SPPU Electronics and Telecom Engineering (Semester 3)
Electrical Circuits & Machines
May 2017
Total marks: --
Total time: --
(1) Assume appropriate data and state your reasons
(2) Marks are given to the right of every question
(3) Draw neat diagrams wherever necessary

Solve any one question from Q.1(a,b) &Q.2(a,b)
1(a) Apply Mesh Analysis & determine current I1 & I2:
7 M
1(b) Explain construction & working principle of current transformer.
5 M

2(a) State and explain Maximum power transfer theorem.
2 M
2(b) The following readings were obtained from O.C &S.C tests on 8 KVA, 400/120 V, 50 Hz transformer:
O.C. test on LV side 120 V 4 A 75 W
S.C. test on HV side 9.5 V 20 A 110 W

Calculate the voltage regulation & efficiency at full load, 0.8 P.f. lagging.
8 M

Solve any one question from Q.3(a,b) &Q.4(a,b)
3(a) Explain the characteristics of D.C. shunt motor. Comment on p.f.
5 M
3(b) Output of 3φ, 415 V Induction Motor running at 2% slip is 36.775 kW. Determine:
i) Rotor speed & Slip speed
ii) Rotor O/P & rotor copper loss
iii) Efficiency of motor at given loading conditions.
Assume Motor is wound for 4-pole & supply frequency to be 50Hz. Given friction & windage losses are 1500 W while stator losses are 3kW.
8 M

4(a) Explain Torque-slip characteristics of 3φ Induction Motor. Explain the effect of Rotor resistance on its characteristics with the help of diagram.
7 M
4(b) A 4 pole, 250 V Dc series Motor has wave connected armature winding with 1254 conductors. The flux pole is 22 mWb when the motor is taking 50 A. The armature & series field coil resistance are 0.3Ω & 0.2Ω Calculate the speed & Torque of the motor & also power developed in watts.
6 M

Solve any one question from Q.5(a,b) &Q.6(a,b)
5(a) What are Brushless Motors? Explain with neat diagram. Explain the operation of unipolar brushless DC Motor.
6 M
5(b) Explain construction, principle & applications of Reluctance Motor.
7 M

6(a) Compare Brushless DC Motor with conventional DC Motor.
6 M
6(b) What are Universal Motors? Explain speed-torque characteristics of compensated type & non-compensated type Universal Motor.
7 M

Solve any one question from Q.7(a,b) &Q.8(a,b)
7(a) What are Stepper Motors? Explain any one type in detail. State its applications.
6 M
7(b) Compare variable reluctance motor with permentent magnet stepper motor.
6 M

8(a) Explain construction & working of AC Sevomotor. State its applications.
6 M
8(b) What are Induction Motor? Explain operating principle of shaded 1φ Induction Motor.
6 M

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