| CPC F03D 15/00 (2016.05) [F03D 9/25 (2016.05); F03D 13/108 (2023.08); H02K 7/116 (2013.01); H02K 7/1838 (2013.01); F05B 2260/301 (2013.01); F05B 2260/40311 (2013.01)] | 20 Claims | 

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               1. A wind turbine powertrain assembly including a gearbox coupled to an electrical power generator for a wind turbine, 
            wherein the power generator comprises a stator at a radially outward position and a rotor in a radially inward position, wherein the rotor comprises a cylindrical field structure that is configured to rotate about a generator rotor axis (R), and wherein the rotor is configured to define a central hollow portion, 
                wherein the rotor further comprises a rotor support frame connected to and structurally supporting the cylindrical field structure, 
                wherein the rotor support frame comprises: 
              a rotor connection flange attaching the rotor support frame to the cylindrical field structure, 
                  a gearbox connecting flange connecting the rotor support frame to an output drive shaft of the gearbox, and 
                  a transition section extending between the rotor connection flange and the gearbox connection flange, the transition section defined at least in part by one or more stepping regions configured to provide access within the rotor support frame for a person standing therein, the or each stepping region shaped to define a surface that is inclined at an angle of less than 30 degrees to the rotor axis. 
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