Electrical Machines - Special purpose machines

Special purpose machines - GATE previous year questions....

1. The developed electromagnetic force and/or torque in electro-mechanical energy conversion systems act in a direction that tends [GATE-1992]
a. to increase the stored energy at constant mmf
b. to decrease the co-energy at constant mmf
c. to increase the co-energy at constant mmf
d. to decrease the stored energy at constant mmf

2. Which material is used in controlling chain reaction in a nuclear reactor? [GATE-1996]
a. Thorium
b. Boron
c. Heavy water
d. Beryllium

3. Ratio of the rotor reluctance X to the rotor resistance R for a two-phase servomotor [GATE-2000]
a. Equal to the induction motor
b. Less than to the induction motor
c. More than to the induction motor
d. More than or Less than to the induction motor

4. List-I lists different applications and List-II lists the motors for these applications . Match the application with the most suitable motor and choose the right combination among the choices given these after
List - I 
A. Food mixer 
B.Cassette tape recorder
C.Domestic water pump
D.Escalator
List - II
1 . Permanent magnet dc motor
2. Single -phase induction on motor
3. Universal motor
4.Three-phase induction motor
5.Dc series motor
6.
[GATE-2003]
a.  A-3,B-6,C-4,D-5
b. A-1,B-3,C-2,D-4
c.  A-3,B-1,C-2,D-4
d. A-3,B-2,C-1,D-4

5. The type of single –phase induction motor having the highest power factor at full load is [GATE-2004]
a. Shaded pole
b. Split phase
c. Capacitor run
d Capacitor start

6. In a single phase induction motor driving a fan load , the reason for having a high resistance rotor is to achieve  [GATE-2005]
a. low starting torque
b. High efficiency
c. Quick acceleration
d. Reduced size

7. For a single phase capacitor start induction motor which of the following statements is valid ? [GATE-2006]
a. the direction of rotation can be changed by interchanging the supply terminals
b. Direction of rotation can not be changed
c. Capacitor is used for Power factor improvment
d.  the direction of rotation can be changed by interchanging the supply terminals

8.  A 3-φ, 3 stack ,variable reluctance step motor has 20 poles on each rotor andstator stack .The step angle of this step motor is  [GATE-2007]
a. 3 degrees
b. 6 degrees
c. 9 degrees
d. 12 degrees

9. Distributed winding and short chording employed in AC machines will result in  [GATE-2008]
a. Increase in EMF and reduction in harmonics
b. Decrease in EMF and induction in harmonics
c. Decrase in EMF and harmonics
d. Increase in EMF and harmonics