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4th Year Electrical - Machines > Syncronous Motors > Flashcards

Syncronous Motors Flashcards

1
Q

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

True or False?

A

True

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2
Q

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

A

Alternator and SCIM

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3
Q

The rotor of a synchronous motor supports the field windings.

True or False

A

True

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4
Q

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

A

Salient pole

Cylindrical

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5
Q

The rotor of a synchronous motor is constructed like the rotor of an induction motor.

True or False?

A

False;

a synchronous motor has physical poles and an amortisseur winding.

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6
Q

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

A

Slip rings and brushes

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7
Q

What holds the rotor in place and maintains the air gap between the rotor and stator?

A

Bearings mounted in the end bells at both ends of the stator

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8
Q

Pull out torque angle for cylindrical rotors

A

90 degrees

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9
Q

Pull out torque angle for salient pole rotors

A

60-70 degrees

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10
Q

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

True of False?

A

True

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11
Q

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

A

Attraction of opposite magnetic poles

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12
Q

The cemf may be varied by changing the:

A

Field excited

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13
Q

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

True or False?

A

True

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14
Q

I armature lags Eresultant by ____ degrees

A

90

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15
Q

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

A

180 degree reference and line and Egen

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16
Q

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

A

Iarm and Vphase

17
Q

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

A

Less leading

18
Q

Iarm lags Eresultant by about 90 degrees because:

A

Stator winding in a impedence is due mostly to inductive reactance

19
Q

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

A

False

20
Q

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

True or False?

A

True

21
Q

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

True or False?

A

True

22
Q

The Vee curve is a plot of:

A

Armature current vs field current

23
Q

Pull out torque angle for cylindrical rotors

A

90 degrees

24
Q

Pull out torque angle for salient pole rotors

A

60-70 degrees

25
Q

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

True of False?

A

True

26
Q

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

A

Attraction of opposite magnetic poles

27
Q

The cemf may be varied by changing the:

A

Field excited

28
Q

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

True or False?

A

True

29
Q

I armature lags Eresultant by ____ degrees

A

90

30
Q

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

A

180 degree reference and line and Egen

31
Q

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

A

Iarm and Vphase

32
Q

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

A

Less leading

33
Q

Iarm lags Eresultant by about 90 degrees because:

A

Stator winding in a impedence is due mostly to inductive reactance

34
Q

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

A

False

35
Q

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

True or False?

A

True

36
Q

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

True or False?

A

True

37
Q

The Vee curve is a plot of:

A

Armature current vs field current

4th Year Electrical - Machines (7 decks)

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