Especially dominant in new markets is the DFIG, also called the wound rotor induction generator. In this machine, the stator windings are directly connected to the grid, while a frequency converter interfaces between the standard wound rotor and the grid. The stator winding connection carries most of the power production, although the frequency converter may carry up to a third of the total power, depending on the operating mode. This configuration allows the machine to control the slip in the generator, and thus the rotor speed can vary moderately, achieving better aerodynamic efficiency. Furthermore, as the converter controls the rotor voltage magnitude and phase angle, partial control of active and reactive power is also possible.