Design Principle for Linear Electrical Machines to Minimize Power Loss in Periodic Motions

This paper describes a novel approach to the design of linear machines that are not run at a steady state operating point. The focus lies on minimizing the power loss to achieve highest possible efficiency. First analytical considerations reveal the potential of designing electrical machines for periodic, accelerated motion. It shows the influence of the machine size on the power losses due to the dependence of machine force as well as moving mass on this parameter. Based on these findings, a simulation model was created with which a linear machine can be optimized for a specific motion and load cycle. The simulation consist of a stationary and a time dependent finite element analysis of the linear machine in conjunction with an operational model that includes a given movement cycle. It was used to design a flat type linear machine for a free piston linear generator. The simulation results validate the analytical calculations and illustrate the differences to conventional design approaches for linear machines.