Loss characteristics of HTS coated conductors in field windings of electric aircraft propulsion motors

Abstract

High-temperature superconducting (HTS) coated conductors (CCs) are widely regarded as a promising candidate to enable very high power density motors. These machines operate at high rotational speeds, with some designs going up to 12 000 rpm. HTS CCs are applied to the field windings of these motors to increase the magnetic loading and hence the power density. Even though the superconducting field windings operate with a DC current, due to the magnetic field environment, losses are present. This paper examines the dynamic and total loss characteristics of YBCO-coated conductors in the frequency range relevant to high-speed motors for electric aircraft propulsion. A multi-layer model was created using the H -formulation and the losses for each layer were highlighted. For the first time, it was shown that the DC transport current region in the HTS layer shrinks as the frequency of the applied field increases due to the increased magnetisation current around the edges of the CC, which reduces the dynamic loss per cycle as the frequency increases. To fully understand the loss distribution in the HTS CC, the total loss in the conductor was investigated. For an applied magnetic field of 100 mT and 800 Hz, more than 30% of the total loss occurs in the copper layer due to the decreased penetration depth of the magnetic field and the skin effect. Results show that to accurately model and understand the losses in superconducting field windings, a multi-layer model should be used, since a significant proportion of loss shifts towards the copper stabilizers. Over all, it was shown that both the dynamic loss as well as magnetisation loss play a crucial role in the estimation of the loss in superconducting field windings.

Electromagnetic properties of curved HTS trapped field stacks under high-frequency cross fields for high-speed rotating machines

“…This paper is a follow-up work of our previous publications [25][26][27][28]. TFSs are a potential field source applied to highspeed HTS machines.…”

“…For now, the electromagnetic behaviour of HTS TFSs under high-frequency fields remains unclear. In addition, according to our previous research work [25][26][27][28], at frequencies higher than 100 Hz, it is necessary to consider the multilayer physical structure of HTS CCs to quantify magnetization loss due to the skin effect. The existence of the copper stabilizers, silver overlayer, and substrate can influence the loss distribution inside CCs [29].…”

A modular and cost‐effective high‐temperature superconducting generator for large direct‐drive wind turbines

“…Also for dynamic loss, it was shown that it is mainly the perpendicular field, which contributes towards the loss [30]. Additionally, the induced loss is highly frequency dependent, a high frequency leads to higher losses [31, 32].…”

Time-variant magnetic field, voltage, and loss of no-insulation (NI) HTS magnet induced by dynamic resistance generation from external AC fields

“…However, the unique behaviors of NI magnets affected by the dynamic resistance have not yet been clearly observed. The dynamic resistance is recognized as an important influence factor occurring in synchronous machine applications [9,17,[26][27][28].…”