JNTU
JNTU B.Tech II ELECTRICAL TECHNOLOGY Previous Question Paper (April/May - 2023 - R16)
Answer all questions in Part A. Answer any one question from each unit in Part B.
Main
What is the use of Swinburne’s test on DC machines?
Answer
Swinburne’s test is used to predetermine the efficiency of a DC machine by treating it as a shunt machine. It is an indirect method that allows calculating efficiency at any load without actually loading the machine, thereby consuming minimal power.
Classify the DC Generators.
Answer
DC generators are classified based on the method of field excitation:
- Separately excited DC generators: The field winding is energized by an external DC source.
- Self-excited DC generators: The field winding is energized by the generator itself. These are further classified into:
- Shunt wound: Field winding is connected in parallel with the armature.
- Series wound: Field winding is connected in series with the armature.
- Compound wound: Contains both series and shunt field windings.
Why is transformer rating measured in KVA?
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State the operation principle of single-phase transformers.
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Define slip and slip speed.
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What are the starting methods of induction motor?
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Define coil span factor.
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Write the EMF equation of an Alternator.
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Mention the applications of shaded pole motor.
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Differentiate between moving coil and moving iron instruments.
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Discuss the construction of DC machines and derive the emf equation of dc generators.
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Explain various performance characteristic with neat sketch in the case of DC series and DC shunt motors.
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A 4-pole d.c. series motor has 944 wave connected armature conductors. At a certain load, the flux per pole is 34.6 mWb and the total mechanical torque developed is 209 N-m. Calculate the line current taken by the motor and the speed at which applied voltage of 500V. Total motor resistance is 3 Ω.
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Draw and explain phasor diagrams of single-phase transformer no load and on load.
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A 250 KVA, single phase transformer has iron losses of 18 KW, full load copper losses are 200 W. Calculate full load efficiency of the transformer at 0.8 power lagging and maximum efficiency at 0.8 power lagging.
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Explain the working principle of a 3-phase induction motor.
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A Three-phase induction motor is wound for four poles and supplied from a 50-Hz supply. Calculate (i) the Synchronous speed (ii) the speed of the rotor when the slip is 3% and the rotor frequency when the speed of the rotor is 900rpm.
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Draw the torque-ship characteristics of three phase induction motor.
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A 6-pole alternator runs at 1000 rpm, and supplies power to a 4 pole, 3 phase induction motor. The frequency of rotor of induction motor is 2 Hz. Determine the slip and speed of the motor.
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Explain in detail about the voltage regulation of an alternator.
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A 550V, 55kVA, 1-Phase alternator has an effective resistance of 0.2 ohms. A field current of 10 A produces an armature current of 200 A on short-circuit and an electromotive force of 450 V on open circuit. Calculate the full load regulation with 0.8 power factor lagging.
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Discuss the differences between two types of alternators.
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A 4-pole, 50 Hz star connected alternator has 6 slots per pole per phase and a two-layer winding with 4 conductors per slot. If the coil span is 150°, find induced emf if the flux per pole is 300 mWb.
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Explain the principle of working of 1-phase capacitor motors.
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Explain the principle of working of AC servomotors.
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Explain the classification of measuring instruments in detail.
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Describe working principle of moving coil Instruments with neat sketches.
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