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# L12 magnetic circuits

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### L12 magnetic circuits

1. 1. ELE101 / 102 Dept of E & E Engg, MIT Manipal 1 Series Magnetic Circuit ( ) gg332211 rg0 gg 3r0 33 2r0 22 1r0 11 gg332211 lHlHlHlHfTotal mm μμ lB μμ lB μμ lB μμ lB SφSφSφSφmmf +++=         +++=+++= grg g g r r r g aμμ l S aμμ l S aμμ l S aμμ l SWhere SSSSce SlucTotal 0 330 3 3 220 2 2 110 1 1 321tanRe = = = = +++=
2. 2. ELE 101 / 102 Dept of E & E Engg, MIT Manipal 2 Exercise Fig. 1 The iron ring shown in Fig. 1, is made up of a material having a relative permeability of 1000 and has a flux density of 2 T in the air gap. For the given dimensions of l1 = 0.15 m, l2 = 0.1 m, l3 = 0.2 m, lag = 1 cm, A1 = A3 = Aag = 2*10-4 m2, A2 = 3*10-4 m2, if the current through the coil is 1.5 A, compute the number of turns required. Neglect leakage flux and fringe effect. 11029 turns
3. 3. ELE 101 / 102 Dept of E&E MIT Manipal 1 Parallel magnetic circuit without air gap +- R A R B R V Analogous electrical circuit 21 φ+φ=φ=== ; aμμ l S; aμμ l S; aμμ l S 3r30 1 AFEB 2r20 2 ADCB r0 AB 1 A B C D E F Φ Φ1 N Φ2 ADCB2AFEB1 ADCB2AFEB1ABTotal SSWhere ),SorS(SMMF mmf)B or ADCB(Path AFEmfPath AB mrequiredTotal mmf φ=φ φφ+φ= +=
4. 4. ELE 101 / 102 Dept of E&E MIT Manipal 1 Parallel magnetic circuit with air gap Φ1 Φ2 A B C DE F Φ +- R A R B V R a R bAnalogous electrical circuit
5. 5. ELE 101 / 102 Dept of E&E MIT Manipal 1 Exercise The core shown has a relative permeability of 4000. Find the current required for the exciting coil to produce a flux of 10 milli Wb in the central limb. Take total number of turns of the coil as 500 turns. ANS: 2.387 A
6. 6. ELE 101 / 102 Dept of E&E MIT Manipal 1 Exercise The core shown has a relative permeability of 4000. Find the current required for the exciting coil to produce a flux of 10 milli Wb in the central limb. Take total number of turns of the coil as 500 turns. ANS: 2.387 A