Code No: RR210205
Set No. 1
II B.Tech I Semester Supplimentary Examinations, November 2007
(Electrical & Electronic Engineering)
Time: 3 hours
Max Marks: 80
Answer any FIVE Questions
All Questions carry equal marks
⋆ ⋆ ⋆ ⋆ ⋆
(a) What are the significances of energy and co-energy of Energy conversion sys-
(b) Derive expression for the magnetic force developed in linear electromagnetic
2. Design a lap winding for 32 conductor, 4 pole d. c. machine. Show also the brush
3. Explain the importance of series field, interpole and compensating windings in d.
c. compound machine.
4. A 250V, 50KW shunt generator has 1000 turns on each pole of its field winding.
On no load a current of 3.5A in the field winding produces a terminal voltage of
250V, but on full load the shunt current has to be increased to 5A for the same
terminal voltage at the same speed. Calculate number of series field turns per pole
required for level compounding.
5. A 4-pole 250V DC shunt motor has lap connected 960 conductors. The flux per
pole is 20mWb. Determine the torque developed by the armature and the useful
torque in Nm when current drawn by the motor is 32A. The armature resistance
is 0.1Ω and shunt field resistance is 125Ω. The rotational losses of the machine
amount to 825W. Derive the formula used.
(a) A 220V shunt motor takes 60A when running at 800rpm. It has an armature
resistance of 0.1Ω. Find the speed and armature current if the magnetic flux
is weakened by 20%, contact drop per brush = 1V. Total torque developed
(b) A 220V series motor runs at 800 rpm, when taking a current of 15A. The
motor has Ra = 0.3Ω and Rf = 0.2Ω. Find the resistance to be connected in
series with armature if it has to take the same current at the same voltage at
600 rpm. Assume flux is proportional to current.
(a) The following readings were obtained in a brake test conducted on a DC shunt
motor, supply volts = 240V, armature current = 35A, shunt field cur