Vol. 60 | nr. 1 | January - March 2012 Article 7

Numerical heat transfer in the design phase of a synchronous superconducting machine

Alexandru M. MOREGA, Ion DOBRIN, Mihail D. POPESCU, Mihaela MOREGA, Lucian PÂSLARU-DANESCU

Abstract

This paper presents preliminary study on thermal stability of a small power prototype, high temperature superconductor HTS synchronous machine, with a particular concern devoted to the rotor part, which is cryocooled by liquid Nitrogen. We also present the heat transfer mathematical model for steady state working conditions and its numerical, finite element method implementation. The numerical simulation results outline the heat transfer mechanisms, the hot spots, and may provide information useful to HTS machine design optimisation. A problem of major concern with an HTS machines is its thermal stability. Unlike classical machines, the rotor part is cryocooled. One primary design challenge for HTS motors is then the design of the cooling system for the rotor superconducting coils, in order to ensure adequate thermal working conditions. First, using a simple 2D axial model, we perform an order of magnitude heat transfer analysis. Next, we consider a 3D model, closer to the real case, and investigate the liquid Nitrogen forced convection cooling of the field winding. The stator that carries the ac winding is cooled by natural convection to the ambient. It may release heat to the rotor too, through radiation, and to the frame, through conduction.

Keywords: high temperature superconductor, synchronous machine, design for testability, electromagnetic field, cryogenic cooling technique, numerical simulation, finite element method

 

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