No abstract

The article is devoted to the study of losses in devices based on high-temperature superconductors of the 2nd generation. The complexity of the devices under study increases from a single rack coil to a winding assembled from several coils, and finally to an electric machine operating in generator mode. This is the way to experimentally study the behavior of 2nd generation high temperature superconductor (2G HTS) carrying a transport current in various conditions: self-field, external DC, and AC magnetic field. Attention is also paid to the losses in the winding during its operation from the inverter, which simulates the operating conditions in the motor mode of a propulsion system.

Current work is dedicated to determination of AC losses of racetrack coils that are intended to be used in HTS motor winding. Coils were tested at temperature of boiling nitrogen with sine waveform current with frequencies from 50Hz to 200Hz and corresponding levels were taken as a basis for comparison. Current waveforms, distinctive for brushless DC and brushless AC motors, induced by high-frequency modulation, were compared. Two coils with same dimensions and numbers of turns, but with different tapes (AMSC/SuperOx) were compared in terms of the levels of losses on described current forms.

Systems with high-temperature superconductors (HTSC) impose new requirements on power conversions, since the main part of the losses in such systems is induced in the semiconductors of the converters. Within the framework of this study, the possibility of improving the static and dynamic characteristics of power semiconductor diodes using cryogenic cooling was confirmed; in some cases, a loss reduction of up to 30% was achieved.

Designing systems of future aircraft is a very complex task due to demanding requirements. Superconducting electrical machines and cables could be a solution due to their high specific power. Developing a system which includes an HTS generator, a rectifier, and an HTS cable needs application of analytical techniques. Besides, some optimization techniques should be used to choose proper device parameters in order to provide maximum specific power of the entire system. This paper describes the main principals of developing such a system and provides the results of preliminary calculation of the specification of the system with a 500kW output power.