B.EI B. Tech D E G R E E END S E M E S T E R EXAMINATIONS, Apr/May 2014
B . E - Biomedical (FULL TIME)
E E 9133/ Basic of Electrical Engineering
IV - S E M E S T E R ( R E G : 2008)
: 3 Hours
Max. Mark : 100
Time
Answer ALL Questions
Part-An0*2 =20 Marks)
1. State Ohms law of magnetic circuit.
2. Compare hysteresis and eddy current losses.
3. State the applications of DC Shunt motor.
4. What is condition for maximum torque in a DC motor?
5. If high frequency A C supply is given to the 50 Hz transformer, what will happen to the
transformer?
6. Why transformer is having highest efficiency among all other rotating machines?
7. State the necessary condition for creating rotating magnetic field.
8. What is condition for maximum torque in an induction motor?
9. Why single phase motors are not self starting?
10. Mention the different types of stepper motors.
Part B-(5*16=80 Mark)
11.
12. a.
(i) Explain the basic principles of magnetic circuits and B-H curve. (Compulsory)
The armature supply voltage of dc motor is 230 V. The armature current is 12 A. the
Armature resistance is 0.8 Q and the speed is 100 rad/s. Calculate induced emf,
electromagnetic torque, electrical power input to the armature, the mechanical
power, armature copper losses and efficiency. (3+3+3+3+2+2)
Or
12. b
Explain the various characteristics of DC motors.
13. (a) A 50 MVA, 110V/400V, 50 Hz single phase transformer has 100 turns on the
secondary side. Calculate
(a) Number of turns in the primary side.
(4 Marks)
(b) Primary and secondary currents
(4 Marks)
(c) Maximum value of flux in the core.
(4 Marks)
(d) Find the frequency in the secondary side(4 Marks)
Or
1/2
13 (b) In a 50KVA transformer, the iron loss is 500W and full load copper loss is 800W. Find
the efficiency at full load at 0.8 pf and maximum efficiency.
14.a. Explain the working principle of synchronous motors and phasor diagram for
synchronous generators.
Or
14. b. Explain the equivalent circuit and torque - slip characteristics of three phase
induction motor.
15. a Explain the working principle of split phase motor and method/for starting single
phase motors.
Or
15.b Explain the following .
(i) Variable reluctance stepper motor
(6 Marks)
(ii) Permanent magnet stepper motor
(6 Marks)
(iii) Comparison between unipolar and bipolar drive (4 Marks)
2/2