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Permanent-magnet (PM) brushless direct current (BLDC) drives are utilized in a variety of applications because of their inherent features and would be even more utilized if their torque performance could be improved. Indeed, when supplied with square-wave currents, the torque-speed characteristic undergoes a drop at high speeds, and a significant torque ripple arises at both low and high speeds due to the commutation phenomena. In this paper, the sinusoidal current supply of the PM BLDC motors is investigated in depth, and an analytical formulation of the torque-speed characteristic, the torque ripple, and the base speed for such a supply are found. Based on the resulting equations, a thorough convenience analysis of the sinusoidal current supply is carried out with respect to the square-wave current in the presence of the commutation phenomena, which is hereafter termed as the real square-wave current supply. Simulation and experimental tests for a study case are given to corroborate the theoretical results. Generation of the sinusoidal current references using Hall sensors is also discussed

Abstract:For the past few years the feasibility of contactless power transfer (CPT) is being explored extensively as a future solution for charging electric vehicles (EVs). Studies report that the main obstacles in CPT are low power efficiency, misalignment tolerance, cost, range and charging time anxiety. This paper presents a review based on existing literature of the CPT systems for EV charging. Different cases of CPT technologies, their principle of operation and equivalent circuit based analysis is carried out. A discussion on compensation strategies and their effectiveness are reviewed and discussed. The design of coil systems for some city electric cars has been referenced in general. At the end recommendations and conclusions are made based on the study and analysis of the information available in literature.

In general, PM BLDC motors are injected with square wave phase currents through PI-PWM control in a-b-c reference plane to ensure maximum torque-per-ampere. The operation of PM BLDC motor in a stationary plane has shown considerable simplification in design, and analysis in the control techniques. The present paper considers the injection of square wave phase current through predictive current control strategies in the stationary plane. For the evaluation of performance, cases of deadbeat predictive control, hysteresis based predictive control, and finite control-set model predictive control (FCS-MPC) methods are considered. Control schemes have been designed for 48V, 660W PM BLDC motor. Comparative evaluation is carried out in terms of the harmonic components available in the current and torque, tracking of the current trajectory in the stationary plane in the low and high-speed region, and execution time of all the control methods. Considered predictive methods are tested on an experimental prototype, and control is implemented through digital Signal Processor (DSP) TMS320F28335. Evaluation leads to the conclusion that predictive control performs better than PI-PWM for reducing commutation torque ripple, keeping current harmonics under control. It is observed that predictive control strategies in the stationary plane, improve the torque-speed characteristic to the wider utilization of constant torque zone of operation as compared to conventional strategies.

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