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Electrical Engineering
Single Phase Induction Motors
Quiz 4
Solution
Q.1.
Which of the following statements regarding repulsion-start induction motor is incorrect ?
It requires more maintenance of commutator and other mechanical devices
It makes quite a bit of noise on starting
In fractional horse power motors, it has replaced the capacitor motors
It is not easily reversed
Q.2.
The rotor of a hysteresis motor is made of
aluminium
cast iron
chrome steel
copper
Q.3.
In case of a reluctance motor, when the load is increased so that it cannot maintain synchronous speed the motor will
Become unstable
Draw excessive armature current and may burn out
Fall out of synchronism and come to stand still
Run as induction motor
Q.4.
The motor used for the compressors is
d.c. series motor
shaded pole motor
capacitor-start capacitor-run motor
reluctance motor
Q.5.
If a particular application needs high speed and high starting torque, then which of the following motor will bepreferred ?
Universal motor
Shaded pole type motor
Capacitor start motor
Capacitor start and run motor
Q.6.
If starting winding of a single-phase induction motor is left in the circuit, it will
run faster
spark at light loads
draw excessive current and overheat
run slower
Q.7.
The rotor slots, in an induction motor, are usually not quite parallel to the shaft because it
improves the efficiency
helps the rotor teeth to remain under the stator teeth
helps in reducing the tendency of the rotor teeth to remain under the stator teeth
improves the power factor
Q.8.
The speed/load characteristics of a universal motor is same as that of
D.C. motor
D.C. shunt motor
D.C. series motor
none of the above
Q.9.
If the capacitor of a single-phase motor is short-circuited
the motor will not start
the motor will run
the motor will run in reverse direction
the motor will run in the same direction at reduced r.p.m.
Q.10.
The repulsion start induction run motor is used because of
good power factor
high efficiency
minimum cost
high starting torque
Q.11.
Which of the following statements regarding hysteresis motor is in incorrect ?
It is extremely sensitive to fluctuations in supply voltage
Its high starting torque is due to its high rotor hysteresis loss
It is extremely quiet in operation
It accelerates from rest to full-speed almost instantaneously
Q.12.
Which of the following single-phase motors has relatively poor starting torque ?
Universal motor
Repulsion motor
Capacitor motor
All single phase motors have zero starting torque
Q.13.
In a universal motor, the most common cause of brush sparking is
open armature winding
shorted armature winding
shorted field winding?
high commutator mica
all of the above
Q.14.
In repulsion motor direction of rotation of motor
is opposite to that of brush shift
is the same as that of brush shift
is independent of brush shift
Q.15.
Which of the following motor will give the highest starting torque ?
D.C. shunt motor
Schrage motor
Repulsion start and induction run motor
Universal motor
Q.16.
If the centrifugal switch of a two-value capacitor motor using two capacitors fails to open then
motor will not come up to speed
motor will not carry the load
current drawn by the motor will be excessively high
electrolytic capacitor will, in all probability, suffer break down
Q.17.
In case of a shaded pole motor the direction of rotation of the motor is
from main pole to shaded pole
from shaded pole to main pole
either of the above depending on voltage
either of the above depending on power factor
Q.18.
If a single phase induction motor runs slower than normal, the most likely defect is
worn bearings
short-circuit in the winding
open-circuit in the winding
none of the above
Q.19.
Centrifugal switch disconnects the auxiliary winding of the motor at about ____ percent of synchronous speed
30 to 40
70 to 80
80 to 90
100
Q.20.
The wattage rating for a ceiling fan motor will be in the range
200 to 250 W
250 to 500 W
50 to 150 W
10 to 20 W
Q.21.
In case of a shaded pole motor the direction of rotation of the motor is
from main pole to shaded pole
from shaded pole to main pole
either of the above depending on voltage
either of the above depending on power factor
Q.22.
The repulsion-start induction-run motor is used because of
good power factor
high efficiency
minimum cost
high starting torque
Q.23.
Which of the following motors has highest starting torque ?
Repulsion motor
Shaped pole motor
Capacitor-start motor
Split-phase motor
Q.24.
In split-phase motor iauxiliary winding is of
thick wire placed at the bottom of the slots
thick wire placed at the top of the slots
thin wire placed at the top of the slots
thin wire placed at the bottom of the slots
Q.25.
A universal motor can run on
only
only
either or
none of the above
Q.26.
Which of the following motor will give the highest starting torque ?
shunt motor
Schrage motor
Repulsion start and induction run motor
Universal motor
Q.27.
The direction of rotation of an hysteresis motor is determined by
interchanging the supply leads
position of shaded pole with respect to main pole
retentivity of the rotor material
none of these
Q.28.
If the capacitor of a single-phase motor is short-circuited
the motor will not start
the motor will run
the motor will run in reverse direction
the motor will run in the same direction at reduced r.p.m.
Q.29.
A centrifugal switch is used to dis- connect 'starting winding when motor has
run for about 1 minute
run for about 5 minutes
picked up about 50 to 70 per cent of rated speed
picked up about 10 to 25 per cent of rated speed
Q.30.
If a particular application needs high speed and high starting torque, then which of thefollowing motor will be preferred ?
Universal motor
Shaded pole type motor
Capacitor start motor
Capacitor start and run motor
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