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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.
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.
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].
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 ed through the action of a magnetic field [1].
Part4 Electronic Technology
Unit 1 Electrical Machines Unit 2Control System Fundamentals Unit 3Applications of Automatic Control
Unit 1 Electrical Machines
Rotating electrical machines have an outside (i.e., stationary) part which is called the stator and an inner (i.e., rotating) part which is called the rotor. As shown in Fig 4.1.1, the rotor is centered within the stator, and the space that is located between the outside of the rotor and the inside of the stator is called the air gap.
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, there are other rotating and linear machines that will not be included here. They operate basically on the same principles.
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.
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.