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

Abstract

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.

Study of the demagnetization behavior of no-insulation persistent-current mode HTS coils under external AC fields by 3D FEM simulation

“…The significance of this applied field is as follows. In recent years, rotating and linear synchronous machines employing NI PCM coils have attracted increasing attention [4,14,33,[85][86][87][88]. In these applications, although the HTS rotor magnets are normally synchronous with the stator field and resemble a static field, they occasionally operate in dynamic conditions and encounter considerable non-synchronous time-varying fields, such as during the acceleration/deceleration and starting/breaking processes (which are frequent for wind turbines), electrical and mechanical vibrations, primary-coil-currentcontrol and out-of-step faults, and active short-circuits of the machine [89][90][91].…”

ASCEND: The first step towards cryogenic electric propulsion

“…The order of magnitude of the cryogenic losses of this class of motors is 1 kW (at cold temperature). Considering this configuration, some machines were designed well beyond the requirement of the electric propulsion system [20].…”