## 3 Results and Discussion
### CVT-Applied Analysis Model Result
#### 3.2.1 Optimization of Shift Pattern by Considering the Motor Operating Point Change  
Figure 11 shows how to change the operating point. The analysis of the operating point of the EV analysis model with a 9.7:1 single reducer showed that, to increase the torque, the operating point had to be changed by reducing the operating RPM of the motor owing to the low driving torque at 2200 rpm or higher.  
Figure 10: HWFET driving cycle.  
Figure 9: FTP-75 driving cycle.  
Table 5 lists the shift range according to the deceleration factor variable for the [A-A\({}^{\prime}\)] movement and the deceleration ratio of the single reducer for its implementation. Based on the deceleration ratio (9.7:1), the lowest shift ratios of the CVT were 1/1, 5, 1/2, 5, 1/3, and 1/4. The highest shift ratio of the CVT was derived by multiplying the CVT span by 6.  
At 2200 rpm or less, the operating point must be changed to reduce the torque by increasing the RPM through a high deceleration ratio. Therefore, the minimum motor rotational speed was limited to 1600 rpm, based on the efficiency map of the motor for the [B-B\({}^{\prime}\)] movement. However, when \(n=3,3.5\), and 4, because the minimum motor rotational speed at 10 km/h was 1600 rpm or less, the minimum motor rotational speed at 10 km/h was restricted to 1200 rpm.  
Figure 12 shows the composite electronic fuel economy values measured by applying a single deceleration ratio, according to the deceleration magnification based on Table 5. The FTP-75 and HWFET modes were measured by the SCT method, similar to the method for calculating the electronic fuel economy and maximum driving distance of the analysis model. The correction factor was multiplied by 0.7. According to the electronic fuel economy measurements, the maximum value was \(n=3.5\). Therefore, this study was conducted based on the value in which the magnification of the single reducer was set to 5.5.  
Figure 11: Strategy of optimal shift pattern in EV with CVT for improving the driving distance.  
\begin{table}
\begin{tabular}{c c c c c c c} \hline  & \multicolumn{4}{c}{**Reduction Ratio**} \\ \hline  & \(n=1.5\) & \(n=2\) & \(n=2.5\) & \(n=3\) & \(n=3.5\) & \(n=4\) \\ \hline Min. ratio & 6.5:1 & 4.85:1 & 3.85:1 & 3.25:1 & 2.75:1 & 2.45:1 \\ Max. ratio & 39:1 & 29:1:1 & 23:1:1 & 19.5:1 & 16.5:1 & 14.7:1 \\ Single reducer ratio & 13:1 & 9.7:1 & 7.7:1 & 6.5:1 & 5.5:1 & 4.9:1 \\ \hline \end{tabular}
\end{table}
Table 5: Comparison of CVT shift range and single-reducer ratio according to deceleration ratio.  
In summary, a CVT-applied model was developed by applying a CVT, based on the EV analytic model, to verify the reliability. The operating point of the electric motor was expected to change due to the combination of the CVT and single-reducer shift ratio; hence, the RPM was increased using a high shift ratio in the high-torque low-RPM section, and the torque was increased using a low shift ratio in the low-torque high-RPM section. Starting from 1/1.5, the existing deceleration ratio of 9.7 was linearly divided by the 1/4 ratio, and the maximum shift ratio was derived by multiplying the CVT span by 6. The change in the operating point of the motor was optimized when \(n=3.5\).