Coreless HTS Synchronous Generator Operating at Liquid Nitrogen Temperatures

Abstract

In this paper we report on our new design of a liquid nitrogen/air cooled 100 KW synchronous generator with core-less rotor. This follows our successful completion of 100 KW generators with a 9 wt% Ni steel core operating at 77 K. In the new design, we demonstrate that a coreless rotor using commercial BSCCO tape is a realistic choice while maintaining the cooling at 57-77 K rather than 25-30 K and still achieving reasonable air-gap flux density. This is made possible by a combination of improved HTS wire technology and a careful optimization of HTS winding and flux diverters. The maximum flux density normal to the broad face of the tape is kept below 0.13 T, even when the air-gap density is raised to 0.5 T. The superconducting winding consists of 22 pancake coils with a total length of around 1250 meters of HTS tape. The required temperatures down to 57 K are achieved by a purpose-designed refrigeration system where liquid cryogen is circulated via a network of well insulated pipes and a stationery-rotating liquid coupling junction.

Superconducting wind turbine generators

“…As power electronic and PWM will be unavoidable to achieve full control of the HTS generator, it is crucial to predict the behavior of such machine under WT like conditions. The losses in HTS rotor which are amplified by the cooling efficiency of rotor cryogenic cooling (ranging from 50 up to 1000 [6] for temperatures ranging in 80[K] to 20[K]), will be function of WT operation conditions. We will address the biggest two contributors to AC loss of HTS in wind turbine generator.…”

High-Temperature Superconducting Wind Turbine Generators

“…Clearly a radical design of the whole superconducting arrangement (both stator and rotor) is not realistic before a new type of superconductors is developed to overcome these ac losses. As a result, a feasible design of the HTSWTG is based on the synchronous generator with the copper stator and the superconductor rotor (Bumby, 1983, Al-Mosawi et al, 2007. HTS coils are generally wound in the form of very thin race-track tapes due to their ceramic features.…”

Alternative Designs of High-Temperature Superconducting Synchronous Generators

“…The second project, currently underway at Southampton University, aims to build such a rotor [7]. Since the HTS tape for the cored rotor was purchased, BiSCCO tapes with substantially higher values of critical current have become available.…”