Evaluation and Mitigation of AC Losses in a Fully Superconducting Machine for Wind Turbine Applications

Abstract

A significant challenge in the design of fully superconducting (SC) machines is managing ac losses in the SC armature. Recent developments in MgB 2 superconducting conductors promise low ac loss conductors suitable for fully SC machines. This paper presents an optimized design targeting low losses and low weight for a 10-MW fully SC generator suitable for offshore wind turbine applications. An outer rotor air-core machine topology is investigated to optimize the design with low weight and low losses. An active shielding concept is used to minimize the pole count without adding excessive weight. This enables a reduction in the electrical frequency for a practical design by a factor of 4 to 5 over current designs, driving ac losses and active components weight lower by an order of magnitude. In this study, armature current is varied to control electrical and magnetic loading in order to minimize losses. A pole count study is conducted to identify the design space suitable for MW scale machines. A comparison is made between active shield, passive shield and a hybrid topology to address the benefits of an active shield for weight reduction. Results suggest that low-pole-count designs with MgB 2 conductors will enable machines with less than 1 kW of ac losses.

Methods of Estimating AC Losses in Superconducting MgB$_{2}$ Armature Windings With Spatial and Time Harmonics

“…Carr proposed an extension to models for stationary fields to estimate losses in constant amplitude rotating fields [15]. These models are used in [42]- [44] to estimate losses. Wilson [16] proposed an analytical model to estimate losses in multi-filamentary conductors.…”

Multi-objective Optimization of a Multi-tooth Flux-switching Permanent Magnet Machine with HTS Bulks

“…T he performance and commercialization level of hightemperature superconducting (HTS) machine have made significant progress since 2000. HTS machine has obvious advantages in volume, quality, and efficiency, which is an ideal solution for large capacity and high torque density propulsion machine and an ideal choice for high-power direct-drive wind turbine [1][2][3]. With the development of industry, the demand for high torque and low speed direct drive is increasing.…”

Instantaneous Loss Integration Method to Estimate AC Losses in Superconductors With Spatial and Time Harmonics

“…F ULLY superconducting (SC) machines have great potential for large wind turbine applications [1]- [5] due to their low operating electrical frequencies, typically 0.1-6 Hz [3], [6]- [9]. Superconductors experiencing alternating fields or currents generate thermal losses within the conductor, a phenomenon known as ac losses [10], [11].…”

“…Carr's proposed ac loss models for stationary and uniform rotating fields to estimate losses in SC [12]. These models are used in [6], [9], [32], [33] to estimate machine losses. Wilson [13] proposed analytical models to estimate losses in multi-filamentary conductors.…”