Eddy Current Losses in Superconducting Secondary of a Linear Synchronous Motor: Calculations and Measurements

Superconducting linear synchronous motor (LSM) with superconducting magnets as its secondary is a promising candidate for driving high-speed transportations. The superconducting secondary operates at an ultra-low temperature environment generally supplied by a complex cryogenic system that contains numerous metal components, in which the eddy current losses are produced due to the magnetic fields from the primary. The ensuing temperature rise will inevitably lead to a reduction in the current-carrying capacity of superconducting secondary and threaten the operation safety of LSM. It is crucial to clarify the eddy current losses. To this end, we established a three-dimensional numerical model based on the A-formulation of Maxwell's equations. In this model, a kind of virtual primary was introduced to efficiently simulate the movement of the secondary instead of through a moving mesh technique since that is no longer suitable for this calculation. Afterwards, a testing setup of the superconducting LSM was constructed and the eddy current losses in the superconducting secondary were measured to validate the model. With the valid model, the eddy current losses in the secondary were systematically studied in consideration of different operating conditions of the LSM, followed by a discussion regarding the influence of cryogenic system on the losses.