Presentation Himanshu Dubey ELECTRIC GENERATOR .pptx

ELECTRIC GENERATOR

1. BANYAN TREE SCHOOL JAGDISHPUR AMETHI SEMINAR TOPIC ELECTRIC GENERATOR SUBMITTED TO MR. MANOJ SRIVASTVA (HOD,PHYSICS DEPARTMENT) UNDER THE SUPERVISION OF MR. ALOK MISHRA SUBMITTED BY HIMANSHU DUBEY

2. CONTENT INTRODUCTION HISTORY PARTS AND FUNCTION EFFICIENCY RESULT WORKING LOSSES USES

3. INTRODUCTION AC generator is a machine that converts mechanical energy into electrical energy. The AC Generator’s input supply is mechanical energy supplied by steam turbines, gas turbines and combustion engines. The output is alternating electrical power in the form of alternating voltage and current. AC generators work on the principle of  Faraday’s law of electromagnetic induction , which states that electromotive force – EMF or voltage – is generated in a current-carrying conductor that cuts a uniform magnetic field. This can either be achieved by rotating a conducting coil in a static magnetic field or rotating the magnetic field containing the stationary conductor. The preferred arrangement is to keep the coil stationary because it is easier to draw induced alternating current from a stationary armature coil.

4. Faraday disk generator The operating principle of electromagnetic generators was discovered in the years of 1831–1832 by  Michael Faraday . The principle, later called  Faraday's law , is that an  electromotive force  is generated in an electrical conductor which encircles a varying  magnetic flux . Brage also built the first electromagnetic generator, called the  Faraday disk ; a type of  homopolar generator , using a  copper  disc rotating between the poles of a horseshoe  magnet . It produced a small  DC voltage . This design was inefficient, due to self-cancelling counterflows of  current  in regions of the disk that were not under the influence of the magnetic field. While current was induced directly underneath the magnet, the current would circulate backwards in regions that were outside the influence of the magnetic field. This counterflow limited the power output to the pickup wires and induced waste heating of the copper disc. HISTORY

5. PARTS AND FUNCTION FIELD The field in an AC generator consists of coils of conductors within the generator that receive a voltage from a source (called excitation) and produce a magnetic flux. The magnetic flux in the field cuts the armature to produce a voltage. This voltage is ultimately the output voltage of the AC generator. ARMATURE The armature is the part of an AC generator in which voltage is produced. This component consists of many coils of wire that are large enough .

6. . PRIME MOVER The prime mover is the component that is used to drive the AC generator. The prime mover may be any type of rotating machine, such as a diesel engine, a steam turbine, or a motor. ROTOR The rotor is driven by the generator’s prime mover, which may be a steam turbine, gas turbine, or diesel engine. Depending on the type of generator, this component may be the armature or the field. STATOR Like the rotor, this component may be the armature or the field, depending on the type of generator .

7. SLIP RINGS In a DC generator, a commutator was used to provide an output whose current always flowed in the positive direction. Slip rings are used in AC generators because the desired output of the generator is a sine wave. The slip ring consists of a circular conducting material that is connected to the rotor windings and insulated from the shaft. Brushes ride on the slip ring as the rotor rotates. The electrical connection to the rotor is made by connections to the brushes. Slip rings are electrical connections that are used to transfer power to and from the rotor of an AC generator.

8. EFFICIENCY Expression for Instantaneous E.M.F Produced: Let position of the coil at any time t. It make angle q with vertical .  If w is uniform angular speed of the coil. Then q = wtB be the strength of magnetic field n be the number of turns in the coil and A area of the coil then magnetic flux with the coil in this position is given by: f = nBA Cos q =  nBA Cos wt . Differentiate w.r.t. time = nBA (-Sin wt ) w = - nBA w Sin wt e = - (-nBA w Sin wt) maximum value of e.m.f. say E0 e = E0 Sin wt .

9. 1) Efficiency of an AC generator is the ratio of the useful power output to the total power input. 2) Because any mechanical process experiences some losses, no AC generators can be 100 percent efficient. 3) Efficiency of an AC generator can be calculated using Equation. 4) Efficiency =(Output /Input )x 100

10. RESULT WHEN THE AXLE OF GENERATING MOTOR IS ROTATED, E.M.F. IS PRODUCED BY IT.        REASON:   CHANGE IN FLUX THROUGH THE WINDING OF MOTOR. THIS E.M.F. REMAINS IN THE CIRCUIT AS LONG AS AXLE IS ROTATED.        HENCE, FARADAY’S LAW OF ELECTROMAGNETIC INDUCTION IS VERIFIED. AS THE SPEED OF ROTOR IS INCREASED, THE VOLTAGE AND CURRENT PRODUCED BY GENERATOR ALSO GET INCREASED.       REASON:  RATE OF CHANGE OF FLUX INCREASES.

11. Working of An Electric Generator The working of the transformer is explained. All metals contain a movable substance called "electric charge". Even uncharged wires are full of charge ! After all, the atoms of the metal are made half of positive protons and half of negative electrons .Metals are special because their electrons don't stay connected to the metal atoms, instead they fly around inside the metal and form a type of electric "liquid ” inside the wires. All wires are full of electric fluid. Modern scientists call this the "electron sea" or "electron gas." It is not invisible, it actually gives metals their silvery shine. The electron gas is like a fluid. When a circle of wire surrounds a magnetic field, and the magnetic field then changes , a circular "pressure" called Voltage appears. This circular voltage try to force the movable charges in the wire to rotate around the circle. In other words ,moving magnets create electric currents in closed circles of wire.  A moving magnet causes a pumping action. If the circuit is not complete, if there is a break, then the pumping force will cause no charge flow.

12. ARMATURE This is a basic law of physics, and it is used by all coil/magnet electric generators. When the circuit is closed and the magnet is moving, charges in the metal are forced to flow. The charges of the light bulb's filament are pushed along. When the charges within the copper wire pass into the thin light bulb filament, their speed greatly increases .

13. LOSSES IN AC GENERATOR Internal Voltage Drop The load current flows through the armature in all AC generators. The armature has some amount of resistance and inductive reactance. The combination of these make up what is known as the internal resistance, which causes a loss in a n AC generator. When the load current flows, a voltage drop is developed across the internal resistance. This voltage drop subtracts from the output voltage and, therefore, represents generated voltage and power that is lost and not available to the load. HYSTERESIS LOSSES Hysteresis losses occur when iron cores in an AC generator are subject to effects from a magnetic field .

14. The magnetic domains of the cores are held in alignment with the field in varying numbers, dependent upon field strength. The magnetic domains rotate, with respect to the domains not held in alignment, one complete turn during each rotation of the rotor. This rotation of magnetic do mains in the iron causes friction and heat. The heat produced by this friction it is called Hysteresis losses . MECHANICAL LOSSES Rotational or mechanical losses can be caused by bearing friction, brush friction on the commutator, and air friction (called windage), which is caused by the air turbulence due to armature rotation. Careful maintenance can be instrumental in keeping bearing friction to a minimum. Clean bearings and proper lubrication are essential to the reduction of bearing friction.

15. USES Aircraft auxiliary power generation, wind generators, high speed gas turbine generators. Hybrid electric vehicle (HEV) drive systems, automotive starter generators. An ac generator, or ‘alternator’, is used to produce ac voltages for transmission via the grid system or, locally, as portable generators. All of our household appliances run on ac current. Ex: Refrigerator, washing machines, oven, lights, fan etc.

16. REFERENCES Wikipedia Slideshow Byju’s.com Vedantu.com

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