NEW
Font size
WorksheetsAC Motor Revision Part 1
Total questions: 20
Worksheet time: 10mins
Humming of motor implies that the motor is ……….?
Refuses to start
Runs at very low speed
Runs at low speed and then stops
None of above.
For smooth starting of three-phase squirrel cage induction motor, the starting.
Rotor resistance
Star-delta
Auto-transformer
Delta
The purpose of blades in a squirrel cage induction motor is ………..?
To reduce the magnetic resistance of the rotor
To cool the rotor
To reduce the electrical resistance of rotor cage
Provide more current.
The disadvantage of starting an induction motor with a star-delta starter is that..?
The starting torque increases and the motor runs with jerks.
During starting high losses result.
Take high starting current
The starting torque is one-third of the torque in case of delta connection
The motor starting current is called?
Full load current
Inrush current
Stator current
Rotor current
If in a 3-phase induction motor, two phases open accidently, the motor will……?
Continue to run depending on load
Run at dangerously high speed
Stop
None of these
The field winding (Rotor winding) of a three phase synchronous machine is excited by….?
Single-phase ac supply.
Dc supply
Three- phase ac supply.
Supply obtained from an inverter
The power factor of AC Motors represented at nameplate as……….?
Sin Ø.
Tan Ø
Cos Ø
None of these.
The difference between the synchronous speed and actual motor (Rotor) speed is called?
Shifting
Skew angle
Slip
Speed switch
The synchronous speed of an induction motor is defined as…………?
The speed of an induction motor at no load.
Natural speed at which a magnetic field rotates
The speed of a synchronous motor.
None of these.
The EMF induced in the rotor of an induction motor is proportional to….?
Relative velocity between flux and rotor conductors.
Voltage applied to stator.
Both (a) and (b) above
Slip.
What is meant by synchronous Wattage of an induction motors?
Stator input in watts.
Rotor output in watts.
Rotor input in watt
Shaft output in watts.
When an induction motor runs at rated load and speed, the iron losses are?
Negligible.
Very heavy.
Independent of supply frequency.
Independent of supply voltage.
In an AC motor, the magnetic field decrease, when the current flow …..
Increases
Fluctuates
Stays the same
Decreases
In an induction motor, rotor runs at a speed
Equal to the speed of stator field
Lower than the speed of stator field
Higher than the speed of stator field
Having no relation with the speed of stator field
The field of an induction motor rotor rotates relative to the stator at……
Rotor speed
Synchronous speed
Slip speed
In an induction motor, rotor bars are usually not quite parallel to the shaft but are given a slight skew
To increase the resulting flux
Reduce the vibration and noise
Both (a) and (b) above
To increase the speed of the motor
Which item in below is not a part of 3 phase AC induction motor?
Stator
Armature
Rotor
Shaft
Induction Motor is the recognized type of Ac motors?
TRUE
FALSE
The details of motor about the speed, voltage and other information’s can be obtain from ………….
Motor Drawing
Motor nameplate
Motor stator
Motor rotor
