## 2 Four Kinds of Machine Structure Parameter Design
### Design of SynRM  
The SynRM and the induction motor are the same in the selection of the motor parameters. The multi-layer magnetic barrier structure is applied in the rotor of the SynRM, so there are many design parameters for the rotor. Figure 2 mainly shows the number of layers of magnetic barriers, the thickness of the d-axis magnetic barriers (W1, W2, W3), the thickness of the q-axis magnetic barriers (W4, W5, W6), the width of the d-axis permeability channels (L1, L2, L3), the width of the q-axis permeability channels (H1, H2, H3) and the \begin{table}
\begin{tabular}{c c} \hline
**Parameter Name** & **Value** \\ \hline Rated power (kW) & 37 \\ Rated speed (rpm) & 1500 \\ Rated voltage (V) & 380 \\ Rated torque (Nm) & 235.6 \\ Number of poles & 4 \\ Number of stator slots & 48 \\ Number of rotor slots & 44 \\ Stator outer diameter (mm) & 380 \\ Stator inner diameter (mm) & 245 \\ Rotor outer diameter (mm) & 243.6 \\ Rotor inner diameter (mm) & 80 \\ Stack length (mm) & 200 \\ Stator tooth width (mm) & 8.3 \\ Slot opening width (mm) & 4 \\ Airgap length (mm) & 0.7 \\ \hline \end{tabular}
\end{table} 
Table 1: Main parameters of the IM. Figure 1: Cross section of the induction machine. width of the rotor magnetic bridge (Rid). In order to obtain a better performance of the SynRM, the influence of various rotor design parameters of the synchronous reluctance motor on motor performance is analyzed. When the number of magnetic barrier layers is greater than or equal to 4, the average torque is almost consistent with the increase in the number of magnetic barrier layers [25]. The more layers in the magnetic barrier, the more difficult it is to manufacture. The SynRM in this paper is designed as a three-layer magnetic barrier structure. The variation in the d-axis and q-axis inductance and power factor with Rid is shown in Figure 3. Under the premise that the magnetic barrier and other structural parameters remain unchanged, the width of Rid gradually increases from 0.5 mm to 3 mm, the salient pole rate K and \(\Delta\)L gradually decrease, and the power factor also decreases rapidly. Under the premise of ensuring the mechanical strength of the rotor, a smaller Rid should be selected to obtain better electromagnetic performance. Under the premise that the magnetic barriers and other structural parameters remain unchanged, when the width of W4, W5 and W6 gradually increases from 4 mm to 8 mm, the average output torque presents a gradually decreasing trend, as shown in Figure 4a, and the torque ripple presents a downward trend, as shown in Figure 4b. In order to reduce the torque ripple, the width of W4 should be correctly selected. As shown in Figure 4c, the power factor is significantly influenced by the width of W4 and W5. Figure 3: Influence of Rid on inductance and power factor: (**a**) d-axis and q-axis inductance; (**b**) power factor. Figure 2: Cross section of the SynRM with three magnetic barriers and all dimensional variables. The relationship between load torque and torque ripple with H2 and H3 is shown in Figure 5. As the width of H2 and H3 increases, the output torque changes slowly. At the same time, the overall torque ripple shows an upward trend. From the above analysis, the widths of H2 and H3 have less influence on the performance of the SynRM. Figure 6 shows the variation in the torque and power factor with the change in the width of the d-axis magnetic barriers. As seen in Figure 6a,b, when the width of W1 increases from 5 mm to 15 mm, the torque ripple gradually decreases. As the width of W2 increases from 5 mm to 15 mm, the torque ripple gradually increases. When the width of W3 increases from 5 mm to 10 mm, the torque ripple shows an overall increasing trend. In Figure 6c,d, as the width of W1 gradually increases, the torque continues to increase, while the output torque changes slowly with the increase in W2's width. Additionally, with the increase in W3's width, the torque increases gradually.