This paper discusses the performance attributes of the open-slot, modular-wound, external-rotor, topology of electrical machine. Combinations of pole and slot numbers are presented for which the winding factor is maximal and torque ripple is minimal. An optimization of the magnetic circuit design of six promising pole-slot configurations is undertaken using a parametric finite element model (FEM) combined with a genetic algorithm (GA). These designs are benchmarked against a conventional 1.5 slots/pole external-rotor brushless dc machine. These candidate electrical machine versions are characterized by having the same external-rotor diameter, total slot area available for the winding and by equal volumes of permanent magnet (PM). Based on the analysis, the most promising motor structure was selected and a prototype wheel-hub motor has been built for application in a small electrical vehicle. Test data from the prototype is used to validate the findings of the initial analyses and practically demonstrate the attributes of the topology.

Design Considerations of a Direct Drive Brushless Machine With Concentrated Windings

Corona discharge refers to the phenomenon when the electric field near a conductor is strong enough to ionize the dielectric surrounding it but not strong enough to cause an electrical breakdown or arcing between conductors or other components. This phenomenon is unwanted and dangerous in high-voltage systems; however, a controlled corona discharge may be used to ionize a fluid and induce motion by directly converting the electrical energy into kinetic energy. Phenomena that involve the direct conversion of electrical energy into kinetic energy are known as electrohydrodynamic (EHD) and have a variety of possible applications today. This paper contains a literature review of the research regarding the EHD effects associated with corona discharges, from the first observation of the phenomenon to the most recent advancements on its mathematical modeling, as well as the advancements on specific applications, such as thrust, heat transfer improvement, boundary layer enhancement, drying, fluid pumping, and cooling.

https://bura.brunel.ac.uk/bitstream/2438/12965/1/Fulltext.pdf

Review on the History, Research, and Applications of Electrohydrodynamics

The emergence of second-generation high temperature superconducting (HTS) tapes has favored the development of large-scale superconductor systems. The mathematical models capable of estimating electromagnetic quantities in superconductors have evolved from simple analytical models to complex numerical models. The available analytical models are limited to the analysis of single wires or infinite arrays that, in general, do not represent actual devices in real applications. The numerical models based on the finite element method using the H formulation of Maxwell's equations are useful for the analysis of medium-size systems, but their application in large-scale systems is problematic due to the excessive computational cost in terms of memory and computation time. Therefore it is necessary to devise new strategies to make the computation more efficient. The homogenization and the multi-scale methods have successfully simplified the description of the systems allowing the study of large-scale systems. Also, efficient calculations have been recently achieved using the T–A formulation. In the present work, we propose a series of adaptations to the multi-scale and homogenization methods so that they can be efficiently used in conjunction with the T–A formulation to compute the distribution of current density and hysteresis losses in the superconducting layer of superconducting tapes. The computation time and the amount of memory are substantially reduced up to a point that it is possible to achieve real-time simulations of large-scale HTS systems under slow ramping cycles of practical importance on personal computers.

https://iopscience.iop.org/article/10.1088/1361-6668/ab0d66/pdf

Real-time simulation of large-scale HTS systems: multi-scale and homogeneous models using the T-A formulation

Light absorption plays an important role in many research areas. Here, we propose and demonstrate a thin ultra-broadband strong light absorber consisting of periodic taper arrays on a gold substrate.

Ultra-broadband strong light absorption based on thin multilayered metamaterials

In this paper, parameters of the Jiles-Atherton (J-A) hysteresis model are identified using a stochastic search algorithm called differential evolution (DE). The J-A hysteresis model's parameters are identified by DE in such a way, that best possible agreement is obtained between the measured and model calculated hysteresis loops. This agreement is furthermore increased by improving the J-A hysteresis model. The improvement is achieved by replacing a constant pinning parameter in the J-A hysteresis model with a variable one. Here, the variable pinning parameter is written as a function of a magnetic field. By DE identified parameters are used in the J-A hysteresis model, which is included in the dynamic model of a single-phase transformer. The effectiveness of the improved J-A hysteresis model and parameters identification approach is verified with experiments and simulations.

Parameter Identification of the Jiles–Atherton Hysteresis Model Using Differential Evolution

PREFACE MATHEMATICAL PRELIMINARIES Introduction The Vector Notation Vector Derivation The Gradient The Divergence The Rotational Second-Order Operators Application of Operators to More than One Function Expressions in Cylindrical and Spherical Coordinates MAXWELL EQUATIONS, ELECTROSTATICS, MAGNETOSTATICS, AND MAGNETODYNAMIC FIELDS Introduction The EM Quantities Local Form of the Equations The Anisotropy The Approximation of Maxwell's Equations The Integral Form of Maxwell's Equations Electrostatic Fields Magnetostatic Fields Magnetodynamic Fields BRIEF PRESENTATION OF THE FINITE ELEMENT METHOD Introduction The Galerkin Method - Basic Concepts A First-Order Finite Element Program Generalization of the Finite Element Method Numerical Integration Some 2D Finite Elements Coupling Different Finite Elements Calculation of Some Terms in the Field Equation A Simplified 2D Second-Order Finite Element Program THE FINITE ELEMENT METHOD APPLIED TO 2D ELECTROMAGNETIC CASES Introduction Some Static Cases Application to 2D Eddy Current Problems Axi-Symmetric Application Advantages and Limitation of 2D Formulations Non-Linear Applications Geometric Repetition of Domains Thermal Problems Voltage-Fed Electromagnetic Devices Static Examples Dynamic Examples COUPLING OF FIELD AND ELECTRICAL CIRCUIT EQUATIONS Introduction Electromagnetic Equations Equations for Different Conductor Configurations Connections Between Electromagnetic Devices and External Feeding Circuits Examples MOVEMENT MODELING FOR ELECTRICAL MACHINES Introduction The Macro-Element The Moving Band The Skew Effect in Electrical Machines Using 2D Simulation Examples INTERACTION BETWEEN ELECTROMAGNETIC AND MECHANICAL FORCES Introduction Methods Based on Direct Formulations Methods Based on the Force Density Electrical Machine Vibrations Originated by Magnetic Forces Example of Coupling Between the Field and Circuit Equations, Including Mechanical Transients IRON LOSSES Introduction Eddy Current Losses Hysteresis Anomalous or Excess Losses Total Iron Losses The Jiles-Atherton Model The Inverse Jiles-Atherton Model Including Iron Losses in Finite Element Calculations BIBLIOGRAPHY INDEX

Nelson Sadowski

Papers

Electromagnetic Modeling by Finite Element Methods

Maxwell Equations, Electrostatics, Magnetostatics and Magnetodynamic Fields