Pickup

Abstract: Electric vehicles have been rapidly gaining in popularity in recent years, and with them inductive charging solutions. The ideal stationary charging system requires no input from the user, and places as few restrictions on either parking location, or environmental conditions (i.e. rain or snow) as possible. The success of inductive charging systems is contingent largely on the design of the magnetic coupling components; i.e. the track pad and the pickup. This paper details a new topology for the track pad, consisting of two largely coplanar, partially overlapping coils positioned such that there is no mutual inductance between them. This arrangement prevents interaction of the two coils, and allows the currents within them to be independent in both phase and magnitude. By controlling the phase and magnitude of the two coil currents, the magnetic field can be shaped to assist in power transfer to a pickup underneath an EV.

Abstract: We describe a new type of optical pickup for use in high-density optical storage systems. By changing a conventional pickup design to include a glass element between the objective and the disk, the transverse resolution of the system can be increased by as much as a factor of 1.5. This system is also less sensitive than conventional systems to variations in disk thickness and disk tilt. We demonstrate how the system has been used as a microscope to inspect an optical disk and describe possible design configurations for an optical pickup.

Abstract: Roadway powered electric vehicles with minimal or no onboard energy storage have been proposed for many years, but the concept has only recently become feasible via three-phase inductive power transfer (IPT) systems. A wide zone can be created over which power transfer is relatively constant. This gives good tolerance to the alignment of the pickup relative to the track allowing simple low-cost pickup structures to be used. While three-phase IPT tracks make the vehicle pickup and power transfer simpler, they are difficult for the power supply to drive due to the presence of mutual coupling between the track phases resulting from the physical layout of the track. These mutual inductances induce voltages within each track phase that, because of the inductor-capacitor-inductor network, cause large currents within the power supply inverter and imbalances within the system. This paper presents an analytical assessment of the problems caused by the interphase mutual inductance, and three possible solutions. Two of the methods involve modifications to the track layout to alter or remove the mutual inductances, while the third and preferred technique requires additional ferrite cores between the various phases to compensate this adverse mutual inductance without affecting the power transfer to the pickup loads.

Abstract: This paper presents a new type of series ac-processing pickup used in inductive-power-transfer applications. The proposed pickup uses an ac switch operating under zero-current-switching conditions in series with a resonant network to produce a controllable ac voltage source suitable for driving incandescent lights. When a rectifier is cascaded onto this pickup, it can also produce a precisely controlled dc voltage. This topology eliminates the need to use an extra buck converter after the traditional series pickup for controlling the output load voltage to a desired value, which may be different from the induced voltage of the pickup. Furthermore, this pickup has the ability to control the inductor current directly, and hence, eliminate the transient inrush current at startup for the series-tuned resonant tank. The circuit is analytically analyzed and the maximum efficiency for a 1.2-kW prototype is measured to be 93%.