Rajasthan Technical University 2009 B.Tech Electrical Engineering Electrical machines (Rajasthan vidyapet university) - Question Paper

BSAE5-BSCH5-BSCO5-BSE5 BSET5-BSMR5-BSM5-BSAE8-BSCH8-BSCO8-SE8-BSET8- BSMR8-BSM8 - ELECTRICAL MACHINE

ans any 3 ques. (Question one is compulsory)

Q.1 find the expression for emf of a transformer?
Q.2 Derive an EMF formula of alternator ?

Q.3 Comparison ranging from Synchronous Motor and Induction Motor ?
Q.4 describe coil span factor and distribution factor in an alternator. Derive the emf
formula of an alternator ?

Q.5 State and discuss thevenin's theorem with the circuit diagram?
Group B (25 Marks)
ans any 3 ques. (Questions six is compulsory)

Q.6 A 40 KVA transformer has an iron loss of 450 w and a full load copper loss of
850 W. If the power factor of the load is 0.8. compute full load efficiency and
maximum efficiency.

Q.7 A 250 V DC shunt motor has armature resistance of 0.25 ?. On load it
takes an armature current of 50 A and runs at 750 RPM. If the flux of the motor is
decreased by 10% without changing the load torque, obtain the new speed of the motor

Q.8 Write short notes on auto transformer. Draw the diagram for the two kinds of auto
transformers. Write its advantage, disadvantage and applications

Q.9 obtain the current through terminal MN in the circuit. Use Thevenins theorem


Q.10. A 3 phase, 16 poles, star connected alternator has 192 stator slots with eight
conductors per slot and conductors of every phase are connected in series. The coil
span is 150° electrical. Determine the phase and line voltages of the machine when
is runs at 375 RPM and flux per pole is 0.064 Wb distribution sinusoid ally over the pole


Group C (25 Marks)
All ques. are Compulsory.

Q.11 Fill in the blanks ( every ques. carry two marks)

1. The equivalent capacitance of identical capacitor in series is ______________ and in parallel is _______________.
2. The main thing common ranging from Hopkinsons test and field's test is that both need _____________________.
3. Compared to the secondary of a loaded step up transformer, the primary has ____________ voltage and ____________ current.
4. A 50 HZ alternator will run at the greatest possible speed if it is wounded for _______________ poles.
5. While running, a synchronous motor is compelled to run at synchronous speed because of ______________________.
Q.11 Multiple option ques.. (Each ques. carry two marks)

1. Armature reaction is an alternator primarily affects
a. Rotor speed
b. Terminal Voltage per phase
c. Frequency of armature current
d. Generated voltage per phase.

2. In a synchronous motor, damper winding is given in order to
a. Stabilize rotor motion
b. Suppress rotor oscillations
c. Develop necessary starting torque
d. Both b and c

Earning:   Approval pending.