JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD
JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech III POWER SEMICONDUCTOR DRIVES Previous Question Paper (February - 2023 - R18)
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
Draw the Speed – Torque Characteristics of DC series motor controlled by single phase semi converter.
Answer
The speed-torque characteristics of a DC series motor fed by a single-phase semi-converter exhibit a non-linear relationship where speed decreases as torque increases. The curve is characterized by a high starting torque at low speeds, with the speed dropping significantly as the load torque increases, following the inverse relationship between speed and flux in a series-wound machine.
What are the advantages and disadvantages of 3-phase fully controlled converters over single phase fully converters?
Answer
Advantages of 3-phase fully controlled converters include higher output voltage, lower ripple content in the output current, and higher power factor compared to single-phase converters. Disadvantages include increased circuit complexity, higher cost due to the requirement of more power semiconductor devices, and the need for a more complex firing circuit.
What do you mean by four quadrant operation?
Answer
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Define Chopper and what are applications of Choppers?
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How do you control the speed of an induction motor?
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Draw the closed loop operation of induction motor with block diagram.
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List out the applications of static Kramers drive.
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Explain the principle of slip power recovery used in control of induction motor.
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What is PWM based Voltage Source Inverter?
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Write the principle of self-control of synchronous motor.
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Part B
Explain the operation of single phase semi-controlled converter connected to DC separately excited motor and obtain voltage current wave forms for continuous current operation.
Answer
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Discuss the working of three phase fully-controlled converters connected to DC series motor and obtain voltage, current wave forms.
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Explain the operation of four quadrant chopper feeding to a DC separately excited motor and draw the wave forms for continuous current operation.
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What is electric braking? Explain various types of braking.
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Explain the operation of two quadrant dc chopper fed separately excited dc motor.
Answer
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Explain the operation of variable frequency control of induction motor by Current Source Inverter.
Answer
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Compare Voltage Source Inverter and Current Source Inverter.
Answer
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Explain the operation of variable frequency control of induction motor by cyclo converter with neat diagrams.
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Explain the Static Scherbius drive operation of an induction motor with a circuit diagram.
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Explain about static rotor resistance control of induction motor with neat diagram and draw the speed-torque characteristics.
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Explain the closed loop operation of synchronous motor drives with neat block diagram.
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Describe VSI fed synchronous motor drive in detail with a suitable block diagram.
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