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SPPU Electronics and Telecom Engineering (Semester 3)
Electrical Circuits & Machines
May 2017
Total marks: --
Total time: --
INSTRUCTIONS
(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:
!mage
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
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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