Non-Invasive Measurements and FEM Analyses for Estimating the Rotor Bar-Lamination Contact Resistance

This research work investigates the phenomenon of interbar currents in induction motors equipped with die-cast alu- minum cages. Flowing in the lamination and distorting the bar current distributions, the interbar currents cause additional stray losses as well as an increase of the joule loss in the cage bars. The contact resistance between the bars and the rotor lamina- tions is the key modeling element for a correct prediction of the interbar currents and the related extra losses. The study presents a new noninvasive method to obtain a reliable estimation of the contact resistance. The proposed hybrid approach is based on a mix of experimental data and Finite Element method (FEM)-based simulation results. A reliable three-dimensional FEM model of a four-pole 15-kW induction motor with closed rotor slots has been used to investigate the impact of variable contact resistance on the interbar currents, rotor joule losses, and the voltage drops along the bars, opening a new perspective for this complex phenomenon and its impact on the stray losses. Finally, the proposed methodologies are critically discussed and the obtained results compared with other relevant research works

Solanum nigrum Fruit Extract Modulates Immune System Activity of Mealworm Beetle, Tenebrio molitor L

: Here, we report the first evidence concerning the modulation of insect immune system activity after applying Solanum nigrum fruit extract (EXT). We focused on two main issues: (1) is EXT cytotoxic for Tenebrio molitor haemocytes? and (2) how EXT affects the basic immune mechanisms of T. molitor. The results indicate cytotoxic action of 0.01 and 0.1% EXT on beetle haemocytes. Both the injection of EXT and incubating haemocytes with the EXT solution on microscopic slides significantly increased the number of apoptotic cells. However, 24 h after injection of 0.1% EXT cytotoxic effect of the tested extract probably was masked by the increased number of circulating haemocytes. Application of 0.01 and 0.1% EXT led to impairment of the activity of basic immune mechanisms such as phenoloxidase activity and the lysozyme-like antimicrobial activity of T. molitor haemolymph. Moreover, the EXT elicited significant changes in the expression level of selected immune genes. However, some of the immunomodulatory effects of EXT were different in beetles with and without an activated immune system. The obtained results are an essential step toward a complete understanding of the EXT mode of action on the T. molitor physiology and its potential usage in pest control

Impact of a Punching Process on the SyRM Iron Loss: SPICE Model as an Effective Tool for Iron Loss Modeling

Many technologies for cutting the magnetic laminations, from which electric motors cores are built, change material properties, among which are magnetizability and iron loss, thus affecting the motor parameters such as motor efficiency. This problem is particularly important for low-power motors, in which the dimensions of the magnetic circuit elements are relatively small. The correct estimation of the motor efficiency is important as early as at its design stage. This is possible when the correct material characteristics are used. This knowledge and analytical model enabling fast estimation of material properties (depending on the actual size) are necessary for engineers, who design electrical motors by analyzing many solution variants in a short time. The author proposes an analytical model of changing material properties, implemented in SPICE software. Its effectiveness was compared with measurement results while being a competitive solution in relation to other analytical models. The proposed SPICE model allowed evaluating material properties for lamination of any width. In the end, the knowledge concerning the material properties was used to calculate the iron loss in the stator of the SyRM motor, showing the need to use the material characteristics calculated for the specified width of the core piece

Stator lamination geometry influence on the building factor of synchronous reluctance motor cores

The study investigates the influence of the lamination geometry on the building factor of stator magnetic cores, quantifying by experiments the influence of the punching and the annealing process. The research and the experimental activity are focused on small fractional power synchronous reluctance motors, where the punching process effect is expected to be very impacting, not only for the stator iron losses increase, but also because the current magnetizing component is dominant in the total adsorbed current. However, the obtained results are particularly interesting for any fractional and low power electric machines, whose cores are built with punched or laser-cut laminations

Assembly effects on stator cores of small synchronous reluctance motors

The paper deals with manufacturing and assembly negative effects on stator cores of fractional-power synchronous reluctance motors. In particular, the experimental activities have been carried out on laminated stator cores used for machines having nominal powers of the range of 100 W-500 W. The considered stator core samples have been produced using two different fabrication technologies to stack together the lamination sheets: the clamping and the welding solution. The measured B-H magnetizing curves and the specific loss trends have been compared with results obtained testing a particular stator core produced with loose laminations (i.e. without clamping or welding). This `ad hoc' magnetic core represents the baseline for the presented comparative study. The collected data have been used in finite element method simulations computing three factors of merit specifically defined to quantify the manufacturing impacts on small synchronous reluctance motors. In the present study, the pressing effect due to the insertion of the magnetic core inside the frame is also experimentally investigated

Modified single sheet tester system for engineering measurements

The paper deals with the construction and calibration concept of a modified single sheet tester systems, suitable to perform low-frequency magnetic measurements in engineering laboratories. Firstly, the authors present the configuration of the proposed tester, which can be easily adapted to lamination sheet samples having various sizes. Then, the calibration procedure of the system, based on measurement and numerical simulation results, is reported in detail. Finally, the proposed system has been used to characterize several magnetic lamination strips, comparing the results with the data provided by the manufacturers. The good agreements found in the results comparison, together with the significant cost reduction of the measurements (both in term of execution time, and tester production costs), make appealing the use of the proposed system for engineering measurements on magnetic lamination samples, also having non-standard dimensions

Dynamics of the line-start reluctance motor with rotor made of SMC material

Design and control of electric motors in such a way as to ensure the expected motor dynamics, are the problems studied for many years. Many researchers tried to solve this problem, for example by the design optimization or by the use of special control algorithms in electronic systems. In the case of low-power and fractional power motors, the manufacture cost of the final product is many times less than cost of electronic system powering them. The authors of this paper attempt to improve the dynamic of 120 W line-start synchronous reluctance motor, energized by 50 Hz mains (without any electronic systems). The authors seek a road enabling improvement of dynamics of the analyzed motor, by changing the shape and material of the rotor, in such a way to minimize the modification cost of the tools necessary for the motor production. After the initial selection, the analysis of four rotors having different tooth shapes, was conducted