Alternating Current (AC) generator is the most important means of producing electrical power. Because most of the electrical power used aboard Navy ships and aircraft as well as in civilian applications is AC. AC generators, generally called alternators, vary greatly in size depending upon the load to which they supply power. For example, the alternators in use at hydroelectric plants, such as Hoover Dam which are tremendous in size, generating thousands of kilowatts at very high voltage levels.

Alternating current (AC) generators also called synchronous generatorsare the primary source of all the electric energy we consume. These machines are the largest energy converters in the world. Generator is a machine that uses magnetism to convert mechanical energy into electric energy. The principle of an AC generator operation are following: a wire loop rotates within the magentic field generated by a magnet, which induces an AC voltage between the loop terminals.

The amount of voltage induced in a conductor as it moves through a magnetic field depends on:

  • The strength of the magnetic field. The stronger the field the more voltage induced.

  • The speed at which the conductor cuts through the flux. Increasing the conductor speed increases the amount of the voltage induced.

  • The angle at which the conductor cuts the flux. Maximum voltage is induced when the conductor cuts the flux at 90­0 , and less voltage is induced when the angle is less than 900.

  • The length of the conductor in magnetic field. If the conductor is wound into a coil of several turns, its effective length increases, and so the induced voltage will increase.

Alternating current generators are built with either a stationary or a rotating dc magnetic field. The stationary field type is usually of relatively small kilovolt-ampere capacity and low voltage rating.