Alternators

The alternator is an AC generator. The working principle of this device is electromagnetic induction. Here conversion of mechanical energy into electrical energy is being done by an electrical machine. Here armature is stationary and hence we can easily insulate it even at higher voltages. It is quite easy to tap electrical energy from stationary armature. Slip rings are brushes are not used here. Operation at higher speeds possible here resulting in larger output. An alternator is composed of a single armature winding mounted on the stator and field windings mounted on the rotor to provide the required magnetic field. A cast iron frame is used as stator. This frame supports the armature core. The two types of rotors used here are projecting pole rotor and smooth cylindrical pole rotor. Projecting pole rotor is used in low and medium speed alternators. Here core is cylindrical made of cast steel with poles rigidly fixed to the core. Cylindrical pole rotor is used in high speed alternators. Three adverse effects experiencing here are voltage drop due to armature resistance, voltage drop due to armature reaction and voltage drop due to leakage reactance.