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WorksheetsUnit-5 Part-3
Total questions: 67
Worksheet time: 17hrs 45mins
1. How many electrical degrees separates from the other two phases phase voltage on the balance three-phase supply?
60˚
90˚
120˚
180˚
1. what degree does the arrow of the magnetic field points straight downward from N to S in the figure
120
360
300
180
what is the position of phase “C” current at 60˚ degrees
Half negative
Half positive falling
Full negative
Half positive rising
which phrases will be meeting at 120 degrees?
Phase C and D
Phase C and A
Phase A and B
Phase B and D
what is the position of phase “A” current at 240 degrees?
Half positive decline
Maximum positive
Half negative on rise
Half negative decline
which direction is the rotor turning?
Clockwise
Counter clockwise
Forward
Downward
As shown in the picture the motor runs counter clockwise. What will happen if you connected L1 to T3 and L2 to T2 and L3 to T1
Motor will run in the same direction
Motor will run in opposite direction
Motor windings will be shorted
Motor will be overloaded
As shown in the picture what will happen if you connect L3 to T3 and L2 to T2 and L1 to T1
motor will overheat
motor will run clockwise
motor will run counter clockwise
motor winding will be shorted
As shown in the picture what will happen if you connect L3 to T3 and L2 to T2 and L1 to T1
motor will overheat
motor will run clockwise
motor will run counter clockwise
motor winding will be shorted
What is synchronous speed?
the speed of the rotating magnetic field
the number of pole pairs on the rotor
the difference between the rotating magnetic field and rotor
the speed measured using the ammeter
The speed of the rotating magnetic field of a three phase induction motor is known as
Stator speed
Synchronous speed
Rotor speed
Slip speed
What is the synchronous speed of an 8-pole 60Hz induction motor
3600 rpm
1800 rpm
2400 rpm
900 rpm
How many poles are there if the synchronous speed of an induction motor is 3600 rpm at 60 Hz frequency?
2
4
6
8
What is the synchronous speed of a 6 pole 50 Hertz induction motor
1800 RPM
1200 RPM
1000 RPM
2400 RPM
The difference between the field synchronous speed and rotor speed?
Sleeve
Slide
Slip
Tachometer
When the three current pass through these winding at 120 it Creates_______
the rotating magnetic field
the number of pole pairs on the rotor
the difference between the rotating magnetic field and rotor
the speed measured using the ammeter
How can you be change the direction of rotation of 3-phase induction motors?
switch two line leads of rotor
switch two line leads of start winding
change any two of the supply wires to motor terminal
change all the supply wires to motor terminal
What happens to the speed of a wound-rotor motor when you add extra resistance to the rotor circuit?
No change in speed
Run faster
Slower
Run noisily
What happens to the speed of a wound-rotor motor when you reduce the coil current?
no change in speed
reduces the rotor speed
increase the rotor speed
run noisily
What happens to the speed of a wound-rotor motor when the all resistance is removed from the to the rotor circuit?
No change in speed
Run faster
Slower
Run noisily
As shown in the picture, shows the rotor of what type of motor?
Synchronous
Universal
Wound rotor
Compound DC motor
Which three-phase induction motor has a variable resistance for smooth speed control ?
synchronous speed motor
squirrel-cage motor
capacitor-start motor
wound-rotor motor
What part contains the winding mounted in the slots of a squirrel-cage motor
shaft
stator
bearing
end shield
What part in squirrel-cage motor, That Create the rotating magnetic field in the motor?
shaft
stator
bearing
end shield
Which is a disadvantage of a three-phase squirrel cage motor?
load variations do not change operating speed
speed control is difficult
it has commutator and slip ring to service
higher maintenance cost
What part in squirrel-cage motor, is the special design of the rotor bars makes the motor run quietly and smoothly?
Rotor bars between the rings are in parallel
Rotor bars between the rings are in series
Rotor bars between the rings are at an angle to the ring
Rotor bars between the rings are closer to each other
What part in squirrel-cage motor that protects the turning rotor and field windings form physical damage?
Bearings
End shield
Fin-fan
Shaft
The part that supports the rotor shaft and keeps the shaft turning smoothly without vibration is called
Stator
End shield
Bearings
Squirrel cage bars
Where you find the current rating of a motor is used to determine the ampacity of branch circuit?
Current rating on NEMA
Current rating on NEC
Current rating on nameplate
Squirrel cage bars
NEC Article 30-142 state that the frame of stationary motor shall be_________
Insulated
Discharged
Testing before work
Grounded
When install the motor must be located in _______________
Ventilation place
Damp place
Heated Place
Wet place
When installing a squirrel-cage motor on continuous duty what should be the cutting carrying capacity of its branch circuit conductor
must be exactly 100% of its motor full-load current ratting
shall be 125% or less than its motor full-load current ratting
it should be twice of its motor full-load current ratting
shall be 125% or not less than the motor full-load current ratting
branch circuit conductors size must be carry ________ current after applying ambient temperature
100% of the motor full load
50% of the motor full load
125% of the motor full load
125% of the motor no full load
When you connect the motor prior to energizing you must?
Turn the rotor by hand checking the rotor turn freely
Operate the motor to the power supply.
Attaché the rotor shaft to the machine?
Turn on the power supply.
Before you place a motor into service you must rune to confirm the operation correctly .Test run the motor for short time
(Approximately two minutes) without load.
(Approximately two minutes) with load.
(Approximately one minutes) without load.
(approximately one minutes) with load
To inspect the motor feeder or branch circuit conductor to insure that it sized correctly for the motor load
Responsibility of the director.
Responsibility of the electrician
Responsibility of the operation
Responsibility of the supervisor
In (NEC Article 430-9) terminals of motors shall be suitably marked or colored where necessary?.
To indicate the correct connection.
To indicate the correct direction.
To indicate the correct rotation.
To indicate the correct shape
A dual voltage three-phase induction motor of nine lead terminals, what is correct connection for high voltage?
In an induction motor, how do you compare the rotor speed to the stator field synchronous speed?
the rotor speed and synchronous speed its the same
the rotor speed is faster than the synchronous speed
the rotor speed is slower than the synchronous speed
the rotor speed is twice the synchronous speed
How do you test the speed of three-phase squirrel-cage motor?
using clamp-on ammeter attached to the rotor shaft
using megger attached to the rotor shaft
using a tachometer attached to the stator
using a tachometer attached to the rotor shaft
The current reading in all the three phases when measured must be
The same for each phase
Different in all the three phase
Same in two phase
None of these
The instrument used to measure running current is___________
Ohmmeter
Tachometer.
Clamp-on ammeter.
Voltmeter.
when measure motor current in three phase circuit the current reading must be results ______________
Different in all the three phase
exceed rating in the nameplate
not exceed rating in the nameplate
Same in two phase
What test is performed in the figure shown
ground test
insulation resistance test
insulation test between winding
continuity test
What test is performed in the figure shown
ground test
insulation resistance test
insulation test between winding
continuity test
What test is performed in the figure shown
ground test
insulation resistance test
insulation test between winding
Continuity test
Why should you remove the motor’s power leads before performing continuity test?
To avoid current paths
To prevent unnecessary ground faults
To avoid induction through the leads
To decrease the resistance
The 3-phase motor with a constant running speed from no-load to full-load capacity is known as
Squirrel cage
Wound rotor
Synchronous
Capacitor start
Identify the part where the rotating magnetic field is produced in a synchronous motor?
slip rings
end shield
stator
bearing
By application of what, allows the rotor of a 3 phase synchronous motor to reach synchronous speed
AC power
DC power
Three phase power
Single phase power
Where is the bearing housed?
Stator
Rotor
End shield
Field coil
Refer the figure shown, a synchronous motor what is the function of part 1?
keep the starting circuit closer to 90° out of phase with the run windings
disconnects the start windings from the motor’s power supply
produce a rotating magnetic field
rotating (moving) of the motor
Refer the figure shown, a synchronous motor what is the function of part 3?
keep the starting circuit closer to 90° out of phase with the run windings
disconnects the start windings from the motor’s power supply
produce a rotating magnetic field
Connection DC supply
Refer the figure shown, a synchronous motor what is the function of part 8?
keep the starting circuit closer to 90° out of phase with the run windings
allows the coil winding to run in Sync With stator field
produce a rotating magnetic field
rotating (moving) of the motor
Part of synchronous motor where the brushes is riding and DC supply is connected to the field coil winding
End shield stator
Rotor
Slip rings
Bearing
Par of synchronous motor when energized, line up the rotors synchronous speed with the stators rotating field?
Squirrel cage winding.
Field coil winding.
Start winding.
Run winding.
How many slip ring have the synchronous motor?
Three slip ring.
Two slip ring.
No slip ring for this motor.
One slip ring.
Part of synchronous motor supply dc power directly to the field coil winding of the rotor?
Slip rings.
Bearings.
End shield.
Rotor shaft.
Part of synchronous motor protect people by forming barrier between them and moving parts of motor.
Slip rings.
Bearings.
End shield.
Rotor shaft
Part of synchronous motor keep the rotor shaft supported and operating smoothly without vibration.
Slip rings.
Bearings.
End shield.
Rotor shaft.
Part of synchronous motor This winding allows the rotor to start up to near synchronous speed
Field coil winding
Squirrel-cage winding
Stator winding
Running winding
What does a synchronous motor need to produce fixed magnetic poles in the rotor?
controlled ambient temperature
controlled single-phase AC supply
controlled DC supply
controlled three-phase AC supply
What is synchronous speed?
the speed of the rotating magnetic field
the number of pole pairs on the rotor
the difference between the rotating magnetic field and rotor
the speed measured using the ammeter
What type of the motor shown below in diagram?
Three phase Squirrel-cage motor.
Three phase synchronous motor.
Three-phase wound –rotor motor.
Split –phase induction motor
What happen when the synchronous motor started?
the rotor speed and synchronous speed its the same
the rotor speed is faster than the synchronous speed
the rotor speed is Less than the synchronous speed
the rotor speed is twice the synchronous speed
Refer the figure shown, the rotor and stator speed what happens to the rotor in figure A?
The rotor is in synchronous speed
The rotor is not up to speed with the stator field
The rotor is in synchronous with the stator field
The rotor running faster than the synchronous speed
Refer the figure shown , the rotor and stator speed what happens to the rotor in figure B?
The rotor is in synchronous speed
The rotor is not up to speed with the stator field
The rotor is in synchronous with the stator field
The rotor running faster than the synchronous speed
