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Chapter 7
DC machines
7.1 Introduction
Direct current (dc) machines were the first electrical machines that
came to industrial use. The use of dc machines is now very much lim-
ited since the power supply is usually available in AC only. However,
they are still used in certain applications like traction, cranes etc.
There are two types of dc machines, the dc generator and the dc
motor. The dc machine which converts mechanical energy into elec-
trical energy is called a dc generator. The dc machine which converts
electrical energy into mechanical energy is called a dc motor.
Mechanical energy Generator Electrical energy
(a) Generator
Electric energy Motor Mechanical energy
(b) Motor
Figure 7.1: Schematic representation of generator and motor
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