Electrical Machines - Dec 2013

Electronics Engineering (Semester 4)

TOTAL MARKS: 60
TOTAL TIME: 2 HOURS (1) Question 1 is compulsory.
(2) Attempt any three from the remaining questions.
(3) Use suitable data wherever required.
(4) Figures to the right indicate full marks. 1 (a) Explain the function of delay line in oscilloscope. What are the types of delay lines?(5 marks) 1 (b) Compare a true RMS meter with an average responding meter.(5 marks) 1 (c) Explain the necessity of damping torque in an indicating instrument.(5 marks) 1 (d) What is back emf. What is the effect of back emf in a.d.c. motor.(5 marks) 2 (a) Explain the digital phase meter using flip-flop. Write its advantages and disadvantages.(10 marks) 2 (b) Draw the circuit diagram of a schering bridge and derive the condition for balance. Draw phasor diagram.(10 marks) 3 (a) Explain different methods for speed control of D.C. motor.(10 marks) 3 (b) Draw and explain the front panel of dual trace oscilloscope.(10 marks) 4 (a) What are the Requirements of a good laboratory type signal generator? Explain A.F. signal generator.(10 marks) 4 (b) Explain the principle of operation of PMMC and moving Iron type of instruments. Compare the two basic types.(10 marks) 5 (a) Explain construction and working of digital frequency meter with the help of neat labelled diagram.(10 marks) 5 (b) Explain starting methods of Induction motor.(10 marks) 6 (a) Write a note on-DSO(10 marks) 6 (b) Explain R-2 R ladder technique used in D to A conversion.(10 marks)

Write short notes on :-

7 (a) Megger(5 marks) 7 (b) FET Voltmeter.(5 marks) 7 (c) Maxwell's Inductance bridge.(5 marks) 7 (d) Function of CT in CRO.(5 marks)