Inductive power transfer systems with large tolerances for roadway powered electric vehicles

Abstract

In this dissertation, three innovative inductive power transfer systems (IPTSs) for roadway powered electric vehicles (RPEVs) are newly introduced to highly enhance its lateral displacements, which is one of the most significant problems for commercialization of RPEVs. For large lateral tolerances, the first and last chapters mainly focus on minimizing a self-inductance variation of pick-up coils with proposed self-decoupled dual pick-up coils and proposed coreless power supply rails, respectively, while the second chapter mainly deals with the use of proposed asymmetric coil sets, where proposed S-type power supply rail is much smaller than a pick-up coil set to enhance its lateral tolerance as well as construction of roadway infrastructures. In chapter 1, self-decoupled dual pick-up coils for large lateral tolerance and low EMF for pedestrians are proposed. By virtue of the self-decoupled characteristic, a self-inductance variation of a pick-up coil set is minimized along lateral displacements and maximum load power over a large lateral tolerance is obtained for the optimum decoupling condition. Analytical models are developed that are applicable to any self-decoupled coils, regardless the coil types such as single/dual pick-ups and core/coreless coils. An optimum decoupling distance between adjacent pick-up coils is determined and found to be independent of the exist-ence of a core plate. A prototype system of 1.5 kW and load quality factor $Q_L$ of 60 for RPEVs was imple-mented and showed fairly good agreements with the theoretical models and simulations. The measured lat-eral tolerance was 90 cm, which is about 1.5 times of the pick-up coil width. In chapter 2, an ultra slim S-type power supply rail of an IPTS for RPEVs, which has a width of only 4 cm, is proposed in this paper. The cross section of the core has a thin S-shape, and a vertically-wound multi-turn coil is displaced inside the core. In this way, the most slim power supply rail is designed, which is crucial for the commercialization of RPEVs. By virtue of the ultra slim shape, a large lateral displacement of 30 cm at an air gap of 20 cm was experimentally obtained, which is 6 cm larger than that of the I-type power supply rail. In addition to the larger lateral displacement, it is estimated that the S-type one has lower EMF than the I-type one because the width of the S-type one is narrower than that of I-type one. The measured maximum efficiency, coil to DC load, was 91%, and the pick-up power was 22 kW. In chapter 3, a universal inductive power transfer system (U-IPTS) is newly proposed to meet the interop-erability between RPEVs and stationary charging electric vehicles (SCEVs) with the satisfaction of the design goals for RPEVs in this paper. The proposed U-IPTS adopts a new coreless power supply rail to increase its operating frequency from the conventional operating frequency of 20 kHz to the new operating frequency of 85 kHz, as specified in the SAE J2954 standard. Also, the proposed coreless power supply rail can firmly guarantee large lateral tolerance because the self-inductance variation of a pick-up coil with the proposed coreless power supply rail does not exist along lateral displacements. Also, contrary to conventional IPTSs for RPEVs, the proposed coreless power supply rail can also be used for pick-ups fabricated by the society of automotive engineers (SAE) J2954 standard for SCEVs. Moreover, the construction of roadway infrastruc-ture, which accounts for more than 80% of the total deployment cost for RPEVs, can be much easier and faster when there are no core plates used for a power supply rail. Experimental results showed good agree-ments with the theoretical models and simulations. By a virtue of proposed coreless power supply rail, the measured maximum efficiency of the proposed U-IPTS was 89 %, which is 3 % higher than that of a conven-tional with-core power supply rail for the pick-up power of 3.3 kW. This is because the core loss of the pro-posed coreless power supply rail can be effectively ignored even though the ampere-turns of a power supply rail are high enough.