Doubly-fed induction motor differential cascade. I. Configuration and analysis in the steady state

In this paper, the configuration and the analysis of a doubly-fed differential cascade (DFDC) in the steady state, is presented. The doubly-fed differential cascade consists of two similar doubly-fed induction machines having their corresponding rotor phases connected. The stators are supplied by voltage phasors of variable frequencies. The rotor recovered slip power of the one machine is used to supply the other machine, through the common rotor connection, maintaining the sum of the two machine speeds constant and equal to the difference of the two stator voltage phasor frequencies. The speed of this differential cascade can be controlled by varying the frequency difference of the two stator voltage phasors. The direction of rotation can be changed by changing the sign of the frequency difference of the stators supply voltages. The set of two doubly-fed induction machines connected in a differential cascade may be used in electrical automobile drive systems.