Published online by Cambridge University Press: 16 July 2025
Introduction
In the next few chapters we shall be engaged in discussions on electrical machines. An electrical machine is an ‘electro-mechanical’ rotating device. Well, is it perfect to call an electrical machine an ‘electro-mechanical’ device? Partly yes, but not exactly. We may better call it an ‘electromagnetic-mechanical’ device. Now what is it all about? A machine is a system which transforms energy. Generally, a machine transforms electrical energy of an electric circuit to a mechanical system via a magnetic circuit or vice-versa. So we can simply draw the transformation of energy in an electric machine by a single line diagram as follows:
Fig. 8.1a represents the action of a generator while Fig. 8.1b shows the action of a motor. Thus, electric machines are of two types namely generator and motor.
Well, are we absolutely right? Yes, partially but not completely. In the next chapter, this myth of machine as ‘electro-mechanical’ convertor will be destroyed. We shall see that a transformer does not really have a mechanical part and yet it is an electrical machine (static). A transformer transforms electrical energy of one electric circuit to another via a magnetic circuit.
Fig. 8.2 is showing the action of a transformer. Thus, a transformer can be called an ‘electro-magneto-electrical’ static device.
In chapter 4 we have seen that when a conducting coil is rotated in a magnetic field, an AC voltage will be induced in the coil. Similarly, if we supply AC voltage to the same coil it will show the motoring action.
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