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Being an integral part of many high-power converters, it is imperative to estimate the natural resonance frequencies of a medium/high-frequency (MF/HF) transformer. Experiment/measurement based methods reported in literature determine the resonance frequencies based on the input impedance measurements. However, their applications are limited if these resonance frequencies are to be estimated prior to the transformer prototyping. To ameliorate the drawback, this article provides a comprehensive modeling procedure for the winding capacitances of a two-winding transformer and its resonance frequency estimation. By integrating the prior capacitance modeling techniques, this article establishes an electrostatic energy based transformation model, which directly translates the static winding capacitances into equivalent model based capacitances. These derived capacitances are further utilized to represent a reduced ${\pi }$ -model of a two-winding transformer, compute its frequency responses and estimate the resonance frequencies. The proposed model based approach is simple and easily executable, and helps avoiding any infeasible transformer design during the preprototyping stage. Experimental results derived from MF transformer prototypes, constructed of solid round, foil, and litz wires, are used to corroborate the theoretical analysis and feasibility of the proposed model based approach. [ABSTRACT FROM AUTHOR]

Gearless and small motors operating at speeds above 10 000 rpm are finding many applications nowadays. Axial flux permanent magnet (AFPM) motors are compact and lightweight compared to radial flux motors and hence, are considered for various high-speed applications. Eliminating the stator core minimizes the associated high-frequency losses, and hence, coreless AFPM motor can be an option for high-speed applications. Furthermore, the coreless AFPM motor design minimizes the cogging torque and the axial attraction force between the stator core and the rotor magnets. However, the reduction of flux linkage in the stator windings is a challenge in coreless AFPM motor. In this article, the advantages and disadvantages of the printed circuit board (PCB)-based AFPM motor for high-speed, low-power applications are investigated. A detailed performance comparison of the PCB-based coreless AFPM motor and the AFPM motor with the laminated stator core is made. Finite-element analysis is carried out for the electromagnetic, mechanical, and thermal comparison of the two motors and the simulation results are presented. Finally, motor prototypes are fabricated and are tested to ascertain the simulation results. [ABSTRACT FROM AUTHOR]

Cascaded multicell converter (CMC) is one of the effective solutions for medium-voltage high-power drives. The inability to regenerate power back to the source is one of the limitations of this converter. The regeneration capability is obtained by using a pulsewidth-modulated active rectifier instead of a conventional three-phase passive rectifier in each cell. However, due to their two-level voltage operation at the input side, an inductor is required for each cell to filter out the switching frequency components from the input current. This paper proposes a new configuration of regenerative CMC based on coupled inductor to achieve multilevel voltage at the transformer secondary terminals. This allows us to operate the rectifier devices at reduced switching frequency. The coupled inductor reduces the total harmonic distortion (THD) of the transformer secondary current and thus the transformer size. The size of the filter inductor and the transformer ratings are compared. The operating principle and the detailed analysis are presented. A technique to bypass a faulty module is proposed. The working of the converter is verified through simulation and experimental studies. [ABSTRACT FROM AUTHOR]

Axial flux-segmented rotor-switched reluctance motor (SSRM) topology could be a potential candidate for in-wheel electric vehicle application. This topology has the advantage of the increased active surface area for the torque production as compared to the radial flux SSRM for a given volume. To improve the performance of axial flux SSRM (AFSSRM), various stator slot/rotor segment combinations and winding polarities are studied. It is observed that the torque ripple is high for the designed three-phase, 12/8 pole AFSSRM. Therefore, the influence of the stator pole and rotor segment arc angles on the average torque and the torque ripple is studied. In addition, the adjacent rotor segments are displaced with respect to the stator, to reduce the torque dips in the phase commutation region. The proposed arrangement is analyzed using the quasi-3-D finite-element method-based simulation study and it is found that the torque ripple can be reduced by 38%. Furthermore, the low-frequency harmonic content in the torque output is analyzed and compared. The variation of the axial electromagnetic attractive force with displaced rotor segments is discussed. The effectiveness of the proposed technique is verified experimentally. [ABSTRACT FROM PUBLISHER]