Electrical Machine, Types of transformer, Phase diagram of transformer and equivalent circuit of transformer

 TYPES OF TRANSFORMER - :

There are many types of transformer -

Measurement 

1.CORE TYPE  TRANSFORMER - : In core type transformer, two winding are arranged as concentric coils, therefore these are called concentric winding or cylindrical winding. The low voltage winding is placed next to the  core and the high voltage winding is placed around the low voltage winding to reduce the insulation material requirement. 

SHELL TYPE TRANSFORMER - : In the shell type of transformer bith primary and secondry winding are wound on tje central limb and the two outer limbs complete the low reluctance flux paths. 

                                            Each winding is subdivided into sections. Low volrage and High voltage subsections are alternatly lut in the form of a sandwich. Therefore, such a winding is placed called sanfwich or disc winding. 

IDEAL TRANSFORMER - :An ideal transformer is one which has following assumptions:

1. Its winding haveno Ohmic resistance, therefore it jas no I2R loss (copper loss). 

2.    There is no magnetic leakage, hence which has no core losses(hystresis as well as eddy current loss). 

3.     The core has infinite permebilitycso that zero magnetizing current is needed to establish the requisite amount of flux in the core. 

MMF BALANCE IN IDEAL TRANSFORMER - 

       N1I1-N2I2=0

         N1/N2=I2/I1

        E1/E2=   N1/N2=I1/I2=K=V1/V2   

        E1I1=E2I2=S2=S1 

or, 

      It showes that the voltampere drawm from the primary supply is equal to the voltampere transfrlerred to the secondary supply without any loss in an ideal transformer. 

V1I1/1000=V2.I2/1000

(KVA)1= (KVA) 2

  INPUT KVA=OUTPUT KVA

Thus the kva input of an ideal transformer is equal the kva output  kva is the same an both sides of transformer. 

PHASE DIAGRAM OF TRANSFORMER - :

1.WHEN TRANSFORMER AT NO LOAD-:

               A transformer is said to be at no load when the second winding is open circuited. Thus, secondary current will be zero. When  an alternative  voltage is applied to the primary, a small current will be zero. When a alternative voltage is applied to the primary, a small current I0 flows in the primary winding. The current I0 is called the no load current or exiting current of the transformer. The no load curren I0 us small og the order of 3%to 5% of the rated current of primary wimding. It can be resolved into two components. 

(a)  The components is called the magnetizing current. it magnetizing the core. it sets up a flux in the core, therefore Im is in phase with. Itcis also called reactive or wattless component of no load current. 

(b). The component is called core current. It is also called active components of mo load active current. it is in phase with the primary induced voltage. the  componant supplies the hysteresis and eddy current loss in the core and the neglible loss in the primary winding. 

 

Electrical Machine, Transformer, Construction of transformer and it's working principle.

 TRANSFORMER - :   A transformer is a static device which transfers electrical energy from one circuit to another circuit without a change of frequency. Transformer worke on electromagnetic induction principle. 

The transformer which dilivers energy at a higher voltage level then it source voltage level then it is called step - up transformer. When the voltage of delivered energy of a transformer is less than its primary voltage than, it is called step- down transformer.

A transformer has no moving parts parts, si it is called static device, therefore it requires minimum repair and maintenance cost. its efficiency is much higher when compared to other apparatus.

CONSTRUCTION - :   A single phase transformer consists of primary and secondary windings put on a magnetic core. Boyh windings are magnetically connected but not electrically. Magnetic core is ised to confinr flux to certain path. A winding and winding connected on load side is called secondary winding.

Transformer cores are made from thin laminated sheets of high grade silicon steel. Since, the laminated reduce eddy current loss and silicon steel reduces hysterisis loss. There are basically two type of transformer cknstruction, the core type and shell type.

WORKING PRINCIPLE OF TRANSFORMER - :  

   Transformer consists of two inductive and colis which are electrically separated but magnetically linked through  a path of low resistance. If one coil is connected to a source of ternative voltage, an alternative flux is setup in the laminated core, most of which is linked with other coli in which is produce mutually - induced emf (according to Faraday's law of electromagnetic induction E=M. dI/dt) 

If the second coil circuit  is closed, a current flows i  it and so, energy is transferred (entirely magnetically) from the first coil to second coil.

   EMF EQUATION OF TRANSFORMER - :      

The primary wi di g draws a small amount of alternative current of instantaneous value  called the exiting current,from the voltage source with posutive direction as indicated on the diagram. The exiting current establishes flux in the core. all of which is assumed confined to the core there is no leakage of flux Consequently, the primary winding has flus linkage.

As per Lenz 's law the positive of this emf oppose the positive current direction and is shown by (+ve) and (-ve) polarity marks on the diagram. According to kirchoff law. 

V==E(winding has zero resistance) 

E1/E2=N1/N2 

E1/N1=E2/N2=K

EMF PER TURN IN PRIMARY=EMF PER TURN IN SECONDARY

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