Self-cascaded machine: a low-speed motor or high-frequency brushless alternator

TLDR

The self‑cascaded machine combines two induction machines into a single unit that resembles a conventional induction motor and is suitable for both low‑speed motor applications and high‑speed brushless alternator use due to its simple, slip‑ring‑free rotor construction. The paper provides a general description of the self‑cascaded machine and its underlying principles. The machine can operate asynchronously with resistance control or synchronously without external rotor connections, and the authors present a theoretical analysis based on doubly stator‑fed operation. The authors derive general performance equations and equivalent static networks for steady‑state operation.

Abstract

The self-cascaded machine is a single-unit version of two separate induction machines connected in cascade. In construction, however, it closely resembles a conventional induction motor. It may be run asynchronously, with resistance control if required, or synchronously without any external connections to the rotor winding. As a motor it is particularly suited to low-speed duties. With its simple and robust form of rotor construction, and the absence of slip rings or rotating diodes, it is also ideally suited for operation at high speeds as a high-frequency brushless alternator. A general description of the machine, and the underlying principles involved, are presented. A theoretical treatment is included based on doubly stator-fed operation of the machine. General performance equations are derived, and equivalent static networks are obtained for steady-state operating conditions.