机电专业英语 教学课件 作者 姚永玉 常云朋 周丽丹 20186 Part4 Electronic Technology.pptVIP

Part4 Electronic Technology Unit 1 Electrical Machines Reading Target 1．Understand the definition of motor and generator. 2．Know the construction and principles of synchronous machines. 3．Grasp the classification of electrical machine and what is the difference between the classification of the rotary motor and linear motor. Text In general, an electrical machine can be defined as an apparatus that can be used either to convert electrical energy into mechanical energy or to convert mechanical energy into electrical energy. If such a machine is used to convert electrical energy into mechanical energy, it is called a motor; however, if it is used to convert mechanical energy into electrical energy, it is called a generator. Any given machine can convert energy in either direction and can therefore be used either as a motor or as a generator. Such conversion is facilitated through the action of a magnetic field [1]. A generator has a rotary motion provided by a prime mover which supplies mechanical energy input. The relative motion between the conductors and the magnetic field of a generator produces an electrical energy output. On the other hand, a motor has electrical energy supplied to its windings and a magnetic field that generates an electromagnetic interaction to produce mechanical energy or torque[2]. In general, each machine has a nonmoving (i.e., stationary) part and a moving (i.e., nonstationary) part. Depending on whether such a machine functions as a generator or a motor, the moving part that is attached to a mechanical system receives mechanical input or provides mechanical output. The motion of such a moving part can be linear (e.g., as in linear motors) ; vibrating or reciprocating (e.g., as in various electrical razors ); or rotating. In this unit, only the rotating electrical machines will be reviewed. They include (1) polyphase synchronous machines, (2) polyphase induction (also called asynchronous) machines, and (3) DC machines. However, the