AC Generator DC Generator & Electric Motor

AC Generator
The major parts of an AC generator are armature coil, field magnet, slip rings, brushes etc. The magnet, which produces magnetic flux in generator, is called field magnet. The direction of flux lines is from North Pole of the field magnet to South Pole.
An armature is a coil at which insulated conducting wire is wound over a laminated soft iron core. The slip rings are circular rings; fused to the ends of the coil. They rotate about the same axis as that of the armature. Brush is an arrangement that is always in contact with slip rings. Current flows to the external circuit through this.
Armature coil rotates continuously using mechanical energy. Simultaneously armature coil deflects the magnetic flux lines and emf is generated in the coil. This continuous motion of the armature coil helps to keep a constant current in the external circuit.
Let’s see the different steps in one complete rotation of the armature coil.
When the armature coil starts rotation, the angle between the axis of the coil and direction of flux be 00.There is no emf is induced in it because of no flux change. After that, the rotation of the armature coil cuts more flux lines and due to this the angle between the axis of the coil and flux becomes 900.Then maximum emf is induced in it. When the coil turns to 1800 with the flux lines, then also the emf becomes zero. When the angle turns from 1800 to 2700 then the direction of flux change become opposite, so the maximum emf is produced in opposite direction. When the coil turns from 2700 to 3600 ,the rate of flux changes reduced to zero and thus emf.
The number of cycles in one second is called the frequency of AC. The unit of frequency is hertz. The frequency of AC used in our house is 50Hz.
DC Generators
As in AC generator, the dc generator also has a field magnet and an armature coil. In dc generators the slip rings are replaced by split rings. In dc generators also, the emf induced by the armature coil is AC in nature. This emf is converted into DC using split ring commutator. The current flows to the external circuit through the graphite brush, is unidirectional.
Let’s see the difference between the emf from a dc generator and a battery.
The emf from battery is of constant intensity and without any fluctuations. But the emf from the dc source is pulsating.

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