Three controls, three variable gear assemblies, an optional hatch or variable propeller pitch, and a variable overlap generator (VO generator), as well as one or more commutator and brushless free direct current generators may be used independently and together to provide constant frequency and voltage output power and to increase the amount of output power generated with the same input water flow or wind speed in a plurality of embodiments useful in wind power generation and water renewable energy generators for any of tidal and ocean current or wave conditions. Two Transgear assemblies side-by-side and sharing the same central shaft may comprise a constant speed motor control, produce required constant frequency and voltage and be reduced in part count and complexity. The variable overlap generator of a marine hydrokinetic or wind power generator may be used as a low torque generator, a high power-rated generator or a control in these applications and may generate more electric power than a conventional fixed power generator (the rotor axially aligned to overlap the stator in a conventional manner) over a wider input range. An electromotive force (EMF) embodiment generates alternating current at constant frequency and voltage in varying wind and water speed conditions.

A coupling for a drive train of a wind turbine between the gearbox and the generator has a drive-side coupling hub, an output-side coupling hub and an intermediate section. The coupling has a torque limiter. In order to create a generic drive train, which is designed such that in the event of an overload, significantly higher energies can be absorbed, the torque limiter has more than two friction elements, in particular disks.

A torque transmitting coupling assembly for a wind turbine configured to rotatably couple a first coupling part to a second coupling part, wherein the first coupling part and the second coupling part are configured to rotate about a longitudinal axis of the torque transmitting coupling assembly, wherein the torque transmitting coupling assembly includes a torque transmitting ring and a compression ring.