## 5 Experimental Results and Discussion  
Figure 9 shows an experimental platform of a PMSM drive system which is designed and implemented to verify the performance of the proposed system loss optimized control strategy. The motor in the test platform is a 21 kW outer rotor surface PMSM, which parameters are listed in the Table 1. The 45 kW PMSM inverter is based on the Si-IGBT power devices to drive the outer rotor PMSM. The Si-IGBT modules used in the experimental platform are the FF300R06 KE3, and the fitted coefficients of FF300R06 KE3 are shown in the Table 2.  
Figure 8: Structure diagram of the proposed system efficiency improvement control system. Figure 9: _Cont._ \begin{table}
\begin{tabular}{c c} \hline \hline
**Parameter** & **Value** \\ \hline Fitted coefficient of conduction characteristics \(a_{e}\) & \(-1.025\times 10^{-5}\) \\ Fitted coefficient of conduction characteristics \(b_{e}\) & \(0.005367\) \\ Fitted coefficient of conduction characteristics \(c_{e}\) & \(0.6158\) \\ Fitted coefficient of conduction characteristics \(a_{f}\) & \(-3.075\times 10^{-5}\) \\ Fitted coefficient of conduction characteristics \(b_{f}\) & \(0.01074\) \\ Fitted coefficient of conduction characteristics \(c_{f}\) & \(0.4758\) \\ Fitted coefficient of switch characteristics \(a_{on}\) & \(6.992\times 10^{-9}\) \\ Fitted coefficient of switch characteristics \(b_{wn}\) & \(5.187\times 10^{-6}\) \\ Fitted coefficient of switch characteristics \(c_{on}\) & \(0.0009089\) \\ Fitted coefficient of switch characteristics \(a_{off}\) & \(6.903\times 10^{-9}\) \\ Fitted coefficient of switch characteristics \(b_{off}\) & \(3.486\times 10^{-5}\) \\ Fitted coefficient of switch characteristics \(c_{off}\) & \(0.00164\) \\ Fitted coefficient of recovery characteristics \(a_{rec}\) & \(-3.107\times 10^{-8}\) \\ Fitted coefficient of recovery characteristics \(b_{rec}\) & \(2.599\times 10^{-5}\) \\ Fitted coefficient of recovery characteristics \(c_{rec}\) & \(0.001242\) \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Fitting coefficients of Si-IGBT modules. \begin{table}
\begin{tabular}{c c} \hline \hline
**Parameter** & **Value** \\ \hline Rated Power & 21 kW \\ Rated Speed & 300 r/min \\ Poles & 22 \\ Slots & 24 \\ Stator Outer Diameter & 278 mm \\ Rotor Outer Diameter & 312 mm \\ Active Length & 170 mm \\ Air Gap Length & 1 mm \\ Number of Turns Per Phase & 104 \\ Spacer Factor & 45\% \\ Phase Resistance & 0.06 \(\Omega\) \\ Phase Inductance & 3.18 mH \\ Rated Current & 74 A \\ Current Density at Rated Torque & 4.25 A/mm\({}^{2}\) \\ Flux Linkage & 0.623 Wb \\ DC Link Range & 360 V–420 V \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Parameters of the outer rotor surface PMSM. Figure 9: Experimental platform of PMSM drive system. (**a**) Si-IGBT based inverter; (**b**) Physical prototype experimental platform; (**c**) Diagram of the experimental platform. The 330 kW, 8000 r/min special dynamometer for HEVs/EVs are applied as the mechanical load for the outer rotor PMSM to simulate the operation load characteristics of EVs. The power converter for PMSM is controlled by a TMS320F28335-based DSP controller (produced by Texas Instruments Company, Dallas, TX, USA). The controller applies the proposed system efficiency improvement control method and traditional MTPA control strategy on the PMSM drive system. The experimental results of the PMSM drive system by MTPA control are shown in Tables 3 and 4. Table 3 shows the experimental results of the Si-IGBT-based PMSM drive system with different power at rated torque, and Table 4 shows the experimental results with different torque at rated speed. Tables 5 and 6 show the performance of the PMSM drive system with the proposed control strategy. The experimental results at rated torque are shown in Table 5, and the experimental results at different torque is presented in Table 6.  
Tables 5 and 6 show that the proposed control strategy can improve the efficiency of the PMSM direct drive system at each operation condition.