TAILIEUCHUNG - Handbook of Small Electric Motors Episode 1

Tham khảo tài liệu 'handbook of small electric motors episode 1', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | CHAPTER 1 BASIC MAGNETICS Chapter Contributors Mark A. Juds Earl F. Richards William H. Yeadon Electric motors convert electrical energy into mechanical energy by utilizing the properties of electromagnetic energy conversion. The different types of motors operate in different ways and have different methods of calculating the performance but all utilize some arrangement of magnetic fields. Understanding the concepts of electromagnetics and the systems of units that are employed is essential to understanding electric motor operation. The first part of this chapter covers the concepts and units and shows how forces are developed. Nonlinearity of magnetic materials and uses of magnetic materials are explained. Energy and coenergy concepts are used to explain forces motion and activation. Finally this chapter explains how motor torque is developed using these concepts. UNITS Although the rationalized mks system of units Système International SI units is used in this discussion there are also at least four other systems of units cgs esu emu and gaussian that are used when describing electromagnetic phenomena. These systems are briefly described as follows. MKS. Meter kilogram second. CGS. Centimeter gram second. Sections to contributed by Mark A. Juds Eaton Corporation. CHAPTER ONE ESU. CGS with e0 1 based on Coulomb s law for electric poles. EMU. CGS with T0 1 based on Coulomb s law for magnetic poles. Gaussian. CGS with electric quantities in esu and magnetic quantities in emu. The factor 4n appears in Maxwell s equation. Rationalized mks. p0 4n X 10-7 H m based on the force between two wires. Rationalized cgs. p0 1 based on Coulomb s law for magnetic factor 4n appears in Coulomb s law. The rationalized mks and the rationalized cgs systems of units are the most widely used. These systems are defined in more detail in the following subsections. The MKS System of Units The rationalized mks system of units also called SI units uses .