling element, the bearing will experience natural vibration and wear problems. This process may cause metal shavings to fall off and affect the operation of the bearing, exacerbating the occurrence and damage of the bearing.

Especially for high-speed motors, due to the structure of the motor itself, the shaft may be relatively small, and there is a high possibility of shaft deflection during operation. Therefore, for high-speed motors, necessary adjustments are often made to the material of the shaft.

(4) Inappropriate hot sleeve process for large motor bearings

For small motors, cold pressing technology is more commonly used for bearings, while for large motors and high-voltage motors, bearing heating technology is more commonly used. There are two heating methods, one is oil heating and the other is induction heating. If the temperature control is not good, excessive temperature can cause bearing performance failure, and after running the motor for a period of time, noise and heating problems may occur.

(5) Deformation and cracks occur in the end cap bearing chamber and bearing sleeve

This problem often occurs in the casting components of large motors. Due to the typical plate-like nature of the end caps, significant deformation may occur during both casting and processing. Some motors may experience bearing chamber cracks during storage, leading to noise and even fatal quality issues during operation.

HZKM-2 Lubricating Oil Abrasion Tester