Electrical Engineering · Question Bank
3P Induction Motors
88 of 135 questions match · page 4 of 5. Answer in your head first, then check the solution.
#61📘 EE Pocket Reviewer RojasEasy
When is cogging in an induction motor occurs?
AIt occurs at high voltage when the number of stator teeth and rotor teeth are equal
BIt occurs at high voltage and when the number of stator teeth and rotor teeth are not equal
CIt occurs at low voltage when the number of stator teeth and rotor teeth are equal
DIt occurs at low voltage and when the number of stator teeth and rotor teeth are not equal
#62📘 EE Pocket Reviewer RojasEasy
An induction motor works with what type of supply voltage?
ADC only
BAC only
CBoth AC and DC
DNone of these
#63📘 EE Pocket Reviewer RojasEasy
In a squirrel cage induction motor, the number of rotor bars is generally
AAn even number
BEqual to the stator poles
CA prime number
DNone of these
#64📘 EE Pocket Reviewer RojasEasy
Which of the following method is used to vary the speed of a squirrel cage induction motor?
ABy pole changing
BBy rheostatic control
CBy varying supply voltage
DBy cascade control
#65📘 EE Pocket Reviewer RojasEasy
What will happen if the rotor of a squirrel cage induction motor is open?
AThe motor runs at very high speed
BThe motor will not run
CThe motor will run at very low speed
DThe motor will run at normal speed but noisy
#66📘 EE Pocket Reviewer RojasEasy
What is the usual range of the full load slip of a three-phase induction motor?
A10% to 20%
B2% to 5%
C20% to 30%
D80% to 95%
#67📘 EE Pocket Reviewer RojasEasy
In a three-phase induction motor, what is the relative speed between the stator flux to the rotor flux?
AZero
BEqual to the synchronous speed
CEqual to the slip speed
DEqual to the rotor speed
#68📘 EE Pocket Reviewer RojasEasy
What is the slip of an induction motor at no load?
AInfinite
BAbout 5 to 10%
COne
DPractically zero
#69📘 EE Pocket Reviewer RojasEasy
A three-phase induction motor is running at slip s (in decimal). What is the rotor output?
A(1 + s) × (rotor input)
B(s) × (rotor input)
C(1 − s) × (rotor input)
D(1/s) × (rotor input)
#70📘 EE Pocket Reviewer RojasEasy
With an increase in supply voltage of an induction motor, which of the following will also increase?
AOperating power factor
BSlip
CTorque
DAll of these
#71📘 EE Pocket Reviewer RojasEasy
The direction of rotation of the field in a three-phase induction motor is dependent on which of the following?
ANumber of poles
BSupply voltage
CSupply frequency
DPhase sequence of supply voltage
#72📘 EE Pocket Reviewer RojasEasy
A wound rotor induction motor is mainly used in which of the following conditions?
AWhen speed control is not required
BWhen cheaper motor is required
CWhen high starting torque is required
DWhen high rotor resistance is required
#73📘 EE Pocket Reviewer RojasEasy
The speed of a three-phase wound rotor induction motor can be increased by which of the following methods?
ABy increasing the supply voltage
BBy decreasing the supply voltage
CBy decreasing the external resistance in the rotor circuit
DBy increasing the external resistance in the rotor circuit
#74📘 EE Pocket Reviewer RojasEasy
In an induction motor, in terms of the slip s, the rotor reactance per phase is proportional to
#75📘 EE Pocket Reviewer RojasEasy
Which of the following is true in a three-phase squirrel-cage induction motor?
AThe rotor conductors are left open
BThe rotor conductors are short circuited through the slip rings
CThe rotor conductors are short circuited through a commutator and sets of brushes
DThe rotor conductors are short circuited through the end rings
#76📘 EE Pocket Reviewer RojasEasy
The “crawling” in an induction motor is caused by which one?
AHigh loads
BLow supply voltage
CIncorrect phase sequence of the supply emf
DHarmonics developed in the motor
#77📘 EE Pocket Reviewer RojasEasy
Reduced voltage starter can be used with which type of induction motors?
ASlip ring type only
BSquirrel-cage type only
CBoth slip ring and squirrel-cage types
DNeither of these
#78📘 EE Pocket Reviewer RojasEasy
The shaft of an induction motor is made from which of the following materials?
ACarbon steel
BCast iron
CStainless steel
DHigh speed steel
#79📘 EE Pocket Reviewer RojasEasy
The frame of an induction motor is usually made from which materials?
ASilicon steel
BCast iron
CAluminum alloys
DPhosphor bronze
#80📘 EE Pocket Reviewer RojasEasy
In a squirrel cage induction motor, why are the rotor bars usually given a slight skew?
ATo reduce the rotor currents
BTo reduce windage losses
CTo reduce the magnetic hum
DTo reduce the eddy currents
More Electrical Engineering topics
