AC Generator Vs. DC Generator

Difference Between AC Generator And DC Generator

Ac and DC generators are the two main types of generators. AC generators produce alternating current. This is electric current that reverses the direction in which it flows. In a typical AC generator, the current in the armature and the external circuit changes direction many times each second.
DC generators produce direct current which always flows in the same direction. In a DC generator, just as in an AC generator, the current in the armature changes direction. But the current in the external circuit flows in one direction.
The way the armature is connected to the outside circuit determines whether the outside circuit carries AC or DC current. In an AC generator, each end of the armature coil is connected to its own metal slip ring. And each of these two slip rings slides against its brush, which is a piece of carbon. The brushes are connected to the outside circuit.
Same brush connects each end of the armature. This means each end of the armature is always connected to the same end of the external circuit. The current in the external circuit changes direction every time the current in the armature changes direction. Thus the external circuit carries alternating current.
A DC generator is similar to an AC generator. But there is one important difference. Each end of the armature coil is connected to one half of a single split ring instead of two separate slip rings. This split ring is called a commutator. Each half of the commutator is separated by a gap or insulation.
In a DC generator, the magnets still induce alternating current in the rotating armature. Each time the armature rotates half a turn, the current in the armature reverses direction. But at the moment the current in the armature reverses, the gap between the commutator pieces lines up with the brushes. In the next instant, each commutator piece connects with the opposite brush. In this manner, one brush always collects the current from the armature. And the other brush always returns the current to the armature. Therefore, the current in the outside circuit flows in the same direction at all times.

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  • swagatam

    How does  the output wave from a DC generator look like? Is it a straight line or square waves?

    Thanks, 
    Swagatam