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4th Year Electrical - Machines > Syncronous Motors > Flashcards

Flashcards in Syncronous Motors Deck (37)
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1

The stator of a three phase synchronous motor supports conductors that may be called the armature?

True or False?

True

2

The stator of a three-phase synchronous motor is like the stator of an

Alternator and SCIM

3

The rotor of a synchronous motor supports the field windings.

True or False

True

4

State the two (2) types of synchronous motor rotor construction

Salient pole
Cylindrical

5

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.

6

The pole windings on the rotor of a synchronous motors are energized through

Slip rings and brushes

7

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

8

Pull out torque angle for cylindrical rotors

90 degrees

9

Pull out torque angle for salient pole rotors

60-70 degrees

10

The rotating magnetic field in the stator revolves smoothly instead of jumping from pole to pole.

True of False?

True

11

The rotor locks into synchronous speed with the rotating field of the stator by:

Attraction of opposite magnetic poles

12

The cemf may be varied by changing the:

Field excited

13

The value of stator current due to voltage Eresultant is limited by Zarmature.

True or False?

True

14

I armature lags Eresultant by ____ degrees

90

15

The torque angle on a phasor diagram representing a synchronous motor is the angle between:

180 degree reference and line and Egen

16

The power factor of a synchronous motor is the cosine of the angle between

Iarm and Vphase

17

A lightly loaded synchronous motor is operating at a leading pf. Adding load causes it to operate:

Less leading

18

Iarm lags Eresultant by about 90 degrees because:

Stator winding in a impedence is due mostly to inductive reactance

19

Normal excitation requires the same value of field current at all values of load

False

20

Low excitation results in lagging power factor, and high excitation results in leading power factor

True or False?

True

21

Unity power factor operation means the lowest line of current for a particular load condition.

True or False?

True

22

The Vee curve is a plot of:

Armature current vs field current

23

Pull out torque angle for cylindrical rotors

90 degrees

24

Pull out torque angle for salient pole rotors

60-70 degrees

25

The rotating magnetic field in the stator revolves smoothly instead of jumping from pole to pole.

True of False?

True

26

The rotor locks into synchronous speed with the rotating field of the stator by:

Attraction of opposite magnetic poles

27

The cemf may be varied by changing the:

Field excited

28

The value of stator current due to voltage Eresultant is limited by Zarmature.

True or False?

True

29

I armature lags Eresultant by ____ degrees

90

30

The torque angle on a phasor diagram representing a synchronous motor is the angle between:

180 degree reference and line and Egen