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This paper introduces the meshless local radial point interpolation method to model eddy-current problems for the first time. The formulation is described and results are compared with those from the ordinary finite-element simulation and the analytical solution

We propose a finite-element scheme which involves the use of the Lagrangian interface technique to model electromagnetic signal propagation in mixed regions of very low and high conductivity. The method has relevance to modeling underground communications in oil or gas wells. There will be a significant jump in electrical conductivity especially at the interface between the iron and the nonmetallic conductive regions

This paper describes a three-dimensional (3-D) overlapping finite-element scheme for modeling movement in electromagnetic devices, which results in a continuously changing air gap. The method uses separate finite-element meshes to model the individual parts of the device. These meshes are coupled together electromagnetically on an interface using the Lagrange sliding interface technique. Treatments of overlapping mesh volumes are also discussed. The method was used to model a jumping eddy-current disc experiment. The results of the simulations compared favorably with measurements.

Despite worldwide efforts and many recent advances, electrical machine modeling using finite elements can be computationally very expensive, especially if three-dimensional models are required. This contribution is concerned with speeding up the process. Some examples of line start permanent magnet machines and induction motors are provided.

The transient characteristics of an experimental test rig consisting of a fixed solid iron stator and moving rotor, when subjected to a step input voltage, are measured. A three-dimensional finite-element scheme that takes into account the nonlinear magnetic properties, eddy-current effects, and the dynamic motion of the rotor was used to simulate the response of the rig. The measurements were used as a benchmark against which the simulation results were compared.

Four finite-element formulations for modeling eddy current problems which involve a rotating conductor are examined and compared. The formulations are based on the A-/spl psi/ representation. The first formulation uses a single fixed mesh, nodal A elements and the Minkowski transformation. The other three schemes have two meshes coupled using a Lagrange interface and the mesh containing the conducting region rotates. Two of the schemes use a nodal A formulation and the third uses edge A elements. The main purpose of the paper is to point out some of the pitfalls which can occur when modeling rotating conductors. By way of example, the four formulations are applied to a spinning annulus test problem.

The electromagnetic launcher at speed is a challenging computational problem as fast time transient electromagnetic fields are involved and the velocity of the moving parts is designed to be very high. A large number of formulations are now available for modeling the electromagnetic behavior of moving conductor devices in 3D. These methods vary in computational expense and accuracy. In this paper, the authors describe and compare some of these methods, and show some examples.

A parameterization technique for use in optimizing electromagnetic devices is described. The method allows a rapid alteration of an initial template 2-D or 3-D finite element mesh of an electromagnetic device so that design studies or optimization be conveniently carried out. Two case studies are described. The examples consist of the voltage generated by a wound rotor generator and the performance of a Fluxset magnetic field measuring device.

A fast-converging solution method with strong coupling, which does not require the calculation of a global Jacobian, is discussed. The method is applied to an equilibrium-type coupled electromechanical system and also to the more general problem of the dynamic evolution of the system.

The authors describe the modeling of the transient dynamic behavior of a solenoidal core type electromagnetic actuator using an overlapping finite element (FE) scheme. The FE scheme allows two topologically unconnected 2D finite element meshes to slide over and overlap each other, whilst still coupled together electromagnetically in a consistent manner. The result is that the same set of FE meshes can be used to model directly a continuously shrinking or expanding air gap. This paper demonstrates, for the first time, that such a FE scheme can be used to model accurately the dynamic closing of the air gap of a linear actuator. The results of the simulation were compared with experimental measurements. It is shown that good agreement between simulated and measured results is obtained.

Some techniques for modeling thin skin depth eddy currents induced by the movement of a conductor through a magnetic field are described. The nonconducting regions are modeled using conventional volume finite elements in terms of the magnetic scalar potential /spl psi/. The magnetic fields in the thin skin are determined approximately using either analytic or numerical solutions to 1D equations for fields in the moving skin.

The treatment of 3D machine problems using the finite element method to model the field is examined. Methods for coupling to external circuits are reviewed and it is shown that symmetry can be taken care of by the suitable scaling of partitions of the system matrix. 3D filament wound coils and massive conductor circuits are discussed.

Two finite element implementations for modelling eddy current problems with velocity are examined here. The formulations are based on the A-/spl psi/ representation. In one finite element implementation, the moving current density is represented as a volume integral term. In the other, volume and surface integral terms represent the moving current density. These formulations are applied to a series of rotational velocity test models differing in conductor topology and the results are compared.

This paper describes a 3D finite element scheme for use in dynamic simulations of electromagnetic devices with moving parts connected to an external circuit. The scheme handles source coils through a special coil region based on the magnetic scalar representation with an additional basis for each coil. The finite element model can be directly coupled to external circuits and motion of moving parts within the model is handled by using a Lagrange sliding interface technique.

This paper describes an efficient scheme for incorporating multiple wire wound coils into 3D finite element electric machine models. The scheme is based on the magnetic scaler representation with an additional basis for each coil. There are no restrictions on the topology of coils with respect to ferromagnetic and conductor regions. Reduced scaler regions and cuts are automatically generated.

Meshless methods are a new class of numerical techniques for solving partial differential equations and have attracted considerable attention in computational mechanics in recent years. Owing to the ‘mesh-free’ characteristic, these methods offer some advantages over the conventional mesh-based finite-element techniques. A formulation for the meshless local Petrov–Galerkin method is described and its application to electromagnetic modelling investigated.

Measurements of the performance of a 5-kVA induction machine are compared with predictions carried out using finite elements and semianalytic techniques. Both transient and steady-state performance results are compared and sufficient dimensions are provided that others may use the experimental results as a benchmark.

A method for finite element modelling of transient 3D eddy currents in magnetically nonlinear media is described. The magnetic vector potential A, with or without the electric scalar potential V, is used inside eddy current regions, coupled to magnetic scalar potentials elsewhere. Time transient torque, current and flux values are compared to measurements taken from a rotational test rig. >

In this letter, we demonstrate an experimental study of using a large area oxide-confined vertical-cavity surface-emitting laser (VCSEL) to pump a Nd:YVO/sub 4/ microchip laser. The maximum output power of 1.2 mW in TEM/sub 00/ mode is obtained with a pump power of 8.2 mW. Experimental results show that the complex transverse modal behavior of VCSELs in the higher injection current may cause an impediment of power scaling.

A novel scheme for automatically generating cuts in the magnetic scalar region of a finite element mesh is presented. Cuts are generated allowing multiply connected eddy current problems to be solved. The scheme has no topological limitations; it has been tested for knotted conductors, interlinked conductors, and hollow conductors. The scheme is fully automatic, requiring just a standard well-formed finite element mesh and appropriate boundary conditions. It has been implemented and tested in the finite element package MEGA for the A psi formulation. >

The use of surface impedance elements and the use of volume elements when modeling at test rig using the MEGA package are compared. The test rig is representative of a turbine generator. The work is supported by practical measurements. Experimental results indicate that it is possible to model 3-D fields in large-scale objects containing nonlinear conducting iron using finite elements. Two methods for modeling the iron are compared: conventional volume elements and surface impedance elements. Both methods give similar results, but the latter method is much more economical. Some complex devices are impractical to model on inexpensive workstations without using surface impedance elements. >

The authors present a scheme for modeling coil guns using finite elements. The relative motion between the coils and the projectile is modeled by using two distinct meshes which are coupled using Lagrange multipliers which depend on the relative position of the two meshes. This scheme allows the inner mesh to slide during the transient simulation without the need to remesh the problem. Results are presented for a simple experiment involving a single coil and aluminum projectile. >

This paper describes a scheme which allows two separate finite element meshes to slide into and thus overlap each other. The Lagrange multipliers method is used to couple the two meshes together at their boundary. Overlapping elements are dealt with by adjusting the contributions of the elements of one of the two meshes to the system matrix according to the extent of overlap in such a way that at total overlap, those elements are effectively decoupled from the model. Applications include the modelling of electromagnetic plunger type devices.

A new technique for modelling time transient thin skin depth eddy currents is presented. The nonconducting regions are modelled using conventional volume finite elements in terms of the magnetic scalar potential /spl psi/. The magnetic fields in the thin skin are determined approximately using 1D finite elements in terms of magnetic vector potentials, Most problems would result in one large volume matrix and many small 1D matrices. A staggered time transient solution to the two sets of equations in /spl psi/ and A is then carried out. A finite element implementation and some test examples are described.

A technique for modelling thin skin depth eddy currents in 3D devices using the magnetic vector potential A is presented. An analytic solution for the magnetic field in the thin skin is used to develop a surface impedance which appears as a surface integral at faces of elements which interface the thin skin eddy current region. The method has been implemented using classical nodal variable finite elements. Results are compared with an analytic solution and measurements from a nonlinear test rig.

A method that allows thin iron sheets to be included in 3-D finite element models of magnetostatic fields is introduced. This method avoids having to model the sheet using volume elements. This is advantageous, as very fine meshes are conventionally required to model sheets which are thin compared to the other dimensions if elements with a poor aspect ratio are to be avoided. The technique has been available in the MEGA package and has proved useful in modeling electromagnetic compatibility problems, in shielding for magnetic resonance imaging magnets, and for the effects of ships and dockyards on the Earth's magnetic field. >

Devices which include moving conductors which are invariant in cross section normal to the direction of motion may be modelled using a finite element scheme which incorporates the Minkowski transformation. Three components of magnetic vector potential and electric scalar potential are required inside the moving medium. When the conductivity of the moving medium is very low, the magnetic field induced by the eddy currents is relatively small and can be neglected. In this case the problem may be formulated more economically in terms of two static scalar solutions. The two methods are compared with each other and with analytic solutions and experimental results.

Cervical cancer is common among women all over the world. Although infection with high-risk types of human papillomavirus (HPV) has been identified as the primary cause of cervical cancer, only some of those infected go on to develop cervical cancer. Obviously, the progression from HPV infection to cancer involves other environmental and host factors. Recent population-based twin and family studies have demonstrated the importance of the hereditary component of cervical cancer, associated with genetic susceptibility. Consequently, single-nucleotide polymorphism (SNP) markers and microsatellites should be considered genetic factors for determining what combinations of genetic factors are involved in precancerous changes to cervical cancer. This study employs a Bayesian network and four different decision tree algorithms, and compares the performance of these learning algorithms. The results of this study raise the possibility of investigations that could identify combinations of genetic factors, such as SNPs and microsatellites, that influence the risk associated with common complex multifactorial diseases, such as cervical cancer. The web site associated with this study is http://140.115.155.8/FactorAnalysis/.

A finite-element scheme for modeling 3-D eddy currents in general thick conductors and thin sheet conductors which can be in electrical contact is described. Volume eddy currents are modeled in terms of the magnetic scalar potential A and sheet eddy currents are modeled in terms of a scalar stream function T. Nonconducting regions are modeled using magnetic scalar potentials. The interface between the general thick conductors and the thin sheet conductors is described. The method has been implemented in the 2- and 3-D electromagnetics software package MEGA. The method yields good results for all cases tried in which the assumption of uniform distribution across the thickness of the sheet is reasonable. Results are presented for tokamak poloidal field coils. >

A technique for use in finite-element models for coupling independent three-dimensional meshes together is presented. The coupling is done at an interface using Lagrange multipliers which can be identified as the normal component of B on the interface. This technique is particularly well suited to the analysis of devices with moving parts where the modeling of the moving parts at different positions is required. The proposed scheme was used to model a switched reluctance motor which has been modeled previously using conventional finite elements. >

A method for solving problems involving eddy currents flowing in thin surface layers in magnetically nonlinear iron is described. It is shown how an extension of the method of D. Rodger and N. Atkinson (1988) for modeling eddy currents in thin sheets can be used to model low skin depth problems using sheet elements which cover the surface of the eddy current regions. The resulting equations can be nonlinear if the permeability is dependent on fields. The volume of the iron need not be modeled using this method. Only the fundamental harmonic of the AC supply is considered and hysteresis effects are ignored. Nevertheless, the method has been shown to be useful in situations where a full volume, nonlinear transient solution would be computationally too expensive. Some experimental results are compared with simulations from the MEGA program package. >

A novel technique for use in finite-element models of devices which move is proposed. Independence meshes are coupled together with a suitable interface, such as the air gap of a conventional electrical machine, using Lagrange multipliers. The proposed approach allows a finite-element mesh to move with respect to an adjacent mesh without any need for remeshing. At different positions, only the terms which couple the meshes together at the interface are altered. While only the problem of producing many different magnetostatic solutions or 'snapshots' of the rotor at different instants in time is addressed here, the authors expect that treating velocity-induced eddy currents in a time-transient situation should be possible by extending the same basic techniques. >

A method which uses finite-element techniques for designing linear tubular brushless DC machines is described. The design technique makes use of approximate calculations to decide the machine dimensions. Finite-element analysis is then employed to calculate a series of designs and determine the optimum one. The effects of variation in slot depth and pole pitch are illustrated. The finite-element analysis is supported by analytical results from using a simple method of calculating electromagnetic force. >

The measurement of the non-bolometric microwave response of a superconducting film may provide a possible method of detecting the co-existence of different phases of the film. Experimental results suggest that increased granularity of a film leads to a larger nonbolometric effect. The main mechanism of the nonbolometric microwave response is thought to be due to the interaction between microwave radiation and the inter granular weak links in the film.

If a logic gate in a logic network of MOS transistors expresses a negative function, which is a logic function that can be expressed as the complement of a disjunctive form of only noncomplemented variables, it is called a negative gate. An algorithm, DIMN, for the design of a MOS logic network with a minimum number of negative gates and irredundant connections among negative gates for a completely specified function was published by the authors in 1985. DIMN is extended here to the case of an incompletely specified function, and an example is given. >