Electra

Concept of Commutation

                      Commutator plays a major role in the case of DC generators. It is necessary to have some idea about commutation that will fetch you in having depth knowledge in DC Generator.

Alternating current alternates in either direction. It is necessary to reverse that one. The reversal of current which can be achieved by means of short circuiting the brushes is known as commutation.

There must be certain period of time for this operation to take place. It is known as time of commutation. This reversal of current produces some effects. The self induced emf is developed when the brushes are short circuited which is the Reactance voltage.

It opposes that reversal which ultimately results in sparking of the brushes. The commutation must be improved to eliminate this effect. The Resistance commutation can be implemented by providing high resistance brushes.

Still we can have better commutation by means of interpoles. It can also be called as emf commutation. It produces external emf which cancels the reactance voltage. The interpole is connected in series with the armature.

It main advantage is that in increase the sparking limit of the machine which result in the creation of the smaller interpole machine with that output.

Concept of Armature Reaction

               The main concept in the DC Generator is the armature reaction. It is the simple thing that we can capture easily. The Main Field system produces the field.

 The armature current also develops its own flux. Since armature is revolving within the main field system it shows some effect on the main field. This effect of flux developed by armature on the main flux is described as an armature reaction.

There are two possibilities based on the effect. It weakens the main flux or it distorts the main flux. The both effects can be described as demagnetizing and cross magnetizing respectively. It is necessary to nullify the effects of these effects.

Demagnetizing effect can be nullified by providing additional turns on each pole. Cross magnetizing effect can be nullified by providing compensating windings in the pole shoes and it is connected in series with the armature. The armature reaction in general is produced by the load current.

Principle and Operation behind a DC Generator

             Power is the main source for our world to move ahead. Generator plays a major role in producing power. I will provide the details of DC Generator that everyone must learn.

DC Generator is a machine which helps in converting Mechanical energy into Electrical energy. The three main things to be needed for the operation of DC Generator are the Magnetic Field, a Conductor and the Motion of the conductor.

Generator consists of an armature and the Field magnet. Field Magnet is responsible for producing the required magnetic field. The conductors are wound over the armature in which the electro motive force is induced by revolving the armature within the field magnet.

The resultant emf developed in the armature is the alternating one. But we need the DC. For that commutator is used which converts the alternating emf into direct current. Commutator rectifies the AC into DC. The DC obtained can be used for various purposes.

Rain

Rain is water that falls in drops from the sky. It forms from droplets of water in the clouds. Droplets are tiny drops. Sometimes there is frozen water in clouds. When it melts, it falls to the ground as rain. Some raindrops are very small. Others are as big as a pencil eraser. They cannot get much bigger, because they break into smaller drops as they fall.

Large raindrops fall as fast as 30 feet (9 meters) per second. Raindrops form from water vapor (VAY puhr), or gas, in the air. The sun’s heat causes water from lakes, rivers, and oceans to rise into the air as water vapor. As it rises, the warm, moist air cools. Cool air holds less water than warm air can hold. As the air cools, the water vapor condenses, or forms droplets. The droplets form clouds. As the clouds cool, the droplets combine with other droplets. When they become too heavy for the air to hold, they fall to the ground as rain.

If the same amount of rain or snow fell everywhere, Earth would get about 34 inches (86 centimeters) each year. But some places get much more, and some get much less. Warm, tropical areas near the equator get more rain than cold areas in the far north and south. The equator is a make-believe line around Earth’s middle. Usually, seacoasts get more rain than other regions.