Numerical Calculations Of Magnetic Field Research Articles

Numerical-field evaluation of an efficiency of a shortening of a three-phase stator winding of a cylindrical magnetic field inductor

The efficiency of cylindrical magnetic field inductors is determined by the value of the field inside their working chamber. This field is driven by a three-phase stator winding. The electrical quantities and magnetic induction in the inductor depend on its shortening. The purpose of this work is to determine the rational shortening of the stator winding. The solution of the problem is achieved on the basis of numerical calculations of magnetic fields in the FEMM software package using the finite element method. The construction of physical and geometric design models of the stator, calculations of magnetic fields and electromagnetic parameters of the inductor are automated using the created Lua script built into the FEMM program. The pictures of the distribution of magnetic field lines with diametric and shortened stator windings are given. A comparison is made between the EMF and the winding voltage, as well as the distribution of the magnetic induction over the surface of the working chamber and along the center line of the teeth with different variants of shortening the winding pitch.

The Method of Determining the Turbogenerator Characteristics Using Automated Numerical Calculations of Magnetic Fields

The Method of Determining the Turbogenerator Characteristics Using Automated Numerical Calculations of Magnetic Fields

Theory and practice of numerical-field determination of the electromagnetic characteristics of turbogenerators with their operation in the power system

The theoretical bases and practical aspects of determining the characteristics of turbogenerators, which connect the electromagnetic quantities inherent in the different modes of their operation in the power system, are presented. This is carried out in the most appropriate form – by the numericalfield method. The calculation of the characteristics points is the solution of the inverse problem in which in most cases there are two basic and two variable values. This requires an iterative calculations. The assignment of the first approximations of the values of the variable quantities and the organization of the iterative characteristics calculation processes are shown. In this way, a number of characteristics of a powerful turbogenerator were obtained, namely, a characteristic of idling, characteristics of longitudinal and transverse magnetization from the stator winding, short-circuit characteristic, adjusting and angular characteristics, as well as a family of U-shaped characteristics. The calculations were performed using the automated numerical calculations of magnetic fields in the FEMM software environment by the finite element method, with the use of the created Lua scripts. Dependencies of standard values, which are connected in standardized characteristics, are additionally accompanied by corresponding functions of electrical and angular values. A number of pictures of magnetic fields corresponding to different specific points of characteristics are given.

DETERMINATION OF ANALYTICAL CALCULATION ERROR OF MAGNETIC FIELD OF HIGH-VOLTAGE CABLE LINES WITH TWO-POINT BONDED CABLE SHIELDS CAUSED BY NON-UNIFORM CURRENT DISTRIBUTION IN THE SHIELDS

This paper deals with the determination of analytical calculation error of magnetic field of high-voltage cable lines in two-point bonded cable shields caused by non-uniformity of the current distribution in the shields. The relative error is determined by comparing numerical calculation of magnetic field obtained in the COMSOL Multiphysics software with the analytical one. It is shown that the maximum value of relative error does not exceed 8 %. The obtained error values are verified by testing the numerical calculation and confirmed by results of experiment. In paper proves the correctness of the analytical calculation of magnetic field of cable lines at the points of its normalization, which is carried out without taking into account the non-uniform current distribution in the cable shields.

The Comparative Analysis of Permanent Magnet Electric Machines with Integer and Fractional Number of Slots per Pole and Phase

The comparison of permanent magnet motors with integer and fractional number of slots per pole and phase was made. The torque developed by the motor and the torque ripples level were chosen as the major criterions. The comparison was made according to the results of equations of numerical calculation of magnetic field in active motors volumes using the finite element analysis. The recommendations on the choice of the most suitable option are given.

Metamodels for New Designs of Outer-Rotor Brushless Synchronous Electric Motors

Abstract The authors consider the possibilities to synthesise metamodels for the analysis and optimisation of brushless synchronous motors. The metamodels are presented for new designs of the outer-rotor permanent magnet synchronous motor and the outer-rotor reluctance motor. The metamodels are synthesised based on the results obtained by the numerical calculations of magnetic field taking into account magnetic saturation. Analysis of the results for the motor magnetic field and tests of the metamodels at the selected and intermediate points shows that these can be synthesised with acceptable accuracy using numerical calculations instead of expensive real experiments.

Application of rod return-current conductors for decreasing the magnetic field of the vacuum diode

Results of the physical simulation and numerical calculations of magnetic field of the high-power vacuum diode with a large electron-beam cross section in the absence and with diode-installed return-current conductors in the form of rods are given. It is shown that the use of rods decreases the magnetic induction at the edge of the beam, while the field in the central part of the diode increases. It is found that the distribution of the magnetic field in the interelectrode cathode-anode gap in the presence of rods depends on the gap length between the back side of the cathode and the walls of the vacuum chamber. The location of the rods that halves the induction of the magnetic field at the edge of the cathode with the reasonable induction increase in the central part is found.

Magnetic Field and Circuit Parameters in an Electromagnetic Generator Supporting a Rotary MR Damper

This paper summarises the results of numerical calculations of magnetic field and circuit parameters in an electromagnetic generator supplying a rotary MR damper. The design and operating principles of the generator are outlined. The distribution of the magnetic flux density vector is obtained, other parameters include its modulus, the magnetic flux from permanent magnets and time patterns of induced voltage and current in the control coil of the damper, power and energy of magnetic field in this coil at different rotational speeds of the induction with respect to the armature.

Improved Characterization of the Magnetic Properties of Hexagonally Packed Wires

SummaryWhen designing passive magnetic components, calculations of the magnetic field distribution inside the winding window become necessary. Numerical calculations, but also other methods like the modal decomposition of the boundary value problem encounter difficulties, when the influence of a great number of wires (e.g. litz wire strands) has to be taken into account. To avoid discretization of a great number of tiny strands, a global property like an equivalent permeability may be used to characterize the macroscopic magnetic behavior (Fig. 1). If the magnetic field is characterized by complex amplitudes, this permeability also has a complex value. Its imaginary part describes the proximity losses in the winding. A possibility to derive this permeability from the properties of a single strand is presented in [1], however, as already stated there, this formula is not equally suited for all frequencies, permeabilities and various ratios of strand diameter to the total litz diameter. Especially for higher frequencies, as stated in [2], most approximation formulas deviate considerably from simulation data.In this paper, an improved complex permeability model for litz wire windings is derived heuristically from a comparison between simulation results and the standard analytical model. It is valid for all strand diameters, strand distances and frequencies, and may be used for accurate numerical calculations of magnetic fields and losses in magnetic components.

Investigation on the Inclination of Cathode Plasma Jets in High-Current Vacuum Arcs in Magnetic Field

The theoretical and experimental studies of cathode plasma jets in vacuum arc and the effect of magnetic field on them have been under way for several years. In this paper, different axial magnetic field electrodes were tested in a vacuum chamber, obvious individual cathode plasma jets were observed, and the cathode-jet inclination was also detected. Based on the numerical calculation of magnetic field in interelectrode region and the measurement of cathode-jet inclination in experimental results, it is proven that the inclination angle of composite magnetic field (the combination of the axial, the azimuthal, and the radial components) is consistent with the inclination angle of cathode plasma jets, which indicates that the cathode plasma jets in the arc column flow along the magnetic-field direction when the high-current vacuum arc is diffused or even constricted slightly. Meanwhile, it was also found that plasma jets far from the cathode surface mixed with each other and became ambiguous when the electrode gap increases to a certain distance.

Relaxation of toroidal plasmas: tokamaks

We do not believe that the minimum energy theory is applicable to driven plasmas. We assume that relaxation occurs towards a state of minimum entropy production rate. As the equilibrium Ohm's law cannot be satisfied in peaked-current density states, the final state must be steadily turbulent. What is new about our theory is, fundamentally: (i) the pressure balance is considered as a relevant constraint upon the relaxed state and this is expressed as an integral relation; (ii) the energy dissipation by turbulence is assumed to be minimal and (iii) anisotropic resistivity is regarded as the main cause of poloidal current. The numerical calculations of magnetic field and current density reproduce typical observations in tokamaks.

Design study for an adjustable phase undulator

This is a presentation of the results of a design study for an adjustable phase undulator. Earlier work described the basic theory of these undulators, whose magnetic fields are adjusted by moving the rows of magnets longitudinally with respect to each other, while keeping the gap fixed. This paper explores further details of a proposed permanent magnet, phase adjustable, soft x-ray undulator that will be used to test theoretical and calculated performance predictions. We present the Hamiltonian mechanics of the electron-beam and numerical calculations of magnetic fields and trajectories of electrons, including end effects. We also discuss the trajectories of off-axis electrons, the vertical focusing effect, the effects of magnetic errors, and finite emittance effects on the x-ray spectrum.