Brushless cascade alternator

A brushless a.c. generator is described which has a mode of operation similar to two wound-rotor induction machines connected in cascade. This cascade machine, which has previously been considered for application as a motor, has single stator and rotor windings in a conventional induction-machine frame. The machine is one of inherently high pole number. As an alternator, therefore, it is suitable for the generation of medium- to high-frequency supplies. The direct excitation current and the alternating output current flow in its one stator winding. Its cylindrical rotor iswound with an extremely simple short-circuited polyphase winding. Since no brushes, slip rings or rotating diodes are needed, the machine may be driven reliably at high speeds. A theoretical treatment is developed which takes account of magnetic saturation both in the steady state and in the transient state. Design and performance details of a prototype 400 Hz, 3000 rev/min., 3-phase machine are also included.