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Summary form only given. This paper analyses the phenomena of wave erection in a coaxially arranged fast erecting MARX generator for finding the importance of delayed sequential synchronization of spark gap switches. A wave propagation model of coaxially arranged MARX generator is made. Simulation shows, that generated output voltage and energy delivered to load is not a monotonous function of delay time. Variation of output voltage with delay in triggering of spark gap is plotted. Similar experimental setup is fabricated and tested with copper sulphate dummy load. Results are compared and discussed in the following sections of the paper.

Summary form only given. This paper presents PIC simulations of spark gap discharge, filled with Argon gas at atmospheric pressure. The rogowsky profile electrodes having an inter-electrode gap distance of 20mm were used in this study. The model is based on explosive electron emission from cathode, secondary emission and neutral Argon gas ionization. The phase space profiles, current density, ionization, temperature and velocity of electron plots are presented. Results show that some simulations are in good agreement with existing experimental data. The simulation data of argon discharge was also compared with our previous work of nitrogen gas discharge1. The difference between the two gases for using them as a dielectric medium in spark gaps is presented.

Summary form only given. This paper deals with the discharge along the surface of angled insulators in compressed gases using 3D finite difference particle-in-cell simulation. The simulation is carried in pure nitrogen at atmospheric pressure. The ionization of neutral atoms of nitrogen takes place by electron impact leading to production of positive ions and secondary electrons. The ionization cross sections of electrons with neutral gas molecules are taken as function of electron energy. The pulse rise time is 5ns with pulse duration of 50ns. The spacer angle `θ' is measured between the inclined surface and line vertical to the electrode. The angle is positive when narrow end is connected to the anode and negative otherwise. The positive spacer angle shows a reduced discharge voltage for a 20mm gap length which is close to the discharge voltage for cylindrical insulators. The negative spacer angle shows a discharge voltage close to the bulk gas gap condition. This is explained by a reduction in the momentum profile of electrons for positive spacer angle which aids in earlier emission of electrons and the discharge path followed is same as that for cylindrical insulators whereas an increase in momentum for negative spacer angle gives a longer discharge path and hence condition close to the bulk gas gap. This finds application in the design of high voltage insulators subjected to impulse voltages.

This paper presents the theoretical analysis of the variations in the drift velocity and ionization coefficient of electrons in the presence of an insulator in gases at high pressure. The model is developed taking into consideration the variation of parameters like drift velocity, ionization coefficient, transit time of travel of electron and streamer length in the presence of insulator which are responsible for flashover of insulator in gases at a reduced voltage unlike the plain gas gap conditions. Some of the parameters calculated theoretically are found to be in close agreement with the existing experimental data.

A numerical model employing FDTD based particle-in-cell code (PIC) is used to study the discharge mechanism across a gas /solid interface. The simulation is carried out with and without an insulator in the anode cathode gap at a pressure of latmosphere and a ramp voltage with a rise time of 5ns and pulse duration of 50ns is used as the input pulse. The profiles of electron densities, avalanche growth, phase profile of electrons, and the gap voltage are calculated with and without an insulator to study the mechanism of discharge in presence of an insulator. Spacer efficiency of 81% is obtained which closely agrees with the existing experimental data.

This paper proposes a method of minimization of torque ripple of brushless dc (BLDC) motors, with un-ideal back EMF under MATLAB 7.1/Simulink environment. An idealized BLDC motor has trapezoidal back EMF waveform. However, for practical reasons like non-uniformity of magnetic material and design trade-off it is hard to produce desired trapezoidal wave shape. Therefore torque ripple appears in conventional control. In this paper, the duty cycle of the pulses is calculated in the torque controller in both normal conduction period and commutation period and in combination with a given commutation sequence fed to the inverter gates so as to minimize ripple. Moreover, the influence of finite dc supply voltage is considered in commutation period. Simulation results show that compared with conventional control, this method results in apparent reduction of torque ripple.