0195136047.pdf

474 MAGNETIC CIRCUITS AND TRANSFORMERS B,T H,At/m 0 −0.2 −0.4 −0.6 −0.8 −1.0 0.6 0.4 1.0 0.8 0.2 − 250 − 200 −1 00 − 50 50 100 1 ...

11.2 MAGNETIC CIRCUITS 475 (c) Next, suppose that the torus (which was originally laminated for reducing the eddy- current losse ...

476 MAGNETIC CIRCUITS AND TRANSFORMERS Flux φ Core N-turn coil Current I (a) Figure 11.2.1Simple magnetic circuit. (a) Mmf and f ...

11.2 MAGNETIC CIRCUITS 477 TABLE 11.2.1Analogy with dc Resistive Circuits DC Resistive Circuit Magnetic Circuit CurrentI(A) Flux ...

478 MAGNETIC CIRCUITS AND TRANSFORMERS Solution The net cross-sectional area of the core is 2. 52 × 10 −^4 × 0. 9 = 0. 5625 × 10 ...

11.3 TRANSFORMER EQUIVALENT CIRCUITS 479 Given
=NI= 500 × 4 =2000 At,g 1 =g 2 = 0 .25 cm, andg 3 = 0 .4 cm;A 1 =A 2 = 0. 5 A 3 ; ...

480 MAGNETIC CIRCUITS AND TRANSFORMERS Transformers may be classified by their frequency range: power transformers, which usuall ...

11.3 TRANSFORMER EQUIVALENT CIRCUITS 481 in whichI 1 andI 2 are the rms value ofi 1 andi 2 , respectively. If the flux varies si ...

482 MAGNETIC CIRCUITS AND TRANSFORMERS + − V 1 = E 1 Z = jXm (a) + − V 1 = E 1 RC jXm (b) + − V 1 RC jXm (c) R 1 jX 1 E 1 + − Fi ...

11.3 TRANSFORMER EQUIVALENT CIRCUITS 483 Note that phasor notation andrmsvalues for all voltages and currents are used. It is ge ...

484 MAGNETIC CIRCUITS AND TRANSFORMERS R 2 ′=a^2 R 2 = ( 2400 240 ) 2 ( 0. 0075 )= 0. 75  X′ 2 =a^2 X 2 = ( 2400 240 ) 2 ( 0. 0 ...

11.3 TRANSFORMER EQUIVALENT CIRCUITS 485 The equivalent circuits shown in Figure 11.3.4 are often known as transformerT-circuits ...

486 MAGNETIC CIRCUITS AND TRANSFORMERS 11.4 Transformer Performance The characteristics of most interest to power engineers arev ...

11.4 TRANSFORMER PERFORMANCE 487 Solution (a) The equivalent circuit of the transformer, referred to the high-voltage (primary) ...

488 MAGNETIC CIRCUITS AND TRANSFORMERS (b) The corresponding phasor diagram is shown in Figure E11.4.1(b). (c) The equivalent ci ...

11.4 TRANSFORMER PERFORMANCE 489 Note that the current at one-half rated load is half of the full-load current, and that the cop ...

490 MAGNETIC CIRCUITS AND TRANSFORMERS (b) During 24 hours, energy output=( 8 × 0. 9 × 50 × 0. 8 )+( 12 × 0. 5 × 50 × 0. 8 )=528 ...

11.5 THREE-PHASE TRANSFORMERS 491 V V/√3 V/(√3a) − + I + aI √ 3 aI (a) Figure 11.5.1Wye–delta, delta–wye, delta– delta, and wye– ...

492 MAGNETIC CIRCUITS AND TRANSFORMERS 11.6 Autotransformers In contrast to a two-winding transformer, the autotransformer is a ...

11.6 AUTOTRANSFORMERS 493 (b) Determine the kVA rating as an autotransformer, and find how much of that is the conducted kVA. (c ...