Earlier alternators were developed by Michael Faraday and Hippolyte Pixii. Later Faraday developed the "rotating rectangle. Lord Kelvin and Sebastian Ferranti also developed early alternators. With time, alternators were designed for varying alternating-current frequencies.
Function of Alternators
The functioning of alternators is same as that of the DC generators. As the magnetic field around a conductor changes, a current is induced in the conductor. The rotating magnet or the rotor turns and it cuts the field across the conductors. Thus, an electrical current is produced which causes the rotor to turn. This rotating magnetic field causes an AC voltage in the stator windings.
In automobiles, alternators are used to charge the battery and to power a car's electric system when its engine is running. One of the biggest advantages of using alternators is that you do not have to use commutator. Therefore, the alternator becomes simpler, lighter, less expensive and rougher.
Alternators used in passenger vehicles and light trucks use Lundell or claw-pole field construction. Salient-pole alternators are used in larger vehicles. The modern day automotive alternators have a voltage regulator built into them. The efficiency of these alternators is limited by various factors like iron loss, fan-cooling loss, bearing loss, copper loss and the voltage drop in the diode bridges.
The automotive alternators used in buses are very large. The old automobiles with negligible lighting and electronic devices have 30-ampere alternator. The 70 amperes alternators are used in passenger cars and light trucks. The largest automotive alternators are mostly water-cooled or oil-cooled.
Alternators in Hybrid automobiles
Alternators in Hybrid automobiles are combined motor or generator that not only crank the internal combustion engine when starting, but also provides it with additional mechanical power for accelerating. They also charge a large storage battery when the vehicle is running at steady speed.
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