Fabrication and performance testing of a 1-kW-class high-temperature superconducting generator with a high-temperature superconducting contactless field exciter*

This paper deals with the fabrication and performance testing of a prototype machine for the world's first implementation of a new type high-temperature superconducting rotating machine (HTSRM), which is charged and operated by the application of a contactless superconducting excitation technique with a rotary-type HTS flux pump based on a permanent magnet. Although this type of flux pump has been actively applied in stationary superconducting applications, its practical demonstration on rotary superconducting applications, namely, rotating machines, has not yet been conducted or reported. Therefore, laboratory-scale hardware implementation was conducted to investigate the feasibility of using an HTS contactless field exciter (CFE) as the field exciter of an HTSRM. Firstly, the various core components were manufactured, assembled, and tested to configure the 1-kW-class high-temperature superconducting generator (HTSG) system. Then, the assembled machine was connected with a conventional induction motor and three-phase resistive load. In non-load tests, the characteristics of the induced voltage of the HTSG, which was generated and affected by contactless field excitation and the operating speed, respectively, were tested and measured. In particular, the charge and discharge behaviors of the field current excited by the HTS CFE were experimentally analyzed based on the induced voltage profiles of the HTSG. Then, the HTSG output characteristics were tested and measured by performing experiments on the characteristics of constant load and constant speed, respectively. The generator test results were satisfactory in terms of output, voltage regulation, and the total harmonic distortion in the voltage and current.Our developed HTS CFE can excite an HTS field coil with 101 A in a noncontact manner, resulting in an operating field current margin of approximately 79% and a decrease of approximately 91.5% in the field excitation loss. In addition, the results demonstrated the possibility of designing HTS magnets with self-protecting features.