## 5 Experimental Results and Discussion
\begin{table}
\begin{tabular}{c c} \hline \hline
**Parameter** & **Value** \\ \hline Fitted coefficient of conduction characteristics \(a_{c}\) & \(4.505\times 10^{-6}\) \\ Fitted coefficient of conduction characteristics \(b_{c}\) & \(0.005021\) \\ Fitted coefficient of conduction characteristics \(c_{c}\) & \(0.04258\) \\ Fitted coefficient of conduction characteristics \(a_{f}\) & \(-3.3\times 10^{-6}\) \\ Fitted coefficient of conduction characteristics \(b_{f}\) & \(0.004911\) \\ Fitted coefficient of conduction characteristics \(c_{f}\) & \(0.5673\) \\ Fitted coefficient of switch characteristics \(a_{on}\) & \(4.141\times 10^{-12}\) \\ Fitted coefficient of switch characteristics \(b_{on}\) & \(1.418\times 10^{-8}\) \\ Fitted coefficient of switch characteristics \(c_{on}\) & \(1.361\times 10^{-6}\) \\ Fitted coefficient of switch characteristics \(a_{off}\) & \(3.48\times 10^{-11}\) \\ Fitted coefficient of switch characteristics \(b_{off}\) & \(8.972\times 10^{-9}\) \\ Fitted coefficient of switch characteristics \(c_{off}\) & \(1.083\times 10^{-10}\) \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Fitting coefficients of the SiC-MOSFET modules. Figure 12: SiC-MOSFETs-based inverter for a PMSM drive system. Tables 10 and 11 show the experimental results of the SiC-MOSFETs-based PMSM drive system by the proposed system efficiency improvement control strategy. The experimental results at rated torque are shown in Table 10, and the experimental results at different torque are presented in Table 11.  
From Tables 10 and 11, it can be seen that proposed system efficiency improvement control method can improve the efficiency performance of the PMSM drive system over the whole operation range. Figure 13 shows that, the proposed control strategy can reduce both the losses of PMSM and losses of power converter, by which the system efficiency is obviously improved. Figure 13 shows that the proposed system efficiency improvement control method can reduce the losses of PMSM and increase the motor efficiency at 1.36% at rated speed. In addition, the proposed control can also decrease the inverter losses, by which the efficiency of power converter can be raised by 3.94% at rated torque. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Motor Speed** & **System Input Power** & **Motor Input Power** & **Mechanical Power** & **Inverter** & **Motor** & **System** \\ (**\#/mia**) & **(kW)** & **(kW)** & **(kW)** & **Efficiency** & **Efficiency** & **Efficiency** \\ \hline
300 & 23.115 & 22.80 & 21 & 98.64 & 92.10 & 90.85 \\
250 & 19.523 & 19.064 & 17.5 & 97.65 & 91.80 & 89.64 \\
200 & 15.969 & 15.366 & 14 & 96.22 & 91.11 & 87.67 \\
150 & 12.44 & 11.709 & 10.5 & 94.12 & 89.67 & 84.41 \\
100 & 8.98 & 8.094 & 7 & 90.13 & 86.48 & 77.95 \\
50 & 5.579 & 4.527 & 3.5 & 81.14 & 77.31 & 62.74 \\ \hline \hline \end{tabular}
\end{table} 
Table 10: Experimental results of the SiC-MOSFETs-based PMSM drive system at rated torque in the system efficiency improvement control. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Motor Torque** & **System Input Power** & **Motor Input Power** & **Mechanical Power** & **Inverter** & **Motor** & **System** \\ (**\#/mia**) & **(kW)** & **(kW)** & **(kW)** & **Efficiency** & **Efficiency** & **Efficiency** \\ \hline
300 & 23.1  
Figure 14 shows the system efficiency of the SiC-MOSFETs-based PMSM drive system under the traditional MTPA control and the proposed system efficiency improvement control strategy. It can be seen from Figure 14 that the proposed control strategy can achieve better system efficiency than the conventional MTPA control for each operation condition of PMSM direct drive system. The system efficiency is increased by 0.93% at rated speed and improved by 3.10% at rated torque. Figure 15 shows the system efficiency difference between the Si-IGBTs-based PMSM direct drive system and the SiC-MOSFETs-based PMSM direct drive system.