In the paper, the modified (compared to the classical asymmetric half-bridge) converter for a switched reluctance machine with an asymmetric rotor magnetic circuit was analysed. An analysis for two various structures of switched reluctance motors was conducted. The rotor shaping was used to obtain required start-up torque or/and to obtain less electromagnetic torque ripple. The discussed converter gives a possibility to turn a phase off much later while reduced time of a current flows in a negative slope of inductance. The results of the research in the form of waveforms of currents, voltages and electromagnetic torque were presented. Conclusions were formulated concerning the comparison of the characteristics of SRM supplied by the classic converter and by the one supplied by the analysed converter.
In the description of small-signal transmittances of switch-mode power converters several characteristic frequencies are usually used, corresponding to poles and zeros of transmittances. The knowledge of these frequencies is important in the design of control circuits for converters and usually are assumed to be constant for a given power stage of a converter. The aim of the paper is to evaluate the influence of converter primary parameters and load conductance on characteristic frequencies. Analytical derivations and numerical calculations are performed for an ideal and non-ideal BUCK converter working in continuous or discontinuous conduction mode.
Power loss mechanisms in small area monolithic-interconnected photovoltaic modules (MIM) are described and evaluated. Optical and electrical losses are quantified and individual loss components are derived for loss mechanisms of small area radial (radius = 1 mm) pie-shaped six-segment GaAs MIM laser power converter. At low monochromatic homogeneous illumination (Glow = 1.8 W/cm2, λ0 = 809 nm) conversion efficiency of the cell, designed for a low irradiance, is reduced by 3.7%abs. due to isolation trench optical losses and by 7.0%abs. due to electrical losses (mainly perimeter recombination). Electrical losses in a device designed for a high irradiance, result in 18%abs. decrease of output power under homogeneous monochromatic illumination (Ghigh = 83.1 W/cm2, λ0 = 809 nm), while 11.6%abs. losses are attributed to optical reasons. Regardless the irradiance level, optical losses further increase if the device is illuminated with a Gaussian instead of an ideal flattop beam profile. In this case, beam spillage losses occur and losses due to isolation trenches and reflections from metallization are elevated. On top of that, additional current mismatch losses occur, if individual MIM’s segments are not equally illuminated. For the studied device, a 29 μm off center misalignment of a Gaussian shaped beam (with 1% spillage) reduces the short circuit current Isc by 10%abs. due to the current mismatch between segments.