The dc shunt machine in Problem 4.13 is provided with a series field winding of Nsr = 5 turns/pole and Rs = 0:05 Ω. It is connected as a long-shunt compound machine. If Rfc = 50 Ω, and the machine is operated as a cumulative compound motor (a) Determine its no-load speed. (b) Determine its full-load speed. Assume no armature reaction.
Problem 4.13
A dc shunt generator (20 kW, 200 V, 1800 rpm) has Ra = 0:1 Ω, Rfw = 150 Ω. Assume that Ea = Vt at no load. Data for the magnetization curve at 1800 rpm are
1. The machine is self-excited.
(a) Determine the maximum generated voltage.
(b) At full-load condition, Vt = Vt (rated), Ia = Ia (rated), If = 1:25 A. Determine the value of the field control resistance (Rfc).
(c) Determine the electromagnetic power and torque developed at full-load condition.
(d) Determine the armature reaction effect in equivalent field amperes (If(AR)) at full load.
(e) Determine the maximum value of the armature current assuming that If(AR) is proportional to Ia.
2. The shunt generator is now connected as a long shunt compound generator.
(a) Show the generator connection.
(b) Determine the number of turns per pole of the series field winding required to make the noload and full-load terminal voltage Vt = 200 V. Rsr = 0:04 Ω and Nf = 1200 turns/pole.