J.K. Sykulski

Applying continuum design sensitivity analysis combined with standard EM software to shape optimization in magnetostatic problems

This paper explores the physical meaning of pseudosources of an adjoint system in a continuum design sensitivity analysis (CDSA) when applied to shape optimization in magnetostatics. An efficient and practical way to compute the required gradient information with standard electromagnetic (EM) software packages is suggested. Based on this novel methodology, designers will be able to deal with practical design optimization of electro-mechanical devices using existing analysis tools without the need to access the complicated code of the EM software. The applicability of the proposed methodology is demonstrated by optimizing the salient pole face shape of a high-temperature superconducting synchronous generator.

Network equivalents of nodal and edge elements in electromagnetics

The paper analyzes the analogies between nodal/edge formulations of finite elements and nodal/loop (mesh) descriptions of network models of electromagnetic fields containing eddy and displacement currents. Both scalar and vector potentials are used. Two types of graphs are introduced: 1) for nodal elements; and 2) for edge elements. It is noted that edge values of potentials A and T are represented by loop quantities in graphs 2). Branch parameters such as reluctances, branch impedances and sources are described. Finally, coupled networks are discussed mixing A-V, /spl Omega/-T, and A-T models.

Comparative study of evolution strategies combined with approximation techniques for practical electromagnetic optimization problems

The paper addresses the practical problem of reducing the number of necessary function calls involving time consuming finite-element solutions by combining various evolution techniques with approximation methods based on Response Surface Methodology. A new algorithm is proposed which offers significant improvement of performance while preserving the quality of the final result. Comparisons are made between the new algorithm and different standard strategies in terms of reliability, efficiency and cost.

Robust Optimization Utilizing the Second-Order Design Sensitivity Information

This paper presents an effective methodology for robust optimization of electromagnetic devices. To achieve the goal, the method improves the robustness of the minimum of the objective function chosen as a design solution by minimizing the second-order sensitivity information, called a gradient index (GI) and defined by a function of gradients of performance functions with respect to uncertain variables. The constraint feasibility is also enhanced by adding a GI corresponding to the constraint value. The distinctive feature of the method is that it requires neither statistical information on design variables nor calculation of the performance reliability during the robust optimization process. The validity of the proposed method is tested with the TEAM Workshop Problem 22.

Solution of Different Types of Economic Load Dispatch Problems Using a Pattern Search Method

Abstract Direct search (DS) methods are evolutionary algorithms used to solve constrained optimization problems. DS methods do not require information about the gradient of the objective function when searching for an optimum solution. One such method is a pattern search (PS) algorithm. This study presents a new approach based on a constrained PS algorithm to solve various types of power system economic load dispatch (ELD) problems. These problems include economic dispatch with valve point (EDVP) effects, multi-area economic load dispatch (MAED), companied economic-environmental dispatch (CEED), and cubic cost function economic dispatch (QCFED). For illustrative purposes, the proposed PS technique has been applied to each of the above dispatch problems to validate its effectiveness. Furthermore, convergence characteristics and robustness of the proposed method has been assessed and investigated through comparison with results reported in literature. The outcome is very encouraging and suggests that PS methods may be very efficient when solving power system ELD problems.

The Implications of the Use of Composite Materials in Electromagnetic Device Topology and Shape Optimization

The use of soft magnetic composites (SMCs) provides electromagnetic device designers with serious challenges. While such materials have the potential of allowing novel 3-D topologies to be used, as well as providing major advantages in recycling at the end of the lifetime of the device, little or no design experience exists in this area. This paper proposes the use of sensitivity based topology optimization as a methodology for assisting designers in this task.

Efficient force calculations based on continuum sensitivity analysis

Using continuum design sensitivity analysis (CDSA), in conjunction with the virtual work principle, equations have been derived for calculating forces without the need to solve the adjoint system. The resultant expressions are similar to the Maxwell stress tensor, but have the important advantage of the integration taking place on the surface of material rather than in the air outside. Implementation of the scheme leads to efficient calculations and improved accuracy.

A novel scheme for material updating in source distribution optimization of magnetic devices using sensitivity analysis

A novel material updating scheme, which does not require intermediate states of a material used, is presented for source distribution optimization problems. A mutation factor to determine a degree of topological change in the next design stage on the basis of a current layout accelerates the convergence of an objective function. Easy implementation and fast convergence of the scheme are verified using two MRI design problems where current and permanent magnet distributions have been optimized, respectively.

Some key developments in computational electromagnetics and their attribution

Key developments in computational electromagnetics are proposed. Historical highlights are summarized concentrating on the two main approaches of differential and integral methods. This is seen as timely as a retrospective analysis is needed to minimize duplication and to help settle questions of attribution

Design of a 100 kVA high temperature superconducting demonstration synchronous generator

The paper presents the main features of a 100 kVA high temperature superconducting (HTS) demonstrator generator, which is designed and being built at the University of Southampton. The generator is a 2-pole synchronous machine with a conventional 3-phase stator and a HTS rotor operating in the temperature range 57–77 K using either liquid nitrogen down to 65 K or liquid air down to 57 K. Liquid air has not been used before in the refrigeration of HTS devices but has recently been commercialised by BOC as a safe alternative to nitrogen for use in freezing of food. The generator will use an existing stator with a bore of 330 mm. The rotor is designed with a magnetic core (invar) to reduce the magnetising current and the field in the coils. For ease of manufacture, a hybrid salient pole construction is used, and the superconducting winding consists of twelve 50-turn identical flat coils. Magnetic invar rings will be used between adjacent HTS coils of the winding to divert the normal component of the magnetic field away from the Bi2223 superconducting tapes. To avoid excessive eddy-current losses in the rotor pole faces, a cold copper screen will be placed around the rotor core to exclude ac magnetic fields.