Slawomir Wiak

Field Models in Electricity and Magnetism

Covering the development of field computation in the past forty years,Field Models in Electricity and Magnetism intends to be a concise, comprehensive and up-to-date introduction to methods for the analysis and synthesis of electric and magnetic fields.A broad view of the subject of field models in electricity and magnetism, ranging from basic theory to numerical applications, is offered.The approach coherently assumed throughout the whole book is to solve field problems directly from partial differential equations in terms of vector quantities.Theoretical issues are illustrated by practical examples. In particular, a single example is solved by different methods so that, by comparison of results, limitations and advantages of the various methods are made clear.The subject of the synthesis of fields and of the optimal design of devices, which are growing in research and so far have not been adequately covered in textbooks, are developed in addition to the more classical subject of analysis.Topics covered include:vector fields: electrostatics, magnetostatics, steady conduction;analytical methods for solving boundary-value problems;numerical methods for solving boundary-value problems;time-varying electromagnetic field;inverse problems;optimization.Field Models in Electricity and Magnetism nresults from the cooperation of three authors, after collecting a separate experience in teaching electromagnetic theory at various levels and in different countries.

The highly efficient three-phase small induction motors with stator cores made from amorphous iron

Applies the field/circuit two‐dimensional method and improved circuit method to engineering designs of the induction motor with stator cores made of amorphous iron. Exploiting of these methods makes possible computation of many different specific parameters and working curves in steady states for the “high efficiency” three‐phase small induction motor. Compares the results of this calculation with the results obtained for the classical induction motor with identical geometric structure.

Application of circuit and field‐circuit methods in designing process of small induction motors with stator cores made from amorphous iron

Purpose – To investigate the use of amorphous iron as the stator core material to increase the efficiency of electric machines in serialised production.Design/methodology/approach – In the design process of a new structure for the induction motor with a stator core made from amorphous iron it is necessary to apply the circuit method and the field‐circuit method. The use of the circuit method allows quick calculations of many versions of the designed motor, but the use of the field‐circuit method is necessary for verification of the maximal value of the flux density in the entire area of the cross‐sections of the motor core.Findings – A new construction for the small induction motor with the stator core made from amorphous iron was designed based on the classical structure of the four‐pole induction motor. In the designed motor a decrease of the electric energy costs was observed, which is much bigger than the material costs, and in effect lower total costs for the designed motor were obtained.Practical im...

Modelling of vertical electrostatic comb‐drive for scanning micromirrors

Purpose – The main aim of this paper is to build an equivalent circuit model of a comb drive microactuator, while the phenomenon of generating the electric fringing field at electrode edges is taken into consideration.Design/methodology/approach – The approach to the comb drives design requires the “leakage capacitance” (appearing at electrode edges) to be introduced to the complex equivalent circuit model. Introducing these capacitances leads to defining the circuit model properly.Findings – Such a complex approach by use of the equivalent circuits model could make it possible to reduce the discrepancy between the field and circuit models. These results were obtained after comparing both field and circuit models.Originality/value – MEMS microdrives are in the area which is being developed very dynamically. Improvements in the mathematical models would permit more precise microdrive design, leading to optimal structure.

Evolutionary Computing and Optimal Design of MEMS

Fostered by the development of new technologies, microelectromechanical systems (MEMS) are massively present on board of vehicles, within information equipment as well as in medical and healthcare equipment. A smart approach to the design of MEMS devices is in terms of the simultaneous optimization of multiple objective functions subject to a set of constraints. This leads to the family of solutions minimizing the degree of conflict among the objectives (Pareto front). Accordingly, in this paper, a procedure of optimal shape design of MEMS based on evolutionary computing is proposed and validated on three case studies.

Dependence of the contact resistance on the design of stranded conductors.

During the manufacturing process multi-strand conductors are subject to compressive force and rotation moments. The current distribution in the multi-strand conductors is not uniform and is controlled by the transverse resistivity. This is mainly determined by the contact resistance at the strand crossovers and inter-strand contact resistance. The surface layer properties, and in particular the crystalline structure and degree of oxidation, are key parameters in determining the transverse resistivity. The experimental set-ups made it possible to find the dependence of contact resistivity as a function of continuous working stresses and cable design. A study based on measurements and numerical simulation is made to identify the contact resistivity functions.

MODELLING AND OPTIMISATION OF INTELLIGENT ELECTROSTATIC COMB ACCELEROMETER

This paper describes the field and circuit modelling of 2D/3D structure of surface micromachined (MEMS) accelerometers. This comb structure has been able to move only within the plane (two-axes movement). The main goal of investigation is to exploit the field method to extract equivalent capacitance characteristics to be treated as the background for equivalent circuit analysis and optimisation process.

Influence of Plasma Jet Temperature Profiles in Arc Discharge Methods of Carbon Nanotubes Synthesis

One of the most common methods of carbon nanotubes (CNTs) synthesis is application of an electric-arc plasma. However, the final product in the form of cathode deposit is composed of carbon nanotubes and a variety of carbon impurities. An assay of carbon nanotubes produced in arc discharge systems available on the market shows that commercial cathode deposits contain about 10% CNTs. Given that the quality of the final product depends on carbon–plasma jet parameters, it is possible to increase the yield of the synthesis by plasma jet control. Most of the carbon nanotubes are multiwall carbon nanotubes (MWCNTs). It was observed that the addition of catalysts significantly changes the plasma composition, effective ionization potential, the arc channel conductance, and in effect temperature of the arc and carbon elements flux. This paper focuses on the influence of metal components on plasma-jet forming containing carbon nanotubes cathode deposit. The plasma jet temperature control system is presented.

Synthesis of Carbon Nanotubes in Thermal Plasma Reactor at Atmospheric Pressure

In this paper, a novel approach to the synthesis of the carbon nanotubes (CNTs) in reactors operating at atmospheric pressure is presented. Based on the literature and our own research results, the most effective methods of CNT synthesis are investigated. Then, careful selection of reagents for the synthesis process is shown. Thanks to the performed calculations, an optimum composition of gases and the temperature for successful CNT synthesis in the CVD (chemical vapor deposition) process can be chosen. The results, having practical significance, may lead to an improvement of nanomaterials synthesis technology. The study can be used to produce CNTs for electrical and electronic equipment (i.e., supercapacitors or cooling radiators). There is also a possibility of using them in medicine for cancer diagnostics and therapy.

Computer models of 3D magnetic microfibres used in textile actuators

Purpose – The purpose of this paper is to discuss the idea of designing and manufacturing intelligent clothes with magnetic fibres. The main goal of the research is to create the universal generator of computer structural models for whole bundles of magnetic microfibres.Design/methodology/approach – The paper presents the algorithm of magnetic microfibers computer modelling. It covers both finite element method (FEM) and reluctance network method. This paper deals with creating 3D computer structural models of magnetic microfibres, which could be introduced as the textile magnetic sensors or actuators. Because of very complicated 3D microfibres structure, it is hoped that the quickest possible method can be found to solve the problem.Findings – The results focus on the methodology presented in the paper which can be implemented in building 3D equivalent B/H curve of the microfibers set by using the field method – combining reluctance network method and FEM. Defining the proper magnetic B/H curves of magne...