When the high speed brushless motor is running, a large amount of loss will lead to temperature rise, and the thermal properties of materials will change accordingly, which will affect the loss of the motor. The cycle will continue until the two interact and the temperature rise stabilizes. In this paper, a coupling method is proposed to calculate the coupling between electromagnetic field and temperature of high-speed brushless motor to achieve information feedback and improve the calculation accuracy.
According to the thermal relative density loading temperature throughout it can be seen that the top temperature around the resistance is large. When the thermal relative density loading design is selected, the temperature at the end of the resistance is 68.8℃, and the temperature of the sub-thermal coupling around the resistance breaking is 72.4℃. The thermistor method was used to carry out the heating experiment on the samples, and the resistance winding temperature was 75.6℃. Compared with the thermal relative density loading method, the deviation of the result obtained by analyzing the coupling of magnetic field and thermal stress was increased by 4.8%. The results obtained by coupling magnetic field with temperature are compared with those obtained by using the thermal relative density loading method. The temperature rise of permanent magnet material and rotor increases and the temperature rise of motor stator decreases.
The operating loss of high-speed brushless motors is converted into heat, which is the local temperature rise that affects the material performance. The resistance value of copper winding increases with the increase of temperature, resulting in an increase in copper consumption. NdFeB is recommended for use in high-speed brushless motors. The temperature coefficient is high, and the remanence induction intensity of NdFeB permanent magnet material is negatively correlated with the temperature. Subsequently, the change of the permanent magnet remanence induction intensity caused by the rise of temperature will cause the change of the core loss, and the core loss will slightly decrease with the rise of temperature. The green electricity of the permanent magnet is negatively correlated with the temperature rise, so the rotating flux of the permanent magnet increases as the temperature rises.
After appeal analysis, it can be seen that some material characteristics and temperature influence each other in high-speed permanent magnet brushless motor. Therefore, through the coupling of the electromagnetic field and temperature field, and considering the interaction of various factors in the calculation process, the practical situation of the high-speed brushless motor can be better simulated.