Informational Encyclopedia

A transformer is a static or stationery apparatus which transformed electric power from one circuit (same frequency) to another circuit. It can raise or fall down the voltage in a circuit but with a regarding to increase or decrease in the current.

The physical basis of transformer is mutual induction between two circuits connected by a common flux. It consists of two inductive coils  which are electrically separated but magnetically connected by a path of low reluctance. The two coils posses high mutual inductance.

If one coil is linked to a source of alternating voltage, an alternative flux is set up in the laminated core. Most of which is connected with the other coil in which it raise mutually induced e.m.f. If the secondary coil circuit is shut down, a current flow in it and so electric energy is converted from

the first coil to second coil. The first coil , in which electric energy is fed from the a.c. supply , it is called primary winding and the other which drawn out the energy is called secondary winding.

In conclusion we can say the transformer is a device which

(a) transfers electric power from one circuit to another.

(b) it does so without a change of frequency.

(c) it accomplishes this by electromagnetic induction

(d) When two electric circuits are in mutual inductive influence of each other

Basic Theory of a Transformer

Let's assume you make them wind which is supplied by a alternative electrical source. The alternative current through the winding creates a consistently changing flux or alternative flux that encompasses the winding. In the event that some other winding is conveyed closer to the past one, clearly some segment of this flux will interface with the second. As this flux is constantly altering in its amplitude and direction, there must be an adjustment in flux linkage in the second winding or coil. As indicated by Faraday's law of electromagnetic induction, there must be an EMF prompted in the second. In that the circuit of the later winding is shut, there must be a present moving through it. This is the easiest type of electrical force transformer and this is the most essential of working rule of transformer. For better understanding, we are attempting to rehash the above clarification in a more short manner here. At whatever point we apply exchanging current to an electric coil, there will be a rotating flux encompassing that loop. Presently in the event that we bring another loop close to the first, there will be a rotating flux linkage with that second curl. As the flux is exchanging, there will be clearly a rate of progress in flux linkage concerning time in the second loop. Actually emf will be prompted in it according to Faraday's law of electromagnetic impelling.

For the use of light an power, the system of distribution of electric energy the field of application of A.C. motors are widely used. Due to rapid use of motors the manufacturers have tried over the last few decades, to perfect various types of ac motors suitable for all classes of industrial drives and for both single and three phases a.c. supply.

This has been rise to bewildering multiplicity of types whose proper classification often offers considerable difficulty. Different a.c. motors may, however be classified and divided into various groups and as following as below.

1: Due to their principle of operation

A: Synchronous motors

(i) Plain  (ii) super

B: Asynchronous motors

a: Induction motors

   (i) Squirrel cage ( single / double)   (ii) Slip ring (external resistance) 

b: commutator motors

    (i) series (single phase / universal)        (ii) compensated ( conductively/inductively)        

   (iii) Shunt ( simple / compensated)   (iv) Repulsion (straight / compensated)          (v) repulsion-start induction      (vi) repulsion induction

2: Due to the type of current

(a) single phase        (b) three phase

3: Due to the speed

(a) constant speed     (b) variable speed    (c) adjustable speed

4: Due to Structural features

(a) open        (b) enclosed     (c) semi-enclosed      (d) ventilated     (e) Pipe-ventilated    (f) riveted frame eye 

Generator Principle

An electrical generator is a machine which converts mechanical energy or power into electrical energy (or Power). The energy conversion is based on the principle of production of dynamically induced e.m.f.

Whenever a conductor cuts magnetic flux,dynamically induced e.m.f. is produced in it according to Faraday's Laws of Electromagnetic induction. This emf causes a current to flow if the conductor circuit is closed. So there are two basic parts of an electrical generator are

1: a magnetic field            2 : a conductor or conductors which can so move as to cut the flux.

Construction of simple loop generator.

A single turn rectangular copper coil ABCD rotating about its own axis in a magnetic field provided by either permanent magnet or electromagnets. The both ends of the coil is fastened to two slip-rings a and b which are insulated from each other and from the main shaft.

Two collecting bushes of carbon or copper press against the slip-rings. Their function is to receive the current induced from the coil and to pass on it to external load resistance R. The rotating coil can be called "armature" 'and the magnets are as "field magnets".

Working of simple loop generator

Imagine the coil is to be revolving in clock-wise direction.As the coil assumes successive position in the field, the flux connected with the charge. Hence the emf is produced in it which proportional to the rate of change of flux linkage. When the plane of the coil is at the right angles to lines of flux i.e when it is in position,l,then flux connected with the coil is maximum but rate of charge of flux linkage is down. It is due to in position , the coil side AB and CD do not cut the flux, rather they slide along them.(they move in parallel).

 Hence there is no emf produced in the coil. If we consider no emf in the coil at the starting position, the angle of rotation will be calculated from the position. As the coil continues revolving more , the rate of change in the flux linkage increases till the position 3 is reached where angle is 90 degrees. Here the coil plane is horizontal and parallel to the lines of flux. As seen the flux linked with the coil is minimum but rate of change of flux linkage is high. Hence, the maximum emf is induced in the coil when in this position.Next quarter from 90 to 180 degrees the flux linked gradually increases but rate of change of flux decreases. From 180 to 360 degrees revolution  the variation in the magnitude of emf are similar to those in the first half revolution.For making the flow of current unidirectional in the external circuit i, the slip rings are replaced by split-rings.The split rings are conducting cylinder typed material which is used to cut two segments insulated from each other by a thin sheet of mica or other insulated material.