The optimization and design of "air-core" homopolar machines

This paper presents a novel method for the design and optimization of "air core" homopolar machines. In this new method, the machine performance equations are formulated in terms of the magnetic vector potential, A. This is in contrast to the conventional approach of formulating the performance equations in terms of the average magnetic flux density in the active region, Ba. Formulating the equations in terms of the magnetic vector potential leads to a straight-forward optimization procedure for maximizing machine power density. A simplistic model is used to illustrate the new formulation. Next, a more complete model is developed and used to establish the functional parameter space for "air core" homopolar machines and identify the technologies needed to improve their performance in terms of maximizing power density. Power densities in excess of 80 kW/kg are obtainable with conventional technology and at average magnetic field intensities of less than 2 T.