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Roll No.
Total No. of Pages : 02
Total No. of Questions : 09
B.Tech. (Electronics Engineering/Electrical & Electronics)
(OE 2012 Onwards) (Sem.-6)
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ELECTRICAL MACHINE
Subject Code : BTEEE-OPA
M.Code : 72838
Time : 3 Hrs.
Max. Marks : 60
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INSTRUCTIONS TO CANDIDATES :
- SECTION-A is COMPULSORY consisting of TEN questions carrying TWO marks each.
- SECTION-B contains FIVE questions carrying FIVE marks each and students have to attempt any FOUR questions.
- SECTION-C contains THREE questions carrying TEN marks each and students have to attempt any TWO questions.
SECTION-A
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- Write briefly :
- Define magnetic field intensity, flux and flux density.
- What are the core losses and how can this loss be minimized?
- Define Faraday's Law of Electro Magnetic Induction.
- What are the conditions for parallel operation of a transformer?
- Draw the no load phasor diagram of a transformer.
- Why are Starters necessary for starting DC motors?
- What is the significance of back emf in a DC motor?
- What are the various methods available for making single phase motor self-starting?
- State the advantage of using capacitor start motor over a resistance split phase motor.
- What are the advantages of cage type induction motor?
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1| M-72838 (S2)-214
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SECTION-B
- Explain the working principle of synchronous machine with neat diagram.
- Draw and explain fully the general block diagram representation of an electromechanical energy conversion device.
- Explain polarity test of single phase transformer with suitable circuit diagram.
- Explain the working principle of capacitor start single - phase induction motor. Why should the auxiliary winding in a capacitor start motor be disconnected after the motor has picked up speed?
- The peak value of flux density in the core of a 300/ 3000 V, 50 Hz 1 -phase transformer is 1.4 Wb / m². If the e.m.f. per turn is 10 volts, calculate :
- Primary and secondary turns and
- Area of cross section of the core.
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SECTION-C
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- Explain the principle of operation of dc machine. Derive the expression for the back emf in a dc motor. Briefly explain the role it plays in starting and running of the motor.
- A cage induction motor has a short-circuit current of 4 times the full-load value and has a full- load slip of 0.05. Determine a suitable auto-transformer ratio if the supply current is not exceed twice the full-load current. Also determine the starting torque in terms of the full-load torque.
- An 8-pole, 400 Vot motor has 960 wave connected armature conductors. The full load armature current is 40 A and flux per pole is 0.02 Wb. The armature resistance is 0.1 ohm and the contact drop is 1 V per brush. Calculate the full load speed of the motor.
NOTE : Disclosure of Identity by writing Mobile No. or Making of passing request on any page of Answer Sheet will lead to UMC against the Student.
2 | M-72838 (S2)-214
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This download link is referred from the post: PTU B.Tech 6th Semester Last 10 Years 2009-2019 Previous Question Papers|| Punjab Technical University
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