Topics Tagged ‘Generator’
When an electrical conductor is moved so as to cut lines of magnetic induction, charged particles in the conductor experience a force in a direction mutually perpendicular to the B field and to the velocity of the conductor. The negative charges tend to move in one direction, and the positive charges in the opposite direction. This induced electric field, or motional emf, provides the basis for converting mechanical energy into electrical energy. In conventional steam power plants, the heat released by the fuel is converted into rotational mechanical energy by means of a thermo cycle and the mechanical energy is then used to drive the electric generator. Thus two stages of energy conversion are involved in which the heat to mechanical energy conversion has inherently very low efficiency.
Also, the rotating machine has its associated losses and maintenance problems. In MHD generation, electrical energy is directly generated from hot combustion gases produced by the combustion of fuel without moving parts. The conventional electrical machines are basically electro mechanical converters while an MHD generator is heat engine operating on a turbine cycle and transforming the internal energy of gas directly into electrical energy.
AC Generators come in two basic types – synchronous and non-synchronous. Synchrono us generators lock in with the fundamental line frequency and rotate at a syn-chronous speed related to the number of poles similar to that of AC Synchronous motors. Synchronous generator stator windings are similar to a three-phase synchronous motor stator winding. Synchronous generator rotor fields may be either salient or non-salient pole. Salient Pole (also called spider or projected pole) means the rotor has distinct pole windings mounted on the rotor shaft using dovetail joints. These pole windings are wound around field poles. Salient Pole rotors are most commonly used in slow speed applications and tend to be at least six poles. Salient pole rotors typically have damper windings to reduce rotor oscillations (caused by large flux changes between the individual poles) during operation.