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

Abstract

Recent developments in low ac loss MgB 2 conductors are of significant importance given renewed interest in fully superconducting (SC) machines. Evaluating ac losses in fully SC machines is a critical step in developing feasible designs. In fully SC machines, SC armature windings experience non-uniform rotating magnetic fields, with spatial and temporal harmonics, which has an undisputed impact on ac losses. Existing ac loss models in the literature, which have been validated for stationary sinusoidal external fields, were extended to constant amplitude rotating fields. There is not enough research on validating the ac loss models for rotating non-uniform magnetic fields with harmonics. This paper proposes simplified methods to estimate the ac losses in conductors with non-uniform rotational applied magnetic fields experienced by the armature in a machine's environment. Extended analytical models are proposed to estimate the ac loss in single and multi-filament MgB 2 conductors. The models are then compared against finite element analysis (FEA) results with Power Law loss estimation to evaluate model fidelity.

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

“…For comparison, ac losses are evaluated using the additionof-harmonic method described in [35] and the instantaneous ac loss method and then compared with FEA. Fig.…”

“…All these models assume uniform rotating fields; this assumption may result in an error in total estimated ac losses and subsequent cryogenic design. Integration of instantaneous losses and addition of harmonics methods are proposed in [35] to accommodate the influence of non-uniform rotating fields.…”

“…This paper presents an extension of the previously proposed ac loss models published in [35]. The extension includes de- The application of the extended models is demonstrated by estimating losses in superconductors with simulated air-gap fields experienced by a Fully SC wind turbine armature winding.…”

“…The FEA models employed in this comparison are experimentally validated in a low-frequency transverse uniform rotating field to establish the feasibility of the proposed models. For comparison, the paper also includes the harmonic addition method described in [35]. Several ongoing efforts exist to measure losses in HTS tapes under rotating magnetic fields [11], [37], [38], but loss prediction models have yet to be validated for MgB 2 conductors, and this paper contributes to this effort.…”

Designing and Commissioning an Experimental Setup to Evaluate AC Losses in Superconductors Under Transverse Rotating Fields

“…This paper experimentally validates the ac losses in MgB 2 wires for wind turbine applications and compares the results against analytical and FEA prediction. The detail of analytical and FEA models can be found in [22], [23]. The rest of the paper is organized as follows; Section II describes the ac loss measurement experimental setup, section III describes the detail of sample preparation, Section IV describes the calorimetric method, Section V describes the calibration and measurement methods, and section VI summarizes the measurement results.…”