chapter 4 dc machine Dristi.pdf

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Overview of Direct Current Machines
u Direct -current (DC) machines are divided int o dc generat ors and dc
mot ors.
u Most DC machines are similar t o AC machines: i.e. t hey have AC
volt ages and current wit hin t hem.
u DC machines have DC out put s j ust because t hey have a mechanism
convert ing AC volt ages t o DC volt ages at t heir t erminals.
u This mechanism is called a commut at or ; t herefore, DC machines are
also called commut at ing machines.
u DC generat ors are not as common as t hey used t o be, because direct
current , when required, is mainly produced by elect ronic rect ifiers.
u While dc mot ors are widely used, such aut omobile, aircraft , and
port able elect ronics, in speed cont rol applicat ions…