AC Loss Modeling in Superconducting Coils and Motors With Parallel Tapes as Conductor

Abstract

Many superconducting power applications contain REBa2Cu3O7−x (or REBCO) coils, where RE stands for "rare earth". Superconducting motors are very interesting for mobile applications like aviation, thanks to their high power per unit weight. In order to reduce the inductance, multi-tape conductors are often used in windings but parallel tapes present coupling AC loss. In this article, we analyze the AC loss of single coils and a full stator of a motor made of windings of parallel tapes, taking several coupling situations into account. Our computer modeling method combines self-programmed and commercial finite-element methods to calculate the current density and AC loss. We found that isolating the tapes along the length provides almost the same AC loss reduction as that obtained by full transposition. This reveals that there are still many unexploited strategies to reduce the AC loss in multi-tape conductors.

Electromagnetic Modeling of Superconductors With Commercial Software: Possibilities With Two Vector Potential-Based Formulations

“…2. AC losses as a function of the transport current (normalized to Ic) of the racetrack coil considered in [16], [28], when the tape turns are electrically insulated ('uncoupled') or in electrical contact ('coupled'). The AC losses computed with the T -A formulation are compared to those computed with the H formulation and the MEMEP method.…”

“…As mentioned in section II-A, the T -A formulation for thick conductors can be used for simulating not only individual conductors with rectangular cross section, but also stacks of coupled coated conductors. Here we present the validation of the model for the latter case, in particular for the stand-alone racetrack coil considered in [16], [28]. The coil is made of 4 cable turns, each made of 13 tape turns, which can be considered as electrically insulated or in electrical contact.…”

“…As an example, Fig. 3 shows the current density distribution in two half-coils of the stator of the superconducting motor considered in [16], [28], whose design is based on that of the SUTOR motor [29]. The average power loss dissipation of the stator coils in the coupled case are higher than in the uncoupled case, increasing from 52.31 W to 111.5 W at 65 K, and from 90.79 W to 173.22 W at 77 K.…”

Computation of Superconducting Stacks Magnetization in an Electrical Machine

“…Moving boundary surrounding regions, allowing a much higher current value compared to AC operation [4,21]. In the end, field cooling seems an easier-to-implement magnetization procedure in an initial prototype.…”

“…HE increase of the power density of rotating electrical machines for relatively low speed, high torque applications, such as wind energy generation [1] or aircraft propulsion [2] must derive from the achievement of higher magnetic flux and current densities during operation, which may be allowed by superconducting technology. Although the application of these kind of materials has been studied long ago [3] in order to improve the performance of electrical machines, their practical utilization has been hindered by the fact that their optimal characteristics for conducting currents are altered under AC field due to the appearance of losses [4], and the requirement of ancillary cooling devices that reduce not only the efficiency of the whole system, but also its reliability.…”