Transformer

 Transformer is a static device which transfer electrical energy without changing frequency and working Principle of transformer is Faraday's low of electro Magnetic 🧲 induction . transformer is corresponding increased and decrease the current .it can change low voltage to high and high voltage to low but it can not function both in one time . A transformer has two windings .one coils is called primary winding to which the given supply and another is secondary winding from which the supply is taken .

CONSTRUCTION OF TRANSFORMER :

 There are two main part's of transformer 

1- CORE : The core of transformer is made on steel laminated assemble for providing continuous Magnetic path 🧲 .in transformer core steel is used for high silicone content.sometime lamination core are become more heat produce and a low hysteresis loss .the Eddy current loss minimize by laminating the core .each laminated core is insulated by light coat varnish .

2- WINDING : The transformer windings are placed on the two limbs or on the central limb. The winding is formed with the enamelled copper wires known as winding . those winding is connected to the supply is the primary winding and anathor  load is connected is known as secondary winding. construction of winding is two types .

(a) Cylindrical Type: The winding is the length of the coil is equal to the length of the limb and is concentrically placed one above the other, that's called cylindrical  winding.

(b) Sandwich Type: In this type method both the winding primary and secondary  are placed one over the other alternately. They are separated by insulation layers. that's are called sandwich type winding .

3- CONSERVATOR : conservator is consists of an airtight cylindrical metal drum .it fitted on transformer kid horizontally .it provide  detachable and an access hole .it used for take up control expansion of oil without allowing come in contact with outside air .

4- BREATHER : normally it's know as breather is the nose of transformer .it's looks like a box .when tempreture change the oil expensed and there is a displacement of air .The displacement of air due to these changes of oil volume takes place through the breather, which extracts the moisture form the air. The breather consists of a small vessel which contains a drying agent like slice gel crystal.

5- BUCHHOLS RELAY : it used as a protective device to inform internal fault in transformer .it is one of most important device in transformer.these device is inform losses of oil used by leakage as well as defect and other bad connection.it is fitted between transformer main tank and conservator .

6. EXPLOSION VENT : it's also a safety device which protect the transformer main tank from the gases induced by any technical defect .

WORKING PRINCIPLE OF TRANSFORMER :  

works on the principle of transformer is mutual induction , if the two coils be placed near to each other and if one is connected to the A.C. supply, the e.m.f. will be induced in the other coil. The e.m.f. induced will be according to the turns in the second coil. The transformer is mostly used in A.C. supply to increase the voltage and thus decrease the current and keep the power same for transmitting the high voltage, and to decrease the voltage at load point .

TYPES OF TRANSFORMERS - 

 According to the core -

- Core type 

- shell type 

- Berry Type

2. According to the voltage - Step up and Step down. 

3. According to the phases - Single-phase and three-phase.

4. According to the power - Lighting Transformer, Power Transformer. 

5. According to the cooling - Self-cooled, air force cooled

-- CORE TYPE : 1. In this type of winding or copper enclose the whole core, so the cooling is good for winding. 

2. It has one magnetic path only.,

3. Average length of core is more.

4. Here area cross-section is less, so more turns are required.

5. On every leg both primary and secondary windings are there so leakage flux is less.

6. It is used for high voltage and less output .

7. Because most of the portion of winding is visible, it is easy to insulate and repair it

-- SHELL TYPE : 1. Here core encloses the copper winding . SO The cooling is good for core.

2. It has two magnetic paths.

3. Average length of core is less. 4. Area cross-section is more soless turns are required.

 5. To reduce losses here the winding is done in pan cakes - primary, secondary, primary secondary, on the centre limb.

6. It is used for low voltage and high output.

7. As most of the winding is enclosed by the iron, so difficulty is experienced in repairs.

-- BERRY TYPE TRANSFORMERS : One leg of many core transformers is jointed at one place and winding is done on that limb. Other limbs are free and are meant for flux paths only. Due to the difficulty of winding on the centre limb and construction, these types are not used.

-- STEP-UP TRANSFORMER:  these  transformer changes low voltage high ampere current into high voltage low current of the same frequency,, is called a step up transformer. 

-- STEP-DOWN TRANSFORMER: These transformer changes high voltage low ampere current into low voltage high ampere current of the same frequency, is called a step-down transformer. 

E. M .F. EQUATION OF A TRANSFORMER : 

TRANSFORMER OIL : basically mineral oil and synthetic oil are used in transformer . it's work is first control heating from core and winding . The Electric strength of oil is almost entirely on its freedom from tendency to to sliding .

AUTO TRANSFORMERS :

 The auto-transformer is used to fitted in a neutral in a 3-wire a.c. supply , in that case the function of the auto-transformer is similar to that of a balancer in a 3-wire d.c. distribution. The auto-transformer used for such purpose is merely a choke coil having centre tap When the load on  two sides is balanced, there is no current in the neutral. When the load is unbalanced the heavier loaded side acts as secondary winding and half the unbalanced load is transformed to the lightly loaded side . 

LOSSES OF TRANSFORMERS : 

I) core / iron loss : in transformer this losses exist in the iron core  .these losses are constant and remain same load at all. 

ii) hysteresis loss : these loss is decrease by using silicone steel laminated which have high Electric resistance .

iii) Eddy current loss : this loss increases e.m.f. in the core that's up a current in the iron core that's called Eddy current loss .

OPEN CIRCUIT TEST : 

In this test One winding of the transformer usually the low voltage side, these supplied with the rated voltage while the secondary is kept at open circuit. Under these conditions normal flux will set up in the core and therefore, normal iron loses will occur. The current taken will be very small and so the copper losses will be negligible. The wattmeter W will indicate the iron losses and the ammeter will give the no-load current

SHORT CIRCUIT TEST :

 in this test a small voltage is applied to the other winding and increase full load current that flow in winding .

SOME IMPORTANT QUESTIONS ANSWER : 

1. What do you mean by transformer ?

Ans=A static machine which converts high voltage to low voltage and vice-versa.

 2. On what principle does the transfomer depend?

Ans=mutual induction

3. What are the essential parts of the transformers?

Ans=Primary-secondary winding and core.

4. What is the name of the winding to which the supply is given?

Ans=primary winding

5. What is the name of the winding from which the supply is taken? 

Ans= secondary winding

6. What is the reason that the core is made laminated?

Ans= Due to eddy current production in solid core which produces heat.

7. How many magnetic paths are there in the core type transformers ?

Ans=one 

 8. How many magnetic paths are there in the shell type transformers ?

Ans=two

9. What do you understand by transformation ratio? 

Ans= 

10. What is complete formula for e.m.f. included in a transformer ?

Ans=

11. For what purpose the transformer oil is filled in the transformer tank 

Ans= To increase the insulation of windings and to cool the windings.

12. What is meant by flash point for transformer?

Ans=Ignition temperature of oil vapour

13. What is meant by fire point?

Ans= That temperature at which the oil fires up.

14. For what purpose is the breather fitted in a transformer ?

Ans= To breath the air. i.e., to give dry air in the transformer when it breathes.

 15. For what purpose is the conservator fitted on the top of transformer ?

Ans= To give the space to the oil when it is heated up in the tank due to the load on the transformer.

16. What material is filled in the breather?

Ans=Silica jell

17 . What is emergency release? 

Ans=A pipe on the top of the tank of transformer which releases gases on the short- circuit

18. What is the relation of flux between no-load and on load?

Ans= Flux is same on no-load and on load.

19. What are the functions of no-load current in a transformer 

Ans=Produces flux and supplies iron loss, copper loas on no-load.

20. What will be the effect on the primary side if the load on the secondary side

Ans= Current increases on the primary side also.