0195136047.pdf

574 ROTATING MACHINES Solid-state control (variable-terminal-voltage control, variable-frequency control, rotor- resistance con ...

13.2 INDUCTION MACHINES 575 For squirrel-cage-rotor machines, the problem is to keep down the starting current while maintaining ...

576 ROTATING MACHINES induction motors are usually two-pole or four-pole, rated at 2 hp or less, while slower and larger motors ...

13.2 INDUCTION MACHINES 577 Te= If^2 ( 1 −S) ωmS R′ 2 − Ib^2 ( 1 −S) ωm( 2 −S) R′ 2 (13.2.21) The following example illustrates ...

578 ROTATING MACHINES power factor, developed power, shaft output power, speed, torque, and efficiency when the motor is running ...

13.2 INDUCTION MACHINES 579 winding currents causes the motor to start. The auxiliary winding is disconnected by a centrifugal s ...

580 ROTATING MACHINES (a) + − Centrifugal switch Auxiliary winding Torque, per unit Torque during starting due to main and auxil ...

13.2 INDUCTION MACHINES 581 S = 1 (zero speed) S = 0 (synchronous speed) Torque, per unit 2 1 Speed or slip (a) (b) + − Auxiliar ...

582 ROTATING MACHINES TABLE 13.2.1Ranges of Standard Power Ratings for Single-Phase Induction Motors Motor Power Range Capacitor ...

13.3 SYNCHRONOUS MACHINES 583 Equivalent Circuit of a Synchronous Machine A review of the material about elementary synchronous ...

584 ROTATING MACHINES (a) jIaXs Ia Ef Vt φ δ (b) jIaXs Ia Ef Vt φ δ (c) jIaXs −Ia Ia Ef Vt φ δ (d ) jIaXs −Ia Ia Ef Vt φ δ Figur ...

13.3 SYNCHRONOUS MACHINES 585 Solution Per-phase terminal voltageVt= 6. 6 × 1000 √ 3 =3811 V Full-load per-phase armature curren ...

586 ROTATING MACHINES and the armature current, I ̄a= E ̄f−V ̄t jXs = Ef cosδ−Vt+jEf sinδ jXs (13.3.7) whereXsis the synchronous ...

13.3 SYNCHRONOUS MACHINES 587 Tmax= Pmax ωm = Pmax 2 πns/ 60 (13.3.12) wherensis the synchronous speed in r/min. In the steady-s ...

588 ROTATING MACHINES (b) Instead of an infinite bus as in part (a), let the power to the motor be supplied by a 1000-kVA, 2300- ...

13.3 SYNCHRONOUS MACHINES 589 Efm= √ 13282 + 941. 52 =1628 V Pmax= EfmVt Xsm = 1628 × 1328 5 = 432 .4 kW per phase, or 1297.2 kW ...

590 ROTATING MACHINES position. The effects of saliency are taken into account by thetwo-reactance theory, in which the armature ...

13.3 SYNCHRONOUS MACHINES 591 maintained on either side of the synchronizing switch. Thus,synchronizingrequires the following co ...

592 ROTATING MACHINES The line-to-line excitation voltage for machineAis √ 3 √ 4. 62 + 1272 = 8 .26 kV. E ̄fB=V ̄t+I ̄BZ ̄B=( 6. ...

13.3 SYNCHRONOUS MACHINES 593 Generator Bus Infinite bus Es ∠ δs jXe Eg ∠ δg Figure 13.3.5Generator connected to an infinite bus ...