# A New Multi-Axial Flux Pm Motor-Generator System for Flywheel Energy Storage
## 3 Results
### Experimental Results
#### 3.2.2 On-Load Operation Regenerative Model  
In this study, the AFPM motor-generator set for FESS was developed for CML. In conventional motor-generator sets developed for FESS, motor windings are used as generator windings, either alone or connected in series and parallel. However, in the suggested AFPM motor-generator system, a separate generator winding is performed. Therefore, CML's most suitable winding type in regenerative mode has been determined separately for A, B, and C windings. Here, A and B are motor windings, and C is generator windings. The AFPM motor-generator set for FESS is gradually loaded in the regenerative mode for winding A. The regenerative mode should achieve the highest energy in the shortest time for CML. Experimental data were obtained by recording current and voltage values on the Fluke 190 series oscilloscope. When the flywheel reached a speed of 460 rpm, the loads were applied to the generator gradually. The values obtained in the regenerative mode for the sixth stage load condition of the A winding are given in Figure 10. Here, A, B, and C are voltage inputs, and D is the current input. As shown in Figure 10, when the load starts, the value of the voltage decreases while the current value increases. Each square on the measurement screen shows an interval of 0.2 s. The maximum current obtained from FESS is 7.28 A. In Table 4, the average voltage phase-neutral (V\({}_{\text{pn}}\)), average current phase-neutral (I\({}_{\text{pn}}\)), and power (Watt/0.5 s) values for each load step are calculated for the A winding in regenerative mode. Values were obtained for the first 0.5 s of the load. It can be seen in Table 4 that as the step increases, the current increases, but the voltage decreases. For the A winding, the highest value of 332.42 watts of power was obtained in 0.5 s at the fourth stage with an average of 2.61 A. The values obtained in the regenerative mode for the sixth stage load condition of the A + B series winding are given in Figure 11. Here, A, B, and C are voltage inputs, and D is the current input. As shown in Figure 11, when the load starts, the value of voltage decreases while the current value increases. The maximum current obtained from FESS is 8.08 A.  
Figure 10: The regenerative mode for the V\({}_{\text{pn}}\)-I\({}_{\text{pn}}\) 6 th stage of A winding. In Table 5, the average voltage phase-neutral (V\({}_{\rm pn}\)), average current phase-neutral (I\({}_{\rm pn}\)), and power (Watt/0.5 s) values for each load step are calculated for the A + B series winding in regenerative mode. It can be seen in Table 5 that as the step increases, the current increases, but the voltage decreases. For the A + B series winding, the highest value of 474.03 Watts of power was obtained in 0.5 s at the second stage and an average of 2.32 A. The values obtained in the regenerative mode for the sixth stage load condition of the A//B parallel winding are given in Figure 12. Here, A, B, and C are voltage inputs, and D is the current input. As shown in Figure 12, when the load starts, the voltage value decreases while the current value increases. The maximum current obtained from FESS is 9.52 A. In Table 6, the average voltage phase-neutral (V\({}_{\rm pn}\)), average current phase-neutral (I\({}_{\rm pn}\)), and power (Watt/0.5 s) values for each load step are calculated for the A//B parallel winding in regenerative mode. It can be seen in Table 6 that as the step increases, the current increases, but the voltage decreases. For the A//B parallel winding, the highest value of 463.25 Watts of power was obtained in 0.5 s at the fifth stage and an average of 3.81 A. \begin{table}
\begin{tabular}{c c c c} \hline
**Stage** & **V\({}_{\rm pn}\) (V)** & **I\({}_{\rm pn}\) (A)** & **Power (Watt)** \\ \hline
1 & 61.491 & 1.058 & 195.258 \\
2 & 52.645 & 1.877 & 296.523 \\
3 & 47.873 & 2.141 & 307.402 \\
4 & 42.331 & 2.617 & 332.429 \\
5 & 33.024 & 3.114 & 308.527 \\
6 & 27.181 & 3.641 & 296.861 \\ \hline \end{tabular}
\end{table} 
Table 4: The electrical values were obtained in 0.5 s for FESS.