Electrical Engineering · Question Bank

3P Induction Motors

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TypeAll 115Problem solving 27Objective 88
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#1📜 EE Pre-Board August 2012📘 PowerhouseEasy
A test used to determine the equivalent resistance of an induction motor is _.
ANo-load Test
BShort-circuit Test
CBlocked-rotor Test
DPolarity Test
#2📜 EE Pre-Board August 2012📘 PowerhouseEasy
In running condition the rotor reactance of a \(3\Phi\) induction motor is proportional to
Ainduced emf
Bslip
Csupply voltage
Drotor resistance
#3📜 EE Pre-Board August 2012📘 PowerhouseEasy
The voltage applied to the stator of a three phase, 4 pole induction motor has a frequency of 50 Hz. The frequency of the emf induced in the rotor is 1.5 Hz. Determine the speed at which motor is running.
A1,450 rpm
B1,455 rpm
C1,460 rpm
D1,465 rpm
#4📜 EE Pre-Board August 2012📘 PowerhouseEasy
In a winding of a \(3\Phi\), 6 pole induction motor, the space angle between two consecutive phases is
A60° mech.
B120° mech.
C180° mech.
D40° mech.
#5📜 EE Pre-Board August 2012📘 PowerhouseEasy
If starting voltage of a SCIM is reduced to 50% of its rated vlue, torque developed is reduced by _ percent of its full load value.
A57.7
B50
C25
D75
#6📜 EE Pre-Board March 2013📘 PowerhouseEasy
A change of 5% in the supply voltage of a three-phase induction motor will produce to its torque a change of approximately _______.
A10%
B5%
C25%
D20%
#7📜 EE Pre-Board March 2013📘 PowerhouseEasy
The voltage applied to the stator of a three-phase, 4-pole induction motor has a frequency of 50 Hz. The frequency of the emf induced in the rotor is 1.5 Hz. Determine the speed at which motor is running.
A1,410 rpm
B1,425 rpm
C1,448 rpm
D1,455 rpm
#8📜 EE Pre-Board March 2013📘 PowerhouseEasy
The rotor of a 220 v, 60 Hz, 4-pole induction motor has a power input of 80 kW. It is observed that the rotor emf makes 90 cycles per minute, Calculate the rotor copper loss.
A2 kW
B5 kW
C3 kW
D4 Kw
#9📜 EE Pre-Board August 2013📘 PowerhouseEasy
To reverse the direction of rotation of a three-phase induction motor, it is necessary to
AInterchange all the three line connections
BReverse the polarity of the rotor circuit
CIncrease the resistance of the rotor circuit
DInterchange any two of the three line connections
#10📜 EE Pre-Board March 2014📘 PowerhouseEasy
For an ac motor, the frequency is 60 Hz and the speed is 300 rpm. What is the number of poles?
A26
B24
C28
D30
#11📜 EE Pre-Board March 2014📘 PowerhouseEasy
If the speed of an Induction motor increases, what happens to the rotor frequency?
AIncreases
BDecreases
CDoes not change
Dfrequency has no relation to the
#12📜 EE Pre-Board March 2014📘 PowerhouseEasy
If supply voltage is changed by 5% for a 3ɸ induction motor, its torque will have a change of
A5%
B25%
C10%
D20%
#13📜 EE Pre-Board August 2014📘 PowerhouseEasy
A three- phase induction motor is taking 40 kW, the slip being 4 , stator losses amount to 800 watts, calculate the total power developed.
A39.200 KW
B40.800 KW
C37.632 KW
D36.732 KW
#14📜 EE Pre-Board August 2014📘 PowerhouseEasy
At a slip of 4% the maximum possible speed of 3Ø, 60HZ squirrel cage induction motor is
A3,600 rpm
B3,456 rpm
C3,200 rpm
D3,000 rpm
#15📜 EE Pre-Board March 2015📘 PowerhouseEasy
A 220 volt, 10 HP, 60 HZ, three-phase induction motor having four poles is operating at full-load slip of 3%. What is the frequency of the rotor current at full-load?
A60 HZ
B18 HZ
C1.8 HZ
D180 HZ
#16📜 EE Pre-Board March 2015📘 PowerhouseEasy
A three-phase motor is rated 50 HP, 440 volts and 85% power factor. What is the rated current if the motor efficiency is 89%?
A57.5 A
B64.7 A
C55 A
D59 A
#17📜 EE Pre-Board March 2015📘 PowerhouseEasy
What is the speed of an induction motor of four poles if the percent slip is 3%?
A1,764 rpm
B1,756 rpm
C1,746 rpm
D1,730 rpm
#18📜 EE Pre-Board March 2015📘 PowerhouseEasy
Find the rotor frequency of an induction motor having 4 poles if the rotor speed is 1,746 rpm.
A60 HZ
B1.8 HZ
C3 HZ
D50 HZ
#19📜 EE Pre-Board August 2015📘 PowerhouseEasy
A six-pole induction motor is connected to a 60 Hz supply and at full load the rotor emf makes 105 complete cycles in 2 minutes. Find the rotor speed.
A1,150 rpm
B1,182.5 rpm
C1,140.5 rpm
D1,170 rpm
#20📜 EE Pre-Board August 2015📘 PowerhouseEasy
Slip ring are made of
ASteel
BCopper
CBakelite
DMica

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