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An ultraslim S-type power supply rail, which has a width of only 4 cm, for roadway-powered electric vehicles (RPEVs) is proposed in this paper. The cross section of the core has a thin S-shape, and a vertically-wound multiturn 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. The construction of roadway infrastructure, which is responsible for more than 80% of the total deployment cost for RPEVs, can be much easier when the width of the power supply rail is so small. To increase portability and to minimize construction time, a foldable power supply module is also proposed in which flexible power cables connect each foldable power supply module such that no connectors are needed during deployment. An effective winding method for minimizing the cable length is proposed, and an optimum core thickness of the proposed power supply rail is determined by FEA simulations and verified by a prototype power supply module. By virtue of the ultraslim 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 maximum efficiency, excluding the inverter, was 91%, and the pick-up power was 22 kW.Index Terms-Foldable power supply module, inductive power transfer system (IPTS), roadway-powered electric vehicle (RPEV), S-type power supply rail.

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This paper proposes pulse width modulation (PWM) methods for low inductance brushless DC (BLDC)motor drives that minimize the commutation torque ripples. An uneven current of non-commutation phase generates the commutation torque ripples. In the low inductance BLDC motor drives, two types of time delays in PWM also induce critical torque ripples. In this paper, the analyses of the time delays in PWM and their effects are introduced. Then, two PWM methods are proposed to eliminate the time delays in the commutation region and the conduction region, respectively. The commutation period is controlled to be synchronized to the switching period. In addition, the proposed methods synchronize the switching period to the commutation interrupt. As a result, the proposed methods effectively maintain the minimum commutation period as well as minimize the commutation torque ripples in the low inductance BLDC motor drives. The validity of the proposed methods is demonstrated by the simulation and experimental results in various driving conditions. The results show that the commutation period is remarkably shortened and the commutation torque ripples are reduced by 27.6% in comparison to the conventional method.