## 5 Final Scheme  
Based on the above analysis, a final scheme is determined. Compared with Case 4, which had the lowest temperature, the magnetic load of the final scheme is further increased to achieve lower temperature rise and smaller motor volume. Furthermore, the final scheme has higher magnetic load and lower current density compared to the initial scheme.  
The parameter comparison between the final scheme and the initial scheme is shown in Table 3. The PM thickness and pole embrace of the final scheme are increased to obtain higher magnetic load, and the parallel winding number is increased to obtain a smaller current density. In addition, the core length of the final scheme is shortened to ensure the same back-EMF. In order to realize the same slot fill rate, the slot area of final scheme is also reduced. Moreover, in final and initial schemes, the back-EMF, the stator outer diameter, and the slot fill rate remain unchanged.  
Figure 18 shows the magnetic flux density distribution of the final scheme obtained by 2D-FEA using Ansys Maxwell software. As shown, the magnetic flux densities of the stator teeth and yoke are 1.6 T and 0.97 T, respectively, and the air-gap magnetic flux density is 0.88 T; these values are increased compared to the initial scheme. Although the magnetic load of the final scheme has increased significantly, the stator magnetic flux density still does not exceed 1.8 T, and does not reach saturation.  
Figure 16: Temperature distribution under four design schemes: (**a**) Case 1; (**b**) Case 2; (**c**) Case 3; (**d**) Case 4.  
Figure 17: The temperature comparisons of four schemes: (**a**) temperature comparisons of stator yoke, rotor yoke, and PM; (**b**) temperature comparisons of stator teeth and winding.  
The core loss and eddy current loss of the PM in the final scheme at rated load are shown in Figure 19. After entering the steady state, the average core loss of the final scheme is 4870 W, the average eddy current loss of the PM is 602 W, and the average copper loss is 8655 W. Compared with the initial scheme, the core loss of the final scheme increases by 1122 W, caused by the increase in magnetic load. In addition, due to the reduction in current density and core length of the final scheme, the copper loss has dropped by 3775 W. The eddy current loss of the PM has not changed substantially in two schemes.  
Figures 20 and 21 show the temperature distribution and comparison at rated load for the final and initial schemes. Compared with the initial scheme, since the copper loss of final scheme decreases more than the stator core loss increases, the temperature of each part of the motor has dropped considerably in the final scheme. The temperature of the stator winding part has dropped the most, reaching 21 \({}^{\circ}\)C. Therefore, in the design of outer rotor LSPMMs, lower current density and higher magnetic load can effectively improve temperature characteristics and reduce the size of the motor.  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Design Scheme** & **Final Scheme** & **Initial Scheme** \\ \hline Core length (mm) & 874 & 917 \\ PM thickness (mm) & 16 & 13 \\ Pole embrace & 0.9 & 0.85 \\ Conductor parallel winding number & 24 & 18 \\ Slot width (mm) & 23 & 23 \\ Slot height (mm) & 112 & 85 \\ Air-gap magnetic flux density (T) & 0.88 & 0.84 \\ Stator teeth magnetic flux density (T) & 1.6 & 1.4 \\ Stator yoke magnetic flux density (T) & 0.97 & 0.53 \\ Current density (A/mm\({}^{2}\)) & 3 & 4 \\ \hline \hline \end{tabular}
\end{table}
Table 3: The parameters comparisons of the final and initial schemes.  
Figure 18: The magnetic flux density distribution of the final scheme.  
Figure 19: The core loss and eddy current loss of PM in final scheme: (**a**) core loss; (**b**) eddy current loss of the PM.  
Figure 20: Whole and partial temperature distribution of final scheme: (**a**) whole temperature distribution; (**b**) partial temperature distribution.