An air-gap element for the isogeometric space-time simulation of electric machines

Purpose Space-time methods promise more efficient time-domain simulations, in particular of electrical machines. However, most approaches require the motion to be known in advance so that it can be included in the space-time mesh. The purpose of this paper is to overcome this problem by proposing the use of the well-known air-gap element for rotor-stator coupling of an isogeometric machine model. Design/methodology/approach First, the authors derive the solution in the air-gap region and then use it to couple the rotor and stator. This coupling is angle dependent and the authors show how to efficiently update the coupling matrices to a different angle, avoiding expensive quadrature. Finally, the resulting time-dependent problem is solved in a space-time setting. Findings Spatial discretization using isogeometric analysis is particularly suitable for coupling via the air-gap element, as nonuniform rational B-splines can exactly represent the geometry of the air gap. Furthermore, the model including the air-gap element can be seamlessly transferred to the space-time setting. Originality/value The air-gap element is well known in the literature. The originality of this work is the application to isogeometric analysis and space-time.