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The resistivity of cured conductive ink films are dependent on a wide range of process parameters. An early indication of the resistivity that is likely to result following curing can enable these parameters to be optimised and, therefore, improve product quality. This paper aims to report on the use of alternating current (AC) impedance measurement techniques on curing printed ink films as a means of assessing the resistivity likely to be attained following the curing process.

Impedance measurements (100 Hz-10 MHz) were performed on curing conductive carbon ink films printed on polyethylene terephthalate substrates during convective heat curing. A jig was designed to incorporate the test structure in an convection oven such that the effect of cure on the structure impedance could be investigated.

The initial impedance was found to decrease with an increase in the measurement frequency. As the ink films were cured, the impedance magnitude across the 100 Hz-10 MHz range converged with the direct current (DC) resistance value. For a given ink, the ratio of initial AC impedance at 10 MHz to final cured resistance was found to be consistent, thus giving a method where final conductivity can be estimated before cure.

Data from printed ink resistance measurements are required to ensure the optimal conductivity of printed devices. However, after the printed structures are fabricated and cured, it is too late to optimise process parameters, leading to significant wastage. AC impedance measurement can give an indication of the final cured resistivity whilst the structure is freshly printed and still in its curing phase, enabling the printing process parameters to be adjusted to improve the resistivity of subsequently printed devices. Measuring AC impedance of printed ink structures in a production environment can, therefore, improve output.

The purpose of this paper is threefold. First, an analytical model based on one-dimensional Dowell’s equation for computing ac-to-dc winding resistance ratio FR of litz wire is presented. The model takes into account proximity effect within the bundle and between bundle layers as well as the skin effect. Second, low- and medium-frequency approximation of Dowell’s equation for the litz-wire winding is derived. Third, a derivation of an analytical equation is given for the optimum strand diameter of the litz-wire winding independent on the porosity factor.

The methodology is as follows. First, the model of the litz-wire bundle is assumed to be a square shape. Than the effective number of layers in the litz wire bundle is derived. Second, the litz-wire winding is presented and an analytical equation for the winding resistance is derived. Third, analytical optimization of the strand diameter in the litz-wire winding is independent on the porosity factor performed, where the strand diameter is independent on the porosity factor. The boundary frequency between the low-frequency and the medium-frequency ranges for both solid-round-wire and litz-wire windings are derived. Hence, useful frequency range of both windings can be determined and compared.

Closed form analytical equations for the optimum strand diameter independent of the porosity factor are derived. It has been shown that the ac-to-dc winding resistance ratio of the litz-wire winding for the optimum strand diameter is equal to 1.5. Moreover, it has been shown that litz-wire winding is better than the solid-round-wire winding only in specific frequency range. At very high frequencies the litz-wire winding ac resistance becomes much greater than the solid-round-wire winding due to proximity effect between the strands in the litz-wire bundle. The accuracy of the derived equations is experimentally verified.

Derived equations takes into account the losses due to induced eddy-currents caused by the applied current. Equations does not take into account the losses caused by the fringing flux, curvature, edge and end winding effects.

This paper presents derivations of the closed-form analytical equations for the optimum bare strand diameter of the litz-wire winding independent on the porosity factor. Significant advantage of derived equations is their simplicity and easy to use for the inductor designers.

The purpose of this paper is to outline the electrochemical noise method as a way of evaluating quickly (screening) coatings formulations in the laboratory. The standard configuration requires two test specimens and a reference electrode. Equipment is relatively inexpensive and is computer controlled. Data analysis is quite simple but to improve accuracy some treatment of the plots may be necessary. Some previously published results for application to water‐borne coatings both intact and when scratched are reproduced here to illustrate the method. Comparison has been made with DC techniques. Application of the method to detached coatings is included.

Rectangular conductors play an important role in planar transmission line structures, multiconductor transmission lines, in power transmission and distribution systems, LCL filters, transformers, industrial busbars, MEMs devices, among many others. The precise determination of the inductance of such conductors is necessary for their design and optimization, but no explicit solution for the AC resistance and internal inductances per-unit length of a linear conductor with a rectangular cross-section has been found, so numerical methods must be used. The purpose of this paper is to introduce the use of a novel numerical technique, the proper generalized decomposition (PGD), for the calculation of DC and AC internal inductances of rectangular conductors.

The PGD approach is used to obtain numerically the internal inductance of a conductor with circular cross-section and with rectangular cross-section, both under DC and AC conditions, using a separated representation of the magnetic vector potential in a 2D domain. The results are compared with the analytical and approximate expressions available in the technical literature, with an excellent concordance.

The PGD uses simple one-dimensional meshes, one per dimension, so the use of computational resources is very low, and the simulation speed is very high. Besides, the application of the PGD to conductors with rectangular cross-section is particularly advantageous, because rectangular shapes can be represented with a very few number of independent terms, which makes the code very simple and compact. Finally, a key advantage of the PGD is that some parameters of the numerical model can be considered as additional dimensions. In this paper, the frequency has been considered as an additional dimension, and the internal inductance of a rectangular conductor has been computed for the whole range of frequencies desired using a single numerical simulation.

The proposed approach may be applied to the optimization of electrical conductors used in power systems, to solve EMC problems, to the evaluation of partial inductances of wires, etc. Nevertheless, it cannot be applied, as presented in this work, to 3D complex shapes, as, for example, an arrangement of layers of helically stranded wires.

The PGD is a promising new numerical procedure that has been applied successfully in different fields. In this paper, this novel technique is applied to find the DC and AC internal inductance of a conductor with rectangular cross-section, using very dense and large one-dimensional meshes. The proposed method requires very limited memory resources, is very fast, can be programmed using a very simple code, and gives the value of the AC inductance for a complete range of frequencies in a single simulation. The proposed approach can be extended to arbitrary conductor shapes and complex multiconductor lines to further exploit the advantages of the PGD.

To model the differential dc gain, base resistance, and current voltage performance of 4H‐Silicon Carbide (SiC) bipolar junction transistors (BJT) operating at and above room temperature. Accurate modeling will result in improved process efficiency, interpretation of experimental data, and insight into device behavior.

The PISCES two dimensional device simulation program is used to allow for modeling the behavior of 4H‐SiC BJT. The physical material parameters in PISCES such as carrier's mobility and lifetime, temperature dependent bandgap, and the density of states are modified to accurately represent 4H‐SiC. The simulation results are compared with the measured experimental data obtained by others. The comparisons made with the experimental data are for two different devices that are of interest in power electronics and RF applications.

The simulation results predict a dc current gain of about 25 for power device and a gain of about 20 for RF device in agreement with the experimental data. The comparisons confirm the accuracy of the modeling employed.

The simulated current‐voltage characteristics indicate that higher gain may be achieved for 4H‐SiC transistors if the leakage current is reduced.

The simulation work discussed in this paper complements the current research in the design and characterization of 4H‐SiC bipolar transistors. The model presented will aid in interpreting experimental data at a wide range of temperatures.

This paper reports on a new model that provides insight into the device behavior and shows the trend in the dc gain performance important for the design and optimization of 4H‐SiC bipolar transistors operating at or above the room temperature.

The paper deals with the experimental validations of the corrective coefficient used to take into account the skin effect in the equivalent circuit rotor resistance of induction motors with squirrel cages.

Locked rotor tests have been performed at several supply frequencies on different induction motors; the collected experimental data have been used to validate the rotor parameters analytical estimation obtained by means of a numerical procedure previously proposed by the authors.

The reported analyses regard both open and closed rotor slots. For frequencies up to 80‐100 Hz, the reported comparison between experimental and calculated skin effect corrective coefficients shows that the adopted model allows to get satisfactory results in terms of accuracy, lower than 3 percent for open rotor slot machines. The upper frequency limit has to be judged taking into account the objective difficulties to estimate accurate values of the rotor parameters from experimental tests.

The proposed algorithm can be easily implemented and added to self‐made induction motor design software tools.

The proposed procedure allows the computation of the skin effect in induction motor squirrel cage without the use of finite element method approaches.

This paper aims to investigate the effect of no-clean flux chemistry with various weak organic acids (WOAs) as activators on the corrosion reliability of electronics with emphasis on the hygroscopic nature of the residue.

The hygroscopicity of flux residue was studied by quartz crystal microbalance, while corrosive effects were studied by leakage current and impedance measurements on standard test boards. The measurements were performed as a function of relative humidity (RH) in the range from 60 to ∼99 per cent at 25°C. The corrosiveness of solder flux systems was visualized by the ex situ analysis using a gel with tin ion indicator.

The results showed that the solder flux residues are characterized by different threshold RH, above which a sudden increase in direct current leakage by 2–4 orders of magnitude and a significant reduction in surface resistance in the impedance measurements were observed.

The findings are attributed to the deliquescence RH of the WOA(s) in the flux and chemistry of water-layer formation. The results show the importance of WOA type in relation to its solubility and deliquescence RH on the corrosion reliability of printed circuit boards under humid conditions.

The classification of solder flux systems according to IPC J-STD-004 standard does not specify the WOAs in the flux; however, ranking of the flux systems based on the hygroscopic property of activators would be useful information when selecting no-clean flux systems for electronics with applications in humid conditions.

Present 3D electromagnetic simulators have high accuracy, but they are time and memory expensive. Because of that, fast and simple expression for impedance is also necessary for initial inductor design. In this paper new efficient method for total impedance calculation of ferrite electromagnetic interference (EMI) suppressor is given. By using an algorithm, it is possible to predict correctly all variations of electrical characteristics introduced by varying geometry parameters of EMI suppressor.

The starting point for calculation of electrical characteristics of EMI suppressor is Greenhouse theory. Greenhouse decomposed inductor into its constituent segments. Basically, all segments of conductive layer are divided into parallel filaments having small, rectangular cross sections. The self‐ and mutual‐inductance were calculated using the concept of partial inductance. Total impedance of EMI suppressor is calculated taking care of dimension of chip size, material that are used and geometry of conductive layer.

The Simulator for Planar Inductive Structures (SPIS™) simulates effects of ferrite materials and geometrical parameters of planar inductive structures. With proposed software tool, designers can predict performance parameters quickly and easily before costly prototypes are built. SPIS™ software offers substantially reduced time to market, and increases device performance. The computed impedances, given by our software tool are compared with measured data and very good agreement was found.

Applied flexible efficient methods for impedance calculation of EMI suppressor are able to significantly increase the speed design of multilayer suppressors for universal series bus, low‐voltage differential signaling and in other high‐speed digital interfaces incorporated in notebooks and personal computers, digital cameras and scanners. Also, ferrite suppressors have been successfully employed for attenuating EMI in switching power supplies, electronic ignition systems, garage door openers, etc.

The paper presents realized structures of ferrite EMI suppressors. New geometries of conductive layer are proposed. In addition, using simple model of inductor, the paper develops a CAD simulation tool SPIS™ for calculation of electrical characteristics of EMI suppressors with different geometry of conductive layer.

Analysis of test data monitored for a number of electric machines from the low volume production line can lead to useful conclusions. The purpose of this paper is to trace the machine performance to find quality-related issues and/or identify assembly process ones. In this paper, the monitoring of experimental data is related to the axial flux motor (AFM) used in hybrid electric vehicle (HEV) and in electric vehicle (EV) traction motors in the global automobile market.

Extensive data analyses raised questions like what could be the causes of possible performance deterioration of the AFM and how many electric motors may not pass requirements during operation tests. In small and medium research units of AFM for HEV or EV, engineers came across a number of serious issues that must be resolved. A number of issues can be eliminated by implementing methods for reducing the number of failing AFMs. For example, improving the motor assembly precision leads to reduction of the machine parameters deterioration.

Assembly tolerances on electric motor characteristics should be investigated during motor design. The presented measurements can be usable and can point out the weakest parts of the motor that can be a reason for the reduced efficiency and/or lifetime of the AFM. Additionally, the paper is addressed to electric motor engineers designing and/or investigating electric AFMs.

Performance of AFM was monitored for a number of identical motors from low volume production line. All tested motors were operated continuously for a long period of time and the tests were repeated every few weeks for half a year to check the reliability of motor design and indicate how much the motor parameters may change. The final results point how many motors fail the requirements of motor performance. A few batches of AFM were selected for testing. Each batch represents a different size (nominal power) of the same type of AFM.

There are few reports that evolutional topology optimization methods are applied to the conductor geometry design problems. This paper aims to propose an evolutional topology optimization method is applied to the conductor design problems of an on-chip inductor model.

This paper presents a topology optimization method for conductor shape designs. This method is based on the normalized Gaussian network-based evolutional on/off topology optimization method and the covariance matrix adaptation evolution strategy. As a target device, an on-chip planer inductor is used, and single- and multi-objective optimization problems are defined. These optimization problems are solved by the proposed method.

Through the single- and multi-objective optimizations of the on-chip inductor, it is shown that the conductor shapes of the inductor can be optimized based on the proposed methods.

The proposed topology optimization method is applicable to the conductor design problems in that the connectivity of the shapes is strongly required.