0195136047.pdf

594 ROTATING MACHINES 13.4 Direct-Current Machines Generally speaking, conventional dc generators are becoming obsolete and incr ...

13.4 DIRECT-CURRENT MACHINES 595 Commutating pole (interpole) Shunt field winding Series field winding Compensating field windin ...

596 ROTATING MACHINES (a) If Ia + − +−Vf Vt Rf Ra Ea (b) If Ia + − + + − + − Vf − Vt Rf Ra Ea Figure 13.4.3(a)Circuit representa ...

13.4 DIRECT-CURRENT MACHINES 597 are usually employed only in machines designed for heavy overload or rapidly changing loads, su ...

598 ROTATING MACHINES Ia = IL Vt IaRa IaRa Ea Ra Ea If +−Vf (a) Field current If Drop due to Open circuit armature reaction Load ...

13.4 DIRECT-CURRENT MACHINES 599 IL = Ia Vt = Ea − Ia(Ra + Rs) + − Vt Ra Ea − Series field Rs + (a) Diverter Ia(Ra + Rs) A B C V ...

600 ROTATING MACHINES EXAMPLE 13.4.1 A 250-V, 50-kWshort-shuntcompound dc generator, whose schematic diagram is shown in Figure ...

13.4 DIRECT-CURRENT MACHINES 601 DC Motor Characteristics We gain an understanding of the speed–torque characteristics of a dc m ...

602 ROTATING MACHINES The schematic arrangement of a shunt motor is shown in Figure 13.4.8(a). For a given applied voltage and f ...

13.4 DIRECT-CURRENT MACHINES 603 in Figure 13.4.9. Note that the no-load speed is very high; care must be taken to ensure that t ...

604 ROTATING MACHINES k 1 = 198 1[( 2 π/ 60 )×1000] = 1. 89 On load,Te =k 1 IfIa,or100= 1. 89 × 1. 0 ×Ia. Therefore, the armatur ...

13.4 DIRECT-CURRENT MACHINES 605 overall efficiency. The speed of the machine is governed by the value of the voltage drop in th ...

606 ROTATING MACHINES the evolution of flexible and efficient converters (see Section 16.1). Thus, the inherently good controlla ...

13.4 DIRECT-CURRENT MACHINES 607 RT 1 = 1. 56 + 0. 78 + 0. 39 + 0. 39 = 3. 12  At starting, the counter emf is zero; the armatu ...

608 ROTATING MACHINES Efficiency As is true for any other machine, the efficiency of a dc machine can be expressed as Efficiency ...

13.4 DIRECT-CURRENT MACHINES 609 Shunt field Series field Field rheostat (a) (b) Input from Electromagnetic power prime mover Ou ...

610 ROTATING MACHINES 13.5 Learning Objectives Thelearning objectivesof this chapter are summarized here, so that the student ca ...

13.6 PRACTICAL APPLICATION: A CASE STUDY 611 Optimum operating point Cp Cp max λ λopt Figure 13.6.1Typical power coefficient ver ...

612 ROTATING MACHINES 3 phase, 50-Hz supply DC link Converter 1 Converter 2 (both fully controlled) sfs fs Induction generator F ...

PROBLEMS 613 supply. The frequency of the supply connected to the stator is 60 Hz. (a) Let the rotor be driven at 3600 r/min in ...