ABSTRACT
A slip-ring induction machine with stator windings connected to the power system directly and rotor windings connected through the power converter is called double-fed machine (DFM). If the converter enables a bidirectional power ¹ow, a DFM will become a universal electromechanical converter. Such a machine can work as a motor and as a generator in both above and below the synchronous speed. že speed range depends on the converter and machine rotor winding ratings. Usually the speed range is limited (about 1:2). žis limit causes that DFM is not o³en used as a motor. že machine is mainly used as a variable-speed generator.
