
22-1
22.1 Introduction
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 ow, 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. e
speed range depends on the converter and machine rotor winding ratings. Usually the speed range is
limited (about 1:2). is limit causes that DFM is not oen used as a motor. e machine is mainly used
as a variable-speed generator ...