Integrated motor drives: state of the art and future trends

With increased need for high power density, high efficiency and high temperature capabilities in Aerospace and Automotive applications, Integrated Motor Drives (IMD) offers a potential solution. However, close physical integration of the converter and the machine may also lead to an increase in components temperature. This requires careful mechanical, structural and thermal analysis; and design of the IMD system. This paper reviews existing IMD technologies and their thermal effects on the IMD system. The effects of the power electronics (PE) position on the IMD system and its respective thermal management concepts are also investigated. The challenges faced in designing and manufacturing of an IMD along with the mechanical and structural impacts of close physical integration is also discussed and potential solutions are provided. Potential converter topologies for an IMD like the Matrix converter, 2-level Bridge, 3-level NPC and Multiphase full bridge converters are also reviewed. Wide band gap devices like SiC and GaN and their packaging in power modules for IMDs are also discussed. Power modules components and packaging technologies are also presented

Anchoring energy and easy direction of non uniform surfaces

The effect of a periodic distribution of easy directions on the surface macroscopic properties of nematic samples are considered. Our analysis shows that the effective surface energy of the sample contains an interference term coming from the two different easy axis. This allows to introduce an effective uniform easy direction, depending on the two easy directions and containing an interference term too, as suggested a few years ago by some researchers

Anchoring energy and easy direction of non-uniform surfaces

The effect of a periodic distribution of easy directions on the surface macroscopic properties of nematic samples are considered. Our analysis shows that the effective surface energy of the sample contains an interference term coming from the two different easy axis. This allows to introduce an effective uniform easy direction, depending on the two easy directions and containing an interference term too, as suggested a few years ago by some researchers

Influence of the microtopography of the SiO covered by PVA layers on the tilt angle of liquid crystals

An evaluation of the tilt angle variation observed recently when unrubbed polyvinylic alcohol is deposited on obliquely evaporated SiO layers is presented. The method of calculation supposes that the variation of the tilt angle is due to the modification of the initial topography of SiO during the coverage process with the polymeric film. The Laplace equation was obtained by minimizing the elastic energy of the system in the uniconstant approximation and was analytically solved. The found variation of the tilt angle is in good agreement with the experimentally observed one

On the Crystal-to-Mesophase Phase Transition in Copper(II) Salts of Even-Chain Fatty Acids

The phase transition from the solid state to the liquid crystal state was investigated for the copper(II) salts of the fatty acids with 10, 12, 14, 16 or 18 carbon atoms in the chain, by measuring the temperature dependence of the conductance and capacitance of a cell containing the material under investigation. The temperatures deduced from these dependences agree reasonably with those found by DSC measurements and with those to be found in the literature. Differences in dielectric behaviour between the samples are qualitatively discussed