L-24(TB)(ET) ((EE)NPTEL)

# L-24(TB)(ET) ((EE)NPTEL) - Module 7 Transformer Version 2...

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Module 7 Transformer Version 2 EE IIT, Kharagpur

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Lesson 24 Practical Transformer Version 2 EE IIT, Kharagpur
Contents 24 Practical Transformer 4 24.1 Goals of the lesson …………………………………………………………………. 4 24.2 Practical transformer ………………………………………………………………. 4 24.2.1 Core loss…………………………………………………………………. . 7 24.3 Taking core loss into account ……………………………………………………… 7 24.4 Taking winding resistances and leakage flux into account ………………………. . 8 24.5 A few words about equivalent circuit ……………………………………………. .. 10 24.6 Tick the correct answer ……………………………………………………………. 11 24.7 Solve the problems ………………………………………………………………… 12 Version 2 EE IIT, Kharagpur

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24.1 Goals of the lesson In practice no transformer is ideal. In this lesson we shall add realities into an ideal transformer for correct representation of a practical transformer. In a practical transformer, core material will have (i) finite value of μ r , (ii) winding resistances, (iii) leakage fluxes and (iv) core loss. One of the major goals of this lesson is to explain how the effects of these can be taken into account to represent a practical transformer. It will be shown that a practical transformer can be considered to be an ideal transformer plus some appropriate resistances and reactances connected to it to take into account the effects of items (i) to (iv) listed above. Next goal of course will be to obtain exact and approximate equivalent circuit along with phasor diagram. Key words : leakage reactances, magnetizing reactance, no load current. After going through this section students will be able to answer the following questions. How does the effect of magnetizing current is taken into account? How does the effect of core loss is taken into account? How does the effect of leakage fluxes are taken into account? How does the effect of winding resistances are taken into account? Comment the variation of core loss from no load to full load condition. Draw the exact and approximate equivalent circuits referred to primary side. Draw the exact and approximate equivalent circuits referred to secondary side. Draw the complete phasor diagram of the transformer showing flux, primary & secondary induced voltages, primary & secondary terminal voltages and primary & secondary currents. 24.2 Practical transformer A practical transformer will differ from an ideal transformer in many ways. For example the core material will have finite permeability, there will be eddy current and hysteresis losses taking place in the core, there will be leakage fluxes, and finite winding resistances. We shall gradually bring the realities one by one and modify the ideal transformer to represent those factors.
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## This note was uploaded on 08/03/2010 for the course ELECTRICAL EE212 taught by Professor Shetty during the Spring '10 term at International Institute of Information Technology.

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L-24(TB)(ET) ((EE)NPTEL) - Module 7 Transformer Version 2...

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