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Electric Power Applications, IEE Proceedings B

Issue 4 • Date July 1988

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Displaying Results 1 - 6 of 6
  • Optimum size of dissipative nonlinear turn-off snubber

    Page(s): 165 - 171
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (841 KB)  

    The use of voltage dependent, saturable capacitors as nonlinear turn-off snubbers for power electronic switches is discussed. Emphasis is placed on the optimisation of such a nonlinear turn-off snubber, is dissipative snubber configuration. The snubber capacitance is optimised in terms of minimum total energy losses (consisting of the stored energy in the capacitor, and the energy loss in the power switch during turn-off). By means of a computer analysis, which uses the exact capacitance-voltage curve of the nonlinear snubber capacitor, the needed energies are calculated and the results presented in clear graphical form. The computer simulation is also verified by means of an experimental measurement. From the results, it is evident that, from an energy point of view, the nonlinear capacitive snubber is about always superior to the normal linear snubber. This conclusion is applicable to the stored energy in the capacitor, total energy losses, as well as to the minimum total energy loss. View full abstract»

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  • New current control scheme for PWM inverters

    Page(s): 172 - 179
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (912 KB)  

    In the paper, a new current control scheme for PWM inverters is described. With this scheme, the inverter switching frequency and output switching pattern are both predefined. Particular output voltage patterns can be selected by minimising a suitable objective function. Thus, the proposed scheme achieves precise current control along with the simultaneous optimisation of a performance objective. These features yield near-sinusoidal currents in the load with reduced current peaks, lower inverter switching frequency, and reduce inverter and load stresses. This type of current control scheme is especially suitable for potentially high performance applications such as AC motor drives and UPS systems. Finally, detailed experimental investigation of the current control scheme is presented. View full abstract»

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  • Analysis of conventional snubber circuits for PWM inverters using bipolar transistors

    Page(s): 180 - 192
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1220 KB)  

    The ideal behaviour of conventional capacitive and inductive snubbers for bipolar transistors in PWM inverters is described in terms of the equivalent circuits that are operational during the switch-on and switch-off sequences. These equivalent circuits are analysed so that all currents and voltages during switching conditions can be predicted analytically, and the describing equations are tabulated. From these results, the losses in the snubber resistors are calculated for each switching event. The analysis is extended to cover the case in which the inverter is carrying sinusoidal current, so that average snubber resistor dissipation is predicted analytically. Theoretical results are compared with experimental results and SPICE circuit simulation. The way in which stray circuit inductances cause departures from the ideal conditions is also discussed. View full abstract»

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  • Analysis of conventional snubber circuits for PWM inverters using bipolar transistors

    Page(s): 180 - 192
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (820 KB)  

    The ideal behaviour of conventional capacitive and inductive snubbers for bipolar transistors in PWM inverters is described in terms of the equivalent circuits that are operational during the switch-on and switch-off sequences. These equivalent circuits are analysed so that all currents and voltages during switching conditions can be predicted analytically, and the describing equations are tabulated. From these results, the losses in the snubber resistors are calculated for each switching event. The analysis is extended to cover the case in which the inverter is carrying sinusoidal current, so that average snubber resistor dissipation is predicted analytically. Theoretical results are compared with experimental results and SPICE circuit simulation. The way in which stray circuit inductances cause departures from the ideal conditions is also discussed View full abstract»

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  • Optimum size of dissipative nonlinear turn-off snubber

    Page(s): 165 - 171
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (548 KB)  

    The use of voltage dependent, saturable capacitors as nonlinear turn-off snubbers for power electronic switches is discussed. Emphasis is placed on the optimum dissipative snubber configuration. The snubber capacitance is optimised in terms of minimum total energy losses (consisting of the stored energy in the capacitor, and the energy loss in the power switch during turn-off). By means of a computer analysis, which uses the exact capacitance-voltage curve of the nonlinear snubber capacitor, the needed energies are calculated and the results presented in clear graphical form. The computer simulation is also verified by means of an experimental measurement. From the results, it is evident that, from an energy point of view, the nonlinear capacitive snubber is always superior to the normal linear snubber. This conclusion is applicable to the stored energy in the capacitor, total energy losses, as well as to the minimum total energy loss View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • New current control scheme for PWM inverters

    Page(s): 172 - 179
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (568 KB)  

    With this scheme, the inverter switching frequency and output switching pattern are both predefined. Particular output voltage patterns can be selected by minimising a suitable objective function. Thus, the proposed scheme achieves precise current control along with the simultaneous optimisation of a performance objective. These features yield near-sinusoidal currents in the load with reduced current peaks, lower inverter switching frequency, and reduce inverter and load stresses. This type of current control scheme is especially suitable for potentially high performance applications such as AC motor drives and UPS systems. Finally, detailed experimental investigation of the current control scheme is presented View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.