Doubly-fed asynchronous machine for low voltage drives

Doubly-fed asynchronoius machines are widey applied as generators in variable wind energy systems. This paper proposes doubly-fed motors for low voltage adjustable speed drives (ASD). With a slip-ring motor and a converter both designed for roughly half the nominal power, the drive is able to provide full torque over the entire speed range. The properties are discussed in comparison with common ASD concepts using cage induction machines. Several control schemes are outlined. A drive in the kW range is chosen to illustrate principle design considerations, and simulations of the drive´s operation are offered.