Electrical Machines - Special Purpose Machines

Special Purpose Machines - IES Previous year questions.....

1. Hysteresis motors are used for Hi-Q record players because of their [IAS-1998]
a. Constant synchronous speed
b. insensitivity to supply voltage fluctuations
c. Extreamly study torque
d. non-dependence on centrifugal switch requirement

2. A two-phase servomotor develops maximum torque at [IAS-1999]
a.  Forward speed  half of the synchronous speed
b. Reverse speed  half of the synchronous speed
c. Synchronous speed
d. Twice the synchronous speed

3. In a shaded-pole induction motor, the rotor runs from the [IAS-2000]
a. shaded portion to the unshaded portion of the pole while the flux in the former leads that of the latter
b. shaded portion to the unshaded portion of the pole while the flux in the former lags that of the latter
c. unshaded portion to the shaded portion of the pole while the flux in the former leads that of the latter
d. Unshaded portion to the shaded portion of the pole while the flux in the former lags that of the latter

4.  Stepper motor are widely used because of [IAS-2001]
a. Wide speed range
b. no need for field control
c. Compatibility with digital system
d. large rating

5. Consider the following types of single phase motors:
1. Capacitor starts induction motor 2. Capacitor start and run induction motor
3. Permanent split capacitor motor 4. Shaded pole motor
The correct sequence of these in the ascending order of magnitude of starting torque is [IAS-2003]
a. 4,3,2,1
b. 2,3,4,1
c. 3,4,2,1
d. 1,2,3,4

6. For a reluctance type motor, if the stator magnetic field angular velocity is 'W' and the actual rotor angular velocity is 'Wr' then which one of the following equation is satisfied if the average electromagnetic torque is NOT zero? [IAS-2004]
a. W=Wr/2
b. W= Wr
c. W=2*Wr
d. W=4*Wr

7. In hand tool applications, which one of the following single phase motor is used? [IAS-2005]
a. Shaded pole motor
b. Capacitor run motor
c. Capacitor start motor
d. Ac series motor

8. In which one of the following is reluctance power developed? [IAS-2006]
a. Salient pole motor
b. Non-sailent pole motor
c. Squirrel cage induction motor
d. Transformer.

9. ) Match List -I with List -II and select the correct answer using the code given below the lists :
List - I
A. General purpose split phase FHP(Fractional HP) motor
B. General purpose capacitor start FHP motor
C. Permanent split capacitor start FHP motor
D. Shaded pole FHP motor
List-II
1. Refrigerator
2. Hair dryers
3. Unit Heaters
4. Fans, Blowers [IAS-2007]
a. A-1, B-2, C-4, D-3
b. A-4, B-1, C-2, D-3
c. A-4, B-1, C-3, D-2
d. A-4, B-3, C-2, D-1

10. The emf induced in a conductor of machine driven at 600 rpm, the peak value of flux density is 1.0 Wb/m 2 ., diameter of machine 2.0 meter and length of machine 0.30 m is [IAS-2010]
a. 41.83
b. 29.58
c. 9.42
d. 18.84

1. Statement (I) : The rotor of a servomotor is built with resistance so that its X/R ratio becomes small. Statement (II): The servomotor has good accelerating characteristics. [IAS-2012]
a. Both are true and Statement (II) correct explanation for Statement(I)
b. Both are true and Statement (II) not  correct explanation for Statement(I)
c. Statement(I) is correct and Statement (II) is false
d. Statement(I) is false and Statement (II) is true