Analysis of the causes of motor winding temperature rise failure
For motors of different series, the designed temperature rise margin is different; for motors of the same series, the physical space may be very tight due to various factors such as power, installation, and component versatility. The non-compliance of motor temperature rise can generally only be found during type testing and operation. The reasons for the non-compliance of motor temperature can be checked and analyzed from the aspects of loss and ventilation.
When the stator current and stator copper loss are large, the motor temperature rise will be high. The rotor copper loss and iron core will also directly affect the motor temperature rise. For ventilation loss, it is necessary to reduce the temperature rise in most cases. The relevant losses will be balanced in the overall effect during the design process, and the comprehensive cost relationship will be handled by balancing the amount of material used.
We have also conducted a relatively detailed analysis on how to adjust and reduce motor losses in the previous content, so this article will not repeat it. However, when the losses deviate significantly from the design and previous type test data, a specific analysis should be conducted.
In motor products, the air path has a greater impact on the temperature rise of the motor. The motor fan, wind cover, cast aluminum rotor wind blades, internal fan, stator winding end size, motor ventilation duct with radial ventilation duct, stator and rotor alignment, etc. will affect the ventilation effect of the motor.
The wind pressure and air volume generated by the rotor fan are limited by the motor structure and efficiency. Keeping the wind path unobstructed and reducing wind resistance can increase the air volume; adjusting the wind resistance ratio of the parallel wind path can reasonably distribute the air volume. Properly adjusting the shape, position and size of the ventilation components to prevent local circulation or ineffective circulation of the air flow can effectively reduce the temperature rise of the motor.
A large part of the heat of the stator winding of the guarded motor is dissipated from the end. The centrifugal fan should be located in the middle of the stator winding end as much as possible so that the cooling air can effectively cool the winding end. There should be an appropriate radial gap between the cast aluminum rotor blades and the end of the stator winding. If the air path is too narrow, the air volume on the surface of the winding end will be reduced. The end of the scattered embedded stator winding is more effective, especially for high-speed motors.
For motors with radial ventilation ducts, if the length of each section of the core does not conform to the drawing, and the axial dimension processing errors of the base, shaft, end cover, etc. are too large, the ventilation slots of the stator and rotor cores will not be aligned, and the airflow generated by the rotor air duct partition will have difficulty entering the stator ventilation slots. The radial ventilation duct distortion during the processing of the stator and rotor cores has a particularly serious impact on the temperature rise of the motor.
In addition to the stator and rotor core and winding factors, the base cavity, the shape and size of the heat dissipation window, and their mutual coordination also have a great influence on the motor air path.
The air duct is one of the factors that have the greatest impact on the performance of motor products, especially the temperature rise and noise performance of the motor. However, most manufacturers do not fully understand the design and control of the air duct. For example, if the casting base solution is directly migrated to the box-type base solution, the compliance of the mechanical dimensions may not necessarily guarantee the consistency of the air ducts. Further research in this area is needed .