TAILIEUCHUNG - Handbook of Small Electric Motors Episode 2

Tham khảo tài liệu 'handbook of small electric motors episode 2', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | CHAPTER 2 MATERIALS Chapter Contributors Allegheny-Teledyne Joseph H. Bularzik Francis Hanejko Robert R. Judd Harold R. Kokal Robert F. Krause Phelps Dodge Company Joseph J. Stupak United States Steel Corporation William H. Yeadon The purpose of this chapter is to assist in the selection of materials used in electric motors. Material choices are largely a function of the motor s application. All materials commonly used in electric motors are covered in this chapter including lamination steel magnets wire and insulation. MAGNETIC MATERIALS Steel Selection Steel is used in most electric motors as the primary flux-carrying member. It is used in stator cores rotor cores armature assemblies field assemblies housings and shafting. It may be solid laminated or in powdered iron forms. Magnetic properties vary with the type being used. This section will cover the magnetic and mechanical properties of these steels. By way of review from Chap. 1 A rectangular block of magnetic material is wound with a coil of wire as in Fig. . If the coil of wire in Fig. gradually has its current increased from zero a magnetizing force 9 will be produced. The block of steel will be subjected to a magnetic field intensity H. Section contributed by William Yeadon Engineering Services PC. CHAPTER TWO MAGNETIC MATERIAL FIGURE Magnetization of materials. This field intensity is proportional to the current times the number of turns of wire per inch of magnetic material being magnetized rr H A turns in or A m As H is increased there is a flux established in the block of material. Since the area of the block is known the flux density is B lines in2 W m2 or T area As the current increases the flux density B is increased along the virgin magnetization curve shown in Fig. . Eventually B will be increased only as if the steel were air. This is called the saturation point of the material. As the applied field is decreased the flux density B is decreased but

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