MACHINES 2

PREFERENCE FOR ELECTRICITY

Energy can neither be created nor be destroyed”. We can only change its forms, using appropriate energy conversion processes

Chemical Energy

Solar Energy

Wind Energy

Hydroelectric Energy

Geothermal Energy

Nuclear Energy

Types of Energy Sources converted into Electrical Energy

chemical energy

energy that is released as the result of electron interactions Ex. Batteries( Dry Cell, Wet Cell and Fuel Cell)

Solar Energy

light and heat energy from the sun

Wind Energy

moving air turns the blades of large windmills or generator to make electricity

Hydroelectric Energy

fast flowing water released from dams in mountains areas can turn water turbines to produce electricity

Geothermal Energy

uses heat energy from the beneath the surface of the earth.

nuclear energy

exists as stored energy which is released as a result of particle interactions with or within the nucleus

Radioactive Decay

fusion

fission

example of nuclear energy

radioactive decay

unstable nucleus, radio isotope decays to a more stable configuration

fission

heavy mass nucleus absorbs a neutrons and splits up into 2 or more nuclei with energy released

fusion

2 light mass nuclei combine to produce more stable configuration with energy released.

electromechanical conversion device

is a link between electrical and mechanical system. The purpose is to change the form of energy.

electromechanical conversion device

can work either as a generator or as a motor, provided pertinent conditions are satisfied for the concerned mode of operation.

dynamo

a rotating electrical machine that converts mechanical energy into electrical energy or electrical energy into mechanical energy

generator action

motor action

Two Principles of Dynamo

generator action

it involves the development of voltage

motor action

it involves the development of force or torque

1. Magnetic Frame or Yoke

3. Pole Coils or Field Coils

2. Pole-Cores and Pole-Shoes

4. Armature Core

5. Armature Windings or Conductors

6. Commutator

7. Brushes and Bearing

DC generators are similar to dc motor in appearance and construction. They have the same stationary and rotating part which consist of the following essential parts

outer frame or yoke

provides mechanical support for the poles and acts as a protecting cover for the whole machine and • It carries the magnetic flux produced by the poles

Pole Cores and Pole Shoes

they spread out the flux in the air gap and also, being of larger cross-section, reduce the reluctance of the magnetic path • they support the exciting coils (or field coils

pole coils

consists of copper wire or strip, are wound coil placed over the core of the poles.

shunt field

series field

compound field

the field windings are constructed into three types:

shunt field

in which there are many turns of fine wire

series field

with few turns of heavy wire

compound field

in which both a shunt and series windings are used

Armature Core

It houses the armature conductors or coils and causes them to rotate and hence cut the magnetic flux of the field magnets.

Armature Windings

virtually the heart of the dynamo, are insulated coils wound in the armature slots.

commutator

The function — is to facilitate collection of current from the armature conductors. converts the alternating current induced in the armature conductors into unidirectional current in the external load circuit

Brushes and Bearings

usually made of carbon, are held in a stationary position by brush holders. The ball bearings are employed to freely rotate the commutator shaft and for quiter operation.

shaft

shaft is made of steel and holds the commutator