Syncronous Motors Flashcards
(37 cards)
The stator of a three phase synchronous motor supports conductors that may be called the armature?
True or False?
True
The stator of a three-phase synchronous motor is like the stator of an
Alternator and SCIM
The rotor of a synchronous motor supports the field windings.
True or False
True
State the two (2) types of synchronous motor rotor construction
Salient pole
Cylindrical
The rotor of a synchronous motor is constructed like the rotor of an induction motor.
True or False?
False;
a synchronous motor has physical poles and an amortisseur winding.
The pole windings on the rotor of a synchronous motors are energized through
Slip rings and brushes
What holds the rotor in place and maintains the air gap between the rotor and stator?
Bearings mounted in the end bells at both ends of the stator
Pull out torque angle for cylindrical rotors
90 degrees
Pull out torque angle for salient pole rotors
60-70 degrees
The rotating magnetic field in the stator revolves smoothly instead of jumping from pole to pole.
True of False?
True
The rotor locks into synchronous speed with the rotating field of the stator by:
Attraction of opposite magnetic poles
The cemf may be varied by changing the:
Field excited
The value of stator current due to voltage Eresultant is limited by Zarmature.
True or False?
True
I armature lags Eresultant by ____ degrees
90
The torque angle on a phasor diagram representing a synchronous motor is the angle between:
180 degree reference and line and Egen
The power factor of a synchronous motor is the cosine of the angle between
Iarm and Vphase
A lightly loaded synchronous motor is operating at a leading pf. Adding load causes it to operate:
Less leading
Iarm lags Eresultant by about 90 degrees because:
Stator winding in a impedence is due mostly to inductive reactance
Normal excitation requires the same value of field current at all values of load
False
Low excitation results in lagging power factor, and high excitation results in leading power factor
True or False?
True
Unity power factor operation means the lowest line of current for a particular load condition.
True or False?
True
The Vee curve is a plot of:
Armature current vs field current
Pull out torque angle for cylindrical rotors
90 degrees
Pull out torque angle for salient pole rotors
60-70 degrees
