Design and Development of a Cryogen-Free Superconducting Prototype Generator With YBCO Field Windings

Abstract

A prototype machine has been developed to study large-capacity wind turbine generators using high-temperature superconducting technology. The superconducting field windings, using 2G YBCO wires, are used in the rotor, whereas the conventional technology is employed in the stator. The racetrack superconducting magnets are cooled directly by two cryo-refrigerators and the operating temperature is 30 K. The cold heads of the refrigerators are installed on the rotor, which is driven by a drive motor, rotating synchronously with a vacuum chamber. A rotary gas seal is employed as the gas slip ring connecting the rotary cold head to a stationary compressor. This paper also presents the electromagnetic characteristics of the prototype machine and the feasibility of the cooling system. Experimental results of back electromotive force are shown at field current from 10 to 100 A and rotating speed from 10 to 30 r/min. The electromagnetic design, based on the finite-element method (FEM), is available in this paper, and the FEM data are coincident with the experimental results very well.