Brushless Self-Excited Synchronous Field-Winding Machine With Five- and Higher Phase Design Using Independently Controlled Spatial Harmonics
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Electric machines used in a variety of sustainable energy applications need to possess high power density, high efficiency, and low manufacturing cost. While permanent-magnet machines (PM) and synchronous field-winding machines (SFM) are the popular option for variable-speed drives, these topologies have undesirable aspects. The permanent-magnets in PMs are made of rare-earth materials having high price volatility and are prone to demagnetization risking machine operations. The SFMs require additional electrical and mechanical components requiring regular maintenance and replacement and add extra volume, weight, and cost to the drive system.
In this dissertation, a novel brushless self-excitation scheme for synchronous field-winding machines is presented. This scheme uses an AC stator with five or higher phases to create two independently controlled rotating magnetic fields at different spatial harmonics, allowing independent magnetic coupling with different rotor windings. The rotor of the proposed machine possesses a field winding, transformer windings, and a diode rectifier that converts induced AC voltages in the transformer windings into a DC voltage for the field winding. A design for a five-phase stator configuration is developed using finite-element analysis tools, and simulation results are presented. Torque and power characteristics of the design are compared with similarly-sized interior permanent-magnet and induction machines.
Chair: Professor Heath Hofmann