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# Full transformer

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# Full transformer

here all MAJOR TOPICS OF TRANSFORMER IS MAINTAIN & WHICH HELPFULL FOR REVISION AND LEANING AND TEACHING

here all MAJOR TOPICS OF TRANSFORMER IS MAINTAIN & WHICH HELPFULL FOR REVISION AND LEANING AND TEACHING

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### Full transformer

1. 1. TRANSFORMER PRATIK ANANDPARA ELECTRICAL DEPARTMENT EMAIL : pratikanandpara1994@gmail.com PH NO : 7405492701
2. 2. CONTENT  What is transformer  Structure and working principle  Construction of transformer  Losses in transformer  Ideal v/s practical transformer  Uses and application of transformer
3. 3. INTRODUCTION  A transformer is a device that changes ac electric power at one voltage level to ac electric power at another voltage level through the action of a magnetic field.  There are two or more stationary electric circuits that are coupled magnetically.  It involves interchange of electric energy between two or more electric systems  Transformers provide much needed capability of changing the voltage and current levels easily.  They are used to step-up generator voltage to an appropriate voltage level for power transfer.  Stepping down the transmission voltage at various levels for distribution and power utilization.
4. 4. WHAT IS TRANSFORMER  A transformer is a static piece of apparatus by means of which an electrical power is transferred from one alternating current circuit to another electrical circuit  There is no electrical contact between them  The desire change in voltage or current without any change in frequency  Symbolically the transformer denoted as NOTE : It works on the principle of mutual induction
5. 5. STRUCTURE OF TRANSFORMER  The transformer two inductive coils ,these are electrical separated but linked through a common magnetic current circuit  These two coils have a high mutual induction  One of the two coils is connected of alternating voltage .this coil in which electrical energy is fed with the help of source called primary winding (P) shown in fig.  The other winding is connected to a load the electrical energy is transformed to this winding drawn out to the load .this winding is called secondary winding(S) shown in fig.
6. 6.  The primary and secondary coil wound on a ferromagnetic metal core  The function of the core is to transfer the changing magnetic flux from the primary coil to the secondary coil  The primary has N1 no of turns and the secondary has N2 no of turns the of turns plays major important role in the function of transformer
7. 7. WORKING PRINCIPLE  The transformer works in the principle of mutual induction  When the alternating current flows in the primary coils, a changing magnetic flux is generated around the primary coil.  The changing magnetic flux is transferred to the secondary coil through the iron core  The changing magnetic flux is cut by the secondary coil, hence induces an e.m.f in the secondary coil “The principle of mutual induction states that when the two coils are inductively coupled and if the current in coil change uniformly then the e.m.f. induced in the other coils. This e.m.f can drive a current when a closed path is provide to it.”
8. 8.  Now if load is connected to a secondary winding, this e.m.f drives a current through it  The magnitude of the output voltage can be controlled by the ratio of the no. of primary coil and secondary coil The frequency of mutually induced e.m.f as same that of the alternating source which supplying to the primary winding b
9. 9. CONSTRUCTION OF TRANSFORMER  These are two basic of transformer construction  Magnetic core  Windings or coils  Magnetic core  The core of transformer either square or rectangular type in size  It is further divided into two parts vertical and horizontal  The vertical portion on which coils are wounds called limb while horizontal portion is called yoke. these parts are  Core is made of laminated core type constructions, eddy current losses get minimize.  Generally high grade silicon steel laminations (0.3 to 0.5mm) are used
10. 10. WINDING  Conducting material is used in the winding of the transformer  The coils are used are wound on the limbs and insulated from each other  The two different windings are wounds on two different limbs  The leakage flux increases which affects the performance and efficiency of transformer  To reduce the leakage flux it is necessary that the windings should be very close to each other to have high mutual induction
11. 11. CORE TYPE CONSTRUCTION  In this one magnetic circuit and cylindrical coils are used  Normally L and T shaped laminations are used  Commonly primary winding would on one limb while secondary on the other but performance will be reduce  To get high performance it is necessary that other the two winding should be very close to each other
12. 12. SHELL TYPE CONSTRUCTION  In this type two magnetic circuit are used  The winding is wound on central limbs  For the cell type each high voltage winding lie between two voltage portion sandwiching the high voltage winding  Sub division of windings reduces the leakage flux  Greater the number of sub division lesser the reactance  This type of construction is used for high voltage
13. 13. LOSSES IN TRANSFORMER  Copper losses : It is due to power wasted in the form of I2Rdue to resistance of primary and secondary. The magnitude of copper losses depend upon the current flowing through these coils. The iron losses depend on the supply voltage while the copper depend on the current .the losses are not dependent on the phase angle between current and voltage .hence the rating of the transformer is expressed as a product o f voltage and current called VA rating of transformer. It is not expressed in watts or kilowatts. Most of the timer, is rating is expressed in KVA.
14. 14. Hysteresis loss : During magnetization and demagnetization ,due to hysteresis effect some energy losses in the core called hysteresis loss Eddy current loss : The leakage magnetic flux generates the E.M.F in the core produces current is called of eddy current loss.
15. 15. IDEAL V/S PRACTICAL TRANSFORMER  A transformer is said to be ideal if it satisfies the following properties, but no transformer is ideal in practice.  It has no losses  Windings resistance are zero  There is no flux leakage  Small current is required to produce the magnetic field While the practical transformer has windings resistance , some leakage flux and has lit bit losses
16. 16. APPLICATION AND USES  The transformer used in television and photocopy machines  The transmission and distribution of alternating power is possible by transformer  Simple camera flash uses fly back transformer  Signal and audio transformer are used couple in amplifier Todays transformer is become an essential part of electrical engineering
17. 17. REFERENCE  Electrical engineering by UA Bakshi  Principal of electrical machine by VK Mehta  Electrical machine by RK Rajput  www.allaboutcircuit.com  www.iiee.com
18. 18. Thank you
19. 19. Ideal Transformer
20. 20. Features of Ideal Trasnformer       Winding resistance core is negligible Core loss negligible Core has constant permiability Maximum efﬁciency(100%) All the ﬂux setup by primary links the sceondary winding purely inductive coils wound on loss free core Practically not possible
21. 21. 1.5 The Ideal Transformer.    An Ideal transformer is a lossless device with an input winding and an output winding. Zero resistance result in zero voltage drops between the terminal voltages and induced voltages Figure below shows the relationship of input voltage and output voltage of the ideal transformer. An Ideal Transformer and the Schematic Symbols. 3
22. 22.  The relationship between voltage and the number of turns. Np , number of turns of wire on its primary side. Ns , number of turns of wire on its secondary side. Vp(t), voltage applied to the primary side. Vs(t), voltage applied to the secondary side. where a is deﬁned to be the turns ratio of the transformer. a N N tv tv s p s p  )( )( Cont’d… 4
23. 23.   The relationship between current into the primary side, Ip(t), of transformer versus the secondary side, Is(t), of the transformer; In term of phasor quantities; -Note that Vp and Vs are in the same phase angle. Ip and Is are in the same phase angle too. - the turn ratio, a, of the ideal transformer affects the magnitude only but not the their angle. )()( tINtIN sspp  Cont’d… atI tI s p 1 )( )(  a V V s p  aI I s p 1  5
24. 24. 1.5.1 Power in an Ideal Transformer.    Power supplied to the transformer by the primary circuit is given by ; where, p is the angle between the primary voltage and the primary current. The power supplied by the transformer secondary circuit to its loads is given by the equation; where, s is the angle between the secondary voltage and the secondary current. Voltage and current angles are unaffected by an ideal transformer , p – s =  he primary and secondary windings of an ideal transformer have the same power factor. sssout IVP cos pppin IVP cos 6
25. 25. POWER TRIANGLE
26. 26. Open delta connection Or V-V connection of three phase transformer
27. 27. •Three phase power is supply by only two transformer It is employed 1.Load is too small 2.One of the transformer is disabled 3.Fault in any on transformer
28. 28. Delta-delta connection means-normal condition 3 transformer Power capacity=3 Vl*Is……………..(1) open delta transformer means-One transformer is removed Power capacity= √3 * Vl*Is…………………(2)
29. 29. Now take ratio of eq(1) & eq(2) • V-V capacity/delta-delta capacity= = √3 * Vl*Is/3 Vl*Is = 1/√3 =0.577 Approx 58%
30. 30. • Example : three phase transformer is made up form three 10 KVA transformer • Total capacity= 10+10+10=30 KVA • One transformer is removed now • Remaining capacity is 20 KVA now • Now transformer needs to transfer 20 KVA but is supplys only = 30*0.57=17.3 KVA • Capacity is reduced in otherwise 66% Load is supplied by both transformer but now only 57% load is carried
31. 31. Disadvantages of OPEN DELTA transformer • efficiency of transformer is decrease • Secondary voltage is become unbalanced due to higher load not perform when load is unbalanced • Average power factor is reduced and both transformer operate at different power fACTOR
32. 32. NAME PLATES OF TRANSFORMER
33. 33. Major manufacturing companies for Trasnformer • ABB INDIA(1889, More than 14000 transformer madeup) • ALSTOM T&D INDIA(1911, market capitalization of Rs 3,099.86 crore) • SIEMENS(1867) • TRANFORMER & RECTIFIER INDIA LTD(1994) • Kirloskar Electric Company Limited
34. 34. 1 Instrument Transformers • A transformer that is used in conjunction with a measuring instrument • It utilizes the current-transformation and voltage transformation properties to measure high ac current and voltage • They also provide isolation
35. 35. 2 Where to use Instrument Transformers • To measure high currents and high Voltages • Why can’t we use voltmeter with very high series resistance and ammeter with very low shunt resistance?
36. 36. 3 Disadvantages of Shunts & Multipliers • Shunts • Time constant should be same for meter and shunt • Power consumed increases • Insulation problems (for high voltages) • No Isolation • Multipliers (Series resistance) • Power consumption • Leakage currents, so good insulators used , hence costly • No isolation
37. 37. 4 Types of Instrument Transformers • Current transformer • Potential (Voltage) transformer
38. 38. 5 Current Transformers • Secondary is usually 5 A (Standard) • 5 A is sufficient for a relay to operate and for a meter to measure
39. 39. 6 Point to note about CT • Primary current depends on load, but not on the burden • Current coil of Wattmeter or Ammeter is connected across the terminal of the secondary or Relay • Secondary operates near short circuit conditions • One of the terminal of CT secondary winding is earthed
40. 40. 7 Types of CT
41. 41. 8 Constructional Details of Window CT
42. 42. 9 Layer 2 Layer 1 Core Constructional Details of Window CT
43. 43. 10 Primary Winding Secondary Winding Primary Connections Constructional Details of wound CT
44. 44. 11 Care, while operating with CT
45. 45. 12 Usually current is measured in terms of voltage across a standard resistor
46. 46. 13 Connections of CT and PT
47. 47. 14 Potential Transformer
48. 48. 15
49. 49. 16 Points to note about PT • Secondary is connected voltmeter or Potential coil of the Wattmeter or Relay • Design is similar to Power Transformer, but Potential Transformers are lightly loaded • Secondary is usually rated for 110 V • Should not be shorted
50. 50. 17 Construction of PT • For the same power rating, Voltage transformer is costly than Power transformer (large core & conductor size) • Output is small (and accurate), but size is large • Can carry more load (2 to 3 times) • Shell type core – Low voltage • Co-axial windings
51. 51. 18 Construction of PT • Insulation: Cotton tape and varnished cambric as insulation for coil • Oil immersed for more than 7 kV • Oil filled bushing for oil filled transformer • If one side of the primary winding is at neutral, one bushing is sufficient
52. 52. 19
53. 53. • Open circuit : Maximum voltage Minimum current • Short circuit : Maximum current Minimum voltage WHY???
54. 54. • Ameter always connects-- Series with terminal • Voltmeter always connect parallel with terminal Why????
55. 55. Open circuit test : Use to find Out Iron loss – Maximum voltage value  Iron Loss/core loss is Constant loss Short circuit test : Use to find out Copper loss/Ohmic loss [(I^2)*R]  Copper loss is variable loss in transformer which is vary according to load it gives maximum temprutre rise value
56. 56. NECESSITY OF TESTING Performance of device and other equipment Find Particular losses like Iron loss, copper loss Check the withstand capacity of terminal maximum and minimum levels of device.
57. 57. Open circuit test(oc test) • Open circuit test always perform on HV side of transformer • HV side side kept open in this test • Open circuit test is use to identify maximum Voltage value of transformer • copper loss is neglected in this test because Currrent value is very Low
58. 58. Short circuit test(Sc test) • SHORT circuit test always perform on LV side of transformer • LV side side kept SHORT in this test • SHORT circuit test is use to identify maximum CURRENT value of transformer • Iron loss is neglected in this test because Voltage value is very Low
59. 59. THREE PHASE SYSTEM BASICS Line voltage VL= voltage between lines Phase voltage Vph= voltage between a line and neutral
60. 60. THREE PHASE SYSTEM BALANCED STAR Line Voltage VL= √3 Vph Line current IL = Iph
61. 61. THREE PHASE SYSTEM BALANCED DELTA Line Voltage VL= Vph Line current IL = √3 Iph
62. 62. THREE PHASE TRANSFORMERS Almost all major generation & Distribution Systems in the world are three phase ac systems Three phase transformers play an important role in these systems 3 phase transformers can be constructed from (a) 3 single phase transformers (b) 2 single phase transformers (c ) using a common core for three phase windings
63. 63. 3 phase Transformer connections By connecting three single phase transformers 1. Star- Star connection 2. Delta- Delta connection 3. Star – Delta connection 4. Delta – Star connection
64. 64. * *The generation of an electrical power is usually three phase and at higher voltages like 13.2 KV, 22 KV or some what higher, Similarly transmission of an electrical power is also at very high voltages like 110 KV, 132 KV, 400 KV. To step up the generated voltages for transmission purposes it is necessary to have three phase transformers.
65. 65. * *Less space *Weight Less *Cost is Less *Transported easily *Core will be smaller size *More efficient *Structure, switchgear and installation of single three phase unit is simpler
66. 66. *
67. 67. *The three cores are arrange at 120° from each other. Only primary windings are shown on the cores for simplicity. *The primaries are connected to the three phase supply. *The three fluxes is also zero at any instant.
68. 68. *Hence the centre leg does not carry any flux. *So if centre leg is removed, any two legs provide the return path for the current and hence the flux in the third leg. *This is the general principal used in the design of three phase core type transformers.
69. 69. * *The primary and secondary winding of three phase transformers as three phase winding can be connected in different ways such as in star or in delta. With suitable connection the voltage can be raised or lowered. *In this section some commonly used connections for three phase transformers are discussed.
70. 70. *Star-Star connection *Delta-Delta connection *Star-Delta connection *Delta-Star connection *Open Delta or V connection *Scott connection or T-T connection
71. 71. **.
72. 72. *Advantages of Parallel Transformer: To maximize electrical power system efficiency—Load demand fulfill To maximize electrical power system availability during Fault & maintenance To maximize power system reliability-No Interrupt during any disturbance To maximize electrical power system flexibility-future expansion
73. 73. Necessary Condition for parallel Transformer Both transformer have 1. Same voltage ratio/Rating 2. Same polarity 3. Same Phase sequence(RYB-ryb) 4. Same percentage Impedance & Phase shift
74. 74. 1) Same Voltage Ratio *. Now say the secondary of these transformers are connected to same bus, *What happen if voltage ratio is not same? Apply KVL on secondary side : Its result voltage difference created between two transformer Ea-Eb ≠ 0 small voltage difference may cause sufficiently high circulating current causing unnecessary extra I2R loss in primary and secondary
75. 75. 2)Same polarity •Both have different polarity than in transformer Can’t nullify(cancel out each others effect)Circulating current This current create ohmic loss in transformer Primary and secondary and efficiency is decrease •So transformer needed to maintain same polarity
76. 76. *3) Same Phase sequence(RYB-ryb) *Opposite phase sequence not give result Ea-Eb ≠ 0  Phase shift create unequal voltage difference in transformer and it results circulating current • small voltage difference may cause sufficiently high circulating current causing unnecessary extra I2R loss in primary and secondary
77. 77. *What is Impdedance? the effective resistance of an electric circuit or component to alternating current, arising from the combined effects of ohmic resistance and reactance. Z=R+j(Xl-Xc)
78. 78. 4)Same percentage Impedance & Phase shift Ea and Eb is out of phase & impedance of transformer are inversely proportional to their MVA ratings Ea-Eb ≠ 0 Phase shift create unequal voltage difference in transformer and it results circulating currentOhmic Loss create
79. 79. Open delta connection Or V-V connection of three phase transformer
80. 80. •Three phase power is supply by only two transformer It is employed 1.Load is too small 2.One of the transformer is disabled 3.Fault in any on transformer
81. 81. Delta-delta connection means-normal condition 3 transformer Power capacity=3 Vl*Is……………..(1) open delta transformer means-One transformer is removed Power capacity= √3 * Vl*Is…………………(2)
82. 82. Now take ratio of eq(1) & eq(2) • V-V capacity/delta-delta capacity= = √3 * Vl*Is/3 Vl*Is = 1/√3 =0.577 Approx 58%
83. 83. • Example : three phase transformer is made up form three 10 KVA transformer • Total capacity= 10+10+10=30 KVA • One transformer is removed now • Remaining capacity is 20 KVA now • Now transformer needs to transfer 20 KVA but is supplys only = 30*0.57=17.3 KVA • Capacity is reduced in otherwise 66% Load is supplied by both transformer but now only 57% load is carried
84. 84. Disadvantages of OPEN DELTA transformer • efficiency of transformer is decrease • Secondary voltage is become unbalanced due to higher load not perform when load is unbalanced • Average power factor is reduced and both transformer operate at different power fACTOR
85. 85. NAME PLATES OF TRANSFORMER
86. 86. Major manufacturing companies for Trasnformer • ABB INDIA(1889, More than 14000 transformer madeup) • ALSTOM T&D INDIA(1911, market capitalization of Rs 3,099.86 crore) • SIEMENS(1867) • TRANFORMER & RECTIFIER INDIA LTD(1994) • Kirloskar Electric Company Limited
87. 87. 1 Instrument Transformers • A transformer that is used in conjunction with a measuring instrument • It utilizes the current-transformation and voltage transformation properties to measure high ac current and voltage • They also provide isolation
88. 88. 2 Where to use Instrument Transformers • To measure high currents and high Voltages • Why can’t we use voltmeter with very high series resistance and ammeter with very low shunt resistance?
89. 89. 3 Disadvantages of Shunts & Multipliers • Shunts • Time constant should be same for meter and shunt • Power consumed increases • Insulation problems (for high voltages) • No Isolation • Multipliers (Series resistance) • Power consumption • Leakage currents, so good insulators used , hence costly • No isolation
90. 90. 4 Types of Instrument Transformers • Current transformer • Potential (Voltage) transformer
91. 91. 5 Current Transformers • Secondary is usually 5 A (Standard) • 5 A is sufficient for a relay to operate and for a meter to measure
92. 92. 6 Point to note about CT • Primary current depends on load, but not on the burden • Current coil of Wattmeter or Ammeter is connected across the terminal of the secondary or Relay • Secondary operates near short circuit conditions • One of the terminal of CT secondary winding is earthed
93. 93. 7 Types of CT
94. 94. 8 Constructional Details of Window CT
95. 95. 9 Layer 2 Layer 1 Core Constructional Details of Window CT
96. 96. 10 Primary Winding Secondary Winding Primary Connections Constructional Details of wound CT
97. 97. 11 Care, while operating with CT
98. 98. 12 Usually current is measured in terms of voltage across a standard resistor
99. 99. 13 Connections of CT and PT
100. 100. 14 Potential Transformer
101. 101. 15
102. 102. 16 Points to note about PT • Secondary is connected voltmeter or Potential coil of the Wattmeter or Relay • Design is similar to Power Transformer, but Potential Transformers are lightly loaded • Secondary is usually rated for 110 V • Should not be shorted
103. 103. 17 Construction of PT • For the same power rating, Voltage transformer is costly than Power transformer (large core & conductor size) • Output is small (and accurate), but size is large • Can carry more load (2 to 3 times) • Shell type core – Low voltage • Co-axial windings
104. 104. 18 Construction of PT • Insulation: Cotton tape and varnished cambric as insulation for coil • Oil immersed for more than 7 kV • Oil filled bushing for oil filled transformer • If one side of the primary winding is at neutral, one bushing is sufficient
105. 105. 19