JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD
JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech II Year ELECTRICAL TECHNOLOGY Previous Question Paper (February -2024 - R16)
Note: i) Question paper consists of Part A, Part B. ii) Part A is compulsory, which carries 25 marks. In Part A, answer all questions. iii) In Part B, Answer any one question from each unit. Each question carries 10 marks and may have a, b as sub questions.
Part A
What are the various losses of a d.c machine?
Answer
The losses in a D.C. machine are categorized into the following types:
- Copper Losses: These include armature copper loss (Ia2Ra), field winding losses (shunt and series field copper losses), and brush contact resistance loss.
- Magnetic (Iron/Core) Losses: These consist of hysteresis loss and eddy current loss occurring in the armature core due to the rotation of the armature in the magnetic field.
- Mechanical Losses: These include friction losses at the bearings and the commutator, as well as windage loss caused by air resistance to the rotating armature.
- Stray Load Losses: These are small additional losses caused by distortion of the main magnetic flux due to armature reaction.
Why brushes are used in DC machines?
Answer
Brushes are used in DC machines to provide a stationary electrical connection to the rotating commutator. Their primary functions are to collect current from the armature conductors in a generator or to supply current to the armature windings in a motor. By maintaining continuous physical contact with the rotating commutator segments, brushes ensure the commutation process, which facilitates the conversion of alternating current induced in the armature coils into unidirectional current at the external terminals.
What is the function of core in transformer?
Answer
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Explain the relationship between number of turns and current in transformer.
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What is the value of slip during starting of induction motor?
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What are the applications of induction motor?
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What is the relationship between speed and frequency in alternator?
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What are the types of alternators?
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What are the examples of indicating instruments?
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What is a synchro? Give its applications.
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Part B
Describe in detail about flux control method of speed control of DC motors.
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Discuss about the construction of DC series machines.
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What are the various characteristics of DC generators? Discuss.
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Explain the working of three point starter in detail.
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Discuss in detail about various types of transformers.
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The maximum flux density in the core of a 200/2000 V, 50 Hz single phase transformer is 2 Wb/m^2. If the EMF per turn is 10 Volt, calculate the number of primary and secondary turns and the area of the core.
Answer
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Explain the working transformer on load with the help of phasor diagram.
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A 5000/200 V, 75 kVA, single phase, 50 Hz transformer has core loss of 600 W and full load copper loss of 800 W. determine the kVA load for maximum efficiency and value of maximum efficiency at unity power factor.
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Explain the working of three phase induction motor in detail. Draw its torque-slip characteristics.
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Give the detailed construction of slip ring induction motor.
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Explain the advantages and disadvantages of DOL starting of induction motors.
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How an alternator operate? Describe in detail.
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Describe in detail about SC test on alternators.
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Derive the EMF equation in alternators.
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Discuss about distribution and coil span factors with the help of examples.
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Explain the working of shaded pole motor in detail.
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Explain the working of AC servo motor in detail.
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Explain the working of stepper motor in detail.
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What is a moving iron instruments? What is its operation?
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