In operation, the sliding bearings of horizontal motors only bear radial loads and are not allowed to bear axial loads. However, due to design and manufacturing factors, the motor itself also has axial loads. This is absolutely unacceptable for sliding bearings without thrust surfaces. For sliding bearings with thrust surfaces, although they can also bear the axial loads generated by the motor itself, there is a certain limit. If the limit is exceeded, the bearing end will heat up, mechanical friction loss will increase, and in more serious cases, the tungsten alloy bearing will melt, causing major mechanical accidents or explosions. This is a major hidden danger for motor products.
Foreign standards and literature clearly specify the marking of the electromagnetic centerline of electric motors and the axial force load on sliding bearings. However, Chinese national standards and electric motor test methods lack such regulations, especially regarding the limits on axial force. Therefore, based on foreign standards and literature and referring to similar foreign product prototypes, a marking plate for the electromagnetic centerline of electric motors was designed and installed, and preliminary research and exploration were conducted on the determination of the axial force load on sliding bearings.
Engraving of the electromagnetic center line
Marking the electromagnetic center line is an important process in the assembly and product testing of medium and large electric motors, and it is also an important guarantee of product quality. At the same time, the marking plate of the electromagnetic center line of the electric motor is also one of the important marks of the brand of electric motor. That is, the electric motor runs on the electromagnetic center line under no-load and load conditions. At this time, it is required to run without axial force. The distance between the shoulder of the motor journal and the thrust surfaces at both ends of the sliding bearing should meet the design specifications or special technical requirements.
Special technical requirements refer to the requirement that, when the motor's rotating shaft is in a non-connected state with the coupling of the drive machinery, the shaft must be displaced a specified dimension towards the non-shaft extension end to allow for maintenance work by disengaging the motor shaft from the coupling. Therefore, the distance between the thrust surfaces at both ends of the sliding bearing and the shoulder of the motor shaft journal is not equidistant, and an indicator line for the electromagnetic centerline is marked. This indicator line also serves as the baseline for the axial force load of the motor itself, which we will discuss and measure.
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