Generators

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Production of Electric energy

Basic of generation of electric energy is a change in magnetic field and a coil placed near it connected to the load. When a magnetic filed changes, an emf is induced with a frequency in respect to the change in magnetic flux. Since coil is connected to load, a load current also flows.Here in the picture, the magnet attached to the spin wheel rotates when water hits it. So it creates a change in magnetic flux. This induces a power in the coil connected to the load. Thus the bulb illuminates.




You may know that how Electrical/Electronic equipments work. Fundamentals for such device is electric power. Since energy can neither be created,  electric power is generated through the process like conversion of mechanical energy, heat energy, wind energy, light energy, etc. More used method in this world is conversion of mechanical energy. Basically the generating stations are classified according to the fuel used for the generation. Here fuel means, the stored energy which is used to generate the mechanical power. For example, in hydroelectric power stations water is the fuel, in wind power stations flow of air is the fuel. Thermal and Nuclear power stations use steam pressure of water to induce the mechanical force to the turbine(prime mover).

Generator consist of many parts. Main such parts are

• Stator Winding
• Field Winding
• Prime mover
• Exciter

 Stator winding are the conductors into which the electromotive force due to change in magnetic flux is induced. These are connected to the grid to supply power for the connected load/ consumers.

Field winding is a field coil used to generate a magnetic field in an electro-magnetic machine, typically a rotating electrical machine such as a motor or generator. It consists of a coil of wire through which a current flows.

In a diesel-electric locomotive, the prime mover is the diesel engine that rotates the main generator responsible for producing electricity to power. In a hydro electric power generator, the prime mover is the turbine that rotates the main generator responsible for producing electricity to power.

An electric generator or electric motor consists of a rotor spinning in a magnetic field. The magnetic field may be produced by permanent magnets or by field coils. In the case of a machine with field coils, a current must flow in the coils to generate the field, otherwise no power is transferred to or from the rotor. The process of generating a magnetic field by means of an electric current is called excitation. This arrangement is known as Excitor.

Generators are classified as:

Electrostatic generators : are those operated on electrostatic principles, by using moving electrically charged belts, plates, and disks that carried charge to a high potential electrode. The charge was generated using either of two mechanisms: electrostatic induction or the triboelectric effect. Such generators generated very high voltage and low current. Because of their inefficiency and the difficulty of insulating machines that produced very high voltages, electrostatic generators had low power ratings, and were never used for generation of commercially significant quantities of electric power. Their only practical applications were to power early X-ray tubes, and later in some atomic particle accelerators.

Direct Current[DC] generators  ;  A dc generator is an electrical machine which converts mechanical energy into direct current electricity. This energy conversion is based on the principle of production of dynamically induced emf.

Alternating Current[AC] generators  ;  Is the same to direct-current generator. The basic principle of a generator is to convert motion into electricity. Providing this motion requires that either a magnetic field is generated and a wire coil is rotated within it, or a magnetic field is rotated within a stationary coil. The turning of a coil in a magnetic field produces motional emfs in both sides of the coil which add. Since the component of the velocity perpendicular to the magnetic field changes sinusoidally with the rotation, the generated voltage is sinusoidal or AC.