Volume 54 (2017): Issue 1 (February 2017)

The paper discusses problems concerning the influence of permanent magnet material characteristics on the low-speed permanent magnet generator losses and output characteristics. The variability of the magnet material and its effect on the output parameters of the machine has been quantified. The characteristics of six different grades of neodymium permanent magnets have been measured and compared to the supplier specification data. The simulations of the generator have been carried out using transient finite element analysis. The results show that magnet materials from different suppliers have different characteristics, which have a significant influence on the generator output parameters, such as efficiency and power factor.

The method considered in the present paper concerns the operational efficiency of the inductor electric machine, which can be improved by placing on the stator and rotor teeth the combs combined from differently shaped teeth and slots. The use on the inductor electric machine stator and rotor teeth of combs as a combination of differently shaped hills (teeth) and valleys (slots) allows raising the specific power of the machine. This effect is determined by the chosen type of a comb element as well as by technological possibilities of the manufacturer. The proposed method could be used moderately in the inductor machines with longitudinally-transversal combing.

The paper presents new designs for synchronous reluctance motors that have external rotor (segment-shaped rotor, rotor with additional non-magnetic space to the quadrature axis of the rotor, and rotor with several flux barriers). Impact of the external rotor configuration on the electromagnetic torque and torque ripple is analysed. Electromagnetic torque ripple factor is calculated for each studied motor using the results of magnetic field numerical calculations.

The article proposes a method of mathematical simulation of electrical machines with thyristor exciters on the basis of the local Fourier transform. The present research demonstrates that this method allows switching from a variable structure model to a constant structure model. Transition from the continuous variables to the discrete variables is used. The numerical example is given in the paper.

Well-structured ZnO nanotubes are obtained by a self-selective etching method with lowering temperatures of growth during the hydrothermal process.

The structural and optical properties of the obtained nanostructures are investigated by various conventional methods.

The goal of the research is to compare the efficiency of ZnO nanotubes to that of ZnO nanorods during lead adsorption process from aqueous solution and demonstrate that hollow nanostructures are more effective than solid nanostructures of the same morphology due to their larger effective surface.

Both nanotubes and nanorods are obtained under similar growth conditions: neither growth solution composition, nor concentration is changed. ZnO morphology is switched only by changing temperature during the growth process.

The measurements are carried out to assess the efficiency of the adsorption per unit weight of ZnO nanorod and nanotube capacity of static adsorption.

The present paper studies the problems of creation of techniques for the analysis of vibro-impact processes in systems with a large number of impact pairs. The used method of singularisation allows refusing from the ideas of the momentary impact and considering interaction hypotheses, which are more realistic than Newtonian ones. We consider the features of synchronous modes of movements of the clap type in systems with parallel impact elements as well as in tubes colliding with intermediate supports. Such modes are most dangerous in terms of the vibration wear of structural elements. The examples of calculation are given for specific designs.

Nanoindentation is a widely-used method for sensitive exploration of the mechanical properties of micromechanical systems. We derive a simple empirical analysis technique to extract stress-strain field (SSF) gradient and divergence representations from nanoindentation data sets. Using this approach, local SSF gradients and structural heterogeneities can be discovered to obtain more detail about the sample’s microstructure, thus enhancing the analytic capacity of the nanoindentation technique. We demonstrate the application of the SSF gradient-divergence analysis approach to nanoindentation measurements of bulk silicon.