EMF = n*k*w
where k is the motors voltage constant and w is the wind turbine's rotational speed. The generator will spin faster and therefore generate more voltage, simply put.
When a gearing is introduced the torque on the generator's rotor is also decreased. This reduces the copper losses
Ploss,copper = r*I^2 ~ r*(T/(k*n))^2
as the current I is directly proportional to the torque T, and inversely proportional to a theoretical motor constant k, in theory. Lower rotor torque thus means that the copper losses are reduced.
Reluctance effects However, the BLDC motor used is affected by quite a lot of reluctance effects. An initial torque of a certain level is needed to overcome the reluctance effects and the motor then rotates a step. Th…