Page 269 - Solutions Manual to accompany Electric Machinery Fundamentals

R  20  N SE  25 turns
F
R  0 to 30 , set to 10  n  1800 r / min
adj
m
The machine has the magnetization curve shown in Figure P8-7. Its equivalent circuit is shown in Figure
P8-10. Answer the following questions about this machine, assuming no armature reaction.

(a) If the generator is operating at no load, what is its terminal voltage?
(b) If the generator has an armature current of 20 A, what is its terminal voltage?

(c) If the generator has an armature current of 40 A, what is its terminal voltage'?
(d) Calculate and plot the terminal characteristic of this machine.

SOLUTION
(a) The total field resistance of this generator is 30 , and the no-load terminal voltage can be found
from the intersection of the resistance line with the magnetization curve for this generator. The
magnetization curve and the field resistance line are plotted below. As you can see, they intersect at a
terminal voltage of 121 V.

263