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When selecting motor bearings, it is particularly important to conduct calculations to verify the bearing loads. The first step in calculating the loads on motor bearings is to determine the forces acting on the bearings at both ends of the motor. In this article, Changhui Instruments discusses the differences in load-bearing capacity between the bearing systems of vertical and horizontal motors, thereby laying a solid foundation for understanding the calculation of motor bearing loads. Motors can be installed in vertical or horizontal configurations, among others. The vertical motor is a common installation type among motors, and its bearing system configuration differs significantly from that of ordinary horizontal motors. Engineers often directly adopt the bearing usage methods for horizontal motors, which leads to various types of failures in the bearings. Therefore, Changhui Instruments will first discuss the differences in load-bearing capacity between vertical and horizontal motor bearings. yunrun.com.cn/tech/3274.html 1. Bearing load of horizontal motors For ordinary horizontal motors, the load borne by the motor’s bearing system is roughly as shown in the following figure: http://yunrun.com.cn/upload/202008/04/202008041533398891.png As can be seen from the figure, the two bearings bear the radial and axial loads on the shaft. The radial loads mainly include the weight of the motor’s rotor and the external radial loads at the shaft extension ends ； The axial load is the external axial load applied to the shaft end of the motor. If the motor is loaded via pulleys, both the belt tension and the weight of the pulleys should be included in the radial load ； If the motor is loaded via a coupling, the weight of the coupling should be included in the radial load ； For motors with unilateral magnetic pulling force, this force should be included in the motor’s radial load. From the configuration of the motor bearing system, it can be seen that the radial load of the motor is shared by the two bearings. If there is an external radial load acting on the motor, the loads on the bearings at the shaft extension end and the non-shaft extension end will differ to some extent due to this load ； If the direction of the external radial load is the same as the gravity of the motor rotor, the load at the shaft extension end will be greater than the radial load at the non-shaft extension end. If the direction of the external radial load is opposite to the direction of the motor rotor’s gravity, then the load at the shaft extension end is less than the radial load at the non-shaft extension end ； At the same time, the external axial load on the motor is borne by the positioning end bearing in the bearing system. 2. Bearing load of vertical motors: In vertical motors, the forces acting on the bearing system inside the motor are as shown in the following image: http://yunrun.com.cn/upload/202008/04/202008041536355429.png. As can be seen from the image, the two bearings in the motor’s bearing system share the axial and radial loads. At this point, the gravity of the motor rotor becomes the axial load on the motor bearing system, while the axial and radial loads at the end of the motor shaft are applied to the shaft ends respectively. For motors driven by pulleys, the belt tension acts as a radial load on the motor’s bearing system, while the weight of the pulley acts as an axial load on the same bearing system ； For coupling loads, the weight of the coupling becomes the axial load on the motor bearing system. Since the motor is installed vertically, there is no unilateral magnetic pulling force caused by shaft gravity deflection, so it does not need to be taken into account. As is known from the knowledge related to motor bearing system configurations, the radial load of the motor is shared by the two bearings, while the axial load is borne by the positioning bearing in the motor bearing system. 3. Comparison of bearing system loads between vertical and horizontal motors. As can be seen from the respective explanations above, for horizontal motors, if there is no axial load from outside, then no other axial load should exist in the motor’s bearing system. Therefore, the motor bearing system is primarily designed to bear radial loads, with bearings at both the fixed and non-fixed ends bearing radial loads as well. For vertical motors, the motor bearing system should not experience any radial load when there is no external load of that type. Therefore, the motor bearing system is primarily designed to bear axial loads. Moreover, all the axial load is borne by the positioning end bearing. Of course, there are some errors in the manufacturing of motors that can result in additional loads; these include poor alignment between the stator and rotor, which leads to uneven air gaps and thus unilateral magnetic pulling forces ； The additional axial load resulting from poor axial alignment of the stator and rotor ； Tipping moments caused by poor form and position tolerances of the motor bearing housing, etc. These loads all belong to deviation loads, resulting from poor control in the production design. Therefore, it cannot be included in normal considerations and calculations. Through the explanations in this article, motor engineers can understand the differences in load-bearing capacity between the bearing systems of vertical and horizontal motors. So what differences in motor design, manufacturing, and usage do such variations in load capacity bring about? For specific details, please refer to the relevant articles on the “Changhui Instrument Network”.