Mechanical Design and Manufacturing of Electric Motors

Wei Tong

• Editore: CRC Press
• Anno: 2022
• ISBN:
  9781000555103
• Edizione: 2
• Argomento: Design
• Categoria: Industrial Design

This Second Edition of Mechanical Design and Manufacturing of Electric Motors provides in-depth knowledge of design methods and developments of electric motors in the context of rapid increases in energy consumption, and emphasis on environmental protection, alongside new technology in 3D printing, robots, nanotechnology, and digital techniques, and the challenges these pose to the motor industry.

From motor classification and design of motor components to model setup and material and bearing selections, this comprehensive text covers the fundamentals of practical design and design-related issues, modeling and simulation, engineering analysis, manufacturing processes, testing procedures, and performance characteristics of electric motors today. This Second Edition adds three brand new chapters on motor breaks, motor sensors, and power transmission and gearing systems. Using a practical approach, with a focus on innovative design and applications, the book contains a thorough discussion of major components and subsystems, such as rotors, shafts, stators, and frames, alongside various cooling techniques, including natural and forced air, direct- and indirect-liquid, phase change, and other newly-emerged innovative cooling methods. It also analyzes the calculation of motor power losses, motor vibration, and acoustic noise issues, and presents engineering analysis methods and case-study results.

While suitable for motor engineers, designers, manufacturers, and end users, the book will also be of interest to maintenance personnel, undergraduate and graduate students, and academic researchers.

1 Introduction to Electric Motors

DOI: 10.1201/9781003097716-1

Electric motors are devices that convert electrical energy into magnetic energy and finally into mechanical energy. Electromagnetism is the basis of electric motor operation by generating magnetic forces necessary to produce either rotational or linear motion. For rotating electric motors, it is the interaction between the stator and rotor magnetic fields that creates motor torque to drive external loads.

Today, electric motors come in a wide variety of types, sizes, styles, winding topologies, magnetic flux loops, operating characteristics, and structural configurations to suit different applications. They have been used almost everywhere in the world, including industrial drives, household appliances, medical devices, electronic products, robots, drones, electrified vehicles, machine tools, spacecrafts, and military equipment. As one of the fastest-growing industrial sectors, electric motor manufacturing represents a major industry worldwide. According to the study conducted by the International Energy Agency [1.1], electric-motor-driven systems account for approximately 53% of total global electricity consumption, or 10,500 terawatt hours (TWh) per year, and emit a total of 6,800 metric tons of carbon dioxide. By 2030, energy consumption from electric motors is expected to rise to 13,360 TWh per year, ticking up CO₂ emissions to 8,570 million metric tons per year. End users now spend USD 565 billion annually on electricity used in these motor-driven systems and by 2030, that could rise to close USD 900 billion [1.2]. In the United States, motor-driven equipment accounts for 64% of the electricity consumed in the manufacturing sector. That is approximately 290 billion kilowatt hours (kWh) of power per year [1.3]. There are more than 40 million electric motors used in manufacturing operation [1.4]. In addition, more than 95% of electric motor’s life-cycle cost is the energy cost. In China, the total power consumption of electric motors is about 3 trillion kWh, accounting for about 64% of the total power consumption [1.5, 1.6]. It is estimated that improving the efficiency of all the world’s motors by just 1% would reduce the motor power consumption by 94.5 TWh of electricity and shrink their CO₂ footprint by the equivalent of 60 million metric tons per year [1.7]. This would significantly reduce the need for new power plants and push down the total environmental cost of electricity generation. There is no doubt that the continuous push for decarbonization will greatly increase global demand for more efficient electric motors.

The report that provides information on the industrial motor market growth, trends, and forecast during the period of 2020–2025 by Motor Intelligence was released in 2019 [1.8]. According to the report, the global market of industrial motors is expected to register a compound annual growth rate of 6.11% during 2020–2025 and reaches a market value of USD 64.25 billion by 2025. However, it is worth noting that this report did not consider the consequence of the COVID-19 pandemic that has severely upended global economy. According to World Trade Organization, the volume of world merchandise trade declined by 5.3% in 2020 as the COVID-19 pandemic disrupts normal economic activity all over the world and is expected to increase by 8.0% in 2021 [1.9]. Nevertheless, in the long term, the market will generate remunerative prospects for producers post COVID-19 crisis. Substantial advances in technology have opened up opportunities to develop and manufacture electric motors for a wide range of applications in industries, such as automation, automotive, agriculture, aerospace, construction, power generation, and other industrial sectors.

1.1 History of Electric Machines

Both electric motors and generators are integral parts of electric powered machines. They have a similar structure, current-carrying loop, and operating mechanisms for converting energy between the electrical form and the mechanical form. However, they have significant differences in terms of function, driving mode, rule followed (e.g., the motor follows Fleming’s left-hand rule, and the generator follows Fleming’s right-hand rule), and power source.

The discoveries of phenomena of static electricity can be traced back to ancient Greece about 2,600 years ago. However, there was little real progress until the English scientist William Gilbert in 1600 described the electrification of many substances and coined the term electricity, the Greek word for amber.

In 1742, Andrew Gordon invented a simple electrostatic device known as electric chimes [1.10]. This is the first device that converts electrical energy into mechanical energy in the form of repeating mechanical motion [1.11]. This device was further developed by Benjamin Franklin in 1752 to detect approaching thunderstorms. Hans Oersted discovered electromagnetism in 1820 and additional works were made by a number of other scientists such as William Sturgeon, Joseph Henry, Ander Marie Ampere, Michael Faraday, Thomas Davenport, Moritz von Jacobi, and Antonio Pacinotti. In 1831, Michael Faraday discovered electromagnetic induction, the principle behind the electric motor and generator. This discovery was crucial in allowing electricity to be transformed from a curiosity into a powerful new technology.

Using a broad definition of motion as meaning any apparatus that converts electrical energy into motion, it is widely accepted that Michael Faraday invented the first direct current (DC) electric motor in 1821. This motor was basically used to confirm his concept of electric motor and had no actual value in application. He succeeded in building the practical electric motor 10 years later. Following his groundbreaking work, many scientists had contributed to the development of electric motors. William Sturgeon invented the first commutator DC electric motor capable of turning machinery in 1832 [1.12]. Moritz von Jacobi built an electric motor in 1834 that actually developed a remarkable output power (about a power of 15 W). The improved version of his motor was released in 1838, which was capable of 300 W output power and could drive a boat occupied with 14 people across a wide river, powered by zinc batteries [1.13]. The first US patent on electr...