AC Motors Flashcards
An AC motor which rotates at the same speed as supply frequency is called.
a synchronous motor
A three phase AC motor is running at speed on constant load. If one phase goes open circuit, the motor will run at.
same speed
Shaded poles in an alternating current motor are intended to.
facilitate starting
In a 3 phase motor, if 1 phase is lost, the motor.
remains at the same speed
A three-phase motor has the windings.
120° apart
To change the direction of a 3-phase induction motor you would.
swap two of the stator connections
A capacitor in a single phase AC motor is to.
provide a phase shift
The slip speed of an induction motor is.
stator speed-rotor speed
An inductance/resistance motor is.
less efficient than a capacitance motor
If a connection to a 3-phase AC motor is disconnected, the motor will.
continue to run
The phases in supply to a 2 phase motor are electrically.
180 degrees apart from each other
Calculate the speed of a 400 Hz, 4 pole machine.
12,000 rpm
A capacitor in a single phase motor is to.
provide a phase shift
Slip on a synchronous motor on start is.
100 %
A shaded pole motor has shaded poles to.
create a rotating field
In a 2 phase induction motor the control winding is fed with.
constant phase AC supply
A 3 phase induction motor can be reversed by.
changing over any two phases
The speed of an AC motor can be affected by the.
pairs of poles
An AC motor which rotates at the same speed as the supply frequency is called.
a synchronous motor
In a synchronous motor, when the motor is running the slip is.
0%
In a two-phase induction motor there are.
4 poles
The speed of a single phase induction motor is dependant on.
the number of pairs of poles
Motor slip is.
the percentage of difference in speeds between the stator and rotor fields
The principal characteristic of a synchronous motor is.
it rotates at a speed that is synchronised with the applied ac current
A simple basic induction motor has.
poor starting torque, good running torque
Which of the following applications would require a ‘continuously rated’ motor?.
Fuel pump motor
A centrifugal speed switch is used.
to cut out the resistor/inductor circuit on an AC motor
Disconnecting one of the phases from a 3-phase motor will cause the motor to.
run at the same speed
The controlling phase on a two phase motor is of a.
variable amplitude
The difference in speed between a synchronous motor’s rotor and stator is known as.
slip speed
What is the purpose of the capacitor used in a single phase AC motor?.
Provides a high starting torque
