EE-304

SBTET,TS
C-16 -EE-304

BOARD DIPLOMA EXAMINATION,(C-16)

DEEE-SECOND YEAR,
THIRD SEMESTER EXAMINATION
DEEE-304, DC MACHINES         Time:3 hours
Total Marks:80
PART-A
3×10=30M
Instructions:
  1. Answer all questions.
  2. Each question carries three  marks.
  1. State  Fleming’s  Right  Hand rule.
  2. Classify DC generators based on field excitation.
  3. Define (i) Lap winding (ii) Wave winding.
  4. State the methods to improve commutation.
  5. Define (i) critical resistance (ii) critical speed .
  6. State the working principle of a  DC motor.
  7. Draw the power flow diagram of a DC motor.
  8. What is the necessity of starter for a DC motor .
  9. List the different methods of speed control of DC motors.
  10. State the advantages of Swinburne’s test.
PART-B
10×5=50M

Instructions:-

  1. Answer any five questions.
  2. Each question carries ten marks.
11.
(a) Derive EMF equation of a DC generator. 5M
(b) A shunt generator delivers 450A at 230V and the resistance of the shunt field and armature are 50 Ω and 0.03 Ω respectively. Calculate the generated  EMF .  Neglect brush drop. 5M
12.
(a)Derive the condition for maximum efficiency of a DC generator. 5M
(b)A 10 kW 250 V DC shunt generator has total rotational losses of 600 W. Its armature and shunt field resistance are 0.5 Ω and 125 Ω respectively. Calculate the efficiency at rated load. 5M
13. Derive the expressions  for  Demagnetizing  Ampere Turns per pole (ATd) and Cross Magnetizing Ampere Turns per pole(ATc) of DC generator.
14.(a). Explain the working of welding generator. 5M
(b). Explain the Internal and external characteristics of  DC shunt generator.5M
15.A 460 V DC series motor runs at 500 rpm and draws a current of 40 A. Calculate the speed and percentage change in torque if the load is reduced so that the motor draws 30A.Total resistance of the armature and field circuit is 0.8 Ω.  Assume flux is proportional to field current.
16.
(a).  Draw the electrical and mechanical characteristics of DC Series motor.  5M
(b). Mention one application of each type of self excited DC motors. 5M
17. Explain the working of 3-point starter with a neat sketch .
18. Explain  Swinburne’s  test with advantages and disadvantages.

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