Temperature rise is a very critical performance parameter for motors , and the temperature rise requirements for motors with different heat resistance grades will vary. Temperature rise is positively correlated with temperature, but the temperature of different parts of the motor is not the same, although its distribution is quite regular. Today, Ms. Can will share with you the temperature distribution of motors with different ventilation structures.
In calculating the temperature rise of an electric motor, the most important aspects are the temperature rise of the windings and the core. These components are both heat-conducting media and distributed heat sources. Their temperatures generally follow a certain spatial curve, resulting in the distinction between maximum and average temperature rise. Although the heating limit of each component of the motor should be based on the maximum temperature rise, in calculations, it is usually sufficient to calculate only the average temperature rise of the heating components as a whole. There is a certain regularity between the average temperature rise and the maximum temperature rise, so the average temperature rise can also be used to measure the motor's heating performance.
Axial temperature distribution of stator windings in symmetrical radial ventilation motors
When using this ventilation system, the airflow through each radial ventilation duct is roughly the same, and the highest temperatures of the windings and core occur in the middle of the motor. The heat converted from copper (aluminum) losses in the middle of the stator winding is partially dissipated into the air through the core and ventilation ducts, and partially conducted along the windings to both ends, dissipating into the air from the winding ends. In motors with a short effective length, end-of-winding heat dissipation plays a significant role in cooling the windings.
Axial temperature distribution of stator windings in axial or hybrid ventilation motors
Generally, when using this type of asymmetrical ventilation system, the location where the highest temperature occurs moves from the middle of the symmetrical ventilation system towards the outlet of the hot air escaping motor.
Axial temperature distribution of surface-cooled enclosed AC motor stator windings
In this type of motor, the losses in the stator winding are mainly dissipated through the core and frame. The heat dissipation conditions at the winding ends are poor, so some of the heat lost at the ends also needs to be transferred through the slots and dissipated through the core. This results in a temperature distribution in the stator winding that is high at both ends and low in the middle.
Temperature distribution of excitation winding
In concentrated multilayer excitation windings, because the height is much greater than the thickness, heat is mainly dissipated from the surface. The heat dissipation conditions on the inner and outer surfaces of these windings are typically different, resulting in an asymmetrical temperature distribution.
Temperature distribution of iron core laminations
Because the thermal conductivity of silicon steel laminations differs significantly along the radial and axial directions (e.g., the thermal conductivity of unpainted silicon steel laminations is 42.5 along the delamination direction but only 0.62 along the perpendicular direction), it can be approximated that the radial temperature distribution of the laminations is uniform, while the axial temperature distribution is non-uniform. If the airflow through the radial ventilation channels on both sides is different, the axial temperature distribution of the core will also be asymmetrical.
The transverse thermal conductivity of stacked silicon steel sheets is related not only to the silicon content of the silicon steel sheets, but also to the inter-sheet insulation material and the degree of compression.
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