0195136047.pdf

600 ROTATING MACHINES

EXAMPLE 13.4.1

A 250-V, 50-kWshort-shuntcompound dc generator, whose schematic diagram is shown in Figure

E13.4.1(a), has the following data: armature resistance 0.05, series-field resistance 0.05, and

shunt-field resistance 130. Determine the induced armature emf at rated load and terminal

voltage, while taking2Vasthetotal brush-contact drop.

A 1

A 2

F 1 F 2 S 1 S 2

(a)

Figure E13.4.1Short-shunt com-

pound generator.(a)Schematic dia-

gram.(b)Equivalent circuit.

E

Rf = 130 Ω

RSe = 0.05 Ω

Ra = 0.05 Ω

+

+ +

− −

−

Vt = 250 V

Vf

If

Ia

It

(b)

Solution

The equivalent circuit is shown in Figure E13.4.1(b).

It=

50 × 103

250

=200 A

ItRSe= 200 × 0. 05 =10 V

Vf= 250 + 10 =260 V

If=

260

130

= 2 .0A

Ia= 200 + 2 =202 A

IaRa= 202 × 0. 05 = 10 .1V

E= 250 + 10. 1 + 10 + 2 = 272 .1V