Investigation of the Temperature State of Electric Motors with a Decrease in the Speed of Rotation of the Rotor

The operation of electric motors as part of a frequency-controlled electric drive has shown that overheating of electric machines is observed with a deep decrease in the speed of rotation. This is partly due to incorrect adjustment of the control law in the frequency converter. The installation of temperature sensors in the stator windings with connection to the built-in temperature protection devices can lead to false disconnections. In the production processes of the agro-industrial complex, such interruptions cause significant technological damage. Modeling in the Comsol software of the main physical processes in an electric machine showed that when the rotation speed decreases, a temperature spike occurs in all parts of the machine and is especially pronounced in the stator windings. Such a temporary excess of temperature is due to the thermal inertia of the windings and stator steel with a sharp decrease in heat transfer due to self-ventilation. A further decrease in temperature is associated with a decrease in losses in the stator steel. The obtained images of temperature fields in the electric motor make it possible to analyze changes in the temperature state of individual parts of the machine in operating modes other than the nominal ones. The manufactured laboratory stand, with an electric motor similar to the model, made it possible to control the temperature in the main parts of the electric machine and compare the results with the simulation data. It is necessary to set time delays when using built-in temperature protection devices.