It has been observed that customers may experience issues with shaft drift or bearing temperature rise due to axial force, regardless of whether the motor in question is high-voltage or low-voltage electric induction ac motor. The optimal operational state of the motor is to ensure the ideal relationship between the motor and the load without any axial force; in fact, different motors exhibit varying degrees of axial force.
In the case of a three-phase induction AC motor, the connection of the stator winding to the power supply results in the generation of a rotating magnetic field. This, in turn, gives rise to the induction of a current in the rotor through electromagnetic induction, which in turn causes the rotor to become magnetised. This process generates electromagnetic attraction and causes the rotor to rotate.
Following the application of excitation, the synchronous motor rotates at the synchronous speed, whereas the asynchronous motor exhibits slip as a result of its rotation. The generation of the motor’s rotating magnetic field attraction is due to the shortest characteristic of the magnetic line of force. The electromagnetic force makes the motor run on the electromagnetic centre line, that is, the electromagnetic force of the motor stator and rotor acts in the radial direction, so that they are balanced with each other, and no axial magnetic force is generated. However, in actual operation, axial force will be generated due to the following factors.
Causes of axial force
● The axial force generated by the flow of cooling air when the motor rotor fan is running at no load.
●Due to factors such as manufacturing process and motor assembly error, the stator and rotor cause the mechanical center line to deviate from the electromagnetic center line of the motor, generating axial force.
●In order to reduce the influence of tooth harmonics in the design, the stator or rotor is made into a skewed slot structure. Therefore, when the load is running, the electromagnetic force forces the rotor to deviate to one end and generates axial force.
The electromagnetic center line of the motor is the reference line for the motor shaft to dock with the driven mechanical equipment coupling. However, since there is no electromagnetic center line mark in the design and manufacturing of the motor, the installation of the motor and the coupling are based on the installation drawings provided in the random documents. The calibration size is based on the designed mechanical center. In this way, the motor will inevitably deviate in actual operation due to the misalignment of the mechanical center line and the electromagnetic center line, that is, the error of the motor installation and coupling docking, generating axial force. The direction of the axial force is a push or pull axial force for the driven mechanical equipment, which causes damage to the bearings or the whole machine of the motor and the driven mechanical equipment.
For the increased safety brushless excitation synchronous motor, there are more factors. Therefore, from the perspective of process manufacturing and processing, improving the quality of the punching sheets; reducing the burrs of the punching sheets; strictly complying with the process discipline of the number of laminations and the lamination pressure, ensuring the length of the stator and rotor cores; eliminating the errors of human installation and assembly, and requiring the technical workers of the enterprise to have high technical quality and fine assembly skills, is the process guarantee for reducing the axial force.
In addition, the designer must be proficient in the processing and manufacturing process, the product assembly process, and comprehensively consider the size and direction of the axial force generated by the inherent factors such as the direction of the motor, the fan layout, and the direction of the skew slot in the structural design, so that they can offset each other or reduce to the minimum. At the same time, the product assembly technical workers must participate in the initial debugging experiment after the product assembly.
In the debugging experiment, it is more important to require the inspection technicians to accurately require the assembly process to adjust the displacement value and displacement direction of the rotor position in the technical documents according to the actual displacement data of the motor center line and the electromagnetic center tested by the no-load and load experiments in the prototype trial assembly experiment.
Wolong, as the leading manufacturer, is always putting these technical inspections as the priority in order to provide customers with the best-quality industry motors of all kinds of types such as the mine motors, explosion-proof ac motors, oil motors, petrol motors and so forth.
Post time: Nov-25-2024