Showing papers in "Compel-the International Journal for Computation and Mathematics in Electrical and Electronic Engineering in 2006"

An energy-based vector hysteresis model for ferromagnetic materials

Abstract: Purpose – Proposes a new quasi‐static vector hysteresis model based on an energy approach, where dissipation is represented by a friction‐like force.Design/methodology/approach – The start point is the local energy balance of the ferromagnetic material. Dissipation is represented by a friction‐like force, which derives from a non‐differentiable convex functional. Several elementary hysteresis cells can be combined, in order to increase the number of free parameters in the model, and therefore improve the accuracy.Findings – A friction‐like force is a good way to represent magnetic dissipation at the macroscopic level. The proposed method is easy to implement and non‐differentiability amounts in this case to a simple “if” statement.Research limitations/implications – The next steps are the extension to dynamic hysteresis and the in‐depth analysis of the identification process, which is only sketched in this paper.Practical implications – This vector model, which is based on a reasonable phenomenological de...

Acoustic simulation of an induction machine with squirrel‐cage rotor

Abstract: Purpose – To present results of research closely linked to real life applications and to resume the work of a period of a few years.Design/methodology/approach – The combination of finite‐element method (FEM) and boundary‐element method is applied to simulate the electromagnetic, mechanical, and acoustic behaviour of an induction machine with squirrel‐cage rotor. The paper gives an overall view of the workflow and the implemented mathematics, starting off with the two‐dimensional, transient electromagnetic simulation and the succeeding three‐dimensional, static electromagnetic simulation. Theory and results of the mechanical and acoustic simulations are discussed.Findings – A main result of the research work is that the simulation of the acoustic behaviour of an electrical machine is very time‐consuming. Furthermore, geometry adoption, especially of the mechanical model, is very sensible.Research limitations/implications – Using the FEM for simulation of structure dynamic problems is often limited to how ...

Identification of the induction motor parameters at standstill using soft computing methods

Abstract: Purpose – The paper sets out to deal with the off‐line identification of induction motor (IM) parameters at standstill. Determination of values of the IM parameters is essential in sensorless drives with regard to accuracy and quality of the control system.Design/methodology/approach – The presented identification method is based on the reconstruction of stator current response to the forced stator voltage step change; thus the cost function is defined in the classical form of the mean squared error between the computed and experimental data. The identification via evolutionary algorithms (EAs) is presented. The considered problem is continuous and thus a continuous version of EA is suggested as more suitable.Findings – This approach has been shown to have several advantages over classical optimisation methods like the ability to cope with ill‐behaved problem domains exhibiting attributes such as: discontinuity, time‐variance, randomness, and, what is particularly important in this application, the abilit...

Properties of sensorless control systems based on multiscalar models of the induction motor

Abstract: Purpose – To develop general forms of multiscalar models of the induction motor and to present properties of the sensorless control systems based on such models.Design/methodology/approach – Previously presented multiscalar model of the induction motor based on a stator current and rotor flux vector is generalized as a model of type 1. New model of type 2 is defined for stator current and the vector which is directly controlled by a voltage vector. The above models are applied in a sensorless control system with speed observer. Dynamical properties of the sensorless control systems are investigated by simulations and experiments.Findings – Application of the multiscalar model of type 2 results in higher exactness of sensorless control system than application of the multiscalar model of type 1. Controlled variables are more smooth in transients.Research limitations/implications – This is not an analytical proof of stability of the control systems.Practical implications – Provides very useful information fo...

Comparison of artificial immune systems and genetic algorithms in electrical engineering optimization

Abstract: Purpose – The purpose of this study is to investigate and compare the ability of a new optimization technique based on the emulation of the immune system to detect the global maximum with multimodal functions and to test the capability of exploring the parameter space with respect to clustering enhanced Genetic Algorithms (GA).Design/methodology/approach – Both algorithms have been tested on analytical test functions and on numerical functions of applicative interest. A set of performance criteria has been defined in order to numerically compare the performances of both optimization strategies.Findings – Results show the great ability of Artificial Immune Systems (AIS) in thoroughly exploring the space of variables. On the other side, GA are faster to converge to the global optimum, but selection pressure can reduce the number of detected local optima.Originality/value – This work is an attempt to assess the performances of a relatively new optimization algorithm based on AIS and to find its behavior on m...

A comparison between axial and radial flux PM motor by optimum design method from the required output NT characteristics

Abstract: Purpose – To design a high power density machine, an automatic design method is proposed. Hopefully, automatic design method uses only the requirements (torque and speed) and the information about sources (voltage and current).Design/methodology/approach – To calculate the volume, a necessary flux density and an inductance are calculated by the permeance method. All mechanical parameters, stator diameter, teeth width, turn number and so on, realize the necessary flux density and an inductance, and these parameters are expressed as a function of a rotor diameter. By using both conditions of current density and copper loss, a rotor diameter which realizes the minimum volume can be obtained.Findings – As a result of an optimum design, 50 kW SPMSM is realized only into 2[L] spaces, which copper loss is only 500[W], 1 percent of the maximum output. Moreover, 50 kW axial flux type machine is realized only into 1.3[L] spaces. Accurate comparison is possible by only optimum designs because these have the solution...

High frequency extension of non‐linear models of laminated cores

Abstract: Purpose – The paper gives a new measurement method of the parameters characterising the magnetic laminations for broadband low‐level signals defined at any operational point.Design/methodology/approach – High frequency phenomena machines fed by PWM inverters are related to low‐level signals corresponding to minor hysteresis loops around the instantaneous working point, which moves on the main loop at the basic frequency. The minor loops are assimilated to ellipses, which are characterised by only two parameters: the incremental magnetic permeability (μ) and the electric conductivity (σ).Findings – For small signals high frequency field components, the laminated steel behaviour can be described by two local parameters (μ, σ) and skin effect. The values of μ and σ do not depend on frequency up to 1 MHz, but only on the operating point.Research limitations/implications – The proposed broadband characterisation should be associated with a Priesach model that defines the operating point for computer simulation...

Novel efficient methods for inductance calculation of meander inductor

Abstract: Purpose – Present 3D electromagnetic simulators have high accuracy but they are time and memory expensive. Owing to a fast and simple expression for inductance is also necessary for initial inductor design. In this paper, new efficient methods for total inductance calculation of meander inductor, are given. By using an algorithm, it is possible to predict correctly all inductance variations introduced by varying geometry parameters such as number of turns, width of conductor or spacing between conductors.Design/methodology/approach – The starting point for the derivation of the recurrent formula is Greenhouse theory. Greenhouse decomposed inductor into its constituent segments. Meander inductor is divided into straight conductive segments. Then the total inductance of the meander inductor is a sum of self‐inductances of all segments and the negative and positive mutual inductances between all combinations of straight segments. The monomial equation for the total inductance of meander inductor has been obt...

A simplified approach to permanent magnet and reluctance motor characteristics determination by finite‐element methods

Abstract: Purpose – To provide a new method for the determination of motor characteristics by means of FE‐methods suitable for multi‐variable design processes.Design/methodology/approach – The process is based on two‐dimensional, steady state and frequency domain FE‐analysis including a stepwise movement of the rotor. The process consists of the following steps: generation of an appropriate FE‐model with specific mesh generation; input of the machines parameters and the parameters of the simulation process; no load simulation: cogging torque T, no load fluxes ψmo and voltages uo and the phase angles of the windings currents; load simulation with given currents: average and the pulsating torque T, fluxes ψl(α), voltages U, two‐axis model parameters ψm, Ld and Lq; determination of operating characteristics: torque T, voltage U, current I, power P, angles β and δ cos ϕ, as functions of speed n. Based on machine parameters from step 3 and 4 determination of losses in the magnets by means of a frequency domain model and...

Comparison of slip surface and moving band techniques for modelling movement in 3D with FEM

Abstract: Purpose – To compare slip surface and moving band techniques for modelling movement in 3D with FEM.Design/methodology/approach – The slip surface and moving band techniques are used to model the rotation of electrical machines in 3D with FEM. The proposed techniques are applied to a permanent magnet synchronous machine. The comparison is carried out at no‐load for the electromotive force (EMF) and the cogging torque. The torque is also compared for the short circuit case.Findings – For both the locked‐step and moving band approaches there is no difficulty in establishing the scalar potential and potential vector formulations. However, if step displacement is not equal to the mesh step, the results can show numerical irregularities. Some improvements have been proposed in order to limit this problem.Originality/value – The results of the EMF and the cogging torque are improved.

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

Abstract: 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...

Mathematical model of an electromechanical actuator using flux state variables applied to reluctance motor

Abstract: – Aims to present a new approach for formulating state‐space equations of an electromechanical actuator using magnetic flux linkages as state variables., – The model is based on employment of discrete databases and their interpolation. The algorithm of determination of databases defining the flux/current characteristics of an actuator is described. Graphical interpretation of variable transformation is presented. A simplified, two‐axis model of reluctance motor is used to illustrate the application of the proposed modelling technique. Comparison with the classical model of the motor is used to verify the validity of the method. Analysis is focused on determination of saturation phenomenon influence on formulation methodology and on correctness of obtained results., – A very good agreement is observed between reference dq model and the proposed model. The main problem of the presented method is the existence of undefined entries in databases. Sufficiently dense databases can be used to overcome the problem., – The model is limited to actuators in which eddy currents and hysteresis phenomenon can be neglected. Future research will be concentrated on evaluation of different interpolation strategies of databases used in the model for realistic saturation conditions., – The model can be used as a library block for testing various control strategies for actuators without standard simplifying assumptions (e.g. sinusoidal winding distribution). It can be implemented in any simulational software (e.g. SIMULINK) as its block diagram is simple and no numerical differentiation is necessary in derivation of the model data., – Presents an extension of state‐space model of an actuator based on database discretised description of variables to two or more state variables.

Magneto-electric network models in electromagnetism

Abstract: Network models of an electromagnetic field containing both eddy and displacement currents are presented. The models consist of magnetic and electric networks coupled via sources. The analogy between the finite element method and the loop and nodal formulations of electric circuits is emphasised. The models include networks containing branches associated with element edges (edge networks) or facets (facet networks). Methods of determining mmf sources of magnetic networks from loop and branch currents in electric circuits, as well as emf sources in electric networks on the basis of the rate of change of loop and branch fluxes in electric networks, have been carefully considered.

Modelling and position control of voltage forced electromechanical actuator

Abstract: Purpose – To present modelling and control technique of an electromagnetic actuator.Design/methodology/approach – A 3D modelling technique of voltage‐forced electromechanical actuator takes into account: motion, magnetic non‐linearity and eddy current phenomena. Control problem of closed loop system is described by coupled electro‐magneto‐mechanical equations and non‐linear PID controller equations.Findings – Presented methodology offers a powerful tool for analysis of control systems with distributed parameters models and may contribute to the improvement of the electromechanical performance of electrodynamic devices.Originality/value – As original contribution a position feedback control using conventional PID controller is applied for iterative determining inverse dynamic problem, that is finding input voltage for a given position of an actuator.

A time‐domain finite element homogenization technique for lamination stacks using skin effect sub‐basis functions

Abstract: Development of an homogenization technique to directly and efficiently take the eddy current effects in laminated magnetic cores within time domain finite element (FE) analyses. The technique is developed for being used within a 3D magnetodynamic b-conform FE formulation, e.g., using a magnetic vector potential. To avoid a fine FE discretization of all the laminations of a magnetic core, this one is considered as a source region that carries predefined current and magnetic flux density distributions describing the eddy currents and skin effect along each lamination thickness. Both these distributions are related and are first approximated with sub-basis functions. Through the homogenization or averaging of the sub-basis functions contributions in the FE formulation, the stacked laminations are then converted into continuums, thus implicitly considering the eddy current loops produced by parallel magnetic fluxes. The continuum is then approximated with classical FE basis functions and can be defined on a coarser discretization. The developed method appears attractive for directly and efficiently taking into account within finite element analyses the eddy current effects, i.e., the associated losses and magnetic flux reduction, that are particularly significant for high frequency excitations. The time domain analysis allows the consideration of both nonlinear and transient phenomena. The averaging of sub-basis functions contributions, describing fine distributions of fields in a FE formulation, leads to an original way to homogenize laminated regions. The proposed method is naturally adapted for time domain analyses and in some sense generalizes what can be done more easily in the frequency domain.

Minimal positive realizations for discrete‐time systems with state time‐delays

Abstract: Purpose – Aims to formulate and solve the minimal positive realization problem for discrete‐time linear single‐input, single‐output systems with many state time‐delays.Design/methodology/approach – A conceptual discussion and approach are taken.Findings – Sufficient conditions for the existence of positive realizations of a given proper rational function are established. A procedure for computation of minimal positive realizations is presented and illustrated by an example.Originality/value – Extends an earlier method for positive discrete‐time systems with many state time‐delays.

Electromagnetic modelling of permanent magnet axial flux motors and generators

Abstract: Purpose – To provide a general framework for the electromagnetic analysis of axial flux motors and generators.Design/methodology/approach – The procedure is based on the solution of Maxwell's equation in a cylindrical frame. All field sources (permanent magnets, windings) are subdivided into filamentary windings. The expansion of the 2D air‐gap magnetic field into a Fourier series is computed at every radius. The contributions of the harmonics are then added to achieve the expressions of the stator and rotor flux densities, back emf and developed torque. Slotting and skewing are taken into account also.Findings – The model can be written in a compact form by introducing a generalisation of the space vectors theory. The analysis is proved to be in accordance both with the finite element analysis and with experimental data.Research limitations/implications – The model does not take into account eddy‐currents and non‐linearities. It does not take into account also specifically 3D phenomena, as the radial com...

Absorbing boundary conditions for compact modeling of on‐chip passive structures

Abstract: Purpose – The paper has the purpose of proposing a new open boundary condition to be used in conjunction with the finite integration technique (FIT) for the modelling of passive on‐chip components.Design/methodology/approach – This boundary condition is ensured by using a virtual layer that surrounds the computational domain.Findings – The paper proves which are the optimal material properties of the equivalent layer of open boundary.Practical implications – When modelling passive on‐chip components with FIT, the method proposed is more efficient than the strategic dual image technique.Originality/value – The paper shows the advantage of this approach – that the analysis algorithm remains unchanged, while saving the field‐circuit compatibility properties, such as current conservation.

Time domain sensitivity analysis of electromagnetic quantities utilising FEM for the identification of material conductivity distributions

Abstract: Purpose – This paper aims to present effective methods for computing electromagnetic field sensitivity in the time domain versus conductivity perturbations in finite elements.Design/methodology/approach – Two‐dimensional cases in linear, isotropic media are considered and two effective methods for sensitivity analysis of a magnetic vector potential in the time domain are described.Findings – The paper finds that the convergence of numerical identification algorithm depends on exact measurement of magnetic flux density. For identification of real cracks the application of data filtering and TSVD regularization of Gauss‐Newton algorithm is necessary.Practical implications – The resultant gradient information may be used for solving inverse problems such as the identification of material conductivity distributions.Originality/value – The algorithms described are based on known methods from established circuit theory – incremental circuit and adjoint circuit, these have been expanded to apply in electromagnet...

Trigonometric interpolation at sliding surfaces and in moving bands of electrical machine models

Abstract: Purpose – To propose trigonometric interpolation in combination with both sliding‐surface and moving‐band techniques for modelling rotation in finite‐element electrical machine models. To show that trigonometric interpolation is at least as accurate and efficient as standard stator‐rotor coupling schemes.Design/methodology/approach – Trigonometric interpolation is explained concisely and put in a historical perspective. Characteristic drawbacks of trigonometric interpolation are alleviated one by one. A comparison with the more common locked‐step linear‐interpolation and mortar‐element approaches is carried out.Findings – Trigonometric interpolation offers a higher accuracy and therefore can outperform standard stator‐rotor coupling techniques when equipped with an appropriate iterative solver incorporating Fast Fourier Transforms to reduce the higher computational cost.Originality/value – The synthetic interpretation of trigonometric interpolation as a spectral‐element approach in the machine's air gap, ...

Artificial neural network based robust speed control of permanent magnet synchronous motors

Abstract: Purpose – The aim of the paper is to find a simple structure of speed controller robust against drive parameters variations. Application of artificial neural network (ANN) in the controller of PI type creates proper non‐linear characteristics, which ensures controller robustness.Design/methodology/approach – The robustness of the controller is based on its non‐linear characteristic introduced by ANN. The paper proposes a novel approach to neural controller synthesis to be performed in two stages. The first stage consists in training the ANN to form the proper shape of the control surface, which represents the non‐linear characteristic of the controller. At the second stage, the PI controller settings are adjusted by means of the random weight change (RWC) procedure, which optimises the control quality index formulated in the paper. The synthesis is performed using simulation techniques and subsequently the behaviour of a laboratory speed control system is validated in the experimental set‐up. The control ...

Direct control for AC/DC/AC converter‐fed induction motor with active filtering function

Abstract: Purpose – Proposes the application of novel control strategy in power transistors (insulated gate bipolar transistors – IGBT) based on AC/DC/AC converter with active filtering function. Seeks to investigate the possibilities of operating drive system under distorted line voltage with unity power factor and reduced dc‐link capacitor.Design/methodology/approach – A novel control strategy is proposed based on direct power and direct torque control with space vectors modulators scheme which seems to be most promising. This method is investigated, implemented and examined in the laboratory setup. Different working conditions are taken into consideration.Findings – Provides information how the proposed system works under motoring and regenerating modes. Good behaviors of the system in steady state in transience are shown. Very good stabilization of the dc‐link voltage under transient is achieved. Almost sinusoidal line current is obtained. Very good compensation of nonlinear load is also achieved.Research limit...

Nonlinear scaled models in 3D calculation of transformer magnetic circuits

Abstract: Purpose – To make easier and faster the designing of transformers using scale models.Design/methodology/approach – The scale modeling in designing of transformers is included. Both computer and physical models of high leakage reactance (HLR) and 3‐phase (TP3C) transformers have been considered. The 3D field computations have been executed for the scaled models, and the results were recalculated to the full‐scaled ones.Findings – It is possible to calculate the scale coefficients for nonlinear models of transformers using finite element method (FEM) software. Obtained coefficients are useful in the designing process. Measurements confirm correctness of the scaling laws.Research limitations/implications – The calculations were done only for transformers and the eddy current was not taken into account.Practical implications – Presented formulae for scale model calculation are very useful for designing of transformers by the engineers. It is possible to design a series of transformers. Only one physical model...

Comparison of numerical and measurement methods of SAR of ellipsoidal phantoms with muscle tissue electrical parameters

Abstract: Purpose – The assessing of the specific absorption rate (SAR) of living organisms or phantoms is difficult to realize and this paper seeks to do this. SAR much more precisely describes the energy absorbed by biological objects than values of electric field strength (E [V/m]) or power density (S [W/m2]) measured at the point of exposition. However, for living objects the assessing of SAR is not an easy task by measuring methods or even in calculation evaluations. Numerical techniques, especially the finite‐difference time‐domain method (FDTD), offer different possibilities of calculations. The important problem with FDTD method introduced to lossy objects with complex shapes is that this method is not verified with the measuring data.Design/methodology/approach – In this work the results of calculations and measuring data of ellipsoidal phantoms filled with specimen of electrical parameters like muscle tissue are presented. The calculations of SAR have been realized for two cases, e.g. for plane wave incid...

Design of magnetically levitated 2D drive

Abstract: Purpose – The paper aims to introduces a design of a planar motor with six degrees of freedom (dof).Design/methodology/approach – The paper provides a description of the model.Findings – The paper finds that this planar motor is magnetically levitated in four dof and magnetically driven in the other two. In the design of the system, structural characteristics of all elements as well as magnetic forces done by magnetic actuators have been taken into account. The model was realized by means fem and then was simulated dynamically in developed Simulink model. The design of the system has been greatly influenced by the sensor system. Hall effect proves have been introduced in some parts of the system. Magnetic flux density, and its direction can be measured in different parts of the system.Originality/value – The paper describes the design of a planar motor with six dof.

Accuracy improvement in nonlinear magnetostatic field computations with integral equation methods and indirect total scalar potential formulations

Abstract: Purpose – The paper seeks to solve nonlinear magnetostatic field problems with the integral equation method and different indirect formulations.Design/methodology/approach – To avoid large cancellation errors in cases where the demagnetizing field is high a difference field concept is used. This requires the computation of sources of the scalar potential of the excitation field.Findings – A new formulation to compute these sources is presented. The improved computational accuracy is demonstrated with numerical examples.Originality/value – The paper develops a novel formulation for the computation of sources of scalar excitation potential.

The multi-mode chaotic behaviors: N+N and 2D N-scroll chaotic attractors

Abstract: Purpose – The purpose of this paper is to present a simulation and realization of the different types of chaotic attractors using the generalized Chua's circuit equations.Design/methodology/approach – This paper presents n+n‐scroll and 2D n‐scroll chaotic attractors by introducing multiple breakpoints to the nonlinearity. Two piece‐wise linear elements controlled with x‐ and y‐state space variables are used. Chaotic scrolls are originated through both x‐ and y‐axes. The current feedback operational amplifiers are preferred in the experimental circuits because of their wide bandwidth.Findings – It is possible to increase the number of the scrolls in two directions by varying the number of breakpoints in the piece‐wise linear characteristics or changing the location of equilibrium points of the system on 2D‐plane. Theoretically developed behaviors are also experimentally tested.Originality/value – The excellent adaptation is observed between theoretical and experimental results. This paper also provides use...

Hysteresis losses in soft magnetic composite materials

Abstract: Purpose – To analyze the Jiles and Atherton hysteresis model used for hysteresis losses estimation in soft magnetic composite (SMC) material.Design/methodology/approach – The Jiles and Atherton hysteresis model parameters are optimized with genetic algorithms (GAs) according to measured symmetric hysteresis loop of soft magnetic composite material. To overcome the uncertainty, finding the best‐optimized parameters in a wide predefined searching area is done with the proposed new approach. These parameters are then used to calculate the hysteresis losses for the modeled hysteresis. The asymmetric hysteresis loops are also investigated.Findings – The classical GAs are good optimization methods when a pre‐defined possible set of solutions is known. If no assumption on solutions is present and a wide searching area range for parameter estimation is selected then the use of the new approach with nested GAs gives good results for symmetric hysteresis loops and further for the estimation of hysteresis losses.Res...

Interpolation technique for effective determination of switching time instants for field‐circuit coupled problems with switching elements

Abstract: Purpose – To provide a numerical technique for the quick and simple determination of the switching time instants for field‐circuit coupled problems with switching elements.Design/methodology/approach – 3D magnetic vector potential formulation coupled to an electrical circuit with switching elements, for example, diodes, is presented. The change of the state of the switching elements is implemented as a modification of the model topology.Findings – Since every step of the singly diagonally implicit Runge‐Kutta methods delivers not only the solution of this time step but also its stage derivatives, they can be efficiently employed to construct a dense‐output‐based interpolation polynomial, with their roots approximating the switching time instants.Originality/value – This paper presents a computationally cheap interpolation approach for quick and accurate determination of switching time instances for field‐circuit coupled problems with switching elements. The proposed technique can be successfully incorpora...

Finite element analysis of saturation effects in a tubular linear permanent magnet machine

Abstract: Purpose – The aim of the paper is to find the simple and accurate model for the analysis of a drive with a tubular linear permanent magnet machine (TLPMM). Attention is paid to the models that take into account the saturation effects and is useful in the calculations of electromagnetic forces.Design/methodology/approach – A circuit model and a field‐circuit model (FCM) are considered. The FCM includes finite element (FE) formulation for the axisymmetric electromagnetic field, equations which define the connections of windings and converter elements, and expressions that describe the control system. The FE method is used to determine the parameters of the circuit model. In order to simplify the circuit model, saturation effects caused by armature reaction are ignored. The electromagnetic force calculation is based on the virtual work principle and uses an approximate expression for the derivative of system co‐energy. The results obtained for the proposed models have been compared.Findings – The proposed FE...