THAPAR INSTITUTE OF ENGINEERING & TECHNOLOGY PATIALA
DEPARTMENT OF ELECTRICAL AND INSTRUMENATION ENGINEERING
UEE306: Electro-Mechanical Energy Conversion
TUTORIAL 1 (Basic Problems on D.C. Generator)
Course Instructors: Dr. Prasenjit Basak & Dr. Amit Kumar
Q1. A D.C. generator has 24 armature conductors. Average e.m.f. induced in one conductor is
2 V and each conductor is designed to handle a current of 5 A. Calculate the rating of this
generator if number of parallel paths in this machine are (a) 2, (b) 4 and (c) 6.
[Answers: (a) 240 W, (b) 240 W, (c) 240 W]
Q2. (a) A 6-pole, 2 circuit wave connected armature has 250 conductors and runs at 1200 RPM.
The emf generated on open circuit is 600 V. Find the useful flux per pole.
(b) An 8-pole, lap connected armature has 960 conductors, a flux of 40 mWb per pole, and a
speed of 400 RPM. Calculate the emf generated on open circuit.
(c) If the armature in (b) were wave connected for 2-circuits, at what speed must it be driven
to generate 400 V?
(d) A 4 pole generator has a flux of 40 mWb per pole and a lap connected armature with 740
conductors. Find the emf generated on open circuit at 1000 RPM.
[(a) 0.04 Wb (b) 256 V (c) 156 RPM (d) 494 V]
Q3. A shunt machine, connected to 250 V mains, has an armature resistance (including
brushes) of 0.12 Ω, and the resistance of the field circuit is 100 Ω. Find the ratio of the speed
as generator to the speed as a motor, the line current in each case being 80 A. [1.08]
Q4. A 2-pole wave connected DC shunt generator charges a 100 V battery of negligible
resistance. The armature of machine is made up of 1000 conductors and has a resistance of 0.5
Ω. The charging currents are found to be 10A and 20A for generator speeds of 1055 and 1105
RPM respectively. Find the field circuit resistance and flux per pole of the generator. Neglect
armature reaction effects. [100 Ω, 6 mWb]
Q5. A 75kW, 250V compound DC generator has following data;
Ra=0.04Ω, Rse=0.04Ω, Rf=100Ω, Brush contact drop Vb=2V(1V each brush).
Compare the generated induced emf when fully loaded in (i) long shunt compound and (ii)
short shunt compound. [276.2V, 276.1V]
Q6. A 1500 kW, 550 V, 10 pole generator runs at 150 RPM. What must be the useful flux per
pole if there are 2500 conductors lap connected and the full load copper losses are 25 kW?
Calculate the area of the pole shoe if the gap density has a uniform value of 0.9 Wb/ m2 and
find the no-load terminal voltage, neglecting armature reaction and change in speed.
[(a) 0.0895 Wb (b) 994 cm2 (c) 559.2 V]