Preface

Electric machines are being used in wide and novel applications throughout the world, driven by the need for greater power efficiency in the transportation, aerospace and defense, and industrial automation markets. The automotive sector is driven by the need for hybrid and electric vehicle technology to meet ever-stringent miles-per-gallon standards. The aerospace and defense sectors are focused on replacing existing power transfer technologies in an aircraft such as the central hydraulic system, with fault-tolerant electric power, where major subsystems such as engine starting, primary flight control actuation, pumps, and braking would be controlled and driven electronically. In the US industrial sector, over 40 million electric motors convert electricity into useful work in manufacturing operations. Industry spends over $30 billion (US) annually on electricity, dedicated to electric motor-driven systems that drive pumps, fan and blower systems, air compression, and motion control. Globally, 42% of all electricity is used in power industries, where two-thirds of this is consumed by electric motors. There is a clear global demand for a comprehensive design methodology to support these new applications and satisfy power efficiency requirements.

With the present trend of global industrial automation, the application of electric drive systems (including power electronics and drive control) is expected to grow rapidly in the next decade. In the automotive sector, the utilization of power electronics and their control to drive electric motors can significantly contribute to control environmental pollution. In addition, intensive environmentally clean photovoltaic and wind energy resources also show a bright future.

As part of electric drive systems, the power semiconductor devices at the heart of modern power electronics are under continuous development. The improved technology in semiconductor processing, device fabrication, and packaging to produce high-density, high-performance, high-reliability, and high-yielding microelectronic chips, together with new semiconductor material discovery, made possible significant reduction in energy consumption, driving these systems to an incredible economical price.

Without doubt, these achievements force the control strategy techniques to evolve rapidly to the newly created drive conditions and adapt to the overall systems performance requirements. In recent years, soft switching converters became the center of interest when compared with more conventional hard switching converters due to their major advantages such as:

• Minimization of switching loss
• Improved efficiency
• Improved reliability due to soft stress
• Reduced electromagnetic emission

The continuous growing interest in the electric drive area relates to the intelligent power electronics modules, where the power and the control are embedded in the same package and interface directly with logic signals. For variable frequency drives, the converter modules and control are mounted directly on the machine for the low and medium power applications.

Readers' Advantage

The book is mainly addressed to design engineers, application engineers, technical professionals, and graduate engineering students with a strong interest in electric machines and drives.

The comprehensive design approach described in this book 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 delivers the multiphysics know-how based on practical electric machine design methodologies. Simulation by design concept elevated in the book constitutes the new paradigm that frames the entire highlighted design methodology, which is described and illustrated by various advanced simulation technologies.

Which Design Problems Are We Trying to Solve?

Throughout this book, we apply knowledge of design best practices into multiphysics and multidomain simulation processes to address a complete electrical machine and drive design.

In the face of global competition, electric machine manufacturers, like manufacturers in most industries, are searching for ways to reduce cost, optimize designs, and deliver them quickly to market. Companies able to achieve these objectives hold a competitive advantage in the marketplace. The ability to predict design performance with simulation software without the time and expense of constructing prototypes plays a significant role in creating this competitive advantage.

Several computation approaches are available to predict electric machine performance, including classical closed-form analytical analysis, lumped parameter models based on the determination of detailed parameters from finite element analysis, and nonlinear time-domain finite element analysis. Each method has advantages and disadvantages. Selecting the best method may not be straightforward because it requires the user to understand the differences among the calculation methods. The fundamental issue differentiating these methods is the trade-off among model complexity, accuracy, and computing time. Engineers use a combination of these calculation techniques as the optimal solution to simulate electric machine performances.

What Motivated Us to Write This Book?

This collaborative work brought together a group of experts from both academia and software industry with strong expertise on electrical machine design and manufacturing. The main idea that fueled our initiative and commitment to make this project a reality was to bring back to the engineering and academic communities a comprehensive expertise and validated know-how on designing electrical machines by simulation.

Why Simulation by Design?

The advancements in modern digital computers brought CAD (computer-aided design) and CAE (computer-aided engineering) tools at the heart of virtual prototyping, reducing the time to design and market and saving cost by reducing and eliminating the physical prototyping need. The embedded 3D-physics design into drive system coupling with the power electronics and control algorithms enables the electric drive community to accurately predict the efficiency and performance of the electrical machine at the heart of the entire drive system.

Without doubt, the design of a simulation model-a virtual prototype-can help tremendously the engineers to build confidence on validating the required technical specifications making critical decisions on design realization and understanding the level of design complexity considering inter-dependencies and design parameter variations, and collaboratively to examine strategic choices for optimization and robustness.

Chapter Description

Chapter 1: Basics of Electrical Machines Design and Manufacturing Tolerances

This chapter discusses fundamental aspects of the state-of-the-art design process and includes examples from industrial practice and case studies to introduce basic concepts and methods. This chapter emphasizes the basic steps in designing a typical electrical machine using power traction application as an example. The chapter starts with magnetic sizing steps and it extends the basic design to thermal constraints. Typical electric motor characteristics used in traction applications such as efficiency map of standardized driving cycles are considered to highlight the electric motor sustainability on dynamic performance. The chapter concludes with the robust design analysis framing a methodology that applies stochastic analysis to study manufacturing tolerances.

Chapter 2: FEM-Based Analysis Techniques for Electrical Machine Design

In this chapter, a detailed description of finite element method (FEM) employed in ANSYS Maxwell software is presented. The numerical technique developed to account for eddy currents in conductive domains on configurations that involve rigid motion is presented, the numerical technique related to multiply connected regions is highlighted, and it also presents the algorithms used for nonlinear iterations and strategies to accelerate the nonlinear convergence. Filed-circuit coupling technology is explained and specific algorithms used to reduce the computation time to reach steady-state conditions are described. High-performance computing (HPC) is a key technology, increasing the capacity of solving large design spaces and reducing significantly the total time computation by solving the time steps on magnetic transient problem simultaneously rather than sequentially. All technologies highlighted in this chapter are explained through sets of case studies.

Chapter 3: Magnetic Material Modeling

This chapter introduces advanced magnetic material modeling capabilities employed in numerical computation. From isotropic nonlinear characteristics to anisotropic behavior corresponding to grain-oriented magnetic materials, the chapter describes the implementation aspects and detailed modeling techniques. Lamination topologies are considered based on special modeling technique with emphasis on core loss computation. Advanced magnetic modeling on vector magnetic hysteresis is presented and specific case studies are used to highlight the computational merits.

Chapter 4: Thermal Problems in Electrical Machines

In this chapter, the heat generation and extraction in...