Motor temperature rise
In the calculation of motor temperature rise, the most important thing is to calculate the temperature rise of the winding and iron core. These components are both thermal conductive media and distributed heat sources, and their temperatures generally follow a certain curve distribution in space, resulting in the distinction between the highest temperature rise and the average temperature rise. Although the heating limit of each component of the motor should be based on the highest temperature rise, when calculating, as a whole, it is usually possible to only calculate the average temperature rise of the heating components. There is a certain regularity between the average temperature rise and the highest temperature rise, so the average temperature rise can also be used to measure the heating situation of the motor.
Temperature distribution of motors with different structures
Temperature distribution of stator winding along the axial direction in motors with symmetrical radial ventilation system
When using this ventilation system, the air volume through each radial ventilation duct is generally the same. At this point, the highest temperature of both the winding and the iron core occurs in the middle of the motor. The heat converted from copper (aluminum) in the middle of the stator winding is partially dissipated into the air through the iron core and ventilation duct, while the other part is conducted along the winding to both ends and dissipated into the air from the winding ends. In a type of motor with a short effective length, the heat dissipation at the end plays a significant role in cooling the winding.
● Temperature distribution of stator winding along the axial direction using axial ventilation system or hybrid ventilation system
Generally speaking, when using a ventilation system with asymmetric ends, the temperature distribution of the stator winding and iron core, where the highest temperature occurs, moves from the middle of the symmetrical ventilation system towards the direction of the hot air escaping from the motor outlet.
Distribution of stator winding temperature along the axial direction in surface cooled enclosed (AC) motors
In this type of motor, the losses in the stator winding are mainly dissipated through the iron core and the machine base. The heat dissipation conditions at the end of the winding are poor, so a part of the heat loss at the end also needs to be dissipated through the slot and the iron core. In this way, the temperature distribution of the stator winding forms a situation of high in both ends and low in between.
Temperature distribution in the excitation winding
In a concentrated multi-layer excitation winding, due to the height being much larger than the thickness, heat is mainly dissipated from the surface. The temperature distribution along the thickness in this type of winding is usually asymmetric due to the different heat dissipation on the inner and outer surfaces of the winding.
Temperature distribution in the laminated iron core assembly
Due to the significant difference in thermal conductivity between the radial and axial directions of the silicon steel sheet stack, it can be approximately assumed that the temperature distribution of the core stack along the radial direction is uniform, while the temperature distribution along the axial direction is uniform
It is uneven. If the airflow through the radial ventilation ducts on both sides is different, the temperature distribution of the iron core along the axial direction will also be asymmetric.
