129538660 Designing Of Single Phase Transformer

DESIGNING OF SINGLE PHASE TRANSFORMER

Submitted for partial fulfillment of award of degree of

BACHELOR OF TECHNOLOGY

In Electrical & Electronics Engineering By Group ID: - 09PJEEE02

Under Guidance of: Dr.Bhavesh Kumar Chauhan

UTTAR PRADESH TECHNICAL UNIVERSITY, LUCKNOW, INDIA MARCH 2013

CERTIFICATE

Certified that Deepika Singh,Shikha Rani andSonia Aggrawal have carried out the research work presented in this report entitled “DESIGNING OF SINGLE PHASE TRANSFORMER” for the award of Bachelor of Technology in Electrical and Electronics Engineering from GautamBuddh Technical University, took now under my supervision. The project report embodies result of original work and studies carried out by student them self and the contents of the project report do not form the basis for the award of any other degree to the candidate or to anybody else.

INTERNAL GUIDE DR.BHAVESH KUMAR CHAUHAN

(Signature)

DECLARATION

We hereby declare that this project report on, “Designing Of Single Phase Transformer”, which is being submitted in partial fulfillment of the Bachelors Of Technology In Electrical And Electronics, is the result of the work carried out by us, under the guidance of Dr. Bhavesh Kumar Chauhan prof. of electrical engineering department of ABES Institute Of Technology

DEEPIKA SINGH

SHIKHA RANI

SONIA AGGRAWAL

Acknowledgement

We take immense pleasure in thankingDr. BhaveshkumarChauhanour beloved Prof.of Electrical Department for having permitted us to carry out this project work. We wish to express my deep sense of gratitude to our Internal Guidefor his able guidance and useful suggestions, which helped us in completing the project work in time. Any attempt at any level cannot be satisfactory completed without the support and guidance of learned people. We would like to express our immense gratitude to ourinternal guide for their constant support and motivation that has encouraged us to come up with this project. We are also thankful to our faculties, friends and classmates who have their whole hearted support at all times of this project.

DEEPIKA SINGH (0929021023) SHIKHA RANI (0929021053) SONIA AGGRAWAL (0929021056)

ABSTRACT Through this report we are going to summarize the early theories on single phase transformer. This includes about the raw materials required such as the core, the coils, insulating wires, cabinets, etc. Here we also give about the assembly of these raw materials and the working principle of basic transformer. The single phase transformer is a static device which transfers electrical energy from one circuit to another circuit without changing the frequency. The aim of the transformer design is to obtain the dimensions of all the parts of the transformer based on the given specification, using available materials economically in order to achieve lower cost,reduced size and better operating performance. In this project, the task of finding optimal design of singlephase transformer has been formulated as nonlinear programming problem, so as to meet thespecification with the minimum cost and improve the efficiency. The transformer has voltage rating 220V on single phase supply and 440V on double phase supply, frequency 50Hz, 3KVA . The design of transformer based on a modification which is done by changing the gauge number of wire used (i.e. 17 No.) due to which voltage carrying capacity increases and the transformer can also work on double phase supply as step up and step down. There are approximately 94 E & I stampings are used in number in the hardware model of transformer. The dimensions of the outer boundaries isappx. to 35cm X 23cm. the weight of model is 13.5 Kg. This model is also coded in the „C‟ language which shows the output of transformer..

TABLE OF CONTENT 1. Chapter-1 Introduction i. Introduction of single phase transformer ii. Working principal of transformer iii. Empirical relations for designing iv. Simple formula v. Equations notes vi. Loss in transformer (i) Copper loss in transformer (ii) Hysteresis loss in transformer (iii) Physical explanation of hysteresis loss (iv) Eddy current losses vii. Core of transformer (i) Purpose of core (ii) Material for transformer core (iii) Manufacturing of transformer core 2. Chapter-2 Literature Review i. The ideal transformer :voltage ratio ii. Leakage reactance: transformer impedance iii. Losses in core and winding iv. Rated quantity v. Regulation 3. Chapter-3 Designing i. Designing of single phase transformer (i). Core design (ii).Winding design (iii). Window area ii. Physical assumption of transformer iii. Raw material required iv. Problem arising in this assumption 4. Chapter-4 Flowcharts i. Flowchart of core design ii. Flowchart of window iii. Overall dimension flowchart iv. Process flowchart 5. Chapter-5 Assembly i. Assembly of single phase step down transformer ii. Selection of stamping no. according to power rating iii. Dimensions of stamping

iv. v. 6. Chapter-6 i. ii. 7. Chapter-7

Steps for assembling transformer Modification in the transformer Output Of Transformer Steps for transformer action Line connections Programming In ‘C’ Language

8. Appendix –A 9. Appendix – B 10. Appendix – C 11. Appendix – D 12. Appendix – E 13. References

CHAPTER 1 INTRODUCTION OF SINGLE PHASE TRANSFORMER Transformer is very important electrical equipment now a day‟s age. The electrical energy transferred from one alternating current to another alternating current circuit without any contact and without changing frequency. The transformer which used in power supply circuit is called POWER TRANSFORMER. Two coils or set of coils are used to construct these transformer. We will study such type of transformer which is used in AC main circuit. In INDIA the standard for AC main supply is 220/230V, 50Hz for one phase supply. It should be kept in mind that frequency of supply is very important factor in the working system of transformer. The transformer designed to work on particular frequency don‟t operate on frequency less than operating frequency but works on high frequency. As already informed that power transformer is made of two coils or set of coils. 

Primary winding



Secondary winding

Primary winding The AC supply is given to the one coil or sets of coil of the transformer are called primary winding.

Secondary winding Those coils through which supply is taken out are called secondary winding. Secondary winding Ns Turns

Primary winding Np Turns Flux ɸ Ip

Primary voltage Vp

Is

Secondary voltage Vs

Working Principle of Transformer When AC supply is given to the primary coils then magnetic flux is produced in iron core and around the coils. The flux voltages produced by AC supply in the primary are also transformed to the secondary coil of the transformer. The voltage produced in the secondary side is stepped-up or stepped –down as compared to voltage given to the primary side. These voltages are proportional to the number of turns wound on the coil of the transformer, supply given to the input and output taken and core size used. The rapidly changing flux due to constant change in AC supply produces current in the core and winding. If the core consist of low resistance metal in the shape of big mass thencurrent produced will be more, heating the core causing loss of electricity. This electriccurrent is called eddy current. To lower the value of eddy current to the minimum the core is divided into small pieces of thin sheet. By insulating the sheets the electrical resistance of the core is increased .By this method the value of eddy current is very much decreased and there is less power loss now. Insulation is provided to lamination is immersed in cold or hot oil and for batter varnish vacuum impregnation method is adopted to reduced eddy current to very small value. The lamination of transformer is insulated with varnish. Mostly two prominent shapes are used. These are: 1. E & I Type 2. T & U Type

Fig .1

Fig .2

Empirical Relations For Designing To construct the transformer calculation are made with the help of formulas. These are of different types. 1. The cross-sectional area of core of transformer is calculated as per the formula given. Core area =√Ws/5.58 where Ws = power output of transformer [wattage] W=A*V A= cross section area of core [sq. inch] 5.58=constant 2. Total output wattage [W] =Output volt [V]*output current [A] 3.Number of turns/volts

Where, V= voltage desired A=effective core cross section area B=flux density of material in gausses 4. Input wattage

P(input)= where 𝝶(%)= efficiency P(out)=total output power deliverd to load 5. Current= Wattage (W)/volt (V)

Switching Supply Core The approximate power a core can support is

Or

The derivation comes from these fundamental equations:

Where,           

P is the power in Watts f is the frequency in hertz, N is the number of turns of wire on the winding, A is the cross-sectional area of the core in square meters, B is the peak magnetic flux density in Teslas, L is the inductance in Henries, r is the radius of a solenoid in meters, l is the length of a solenoid in meters, is the dimensionless relative permeability is a constant with units of meters/Henry is a constant with units of Henries/meter

There are two approaches used in designing transformers. One uses the long formulas, and the other uses the WA product. The WA product is simply the cores window area multiplied by the cores area. Some say it simplifies the design, especially in C-core (cut core) construction. Most manufacturers of C-cores have the WA product added into the tables used in their selection. The designer takes the area used by a coil and finds a C-core with a similar window area. The WA product is then divided by the window area to find the area of the core. Either way will bring the same result. For a transformer designed for use with a sine wave, the universal voltage formula is:

√ Thus,

E=

Where,         

E is the sinusoidal rms or root mean square voltage of the winding, f is the frequency in hertz, N is the number of turns of wire on the winding, a is the cross-sectional area of the core in square centimeters or inches, B is the peak magnetic flux density in Teslas or Webers per square meter, gausses per square centimeter, or lines (Maxwell‟s) per square inch. P is the power in volt amperes or watts, W is the window area in square centimeters or inches and, J is the current density. Note: 10 kilogauss = 1 Tesla.

This gives way to the following other transformer equations for cores in square centimeters:

The derivation of the above formula is actually quite simple. The maximum induced voltage, e, is the result of N times the time-varying flux: e = N* If using RMS voltage values and E equal the rms value of voltage then: e=E and

√

Since the flux is created by a sinusoidal voltage, it too varies sinusoidally: φ(t) = Φ

=A

, where A = area of the core

Taking the derivative we have: dφ(t)/dt = wA Substituting into the above equation and using w= 2 with the maximum value yields

f and the fact that we are only concerned

√ The formulas for the imperial (inch) system are still being used in the India by many transformer manufacturers. Most steel EI laminations used in the India are measured in inches. The flux is still measured in gauss or Tesla, but the core area is measured in square inches. 28.638 is the conversion factor from 6.45 x 4.44 (see note 1). The formulas for sine wave operation are below. For square wave operation, see Note (3):

To determine the power (P) capability of the core, the core stack in inches (D), and the windowarea (Wa) product, the formulas are:

Where,        

P is the power in volt amperes or watts, T is the volts per turn, E is the RMS voltage, S is the current density in circular mils per ampere (Generally 750 to 1500 cir mils), W is the window area in square inches, C is the core width in square inches, D is the depth of the stack in inches and, Wa is the product of the window area in square inches multiplied by the core area in square inches. This is especially useful for determining C-cores but can also be used with EI types.

Simpler Formulae A shorter formula for the core area (a) and the turns per volt (T) can be derived from the long voltage formula by multiplying, rearranging, and dividing out. This is used if one wants to design a transformer using a sine wave, at a fixed flux density, and frequency. Below is the short formulas for core areas in square inches having a flux density of 12 kilogauss at 60 Hz (see note 2): √

and for 12 kilogauss at 50 Hz: √

Equation Notes 

Note 1: The factor of 4.44 is derived from the first part of the voltage formula. It is from 4 multiplied by the form factor (F) which is 1.11, thus 4 multiplied by 1.11 = 4.44. The number 1.11 is derived from dividing the rms value of a sine wave by its average value, where F = rms / average = 1.11.



Note 2: A value of 12 kilogauss per square inch (77,400 lines per sq. in.) is used for the short formulas above as it will work with most steel types used (M-2 to M-27), including unknown steel from scrap transformer laminations in TV sets, radios, and power supplies. The very lowest classes of steel (M-50) would probably not work as it should be ran at or around 10 kilogauss or under.



Note 3: All formulas shown are for sine wave operation only. Square wave operation does not use the form factor (F) of 1.11. For using square waves, substitute 4 for 4.44, and 25.8 for 28.638.



Note 4: None of the above equations show the stacking factor (Sf). Each core or lamination will have its own stacking factor. It is selected by the size of the core or lamination, and the material it is made from. At design time, this is simply added to the string to be multiplied. Example; E = 4.44 fNaBSf.

The invention of the power transformer towards the end of the nineteenth century made possible the development of the modern constant voltage AC supply system, with power stations often located many miles from centers of electrical load. Before that, in the early days of public electricity supplies, these were DC systems with the source of generation, of necessity, close to the point of loading. Pioneers of the electricity supply industry were quick to recognize the benefits of a device which could take the high current relatively low voltage output of an electrical generator and transform this to a voltage level which would enable it to be transmitted in a cable of practical dimensions to consumers who, at that time, might be a mile or more away and could do this with an effi ciency which, by the standards of the time, was nothing less than phenomenal.Today‟s transmission and distribution systems are, of course, vastly more extensive and greatly dependent on transformers which themselves are very much more efficient than those of a century ago.

Losses In Transformer As the electrical transformer is a static device, mechanical loss in transformer normally does not come into picture. We generally consider only electrical losses in transformer. Loss in any machine is broadly defined as difference between input power and output power. When input power is supplied to the primary of transformer, some portion of that power is used to compensate core losses in transformer i.e. Hysteresis loss in transformer and Eddy Current loss in transformer core and some portion of the input power is lost as I2R loss and dissipated as heat in the primary and secondary winding, as because these windings have some internal resistance in them. The first one is called core loss or iron loss in transformer and later is known as ohmic loss or copper loss in transformer. Another loss occurs in transformer, known as Stray Loss, due to Stray fluxes link with the mechanical structure and winding conductors.

Copper Loss In Transformer Hysteresis loss and eddy current loss, both depend upon magnetic properties of the materials used to construct the core of transformer and its design. So these losses in transformer are fixed and do not depend upon the load current. So core losses in transformer which is alternatively known as iron loss in transformer and can be considered as constant for all range of load.

Hysteresis Loss In Transformer Hysteresis loss in transformer can be explained in different ways. We will discuss one of them, i.e. Physical explanation.

Physical Explanation Of Hysteresis Loss The magnetic core of transformer is made of ′Cold Rolled Grain Oriented Silicon Steel′. Steel is very good ferromagnetic material. This kind of materials is very sensitive to be magnetized. That means whenever magnetic flux passes through, it will behave like magnet. Ferromagnetic substances have numbers of domains in their structure. Domains are very small region in the material structure, where all the dipoles are paralleled to same direction. In other words, the domains are like small permanent magnet situated randomly in the structure of substance. These domains are arranged inside the material structure in such a random manner, that net resultant magnetic field of the said material is zero. Whenever external magnetic field or mmf is applied to that substance, these randomly directed domains are arranged themselves in parallel to the axis of applied mmf. After removing this external mmf, maximum numbers of domains again come to random positions, but some few of them still remain in their changed position. Because of these unchanged domains the substance becomes slightly magnetized permanently. This magnetism is called “Spontaneous Magnetism". To neutralize this magnetism some opposite mmf is required to be applied. The magneto motive force or mmf applied in the transformer core is alternating. For every cycle, due to this domain reversal there will be extra work done. For this reason, there will be a consumption of electrical energy which is known as Hysteresis loss of transformer.

Eddy Current Loss In transformer we supply alternating current in the primary, this alternating current produces alternating magnetizing flux in the core and as this flux links with secondary winding there will be induced voltage in secondary, resulting current to flow through the load connected with it. Some of the alternating fluxes of transformer may also link with other conducting parts like steel core or iron body of transformer etc. As alternating flux links with these parts of transformer, there would be a locally induced emf. Due to these emfs there would be currents which will circulate locally at that part of the transformer. These circulating current will not contribute in output of the transformer and dissipated as heat. This type of energy loss is called eddy current loss of transformer. This was a broad and simple explanation of eddy current loss.

Core of Transformer Purpose Of Transformer Core In an electrical power transformer there are primary, secondary and may be tertiary windings. The performance of a transformer mainly depends upon the flux linkages between these windings. For efficient flux linking between these winding one low reluctance magnetic path common to all windings, should be provided in the transformer. This low reluctance magnetic path in transformer is known as core of transformer.

Material For Transformer Core The main problem with transformer core is, its hysteresis loss and eddy current loss in transformer. Hysteresis loss in transformermainly depends upon its core materials. It is found that a small quantity of silicon alloyed with low carbon content steel produces, material for transformer core which has low hysteresis loss and high permeability. As the increasing demand of power ratings, it is required to further reduce the core losses and for that another technique is employed on steel, which is known as cold rolling. This technique arranges the orientation of grain in ferromagnetic steel in the direction of rolling. The core steel which has under gone through the both silicon alloying and cold rolling treatments is commonly known as CRGOS or Cold Rolled Grain Oriented Silicon Steel. This material is now universally used for manufacturing for transformer core. Although this material has low specific iron loss but still it has some disadvantages, Like it is susceptible to increase loss due to flux flow in direction other than grain orientation and it also susceptible to impaired performance due to impact of bending, blanking the cutting CRGOS sheet. Both surfaces of the sheets are provided with an insulating of oxide coating.

Manufacturing Of Transformer Core During core manufacturing in factory some factors are taken into consideration, a) Higher reliability b) Reduction iniron loss in transformer and magnetizing current c) Lowering material cost and labor cost d) abatement of noise levels

Quality checking is necessary at every step of manufacturing to ensure quality and reliability. The sheet steel must be tested for ensuring the specific core loss or iron loss values. The lamination should be properly checked and inspected visually, rusty and bend lamination to be rejected. For reducing the transformer noises the lamination should be tightly clamped together and punch holes should be avoided as far as possible to minimize cross flux iron losses. The air gap a the joint of limbs and yokes should be reduced as much as possible for allowing maximum smooth conducting paths for magnetizing curren

CHAPTER-2 LITERATURE REVIEW THE IDEAL TRANSFORMER: VOLTAGE RATIO A power transformer normally consists of a pair of windings, primary and secondary, linked by a magnetic circuit or core. When an alternating voltage is applied to one of these windings, generally by definition the primary, a current will flow which sets up an alternating m.m.f. and hence an alternating flux in the core. This alternating flux in linking both windings induces an e.m.f. in each of them. In the primary winding this is the „back-e.m.f‟ and, if the transformer were perfect, it would oppose the primary applied voltage to the extent that no current would flow. In reality, the current which flows is the transformer magnetizing current. In the secondary winding the induced e.m.f. is the secondary open-circuit voltage. If a load is connected to the secondary winding which permits the flow of secondary current, then this current creates a demagnetizing m.m.f. thus destroying the balance between primary applied voltage and backe.m.f. To restore the balance an increased primary current must be drawn from the supply to provide an exactly equivalentm.m.f. so that equilibrium is once more established when this additional primary current creates ampere-turns balance with those of the secondary. Since there is no difference between the voltage induced in a single turn whether it is part of either the primary or the secondary winding, then the total voltage induced in each of the windings by the common flux must be proportional to the number of turns. Thus the well-known relationship is established that: And, in view of the need for ampere-turns balance:

Where, I and N are the induced voltages, the currents and number of turns respectively in the windings identified by the appropriate subscripts. Hence, the voltage is transformed in proportion to the number of turns in the respective windings and the currents are in inverse proportion (and the relationship holds true for both instantaneous and r.m.s. quantities). The relationship between the induced voltage and the flux is given by reference to Faraday‟s law which states that its magnitude is proportional to the rate of change of flux linkage and Lenz‟s law which states that its polarity such as to oppose that flux linkage change if current were allowed to flow. This is normally expressed in the form

But, for the practical transformer, it can be shown that the voltage induced per turn is Where K is a constant, Φm is the maximum value of total flux in Webers linking that turn and f is the supply frequency in Hertz. The above expression holds good for the voltage induced in either primary or secondary windings, and it is only a matter of inserting the correct value of N for the winding under consideration. For design calculations the designer is more interested in volts per turn and flux

density in the core rather than total flux, so the expression can be rewritten in terms of these quantities thus: WhereN = volts per turn, which is the same in both windings Bm=maximum value of flux density in the core, Tesla A = net cross-sectional area of the core, mm2 f = frequency of supply, Hz. For practical designs Bm will be set by the core material which the designer selects and the operating conditions for the transformer, A will be selected from a range of cross-sections relating to the standard range of core sizes produced by the manufacturer, whilst f is dictated by the customer‟s system, so that the volts per turn are simply derived. It is then an easy matter to determine the number of turns in each winding from the specified voltage of the winding.

LEAKAGE REACTANCE: TRANSFORMER IMPEDANCE Mention has already been made in the introduction of the fact that the transformation between primary and secondary is not perfect. Firstly, not all of the flux produced by the primary winding links the secondary so the transformer can be said to possess leakage reactance. Early transformer designers saw leakage reactance as a shortcoming of their transformers to be minimized toas great an extent as possible subject to the normal economic constraints. With thegrowth in size and complexity of power stations and transmission and distribution systems, leakage reactance – or in practical terms since transformer windings also have resistance – impedance gradually came to be recognized as a valuable aid in the limitation of fault currents. The normal method of expressing transformer impedance is as a percentage voltage drop in the transformer at full-load current and this reflects the way in which it is seen by system designers. For example, an impedance of 10 per cent means that the voltage drop at full-load current is 10 per cent of the open-circuit voltage, or, alternatively, neglecting any other impedance in the system, at 10 times full load current, the voltage drop in the transformer is equal to the total system voltage. Expressed in symbols this is:

where Z is√ , R and X being the transformer resistance and leakage reactance respectively and IFL and E are the full-load current and open circuit voltage of either primary or secondary windings. Of course, R and X. may themselves be expressed as percentage voltage drops, as explained below. The „natural‟ value for percentage impedance tends to increase as the rating of the transformer increases with a typical value for a medium sized power transformer being about 9 or 10 per cent. Occasionally some transformers are deliberately designed to have impedances as high as 22.5 per cent.

LOSSES IN CORE AND WINDINGS The transformer also experiences losses. The magnetizing current is required to take the core through the alternating cycles of flux at a rate determined by system frequency. In doing so

energy is dissipated. This is known variously as the core loss, no-load loss or iron loss. The core loss is present whenever the transformer is energized. On open circuit the transformer acts as a single winding of high self-inductance, and the open-circuit power factor averages about 0.15 lagging. The flow of load current in the secondary of the transformer and the m.m.f. which this produces is balanced by an equivalent primary load current and its m.m.f., which explains why the iron loss is independent of the load. The flow of a current in any electrical system, however, also generates loss dependent upon the magnitude of that current and the resistance of the system. Transformer windings are no exception and these give rise to the load loss or copper loss of the transformer. Load loss is present only when the transformer is loaded, since the magnitude of the no-load current is so small as to produce negligible resistive loss in the windings. Load loss is proportional to the square of the load current.

RATED QUANTITIES The output of a power transformer is generally expressed in megavolt-amperes(MVA), although for distribution transformers kilovolt-amperes (kVA) is generally more appropriate, and the fundamental expressions for determining these, assuming sine wave functions, are as follows. Single-phase transformers Output = 4.44 f Φm NI with the multiplier 10_3 for kVA and 10_6 for MVA.

REGULATION The regulation that occurs at the secondary terminals of a transformer when load is supplied consists, as previously mentioned, of voltage drops due to the resistance of the windings and voltage drops due to the leakage reactance between the windings. These two voltage drops are in quadrature with one another, the resistance drop being in phase with the load current. The percentage regulation at unity power factor load may be calculated by means of the following expression:

This value is always positive and indicates a voltage drop with load. The approximate percentage regulation for a current loading of a times rated full-load current and a power factor of cosφ2 is given by the following expression:

where percentage resistance voltage at full load

At loads of low power factor the regulation becomes of serious consequence if the reactance is at all high on account of its quadrature phase relationship.

CHAPTER-3 Designing Of Single Phase Transformer Core Design:The starting point is the design of small transformer is the choice of turns per volts. The values of turns per volt are given in Table 1.

VA

10

Turns per volt

23.3

15

17.5

20

14.0

25

11.7

50

7.0

75

5.6

100

4.6

150

300 500

750

1000

4.0

2.8

2.3

1.7

1.6

Now

,Turns per volt Te

Flux in the core The frequency of the transformer is specified and the value of turns per volt Te is taken from table .therefore flux core is known. Net area of core Agi= .the value of maximum flux density Bm is assumed to be 1Wb / . Gross area of core Agi=Ai=Ai/0.9 The core is made up of any of the following combination of stamping: 1- E&I Stampings

2- T&U Stampings

E

E

D

A

D C

C

E

E

B

Fig.3

B

Fig.4

A square section is normally used for the central limb, i.e. the depth of the core is made equal to the width the central limb Or width of central limb A=√Agi A standard stamping giving a width A nearly equal to the value calculated above may be used.

Winding Design:Current in the primary winding Ip=VA/η The efficiency of small transformer varies from 80 to 96%. Turns in primary winding Tp = Vp Te Current in secondary winding Is = VA/V Area of secondary winding conductor a(s)=I(s)/δ(s) . Secondary winding turns Ts = 1.05 Vs Ts

Window Area:Space is required in the window for: (i) Primary winding

(ii)

Secondary winding

(iii)

Insulation and the former (bobbin) on which the winding are supported

Space required for primary winding = Space required for secondary winding = Space factor S = o.8 (d/d1)2=area of the copper in window/area of window d = diameter of bare conductor and d1= diameter of insulated conductor The space required for insulation and former is estimated as 20% of that required for the winding. Window area required Aw = 1.2(window area required for primary and secondary windings).

Physical Assumption For Transformer:Firstly we decide to design a transformer working on 220 v and 50 Hz input supply and gives 3A at 50 v .So calculation are done according to this data. Volt ampere rating of transformer = From table, turns per volt Te =4.0

Taking a flux density of 1.0 Wb/ Net iron area core, Ai= Gross core area Taking a square section for the limb. Width of central limb A= 12.5

Primary Winding:The efficiency of this transformer is assumed as 92%. Primary winding current Taking a current density of 2.33A/ Area of primary winding conductor ap= Diameter of bar conductor =0.626mm. Using enameled conductor. The nearest standard conductor has bare diameter=0.63mm.the diameter of insulated conductor is 0.707mm Space factor for primary winding=0.8 =0.635 Area of primary conductor used ap= Number of primary winding turns Tp=VpTe=

Winding space required by primary winding =

=

Secondary Winding:Secondary winding Is=3A Area of secondary winding conductor as = Diameter of bare conductor =1.285mm Using enabled conductor for secondary winding. The nearest standard conductor has bare diameter =1.32mm Diameter of insulated conductor =1.42mm Space factor for secondary winding =0.8(

⁄

Area of secondary winding conductor as= Number of secondary winding turns Ts=1.05VsTe= Window space required by secondary winding =

) r

Raw Material Required:1. Insulated wires:Wire covered with some non-conducting materials, such as plastic or silk, used for conducting electricity. We used insulated cable for reducing loss and prevent short circuit.

2. Plastic bobbins:A spool or reel that holds thread or yarn for spinning, weaving, knitting, sewing or camping lace. We used bobbin for wrapping core and copper wire .We have different size bobbin which are selected by according to power rating.

3. Nuts and screws: We required nuts and screws for fixing the core.

4. Cabinets:Cabinet is a cupboard used for holding or storing things, or a group of adviser.

5. Cables.

6. Wooden bars:A wooden bar or frame by which two draft oxen are joined at the head or necks for working together. 7. Iron cores:We have two type of core but we mostly used E&I type core because in it losses are less. 8. Varnish:A liquid preparation that applied to a surface drives to form a hard lustrous typically transparent coating .we used varnish due to which copper winding are become hard .if we don‟t varnish than copper winding starts vibration when current starts flowing through them . We used air-varnish because it becomes hard when come in contact with air.

Problem Arising In This Assumption In the pre assumed transformer it is difficult to maintain efficiency 92 % due to its very small size and practical use of this transformer is difficult because these transformer are used to operate relay on mobile charger .Its size is very small so specification of data is not accurate and the size of core used for this transformer is very small and not available in commercial market .And we are designing a single phase transformer for project purpose and itwas not suitable for project so we skip this idea and decide to designing a transformer with high rating whose manufacturing material is easily available in market .so we decide our rating 3000 VA. But calculation of 3KVA transformer is not to easy and not possible from above data and formulas .we used standard data given by transformer manufacturing companies.

CHAPTER-4 Flowcharts 1. Flow chart of core design

START

Et,K,Q,Bm,Ki,Type of core ,f

Et=k(Q)0.5

ɸm=Et/(4.44*f)

Ai=ɸm/Bm Bm Agi = Ai / Ki

d=(ɸm/Bm*x)0.5

a=? b=? c=? d=?

Select the suitable a,b,c,d and get the value of lamination

END

x

2. Flow chart for window start

ɸm,f,Bm,Ai,d

8/(30+KV),10/(30+KV),12/(30+KV)select any one

Q=3.33*f*m*Kw*Aw*Ai*(10)-3 Raio of width and Ww=(Ai/x) Hw=xl*Ww Height of window(xl) Hw=xl*Ww

D=Ww+d

N Check (Ww)max=0.7d?

Mostly space factor is 0.9 Y

END

3. Overalldimension flow chart

Overall dimension

start

d,Ww,D,Hy,a

D=d+Ww,H=Hw+2HY W=2D+a.Dy=a

END

4. Process flowchart order

design

Design approval

LT coil winding

Order final HT coil winding

insepection Issue job order

Core design Raw material

Core cutting

ispection Core coil assembly

insepction

In process Core assembly

heating

fitting

Take up connector

measurement

testing

packing

dispatch

Follow up

CHAPTER-5 Assembly Of Single Phase Step Down Transformer Our purpose is to design a single phase step down transformer of 3kVA,for this purpose we require some raw materials which are as follows:1.BOBBIN:- We have different size of bobbins for wrapping wire, which are selected according to power rating. We can use a plastic bobbin but we are using a bobbin made by thick insulated paper (cardboard type). 2. E&I STAMPINGS:-For making the iron core of the transformer we are using the combination of E&I stampings. As we know the rating of our transformer is 3 kVA so we need a 7 number stamping. These stampings are made up of Ukrane.

Selection Of Stamping NO. According To Power Rating This table is manufactured by Japan Company whomanufactures the raw material of transformer Efficiency of these transformer is approx. 90%.

Power

0.5KVA

Bobin size

1.5"

2"

1KVA

2KVA

3"

3KVA

3"

4KVA

5KVA

7.5KVA

10KVA

4"

3"

4"

5"

Core No.

4No.

4No.

7No.

7No.

N1

820

513

342

257

8No.

192

8No.

270

8No.

8No.

202

165

So we select 7 no. core or stamping for the transformer.

Dimensions Of Stamping

No. of stamping

7

B

A

2"

6"

C

5"

D

E

1"

1"

4:-CLAMP:-Clamps are used to hold the core & protect the winding these are made up of aluminum. 5:-WIRES USED FOR PRIMARY & SECONDARY WINDINGS:- Copper wires are used for primary & secondary windings because copper is a very good conductor & improves the efficiency. 6:-INSULATION : Different insulations are used i.e. insulation paper in coil, insulating tape on wires & varnish on core because if we do not apply varnish then the core start vibrating when current pass through them & produce humming sound. 7:-VOLTMETER:-To measure the input and output voltage we use a voltmeter of 320volts rating for single phase transformer but we are using a voltmeter of 500 volts 8:- REGULATOR SWITCH: - For controlling voltage ¤t regulator with 8 tapings are used. 9:-RELAY: - An electromagnetic attracted armature type relay is used to control the operations of transformer of rating 10 amp & 24 volts

Steps For Assembling Transformer Step1:1. First of all we have to make the coil which is made by wrapping the wire on the bobbin, we have bobbin made by a thick insulated paper we wrap the wire on it & the wire used is of gauge no.17, after one layer is done insulated paper is wrapped over it & this process is repeated till 8 layers are made & we get 8 wires at the receiving end. 2. When the coil is completed the wires are coated with insulating tape.

3. Now our coil is prepared next step is to make the core.

Step 2:1. A square section is used for central limb of coil i.e. depth of core is made equal to the width of the central limb of the core. 2. For making the core we have to use a combination of E&I stamping. 3. We will make a core by placing firstly the E stamping one over other from opposite sides of the coil; this process is repeated till we reach the end of the coil as shown in figure.

4. One thing which we should keep in our mind is that only one stamping is inserted at a time from both ends because if we insert 2, 3, or 4 stampings at a time then the efficiency will be reduced& there are chances of vibrations at the time of operation.. 5. After inserting E stampings, I stamping is inserted between 2 E stampings carefully to complete the core.

6. 2 Clamps are used to hold the core with the help of nuts &screws, after that insulation is done by varnish to reduce the vibrations & humming sound.

7. Now are transformer is ready to operate.

Modification In The Transformer:We have done a modification in our transformer designing to make our transformer work on double phase, which we have done by increasing the gauge number of wire to increase the voltage capacity of it. When we increase the number of gauge the thickness of wire gets decreased but the voltage carrying capacity is increased. If we want to double the voltage then the number of gauge should be increased by 3,& if we want to reduce the value of voltage to half then the number of gauge is decreased by 3.

GAUGE SCALE (Scale using for measurement of wire)

CHAPTER-6 OUTPUT OF TRANSFORMER Setup For Transformer Action 1. Adjust the transformer, selector switch, on/off switch, lamp & meter etc., in such a way length of wire used is minimum. 2. After this remove the insulated polish on the ends of the wire coming from the all tapping of the transformer. Take care that only that portion of insulated polish is removed which is required to connect it with the selector switch 3. Now take out the neutral wire from the three wires of incoming power supply, connect this neutral wire with the common end of the transformer. This common point of transformer is connected to the output socket. 4. The ground wire of the input power supply is tighten with screw at the cabinet of the transformer. 5. The phase wire of the input supply is connected to the on/off switch through a fuse wire; this wire from the on/off switch is connected to the pole of up/down mode switch. In this switch the end of the up mode connection is connected to the tapping number 1of the transformer. The connection from end of down mode goes to the tapping no.8 of the transformer.

6. Taking into consideration the position of the selector switch & steps in the transformer rest of the transformer tapping is connected to the pins of the selector switch.

7. The pole of the selector switch is connected to the output socket.

8. The changes in the voltage can be observed from the different positions of the selector Switch.

LINE CONNECTIONS For Down Connection:-

DOWN TRANSFORMER

250V

UP SWITCH

ON OFF SWITCH

240V

230V

220V

FUSE 5

210V 4

P

6

3

N

7

200V

POLE 2

8 1

3 PIN SOCKET OUTPUT

190V 1 POLE 8 WAY ROTTERY SWITCH

180V

E

180 V

P

PILOT LAMP

V 0V

N

For Up Connection:-

DOWN TRANSFORMER

250V

UP SWITCH

ON OFF SWITCH

240V

230V

220V

FUSE 5

210V 4

P

6

3

N

7

200V

POLE 2

8 1

3 PIN SOCKET OUTPUT

190V 1 POLE 8 WAY ROTTERY SWITCH

180V

E

180 V

P

PILOT LAMP

V 0V

N

CHAPTER-7 PROGRAMMING IN ‘C’ LANGUAGE #include<stdio.h> #include #include<math.h> #include #define pi 3.141592654 #define muo 0.000001256 int i; float Et,K,KVA,m,Bm,Ki,f,PHIm,Ai,Agi,ct,d,p,q,r,s; /* Et = Voltage per turn, KVA=KVA rating, Bm=Flux density in the core Ki=Stacking factor f= Frequency m=Number of phase PHIm=Flux in the core Ai=Net iron area Agi=Gross iron area ct=type of core d=dimension of the core p,q,r,s=dimension of the core */ float KV,Kw,delta,ratio1,Aw,Hw,Ww,D; */ KV=primary winding voltage Kw=Window space factor f=Frequency of the line voltage delta=Current density in the winding Aw=Window area ratio1=ratio height to width of window Hw=Height of the window Ww=Width of the window D=Distance b/w adjacent core centers */ Float FDy,Agy,Dy,Hy: /* ratio1=Ratio area of yoke to limbs FDy=Flux Density in the yoke Ay=Area of the Yoke Agy=Gross area of the yoke Dy=Depth of the yoke Hy=Height of the yoke */

/*

Float H,W,Df; H=Height of the frame W=Width of the frame Df=depth of the frame

*/

*/

Float Vis,Ctype; Float Vsp,Ts,Isp,as,x,y,delta1,as1,z,x1,y1,Ts1,lay,Lcs; Int c; Vis=Secondary Line Voltage Ctype=core Type Ts= Turn Per Phase ISp=Secondary Current per phase delta=Current density in the winding as=Area of the secondary conductor x,y=Dimension of secondary conductor delta1=Modified Current Density as1=Modified Area of Secondary Winding z=Covering of the conductor x1,y1=Dimension of conuctor with proper lamination Ts1=Turns along the axial depth Lay=Number of Layer b/w the conductor cls=Clearance b/w the Winding cly=Thickness of the pressboard winding bs= Radial depth of the low voltage winding di=Insulation for the circumscribing circle dc=diameter of the circumscribing circle Id=Inside Diameter Od=Outside Diameter lvi=Insulation b/w winding and core st=number of strip

*/ int c1; float Vlp,Vpp,Tp,Vc,Nc,Vc1,Ncn,Nct,Tp1,Tp2,tp,tc,Ncl,Tncl,lpp,ap,ap1; float dp,dp1,dp2,Hip,dbc,Lcp,clc,ti,bp,T,lDhv,ODhv,con,stp,ca,cr,dp3; */ Vlp=Primary line current Vpp=Primary phase current Tp=Primary Turns per phase Vc=Voltage per coil Nc=Number of coil Vc1=Modified voltage per coil Ncn=Number of normal coil Nct= turns in the normal coil Tp1=Modified turns after considering tapping Tp2=Total costumer turn tp=percentage tapping

tc=Turns per coil Ncl=Number of layers Tncl=Turn per layer Ipp=Primary phase current ap= Area of primary conductor ap1= Modified area of primary conductor dp=Calculated diameter dp1=Standard diameter of calculated diameter dp2=Insulated diameter of primary conductor Hlp=axial depth of the coil Dpc=sepration b/w adjacent coil Lcp=Axial length of the HV winding clc=Clearance ti=Thickness of the Insulation b/w the layer bp=Radial debth of the HV coil T=Thickness of insulation b/w HV and LV IDhv=Inside diameter of the HV winding ODhv=Outside diameter of the HV winding */ float Lmtp,Lmts; float Dpm,Dsm,Rp,Rs,Ref,ep,rop,ros; float Dm,Lmt,Lc,Xp,epx,epi; float Li2r,Ls,Pi2r,Ni,Ny,Wl,Lcl,Wy,Lyl,Pi; float Pc,Lt,eff; float atc,aty,Mmmf,Ato,lm,ll,lo,per; /***************************************************************************** ************

Core Design Of The Transformer ****************************************************************************** ************ Void cd( ) { clrscr( ); File *fp; fp=fopen(“c:\\machine\\trans\\cD.txt”,”w”); printf(“\t\t\t CORE DESIGN”); fprintf(fp,”\n/************************\n”); fprintf(fp,‟‟\t\t\t CORE DESIGN OF THE TRANSFORMER\n”); fprintf(fp,”******************************************/n\n\n\n\n”); printf(“Enter the KVA rating of the transformer (KV);”); scanf(“%f”,&KVA); fprintf(fp,”KVA rating of the transformer is % 0.2fKVA”,KVA); printf(“\nFor distribution transformer K=0.45,\n\nFor Power transformerK=0.6to0.7\n”); printf(“\nEnter the value of K:”);

scanf(“%f”,&K); fprintf(fp,”\nValue of K is %0.2fV”,Et); Et=K*Sqrt(KVA);//Voltage per turn fprintf(fp,”\nVoltage per Turn is %0.2f v”,Et); printf(“\nEnter he value of line frequency(Hz):”); scanf(“%f”,&f); printf(“\nEnter the number of phases:”); scanf(“%f”,&m); fprintf(fp,”\nNumber of phase of the transformer is %0.0f,”,m); fprintf(fp,”\nLine Frequency is %0.0f Hz”,f); PHIm=Et/(4.44*f);//Flux in the core fprintf(fp,”\nFlux in the core is %0.6f Wb”,PHIm); printf(\nDistributed transformer Bm=1 to 1.35 Wb/m^2.\n”); printf(“\nPower transformer bm=1.25 to 1.45 Wb/m^2.\n”); printf(“\nEnter the value of Flux density(Wb/m^2);”); scanf(“%f”,&Bm); fprintf(fp,”\nFlux density is %0.4f Wb^2”,Bm); Ai=PHIm/Bm;//Net Iron Area fprintf(fp,”\nNet iron area is % 0.6fm^2”,Ai); printf(“\nThe Net Iron Area is %f m^2\n”,Ai); printf(“\nEnter the value of stacking factor:”); scanf(“%f”,&Ki); fprintf(fp,”\nStacking factor is %0.2f”,Ki); Agi=Ai/Ki//Gross Iron Area fprintf(fp,”\nGross iron area is %0.6fm^2,”Agi); printf(“\nEnter the type of the core:\n1-Square\n2-Cruciform\n3-3Stepped\n44stepped\n:”); scanf(“%d”,&i); switch(i) { Case1: printf(fp,”\nType of the core is square”); ct=0.45: //Square Core d=sqrt(Ai/ct): //diameter of the core fprintf(fp,”\nDiameter of the core is %0.4fm”,d); p=sqrt(0.5)*d: //dimensions printf(“\nThe Dimension is %0.3f”,p); break; Case2: fprinf(fp,”\nType of the core is Cruciform”); Ct=0.56 //Cruciform core d=sqrt(Ai/ct); fprintf(fp,”\nDiameter of the Core is %0.4fm”,d); p=0.85*d; q=0.53*d; printf(“\nThe Dimension is 5f*%f”,p,q);

fprintf(fp,”\nThe Dimension is %0.3f*%0.3f”,p,q); break; Case3: fprintf(fp”\nType of the Core is 3 stepped”); ct=(0.6); //3 Stepped Core d=sqrt(Ai/ct); fprintf(fp,”\nDiameter of the core is % 0.4f m”,d); p=0.42*d; q=0.7*d; r=0.98d; printf(“\nThe Dimension is %f*%f*f”,p,q,r); fprintf(fp,”\nDiameter of the Core is %0.4f m”,d); break; } fclose(); Clrscr(); }

****************************************************************** to be contd……….

APPENDIX-A Dimensions No.

A

B

c

D

E

Remarks

17

1 / 2"

1.1 / 2"

1.1 /4 „

1 / 4"

1 / 4"

21

5/8"

2"

1.9 / 16"

5 / 16"

3 / 8"

10

5/8"

2..3/ 8"

2.1 / 8"

3 / 8"

3 / 8"

1

31/32"

2.17/32"

2.1 / 8"

5 / 16'

5 / 16"

74

11/16"

2.1/16"

2.1 / 4"

11 / 32"

11 / 32"

23

3 / 4"

2.1 / 4"

1.23 / 32"

3 / 8"

3 / 8"

11

3 / 4"

3"

1.7 / 8"

3 / 8"

3 / 8"

2

3 / 4"

3"

2.1 / 4"

3 / 8"

3 / 8"

30

20mm

60mm

50mm

10mm

10mm

31

7/8"

2.5 / 8"

2.3 / 16"

7 / 16 “

7 / 16"

45

7/8"

2.5 / 8"

2.3 / 16"

7 / 16”

7 / 16"

4 holes

15

1"

3"

2.1 / 2"

1.2”

1.2"

4 holes

44

1"

3"

2.1 /2"

1 / 2"

1 / 2"

4 holes

14

1"

3.5 / 16"

2.5 / 8"

17 / 32"

1 / 2"

4 holes

4

1"

3.13 / 16"

3.13 / 16"

17 / 32"

1 / 2"

4 holes

33

28mm

84mm

70mm

14mm

14mm

4 holes

3

1.1 / 4"

3.3 /4 “

3.1 / 8"

5 / 8"

5 / 8"

4 holes

13

1.1 / 4"

4”

3.1 / 2"

1 / 2"

1 / 2"

4 holes

16

1.1 /2"

4.1 / 2 “

3.3 / 4"

3 / 4"

3 / 4"

4 holes

5

1.1 / 2"

4.3 / 4”

3.3 / 4"

3 / 4"

3 / 4"

4 holes

6

1.1 / 2"

5”

4.2 / 2"

3 / 4'‟

3 / 4"

4 holes

7

2"

6”

4.15 / 16"

1"

1"

4 holes

43

2"

6”

5"

1"

1"

4 holes

8

2"

7.1 / 4”

6.3 / 4"

1"

1"

4 holes

4 holes

APPENDIX-B

WEIGHT TABLE

RAW MATERIAL

WEIGHT IN Kg

CORE

10

COIL

OTHER (RELAY WIRE,E.T.C)

TOTAL

2.9

0.6

13.5

APPENDIX-C COST TABLE

MATERIAL

COST AS PER MARKET VALUE IN Rs.

CORE

1600

COIL

1800

CLAMP

BOLT

BOBIN

TOTAL TOTAL COST COST

40

40

80

3560 3560

APPENDIX-D PICTURES OF HARDWARE MODEL:-

APPENDIX-E USES OF TRANSFORMER A transformer is used in almost all a.c. operations 

In voltage regulator for T.V., refrigerator, computer, air conditioner etc. In the induction furnaces.



A step down transformer is used for welding purposes.



A step down transformer is used for obtaining large current.



A step up transformer is used for the production of X-Rays and NEON advertisement.



Transformers are used in voltage regulators and stabilized power supplies.



Transformers are used in the transmissions of a.c. over long distances.



Small transformers are used in Radio sets, telephones, loud speakers and electric bells etc.

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