Single Phase Motor Questions Answers

101. The output of a stepper motor is in the form of

(a) linear movements.
(b) angular movements.
(c) either (a) or (b).
(d) none of the above.

102. For speeds higher than say 3000 rpm, the machine used is

(a) induction motor.
(b) synchronous motor.
(c) universal motor.
(d) none of the above. [A.M.I.E. Sec B. Elec. Machines Summer 1995]

103. The stator and rotor pole number may be different in a

(a) pole changing induction motor.
(b) reluctance motor.
(c) repulsion motor.
(d) synchronous motor. [U.P.S.C. I.E.S. E.E.-II, 1993]

104. Which of the following motors is relatively free from mechanical and magnetic vibrations and give least noise ?

(a) Shaded pole motor.
(b) Universal motor.
(c) Hysteresis motor.
(d) Reluctance motor.

105. AC servomotor is basically a

(a) universal motor.
(b) capacitor motor.
(c) 2-phase induction motor.
(d) 3-phase induction motor.

106. Two stator windings of ac servomotors are oriented ……… electrical degrees apart.

(a) 90 [/expander_maker]
(b) 60
(c) 120
(d) 180

107. Consider the following statements regarding ac servomotor:

1. The torque-speed curve has negative slope.
2. It is sensitive to noise.
3. The rotor has high resistance and low inertia.
4. It has slow acceleration.

Which of the following are the characteristics of ac servomotor as control component?
(a) 1 and 2.
(b) 2 and 3.
(c) 1 and 3.
(d) 2 and 4.

108. An ac servomotor (2-phase induction motor) has a rotor with

(a) high resistance winding.
(b) very small diameter to reduce inertia.
(c) very small axial length to reduce inertia.
(d) both (a) and (b).
(e) both (a) and (c).

109. The drag cup rotor is employed in a two phase induction motor to give

(a) low inertia.
(b) high inertia.
(c) low torque.
(d) high torque.

110. AC servomotor has the drawback of

(a) commutation problem.
(b) low starting torque.
(c) poor reliability.
(d) all of these.

112. Which one of the following statements is not true for an ac servo-motor ?

(a) Has low inertia rotor.
(b) Is a single phase motor.
(c) Has slip torque characteristic as straight line with negative slope.
(d) Reference voltage frequency is high compared to signal frequency.

113. For stability of an ac servomotor

(a) a negative slope on the torque speed curve is necessary.
(b) linearized torque-speed curve is essential.
(c) the ratio of the rotor reactance to rotor resistance should be high.

114. If a conventional motor is used for servo-applications, the system becomes unstable due to

(a) large diameter of rotor.
(b) small axial length of rotor.
(c) low resistance of rotor.
(d) high resistance of rotor.

115. While a 2-phase ac servomotor is in operation, if the voltage across the control field winding becomes zero, then the motor has a tendency to run as a single phase induction motor. To prevent this

(a) rotor having high mass moment of inertia is used for such a motor.
(b) drag cup type of light rotor and high resistance is preferred.
(c) a low resistance is used.
(d) the number of turns in the control field winding used is less than the main reference winding. [U.P.S.C. I.E.S. E.E.-II, 1993]

116. A linear servomotor must have

(a) high rotor resistance.
(b) high rotor reactance.
(c) a large air gap.
(d) both high rotor resistance and reactance. [I.E.S. E.E.-II, 2005]

117. A two-phase servomotor develops maximum torque at

(a) forward speed of one-half of the synchronous speed.
(b) backward speed of one-half of the synchronous speed.
(c) synchronous speed.
(d) a speed of twice the synchronous speed. [U.P.S.C. I.E.S. 1999]

118. Ratio of the rotor reactance X to the rotor resistance R for a 2-phase servomotor

(a) is equal to that of a normal induction motor.
(b) is less than that of a normal induction motor.
(c) is greater than that of a normal induction motor.
(d) may be less or greater than that of a normal induction motor. [GATE E.E 2000]

119. A stepper motor is a ……. device.

(a) hydraulic
(b) pneumatic
(c) electromechanical

120. The input to a stepper motor is in the form of

(a) frictional force.
(b) electric pulses.
(c) mechanical inertia.
(d) viscous damping force.