## 4 Experimental Result  
After those simulations and the analysis in Section 3, optimized scheme II is a viable option according to the simulation results. With the aim of reducing the cost of manufacturing, except for the optimized components, all the other parts are consistent with the original motor structures, and then we assemble them into a prototype motor. Before the assembly, the weight of the important parts like the cores, magnets and windings are measured. It should be noted that in the same part of the motor, two different structures use the same material. The comparison of the materials' quantity between the two different structures is represented in Table 11.  
From Table 11, it can be seen that, compared with the original one, the optimized scheme brings a reduction of nearly 8% in the total mass of the motor and especially reduces 8.7% of the use of the permanent magnets, thereby significantly reducing the cost of the motor. With the basically equivalent output torque capability, the axial length of the core is reduced by 10 mm; therefore, the power density of the motor can be effectively improved. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Part of Motor** & **The Original** & **The Optimized** \\ \hline Stator core temperature & 77.3 \({}^{\circ}\)C & 78.0 \({}^{\circ}\)C \\ Rotor core temperature & 85.2 \({}^{\circ}\)C & 87.8 \({}^{\circ}\)C \\ Magnet temperature & 85.4 \({}^{\circ}\)C & 87.9 \({}^{\circ}\)C \\ Winding temperature & 96.5 \({}^{\circ}\)C & 101.5 \({}^{\circ}\)C \\ \hline \hline \end{tabular}
\end{table} 
Table 10: The steady-state highest temperature of major motor component. Figure 19: The temperature curves of two different models in rated condition. The optimized prototype motor was manufactured by adopting the new arrangement of the stator windings and \"\(\
abla\)-type\" magnetic-pole rotor topology and is displayed in Figure 20. The experiments shown in Figure 21 have been carried out on a prototype motor under the closed-loop current control in the laboratory. In the operation, the prototype motor with a commercial variable-frequency drive is mechanically connected to the generator for providing the input torque. The generator is used as the power supply of 380 V/50 Hz and connected to the water resistance load. The measurement system of the prototype motor has three parts: a measuring instrument of the torque and the power, which is used to monitor the torque and the power of the rotor shaft by a torque transducer, and its accuracy degree is \(\pm\)0.1%; a multifunctional digital power meter, which is used to measure the voltages, currents and powers of each-phase \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Parameter of Motor** & **The Original** & **The Optimized** & **Change amp.** \\ \hline Axial length of the core & 146 mm & 136 mm & 10 mm\(/-\)6.8\% \\ Mass of stator core & 10.25 kg & 9.42 kg & \(-\)8.1\% \\ Mass of rotor core & 5.98 kg & 5.48 kg & \(-\)8.4\% \\ Mass of magnets & 1.62 kg & 1.48 kg & \(-\)8.7\% \\ Mass of windings & 4.86 kg & 4.53 kg & \(-\)6.8\% \\ Total mass & 22.70 kg & 20.91 kg & \(-\)8.0\% \\ \hline \hline \end{tabular}
\end{table} 
Table 11: The materials’ quantity of motor. Figure 21: Schematic of the testing stand. Figure 20: The prototype motor: (**a**) assembled; (**b**) stator; and (**c**) rotor. stator winding for the prototype motor, and the measurement accuracies of the voltage, current and power are \(\pm\)0.1 V, \(\pm\)0.1 A and \(\pm\)0.1 kW, respectively; and an incremental encoder, with a resolution of 1024 cycles/r, which is used to obtain the speed signal. The calibration experiments were carried out on the prototype motor in the laboratory under the no-load and with-load conditions within the speed range of 1000-9000 rpm, and the EMFs, mechanical and external characteristics, efficiency, temperature rise were measured in the experimental platform shown in Figure 22.  
The no-load experiments were carried out on both the original and optimized motors, and the experiment data of the EMFs are recorded.