## 2 Preliminary Results and Research Methodology
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Parameter** & **PMSM Spoke** & **PMSM IPM** & **Unit** \\ \hline Mechanical Power & 2.76 & 2.74 & kW \\  Rotor speed & 4203 & 4203 & rev/min \\  Average torque & 6.27 & 6.24 & Nm \\  Torque ripple & 8 & 8.1 & \% \\  PM Joule losses & 7.82 & 4.34 & W \\  Total Joule losses & 31.34 & 34.72 & W \\  Rotor Iron losses & 9.23 & 6.75 & W \\  Total Iron losses & 129 & 77.7 & W \\  Rotor iron mass & 3.4 & 2.71 & kg \\  Efficiency (mechanical & 94.51 & 96.06 & \% \\  losses not included) & & \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Comparative simulation results. Figure 2: PMSM studied variants: (**a**) Spoke-type rotor; (**b**) Interior PM rotor. the Finite Element Method (FEM) simulated phase voltage and prototype measured phase voltage at 896.4 rev/min is presented. The voltages were almost identical, the main difference being at amplitude level, probably due to one or several of the following: higher airgap for the prototype due to manufacturing tolerances, iron core lower-quality properties, and voltage probe measurement error. This test also allowed the determination of the back-EMF constant (Ke) of the machine prototype. The synchronous inductances of the spoke-type PMSM were measured using an LCR meter. It is well known that stator inductances of interior permanent magnet synchronous machines are different on \(d\) and \(q\) axes (Ld < Lq) due to the reluctance on the \(q\) axis. Therefore, the measurements were performed by locking the rotor aligned positions with the two axes. For the \(d\)-axis phase 1 inductance, the alignment of the rotor to phase 1 was achieved by feeding the phase with positive potential, and by feeding phases 2 and 3 with negative potential. For the \(q\)-axis phase 1 inductance, the alignment of the rotor was achieved by leaving phase 1 floating, feeding phase 2 with positive potential, and feeding phase 3 with negative potential. A comparison of the measured and FEM determined parameters is presented in Table 2.  
A good correlation between the measured and estimated values can be noticed. The most notable difference was for the motor phase resistance, where the FEM-computed value was 24.3% smaller than the measured value. In the simulations, only the active parts or the windings were considered, without considering the connections to the terminals and longer-end windings. The differences between the other three electrical parameters (measured versus FEM-computed) can be explained by the fact that the manufactured machine could not be built exactly like the machine considered in simulations: different airgap lengths, different materials (PMs, iron core) and properties, etc. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Parameter** & **Symbol** & \
\begin{tabular}{c} **Value** \\ **Measured** \\ \end{tabular} &
\begin{tabular}{c} **Value** \\ **FEM-Computed** \\ \end{tabular} & **Unit** \\ \hline Motor phase resistance & \(R_{s}\) & 0.0037 & 0.0028 & \(\Omega\) \\ \hline Back-EMF electrical constant & \(K_{e}\) & 0.0718 & 0.0768 & V.s/rad \\ \hline \(d\)-axis inductance & \(L_{d}\) & 0.000061 & 0.000067 & H \\ \hline \(q\)-axis inductance & \(L_{q}\) & 0.000121 & 0.000146 & H \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Simulation and experimentally determined electrical parameters. Figure 3: PMSM FEM simulated phase voltage (red) vs. prototype phase measured voltage (blue).