0195136047.pdf

554 ROTATING MACHINES e T Te, ωm (a) i + − v Field Armature e Te T, ωm (c) i + − v Field Armature e Te T, ωm (b) i + − v Field A ...

13.1 ELEMENTARY CONCEPTS OF ROTATING MACHINES 555 satisfyingωs=ωm±ωr, which relates electrical and mechanical angular speeds, ex ...

556 ROTATING MACHINES Synchronous speed= 120 f P r/min (13.1.2) wherefis the frequency of the system of which the machine is a p ...

13.1 ELEMENTARY CONCEPTS OF ROTATING MACHINES 557 Figure 13.1.4Sketch of damper bars located on salient- pole shoes of a synchro ...

558 ROTATING MACHINES Elementary Induction Machines In the discussion that followed Equation (12.4.32), the third possible metho ...

13.1 ELEMENTARY CONCEPTS OF ROTATING MACHINES 559 the motor. The rotor winding is usually short-circuited through external resis ...

560 ROTATING MACHINES then be rotating in the direction opposite that of the rotating mmf, so the machine will act as a brake an ...

13.1 ELEMENTARY CONCEPTS OF ROTATING MACHINES 561 Torque 2 1 0 − 1 −ωs RS 0 P ωs Speed 2 ωs Slip Braking region Motor region Gen ...

562 ROTATING MACHINES Torque 0 ωs Speed Figure 13.1.7Approximate shape of torque–speed curve for a single-phase induction motor. ...

13.2 INDUCTION MACHINES 563 Field Shunt field Series field Field rheostat Field rheostat (a) (c) (d) (b) Dc source Armature Arma ...

564 ROTATING MACHINES flow of mechanical power. At standstill, however, the machine acts as a simple transformer with an air gap ...

13.2 INDUCTION MACHINES 565 and a magnetizing componentI ̄mlaggingE ̄ 1 by 90°. A shunt branch formed by the core-loss conductan ...

566 ROTATING MACHINES speed. Returning to the analogy of a transformer, and considering that the rotor is coupled to the stator ...

13.2 INDUCTION MACHINES 567 and the equivalent circuit may be redrawn as in Figure 13.2.5(b).R 2 ′is the per-phase standstill ro ...

568 ROTATING MACHINES Pm=Pg( 1 −S)=Tωm=m 1 (I 2 ′)^2 R′ 2 ( 1 −S) S (13.2.6) This much power is absorbed by a resistance ofR 2 ′ ...

13.2 INDUCTION MACHINES 569 Zt=R 1 +jXl 1 + jXm ( R′ 2 S +jX′l 2 ) R 2 ′ S +j(XM+X′l 2 ) = 0. 3 +j 0. 5 + j 15 ( 7. 5 +j 0. 2 ) ...

570 ROTATING MACHINES an expression forI 2 ′. To that end, let us redraw the equivalent circuit in Figure 13.2.8. By applying Th ...

13.2 INDUCTION MACHINES 571 Tmax= 1 ωs 0. 5 m 1 V 12 a R′′ 1 + √ (R′′ 1 )^2 +(X′′ 1 +X′l 2 )^2 (13.2.15) which can be verified b ...

572 ROTATING MACHINES EXAMPLE 13.2.2 For the motor specified in Example 13.2.1, compute the following: (a) The load componentI 2 ...

13.2 INDUCTION MACHINES 573 I2 start′ = 122. 9 √ ( 0. 281 + 0. 15 )^2 +( 0. 489 + 0. 2 )^2 = 122. 9 0. 813 = 151 .2A Tstart= 1 1 ...