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This study deals with the design, implementation and experimental performance of all silicon carbide pulse width modulation (SiC PWM) rectifier-based off-board ultrafast chargers (UFCs) for lithium titanate batteries of heavy electric vehicles. Different UFC configurations are proposed, depending upon the nominal battery voltage (400-1000 V DC) and charge capacity. Operating principles and control of UFC at unity and leading power factors are assessed and corresponding operating modes of PWM rectifier are discussed. The combined effect of reverse conduction characteristic of SiC power metal oxide semiconductor field effect transistor (MOSFET) and built-in SiC Schottky diode is taken into account in all the analyses carried out. The operating performance of the developed UFC, such as the switching characteristics of SiC power MOSFET modules, efficiency, input current total demand distortion (ITDD), and thermal limitations of the SiC PWM rectifier have been assessed for various charge voltages and charge capacities, both by computer simulations and laboratory tests. Power circuit layout considerations of the proposed system are also given in this study. Excellent performance results for 10 kHz switching frequency are obtained from the developed 200 kW UFC, with operating efficiencies higher than 98.5% for all charging rates up to five times the battery capacity, and ITDDs <2.2% for the whole operating range.

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The design and development of a high-performance 165 kVA, 750 V DC all-silicon carbide (SiC) traction converter for new generation light rail transportation systems (LRTSs) are described. In the design of the traction motor drive, the efficiency of the overall system is maximized and the line current harmonic content of the traction motor is minimized. A complete mathematical model of the physical system is derived to carry out real-time simulations and proper control of the LRTS on a real rail track. The electrical and thermal performances of traction-type SiC power MOSFET modules are compared with those of alternative hybrid and Si-IGBT modules for various switching frequencies. The implementation of the developed system is also described. The performance of the resulting system is verified experimentally on a full-scale physical simulator as well as for various track conditions. Very promising results for the next generation railway traction motor drives have been obtained in terms of performance criteria, such as very high efficiency, low harmonic distortion of the motor line current, low cooling requirement, relatively high switching frequency, and hence, superior controller performance. The effects of the SiC power MOSFET operation on the insulation of the available traction motors are also examined experimentally. This paper is accompanied by a video demonstrating the experimental work.