Prototype of Kinetic Energy Storage System for Electrified Utility Vehicles in Urban Traffic

This paper presents theoretical and experimental results on the ongoing construction of a high-speed (30000 rpm) kinetic energy storage system (KESS). The purpose of the device is to function as a power buffer storing up to 1kWh, primarily for utility vehicles in urban traffic. The KESS is connected in series between the primary power source and the tractionmotor of the vehi-cle. It comprises a composite rimof carbon and glass fiber in an epoxymatrix. The power to/from the rotating rim is transferred through an integrated double wound three-phase PM machine. The machine is levitated axially using four units with segmented Halbach arrays in a repulsive con-figuration. Radial centering is achieved through eight separate active electromagnetic actuators controlled by an FPGA. The geometries of the passive thrust units as well as the active actuators were designed using linked CAD and FEM tools controlled by advanced optimization algorithms. The simulated repulsive force from the thrust magnets was verified experimentally. Additionally, the corresponding negative stiffness in radial direction as well as the power loss due to induced eddy currents were simulated. The optimization of the active magnetic bearing (AMB) actuators resulted in a geometry with low resistive power loss, while generating a high current stiffness at the expense of maximum force.