## 7 Discussion  
This paper analyzes the air gap flux density, tooth radial flux density, and yoke tangential flux density of PMSM by changing the direct and quadrature axis currents when the PMSM is in different  
Figure 21: Comparison curve of core loss measurement and calculation.  
Figure 20: The motor prototype, controller and experimental bench.  
operating conditions. Additionally, this paper studied the change in the iron loss of the motor in the constant torque area and constant power as the speed changes, and the core loss of the PMSM under MTPA or field weakening control were studied.  
When the motor is running at 1000 rpm, 3185 rpm and 6000 rpm, the trend of the PMSM loss considering the effect of magnetic saturation was consistent with the trend of loss without considering the magnetic saturation. However, under the same operating point, when the magnetic saturation was considered, the electromagnetic parameters changed nonlinearly. The current harmonics under SVPWM control were larger than those without magnetic saturation, making the stator magnetic field harmonics of the motor increase. The stator core loss increases and different motor control methods (MTPA or field weakening control) had different influences on the proportion of stator hysteresis loss, eddy current loss, and additional loss.  
In the 1000 rpm working area, the PMSM loss was dominated by hysteresis loss. The motor did not enter the field weakening zone. As the load torque increased, especially when the torque was high, the phase current of the motor, when magnetic saturation was considered, was significantly higher than the phase current when magnetic saturation was not considered. The armature effect of the winding current was low, and the fundamental flux density was high; therefore, the proportion of hysteresis loss in total loss had a slight upward trend, while the proportion of eddy current loss and additional loss in total loss decreased.  
In the 3185 rpm working area, the PMSM control mode was divided into MTPA control and field weakening control according to the size of the load torque. When the load torque was less than the rated torque, the PMSM was under MTPA control, and the increase in frequency increased the proportion of the PMSM eddy current loss, and the stator core loss increased with the increase in torque. As the torque increased, the PMSM enters the field weakening control area, the demagnetization current increased, and the total motor loss decreased, but the internal flux density harmonic content of the stator increased. At this time, the proportion of hysteresis loss in the total loss decreased. The proportion of eddy current loss and additional loss in total loss increased accordingly.  
In the 6000 rpm working area, the PMSM adopted field weakening control, and the magnetic saturation effect had little influence on the stator core loss. With the increase of load torque, the degree of field weakening increased, and the increase of demagnetization current made the fundamental flux density of the stator decrease, the harmonic content increased, and the stator core loss increased slightly, but the magnitude of the change was not large. The proportion of loss in the total loss decreased slightly, while the proportion of eddy current loss and additional loss in the total loss increased.