# Parametric Selection of Optimized Epicyclic Gearbox Layouts for Wind Power Plant Applications
## 4 Results
### Data Presentation
#### 4.2.2 Three-Carrier Gear Train Data  
As previously mentioned, the three-carrier gear trains were obtained by combining two-carrier gear trains having a transmission ratio \(\left|\left|i\right|\right|=0.08\) with a simple planetary having a transmission ratio of \(i=0.25\). As for simple two-carrier trains, 2-SPEED software was used to analyze and test the 126 possible gear train variants. The gear trains in Tables 17 and 18 are listed according to the criterion of minimal mass, with positive transmission ratios in Table 17 and negative in Table 18.  
The gear trains in Tables 19 and 10 are listed according to the criterion of minimal larger ring gear reference diameter, with positive transmission ratios in Table 19 and negative in Table 110.  
The gear trains in Tables 11 and 12 are listed according to the criterion of maximum efficiency, with positive transmission ratios in Table 11 and negative in Table 12.  
The third-stage single-carrier gear train for three-carrier trains is a simple calculation, with the data provided in Table 1:According to the data from Tables A3 and A4, the S26 EW(N) and S26 NW(E) gear trains also provide the best solution from the standpoint of the minimal largest ring gear reference diameter in the category of \(|\,i|=0.02\). A more detailed overview of the properties of these gear trains is found in Figure 10.  
The minimal largest reference diameter is achieved with gearset S26 EW(N) with the combination of \(t_{\rm I}=8\) and \(t_{\rm II}=4.5\) for \(i=0.02\), while gearset S26 NW(E) achieves this for \(t_{\rm I}=7.8333\) and \(t_{\rm II}=4.6667\) for \(i=-0.02\). Analysis of the data from Tables A3 and A4 demonstrates that S26 EW(N) and S26 NW(E) provide the best solution according to the additional criterion of efficiency, as other solutions that provide a smaller diameter have efficiencies well below 50%. Figure 10: (**a**) Relationship of the minimal largest ring gear reference diameter of the S26 EW(N) gearest to the ideal torque ratios \(t_{\rm I}\) and \(t_{\rm II}\) for \(i=0.02\); (**b**) relationship of the minimal largest ring gear reference diameter of the S26 NW(E) gearest to the ideal torque ratios \(t_{\rm I}\) and \(t_{\rm II}\) for \(i=-0.02\). Figure 9: (**a**) Relationship of the mass of the S26 EW(N) gearest to the ideal torque ratios \(t_{\rm I}\) and \(t_{\rm II}\) for \(i=0.02\); (**b**) relationship of the mass of the S26 NW(E) gearest to the ideal torque ratios \(t_{\rm I}\) and \(t_{\rm II}\) for \(i=-0.02\). The best solution from the standpoint of maximum efficiency is provided with the S16 NW(E) and S16 EW(N) gear trains which also provide the best solution even from the standpoint of maximum efficiency in the category of \(\mid\!i\!\mid\!\mid=0.02\), according to the data from Tables 10 and 11, with a more detailed overview of the properties of this gearset in Figure 11.  
The maximum efficiency is achieved with gearset S16 NW(E) with the combination of \(t_{\rm I}=8\) and \(t_{\rm II}=5\) for \(i=0.02\), while this is achieved with gearset S16 EW(N) for \(t_{\rm I}=8\) and \(t_{\rm II}=5.1667\) in the case of \(i=-0.02\). Analysis of the data from Tables 10 and 11 demonstrates that S16 NW(E) and S16 EW(N) provide the best solution according to the additional criterion of efficiency. For \(i=0.02\), S16 NW(E) has a marginally lower efficiency than the best solution; however, it is the best solution from the standpoint of gear train weight and maximum gear train diameter as it is 1700 kg lighter than the highest efficiency solution. For \(i=-0.02\), S16 EW(N) is tied in efficiency with S26 EW(N); however, S16 EW(N) is the better solution as its almost 1300 kg lighter for the same torque input. According to the data from Tables 11 and 11, the S16 NW(E) and S26 NE(W) gear trains provide the best solution from the standpoint of minimal mass in the category of \(\mid\!i\!\mid\!\mid=0.08\).