Marius Rosu

Hysteresis model for finite-element analysis of permanent-magnet demagnetization in a large synchronous motor under a fault condition

This paper describes a rare-earth-transition metal alloy permanent-magnet (Nd/sub 2/Fe/sub 14/B) hysteretic behavior model within finite-element analysis. The present work analyzes the demagnetization states of permanent magnets during fault conditions in a permanent-magnet synchronous motor and characterizes the ability of the motor to sustain the designed rated outputs after the fault conditions occur.

Automated Multi-Objective Design Optimization of PM AC Machines Using Computationally Efficient FEA and Differential Evolution

The design optimization methods described in this paper are employing an ultrafast computationally efficient finite element analysis technique. A minimum number of magnetostatic solutions are used for the analysis, which makes possible the study of thousands of candidate motor designs with typical PC-workstation computational resources. A multi-objective differential evolution algorithm that considers a large number of independent stator and rotor geometric variables and performance criteria, such as average and ripple torque, losses, and efficiency, is used. The optimization method is demonstrated on different permanent magnet (PM) ac synchronous motors in the kilowatt and megawatt power ranges. For the low-power PM ac machine study, a nine-slot six-pole topology is considered. For the high-power PM ac machines, four case studies were carried out with the following: fractional-slot embedded surface PM (SPM), fractional-slot interior PM (IPM), integer-slot SPM, and integer-slot IPM, respectively. Four motor topologies are systematically compared based on optimal Pareto sets. The design optimization of IPM motors includes an additional search for an optimum operating torque angle corresponding to the maximum-torque-per-ampere condition.

Automated bi-objective design optimization of multi-MW direct-drive PM machines using CE-FEA and differential evolution

Design optimization of a multi-MW direct-drive PMAC machine based on computationally efficient-FEA (CE-FEA) and multi-objective differential evolution (DE) algorithm is presented in this paper. The CE-FEA based models allow ultra-fast analysis and design of synchronous electric machinery. In this work, a DE algorithm is used to vary a large number of stator and rotor parameters to optimize multiple objectives, such as average torque, efficiency, the cogging and the ripple torques that are evaluated using CE-FEA. The method is demonstrated on a motor for a direct-drive rated at 20 MW and 150 r/min. The following four case-study machines are optimized: 1) fractional-slot embedded surface-PM, 2) fractional-slot interior-PM, 3) integer-slot embedded surface-PM, and 4) integer-slot interior-PM. Design optimization of interior-PM machines includes an additional search for an optimum operating torque angle corresponding to the maximum torque per ampere (MTPA) condition.

A New Algorithm to Consider the Effects of Core Losses on 3-D Transient Magnetic Fields

As a follow-up to our previous effort to consider the effects of steel lamination core loss on 3-D transient magnetic fields, a new algorithm is proposed to eliminate possible convergence problems and improve computation efficiency when a strong eddy core-loss component is involved. The proposed approach is validated by two application examples in terms of the power-balance testing, that is, the increase of input power between considering the core-loss effects and without considering core-loss effects must be equal to the total core losses.

Time decomposition method for the transient simulation of low-frequency electromagnetics

A highly robust and efficient parallel computing method for the transient simulation of low-frequency electromagnetics is proposed. In this method, time subdivision is introduced to control the memory usage and nonlinear convergence and a block forward substitution method is applied to solve the formulated block matrix.

Construction of magnetic hysteresis loops and its applications in parameter identification for hysteresis models

This paper presents an algorithm to construct the major and symmetric minor hysteresis loops based on the normal magnetization curve, the intrinsic coercivity, and optionally the residual flux density. All these input data are normally available from the manufacturers. Some typical hysteresis loops constructed from the magnetization curve are validated by the measured hysteresis loops. Two application examples are presented: 1) to identify the parameters of classic Preisach model based on the constructed hysteresis loops; 2) to identify the parameters of a play model, and then to simulate a hysteresis motor based on the constructed major loop.

Complete Nonlinear Magnetic-Thermal-Stress Design of Radial Field Multipole NdFeB Permanent Magnet Cylinder

This paper presents a complete modeling approach for the analysis of the magnetization of a radial field multipole NdFeB permanent magnet cylinder. The simulation approach involves the 3D finite element parametric study of a permanent magnet rotor structure to extract electromagnetically equivalent state space variables. These variables are transferred to a circuit simulator where the genetic algorithm is used to optimize the circuit parameters of the magnetizing fixture. To validate the results of the optimized solution, a 3D time-stepping finite element analysis coupled with an embedded circuit simulator is employed. Further, a transient thermal analysis is performed to determine the effect of the resistive losses in the permanent magnet during the electromagnetic pulse. The high forces generated during magnetization process are solved by means of a 3D finite element analysis static stress simulation and the structural deformation is computed

Multiphysics simulation by design for electrical machines, power electronics and drives

This book combines the knowledge of experts from both academia and the software industry to present theories of multiphysics simulation by design for electrical machines, power electronics, and drives. The comprehensive design approach described within supports new applications required by technologies sustaining high drive efficiency. The highlighted framework considers the electric machine at the heart of the entire electric drive. The book also emphasizes the simulation by design concept—a concept that frames the entire highlighted design methodology, which is described and illustrated by various advanced simulation technologies.

Decoupled magnetoelastic finite element method including magnetostriction effects in electrical machinery applications

Magnetostriction is one of the main causes of noise and vibration in electric machinery and equipment. A decoupled method is proposed to handle the computation of magnetostriction effects and inverse magnetostriction effects in ferromagnetic materials. To consider effect of magnetostriction in structure solver, the derived magnetostriction from magnetic field solution is converted to volumetric force density and applied as external load. The effect of invers magnetostriction on magnetic field is taken account by reconstructing the nonlinear BH curves along each local major axis. The proposed method can be applied to model magnetostriction on different mesh with different solver. With this method, the magneto-elastic Multiphysics coupling can be handled with great flexibility and reliability.

Analytical computation of end-winding leakage inductance for multi-phase AC machines

An analytical method that considers both fringing and leakage fluxes in the winding end region is proposed to compute the end-winding leakage inductance. The fringing effects are considered by a small equivalent core extension which produces the same flux linkages in the coils. To compute the leakage inductance related to the leakage fluxes, the end coils are modeled by serially connected helical filaments. The Neumanns integrals for the computation of the mutual inductance between any two filaments are performed by the algorithm of 2D 5-point Gaussian quadrature.