Antonios G. Kladas

Internal Permanent Magnet Motor Design for Electric Vehicle Drive

Power compaction and high efficiency are two key advantages of permanent magnet motors. This paper proposes an enhanced internal permanent magnet motor that delivers high torque, power compaction, and exceptionally high efficiency in the same operation area. The advantage of the proposed scheme is the magnetic flux accumulation in the air gap, which allows much higher values of magnetic flux density, compared to a surface permanent magnet motor of the same size. The original contribution of this paper resides on the adopted motor configuration, enabling to efficiently utilize the energy stored in the permanent magnet and to provide total loss minimization at the most frequently used speed range.

Harmonic Impact on Distribution Transformer No-Load Loss

The losses in European Union distribution transformers are estimated at about 33 TW ·h/year, whereas reactive power and harmonic losses add a further 5 TW ·h/year. The reduction of distribution transformer no-load loss is particularly important as the ratio of no-load to load losses is nearly three. In this paper, the no-load operation of wound-core transformers under sinusoidal and distorted supply-voltage conditions is investigated. For that purpose, a 2-D nonlinear transient finite-element analysis taking into account hysteresis has been developed. The hysteresis model is based on a modified Jiles-Atherton representation, and the proposed analysis is compared to experimental data.

Fast Photovoltaic-System Voltage- or Current-Oriented MPPT Employing a Predictive Digital Current-Controlled Converter

In this paper, a photovoltaic (PV)-system maximum power point (MPP) tracking (MPPT) control strategy employing a predictive digital current-controlled converter implemented in conventional hardware resources is presented. Two current programmed controllers (finite-state predictive control and valley current control) have been integrated into a system with current- or voltage-oriented MPPT. The modifications applied to the perturb-and-observe algorithm enable the MPP tracker to interact rapidly with the controller accounting also for abrupt irradiance drops by considering voltage and current limitations. The implementation of digital control in PV systems entails significant advantages of speed and accuracy, although the controller converges correctly at the MPP under irradiance variations featuring fast dynamic response. The proposed controller scheme has been experimentally demonstrated on a digitally current-controlled boost converter delivering power from a PV system.

Permanent-Magnet Shape Optimization Effects on Synchronous Motor Performance

The magnet shape in permanent-magnet (PM) synchronous motors substantially affects the back-electromotive-force (EMF) waveform and the stator iron losses, which are of particular importance in traction applications, where the energy available in the battery box is limited. This paper presents a methodology based on geometry optimization, providing sinusoidal back-EMF waveform. The method has been applied in a surface PM motor case for electric vehicle, and its validity has been checked by measurements on two prototypes, the first one with constant magnet width and the second one with optimized magnet shape.

Power Generation Optimization From Sea Waves by Using a Permanent Magnet Linear Generator Drive

This paper presents the design procedure and modeling methodology for a four sided linear permanent magnet generator used in sea wave energy extraction applications. Appropriate coupled magnetic-electric-mechanical models for the analysis of the linear permanent magnet (LPM) generator and the hydraulic system have been developed. The effects of permanent magnet configuration on the overall system performance have been investigated. The proposed models suitability has been checked through measurements in a 16 kW prototype power plant.

Leakage flux and force calculation on power transformer windings under short-circuit: 2D and 3D models based on the theory of images and the finite element method compared to measurements

The paper compares different techniques based on the theory of images and the finite element method enabling to calculate the leakage field and the static electromagnetic forces on the windings of power transformers. The models developed have been applied to the one phase part of a three phase shell type power transformer and the results are verified experimentally. Both cases, that of approximate two dimensional analysis and the three dimensional configuration, have been studied. A particular three dimensional finite element formulation involving only a scalar potential was found to be suitable for this class of problems. >

Analysis of Transformers Working Under Heavily Saturated Conditions in Grid-Connected Renewable-Energy Systems

In recent years, researchers have proposed transformerless solutions for connecting renewable-energy power plants to the grid. Apart from lack of efficiency and increased cost and weight of the transformer, one of the reasons is the dc input current that causes transformer saturation. The purpose of this paper is the development of a finite-element computational tool that is going to aid transformer manufacturers in designing distribution transformers specifically for the renewable-energy market. It is based on a generalized macroscopic representation of electrical steels used in the transformer manufacturing industry that enables the accurate evaluation of electromagnetic field distribution of transformer cores under heavily saturated conditions. Its advantages over conventional formulations include numerical stability, numerical accuracy, and reduction of iterations of the Newton-Raphson method. An experimental verification of the proposed method is carried out.

Electromagnetic Forming Tools and Processing Conditions: Numerical Simulation

Finite element (FE) modeling is used to simulate the electromagnetic forming process. Two industrial tools are considered: a four-turn compression coil with a ferromagnetic screen and a stepped field shaper as well as a seven-turn pancake coil with a ferromagnetic outer screen. Details on FE model building are thoroughly discussed. The input load is the current of the coil, which can be experimentally measured. The deformation characteristics of the workpiece as well as the electromagnetic variables of the high-energy rate process (i.e., the magnetic flux density around the conductors and the Lorentz forces acting on the workpiece) are calculated numerically. The effects of the various parameters of the electromagnetic forming process, such as initial charging voltage, workpiece material, and geometry as well as holding devices, are analyzed either theoretically or through FE modeling. In most cases, the dependent variable is the Lorentz force acting on the workpiece. The numerically calculated and analytical electromagnetic results are in good agreement. The present analysis is useful for the practical realization of the electromagnetic forming process, contributing also to a better understanding of its principles.

Geometry Optimization of PMSMs Comparing Full and Fractional Pitch Winding Configurations for Aerospace Actuation Applications

Optimization of electromechanical aerospace actuators requires a multi-objective and comparative analysis in order to account for performance and manufacturing cost terms. This paper introduces a particular optimization methodology presenting stable convergence characteristics which has been applied to optimize the geometry of both Fractional Slot Concentrated Winding (FSCW) and Full Pitch Concentrated Winding (FPCW) permanent magnet motor configurations. The proposed algorithm combines technical and physical advantages of the FSCWs and FPCWs into an optimally shaped stator-winding configuration. The resultant motor design has been validated through a prototype and experimental results illustrated its suitability for aerospace actuation applications.

A Parallel Mixed Integer Programming-Finite Element Method Technique for Global Design Optimization of Power Transformers

Transformer design optimization is determined by minimizing the transformer cost taking into consideration constraints imposed both by international specifications and customer needs. The main purpose of this work is the development and validation of an optimization technique based on a parallel mixed integer nonlinear programming methodology in conjunction with the finite element method, in order to reach a global optimum design of wound core power transformers. The proposed optimization methodology has been implemented into software able to provide a global feasible solution for every given set of initial values for the design variables, rendering it suitable for application in the industrial transformer design environment.