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APJ ABDUL KALAM TECHNOLOGICAL UNIVERSITY
FIFTH SEMESTER B.TECH DEGREE EXAMINATION, DECEMBER 2017

Course Code: EE311
Course Name: ELECTRICAL DRIVES & CONTROL FOR AUTOMATION (AU, ME)
Max. Marks: 100 Duration: 3 Hours
PART A

Answer any three full questions, each carries 10 marks. Marks

1 8) Derive an expression for the e.m.f generated in a d.c machine. (4)

0) Whatis meant by armature reaction? How does it will affect the main field flux? (2)

c) List out the different methods of excitation. Explain. (4)

2 a) Ad.c shunt generator operating at 850rpm is given below (8)

Eg(V): 12 40 102 176210 240 256
I{A):0 0.51 2 345
The machine has 6 poles. The type of winding is lap. The number of conductors
in the armature is 540. http://www.ktuonline.com
i) Calculate residual flux per pole.
11) The no load e.m.f for a total shunt field resistance of 1202.
൧) The critical field resistance of the field circuit.
iv) The critical speed for the shunt field resistance of 1202.
b) Define critical speed and critical field resistance of a d.c shunt generator. (2)
3 2) Derive an expression for the electromagnetic torque developed in a d.c motor. (2)
9) Ad.c shunt motor runs at 1300rpm on no-load drawing 5A from 220V mains. Its (8)
annature and field resistance are 0.24Q and 11062 respectively. When loaded
.the motor draws 60A from the mains. Calculate the speed when the motor is
loaded. Assume that the armature reaction demagnetizes the field by 3%. Also
calculate the internal torque developed at no load and on load. What is the motor
shaft torque at load?

4 a) Derive the speed-torque characteristics of ad.c shunt and 6,0 series motor. (4)
b) What are the losses occurring in a d.c motor and how do they vary with load (3)
current?
c) Why astarter is required for starting a d.c motor? (3)
PART B

Answer any three full questions, each carries 10 marks.

5 2) Derive the e.m.f equation of a single phase transformer. (4)

b) Draw the phasor diagram of a |-phase transformer at no load and derive the (4)
equivalent circuit.

c) Explain the difference between an ideal transformer and an actual transformer (2)

6 a) What are the losses produced in a transformer and derive the condition for (4)

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