A field winding circuit for an alternator includes an electromagnetic coil including a first winding portion and a second winding portion electrically connected in series. The winding circuit comprises a first switch, a second switch and a third switch configured to selectively connect one or both of the first and second winding portions to output terminals of the winding circuit. The winding circuit comprises an electronic controller configured to: determine the output power required by an electrical load connected to the stator output terminals, compare the required output power to a threshold value, connect only one of the first and second winding portions to the output terminals if the required output power is below the threshold value and connect both the first and second winding portions to the output terminals if the required output power is below the threshold value.

A wind turbine that includes a housing, an asynchronous generator disposed in the housing and configured to be electrically connected to a power grid connection; a power converter circuit disposed in the housing and configured to be electrically connected to the asynchronous generator; and a variable impedance device disposed in the housing, connected to the generator and configured to limit current by varying impedance in response to a transient current. The wind turbine delivers reactive power to the power grid when the variable impedance device varies impedance in response to the transient current. The variable impedance device can be arranged in series between the asynchronous generator and the power grid connection, or can be in a shunt arrangement between the asynchronous generator and a neural point.

A wind turbine that includes a housing, an asynchronous generator disposed in the housing and configured to be electrically connected to a power grid connection; a power converter circuit disposed in the housing and configured to be electrically connected to the asynchronous generator; and a variable impedance device disposed in the housing, connected to the generator and configured to limit current by varying impedance in response to a transient current. The wind turbine delivers reactive power to the power grid when the variable impedance device varies impedance in response to the transient current. The variable impedance device can be arranged in series between the asynchronous generator and the power grid connection, or can be in a shunt arrangement between the asynchronous generator and a neural point.

A device for increasing fault clearing time is provided having a component part designed to identify a short circuit event and load resistors connectable in the event of a fault such that the turbine power transmitted to the shaft is electrically absorbed by the generator and converted into heat until the grid comes back online.