DC MACHINES PTU PAPER

Download Previous Year PTU University Question  Paper of EMEC & DC Machines EE-202 4th Sem B.Tech EE PTU April 2013 Paper

B.Tech. (EE-2011 Batch)

EMEC & DC Machines

Subject Code : EE-202          Paper ID : [ A0407]

Time : 3 Hrs.                          Max. Marks : 60

INSTRUCTIONS TO CANDIDATES :
1. SECTION-A is COMPULSORY consisting of TEN questions carrying TWO marks each.
2. SECTION-B contains FIVE questions carrying FIVE marks each and students have to attempt any FOUR questions.
3. SECTION-C contains THREE questions carrying TEN marks each and students have to attempt any TWO questions

EMEC & DC Machines EE-202 4th Sem B.Tech EE PTU April 2013 Paper

SECTION-A

Q1. Write Short Notes on :

  a) Why there is need of starters for DC motors?
  b) List the main parts of DC machine. What is importance of a commutator?
  c) How can we obtain the internal characteristics from external characteristics of a DC shunt generator?
  d) State and briefly discuss the principle of electromechanical energy conversion with one simple example.
  e) Define winding factors and benefits of short pitched coils.
  f) What is the function of compensation winding in a DC machine?
  g) If DC motor fails to start when switched on. What could be the possible reasons and remedies?
  h) When load is removed, _______ motor will run at the highest speed.
   i) Show the energy in magnetic field is expressed as E=l/2mH2=b2/2m
  j) Draw schematic diagram of a metadyne generator which behaves as a constant current generator.

                                      SECTION-B

Q2. Attempt any FOUR questions.                                                                    5×4=20

    2. What is commutations? What causes sparking on the commutator surface and how can it be avoided? Explain.
    3. Discuss flow of energy in electromechanical devices via coupling fields to confirm the generating and motoring principles.
   4. Classify DC generators. Show VI characteristics of all type of DC generators.
   5. Explain why the speed torque characteristic of DC shunt motor is not linear in the high torque region.
   6.A 60 KW, 250 V shunt motor takes 16A when running at 1440 The resistance of the armature and field are 0.2 Ohm and 125 Ohm respectively.When hot

    a) Estimate the efficiency of the motor when taking 152A.
    b) Also estimate the efficiency if working as a generator and delivering a load current of 152A at 250 V.

                                     SECTION-C

Q3. Attempt any TWO questions.                              2×10=20

  7. (a) What is the percentage saving in feeder copper if the line voltage in a 2-wire dc system is raised from 200 volts to 400 volts for the same power transmitted over the same distance and having the same power loss?
     (b) Show that in a string of suspension insulators, the disc nearest to the conductor has the highest voltage across it. (6,4)
  8. (a) Describe the Receiving end circle diagram for long transmission lines based on ABCD constants.
      (b) Discuss the effect of earth on capacitance of conductors. (6,4)
   9. Write short notes on any two of the followings :
       (a) Synchronous phase modifiers
       (b) Kelvin’s law
      (c) Compensation of transmission lines. (2×5)

EMEC & DC Machines EE-202 4th Sem B.Tech EE PTU April 2013 Paper

Get Started

Section a EMEC & DC Machines EE-202 4th Sem B.Tech EE PTU April 2013 Paper

Why there is need of starters for DC motors?

Expain Why there is need of starters for DC motors.
  

List the main parts of DC machine. What is importance of a commutator?

Main parts of DC machine.

Importance of a commutator.
  

How can we obtain the internal characteristics from external characteristics of a DC shunt generator?

Obtain the internal characteristics from external characteristics of a DC shunt generator.
  

State and briefly discuss the principle of electromechanical energy conversion with one simple example.

Principle of electromechanical energy conversion with one simple example.
  

Define winding factors and benefits of short pitched coils.

Winding factors and benefits of short pitched coils.
  

What is the function of compensation winding in a DC machine?

Function of compensation winding in a DC machine.
  

If DC motor fails to start when switched on. What could be the possible reasons and remedies?

Explain If DC motor fails to start when switched on.

What could be the possible reasons and remedies.
 

When load is removed, _______ motor will run at the highest speed.

When load is removed, _______ motor will run at the highest speed.

Show the energy in magnetic field is expressed as E=l/2mH2=b2/2m

Prove the energy in magnetic field is expressed as E=l/2mH2=b2/2m
  

Draw schematic diagram of a metadyne generator which behaves as a constant current generator.

Schematic diagram of a metadyne generator which behaves as a constant current generator.

EMEC & DC Machines EE-202 4th Sem B.Tech EE PTU April 2013 Paper 

Section B :EMEC & DC Machines EE-202 4th Sem B.Tech EE PTU April 2013 Paper              

What is commutations? What causes sparking on the commutator surface and how can it be avoided? Explain.

Commutation and Causes sparking on the commutator surface.
   

Discuss flow of energy in electromechanical devices via coupling fields to confirm the generating and motoring principles.

Flow of energy in electromechanical devices via coupling fields to confirm the generating and motoring principles.
   

Classify DC generators. Show VI characteristics of all type of DC generators.

Types of DC generators.

Show VI characteristics of all type of DC generators.
   

Explain why the speed torque characteristic of DC shunt motor is not linear in the high torque region.

Why the speed torque characteristic of DC shunt motor is not linear in the high torque region.
 

A 60 KW, 250 V shunt motor takes 16A when running at 1440 The resistance of the armature and field are 0.2 Ohm and 125 Ohm respectively.When hot

60 KW, 250 V shunt motor takes 16A when running at 1440 The resistance of the armature and field are 0.2 Ohm and 125 Ohm respectively.When hot

    

a) Estimate the efficiency of the motor when taking 152A.

Estimate the efficiency of the motor when taking 152A.
   

b) Also estimate the efficiency if working as a generator and delivering a load current of 152A at 250 V.

Estimate the efficiency if working as a generator and delivering a load current of 152A at 250 V.

EMEC & DC Machines EE-202 4th Sem B.Tech EE PTU April 2013 Paper 

EMEC & DC Machines EE-202 4th Sem B.Tech EE PTU April 2013 Paper

Get Started https://www.youtube.com/watch?v=UHX6f8TIvX8https://www.youtube.com/watch?v=M_RR6LVICp0https://www.youtube.com/watch?v=mV41CMWonN4https://www.youtube.com/watch?v=s0LVPE0Q3LE&list=PLA9Q9SDZ781WXNAWit379A4CRLMvjGiUw&index=14&t=0s

Section c :-EMEC & DC Machines EE-202 4th Sem B.Tech EE PTU April 2013 Paper              

What is the percentage saving in feeder copper if the line voltage in a 2-wire dc system is raised from 200 volts to 400 volts for the same power transmitted over the same distance and having the same power loss?

Find percentage saving in feeder copper if the line voltage in a 2-wire dc system is raised from 200 volts to 400 volts for the same power transmitted over the same distance and having the same power loss.

Show that in a string of suspension insulators, the disc nearest to the conductor has the highest voltage across it.

Show that in a string of suspension insulators, the disc nearest to the conductor has the highest voltage across it. 

Describe the Receiving end circle diagram for long transmission lines based on ABCD constants.

Explain Receiving end circle diagram for long transmission lines based on ABCD constants.

Discuss the effect of earth on capacitance of conductors.  

Effect of earth on capacitance of conductors.  

Write short notes on of the followings : (a) Synchronous phase modifiers

Write short notes on 
(a) Synchronous phase modifiers

Write a Short Note on (b) Kelvin’s law

Short Note on (b) Kelvin’s law

Write a Short Note on (c) Compensation of transmission lines.

 Short Note on (c) Compensation of transmission lines.

EMEC & DC Machines EE-202 4th Sem B.Tech EE PTU April 2013 Paper 

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