A 25 kW, 240 V self excited dc shunt generator has a field circuit resistance of 62.5 02, and an armature resistance of 0.05 0. When delivering rated current at rated speed and voltage, calculate % Efficiency when rotational losses are 1200W, and iron losses are 600W. Note that Copper losses must be calculated too. No Units!

1A. Which of the following is/are a method of providing field excitation for a DC generator. a) separately excited shunt b) self-excited series c) self-excited shunt d) all of the above 1B. Which type of field winding typically has the higher resistance? a) series b) shunt

A 12-kW, 250-V dc. shunt generator has armature and field resistances of 0.68 ohm and 120 ohm. respectively. Determine the total armature power developed in generator.

Exercise 2 A shunt generator delivers 14A at 270V and the resistance of the shunt field and armature are 100 Q and 0.75 Q2, respectively. Calculate: i. The generated emf and the efficiency of this operating condition. ii. The generated emf if the shunt field impedance was triple and if it was double and the efficiency of these cases. iii. What emf could serve tha same active power of load but at load voltage of 240V and the efficiency in this case.