# Parametric Selection of Optimized Epicyclic Gearbox Layouts for Wind Power Plant Applications
## 6 Conclusions  
Mechanical planetary multiplier gearboxes are highly important for wind power turbine operation, with gearbox units being designed as two-stage or three-stage planetary gear trains due to the required transmission ratio range. As the design of multi-carrier gear trains is a broad and highly complex area, the kinematics of the gear train must be the result of an analytical approach determined by the application requirements to provide optimal performance. The goal of this article was to select the optimal design solution for a 700 kW wind turbine application, while taking into account both two-carrier and three-carrier gearbox solutions. The torque method was implemented into the 2-SPEED software, which was purposely developed for the calculation and evaluation of two-carrier gear trains. The software was used to calculate all possible multiplier combinations and then ranked the solutions according to the application constraints. Five candidate solutions have been filtered out, from which three are considered for implementation into gear trains. S16 NW(E) is considered for three-carrier gear trains, while S26 EW(N) and S26 NW(E) are considered for two-carrier trains as equally good solutions, although S26 EW(N) should be given priority as it is a technologically simpler build that does not require hollow shafts. The actual decision between a two-carrier or a three-carrier design essentially depends on the application demands, as a two-carrier design will be heavier but have a slightly higher efficiency than a three-carrier design. The three-carrier design will also have a smaller largest ring gear diameter size. The importance of the purposefully developed 2-SPEED software must be mentioned, as it guarantees that the optimal solution will be obtained. This can be observed by inspecting Tables 12-12. There are 126 possible solutions for every table; however, the software has sifted through the complete solution and listed only the viable solutions, ranked from best to worst according to the selection criteria. This becomes obvious as the top 2-3 solutions listed in the tables are viable, while the solutions listed next become considerably worse. One of the directions for future research is to consider the direction of rotation of the output shaft, due to the gyroscopic properties of the combined turbine, gearbox, and generator system. The purpose of this research would be to determine whether the direction of rotation of the generator may be used to counter the gyroscopic effect of the turbine and, therefore, reduce the load on the load bearing structures and control systems. Conceptualization, S.T. and Z.V. ; methodology, S.T., Z.V., K.M. and D.M. ; software, S.T. ; validation, S.T., K.M. and D.M. ; formal analysis, S.T., Z.V., K.M. and D.M. ; investigation, S.T., Z.V., K.M. and D.M. ; data curation, S.T. and D.M. ; writing--original draft preparation, S.T. and Z.V. ; writing--review and editing, K.M. and D.M. ; visualization, K.M., Z.V. and S.T. ; supervision, S.T. All authors have read and agreed to the published version of the manuscript. This research was funded by the UNIVERSITY OF RijekA, projects number uniri-iskusni-tehnic-23-298 and uniri-iskusni-tehnic-23-168. Not applicable. Raw synthesis data are available from the corresponding author upon reasonable request. This work has been supported by the University of Rijeka under projects number uniri-iskusni-tehnic-23-298 and uniri-iskusni-tehnic-23-168. The authors declare no conflicts of interest. The funders had no role in the design of this study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.