# EDC Important Questions for Univesity Exam Nov/Dec 2016

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#### EE6365 Electrical Drives & control. Important Questions for Univesity Exam Nov/Dec 2016

EE6365:Â  Electrical Drives & control.

###### EDC Important Questions for Univesity Exam Nov/Dec 2016

EE6365:Â  Electrical Drives & control.

Model Exam, Oct 2016

Time: 3 hoursÂ Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â  Semester: IIIÂ Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â  Total marks 100

Part â A (10 x 2 =20)

• Define cooling time constant
• Draw the block diagram of electrical drive
• Mention any four factors influencing the choice of electric drives
• What is the basic difference between a 3point starter and a four point starter
• What are the advantages of three phase slip ring induction motor
• What is a dc chopper?
• Mention the advantages of slip power recovery scheme
• Define duty cycle of a dc motor
• What are the main features of v/f control
• List the applications of a.c. regulator based variable speed induction motor

Part â B (65Marks)

• a) (i)Â Â Â Â Â Â Â Â  Discuss in detail the factors influencing the choice of electric drive. Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â  Â (6)

(ii)Â Â Â Â Â Â Â  Explain the method of estimating equivalent continuous power rating of a motor for Â Â Â Â Â Â Â Â  Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â  short time load applicationsÂ Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â  Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â  (7)

(Or)

1. a)Â Â Â Â Â Â Â Â  (i)Â Â Â Â Â Â Â Â  Derive the expression for a thermal model of motor for cooling curve. Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â  Â (8)

(ii)Â Â Â Â Â Â Â  Explain the classes of duty of motor. Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â  Â Â Â Â Â Â Â Â Â Â Â  Â (5)

• a) Derive the different methods of braking of dc motor with a neat sketch.Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â  Â Â Â Â Â Â Â Â Â Â  (13)

(Or)

1. b) Â Â Â Â Â Â Â  (i)Â Â Â Â Â Â Â Â  Draw and explain the speed characteristics of 3 phase induction motor Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â  Â (5)

(ii)Â Â Â Â Â Â Â  Explain the principle of operation of capacitor start and run single phase induction Â Â Â Â Â Â Â Â Â Â Â  Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â  motor Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â  Â Â Â Â Â Â Â Â Â Â Â (8)

• a) Explain the three point starter operation with neat sketch Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â  Â Â Â Â Â Â Â Â Â Â Â (13)

(Or)

1. b)Â Â Â Â Â Â Â Â  Sate and explain the various starting methods of squirrel cage induction motorÂ Â Â Â Â Â  Â Â Â Â Â Â Â Â Â Â  (13)
• a) (i)Â Â Â Â Â Â Â Â  Sate and explain various methods of controlling speed of d. c. shunt motorÂ Â Â Â Â Â Â Â Â Â Â Â  (7)

(ii)Â Â Â Â Â Â Â  Explain in detail the single phase semiconverter speed control for D.C. drive for Â Â Â Â Â Â Â Â Â Â Â Â Â Â  Â Â Â Â Â Â Â Â Â Â Â  separately excited motor Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â  Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â  Â (6)

(Or)

1. b) Discuss the Ward-leonard speed control system with a neat circuit diagram. Also write the Â Â Â Â Â Â Â Â Â Â  Â Â Â Â Â Â Â Â Â Â Â  advantages and disadvantages Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â  Â Â Â Â Â Â Â Â Â Â Â (13)
• a) Sate and explain the various schemes adopted for speed control of induction motor using voltages source inverter Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â  Â Â Â Â Â Â Â Â Â Â Â (13

(Or)

1. b) What is meant by slip power recovery scheme? Explain with necessary diagram? Â Â Â Â Â Â Â Â Â Â Â Â Â (13)

Part â c (15Marks)

• Devive the torque equation of three phase induction motor and derive torque slip characteristics

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