Development and Laboratory Testing of a Self-Excited Synchronous Machines without Permanent Magnets

Abstract

Today, self-excited synchronous machines are the object of increasing interest because they use neither brushes nor permanent magnets. In fact, the price of rare earth metals is considerably high and still raising. This is the main reason why researchers are looking for suitable alternatives to permanent magnets in the construction of rotating electrical machinery. This paper deals with the design and laboratory testing of a synchronous machine with an efficient layout and an economic construction. The proposed self-excited machine exploits the space harmonics of the magneto-motive force to produce the excitation field. The model analysis is based on the computation of the back EMFs that are associated to the magneto motive force components. The mathematical model suggests an easy way to decouple the rotor windings. The machine has been built and experimental tests have been performed in order to validate the electrical behavior.

Electromagnetic Characterization of Hyperconducting Aluminum Litz Wires at Cryogenic Temperatures

“…The use of liquid hydrogen as an aviation fuel has led to increasing interest in cryogenic technologies for enhancing the performance of conductors [2] for cables, electric machines and drives [3][4][5], potentially leading to a significant reduction in conductor losses [6][7]. Regarding the winding materials for cryogenic electric machines (CEMs), two types are commonly considered: superconducting materials and hyperconducting materials.…”