Scaling studies of High Speed High Temperature Superconducting Generator

The sizing of a high speed, high power density, high temperature superconducting (HTS) electric generator is discussed here. Previous work discussed the advantages of a homopolar inductor alternator (HIA) machine topology for the high speed, high power density application - i.e., the enhanced magneto-motive force (MMF) capability of the HTS coil combined with high rotor tip velocity and a liquid cooled 'air gap' wound armature. In this work we present the sizing/scaling of a family of machines based on this topology. The goal of this exercise is to obtain power entitlement and power density of the machine for a given physical size within mechanical, thermal and electrical constraints. A prototype machine was designed and tested [1] validating the assumptions used in this sizing/scaling model. Effects of some key design changes are also discussed. Power densities in the range of 4.2-8.8 kW/kg can be obtained depending on the rotor material, and HTS wire, for 3-5MW rating. Comparison is made with high speed permanent magnet (PM) machines indicating a significant weight reduction - at least 500 kg for a 5MW machine or 1000 kg for a 15.6MW machine.