Synchronous Motors Flashcards

1
Q

Synchronous Motors require a magnetic field in the rotor to rotate. The field can be supplied by:

A

A brushless excitation source
A brushed dc excitation source
A permanent magnet

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2
Q

Name the two starting characteristcs of a Synchronous Motor:

A

Low starting current per horsepower
Low starting torque

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3
Q

What are the two names for a Synchronous Motor operating at no load for PFC?

A

Synchronous Condenser
Rotary Capacitor

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4
Q

The rotor of a synchronous motor is constructed like the rotor of an induction motor. T or F?

A

False

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5
Q

Synchronous Motors are doubly excited machines. T or F?

A

True. It means they have two electrical inputs, the stator and the rotor.

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6
Q

The rotational frequency or speed of the stator’s rotating magnetic field is directly proportional to what?

A

To the frequency of the supply voltage

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7
Q

Name the three common methods to start a Synchronous Motor:

A
  • Use a shaft-mounted induction motor to start the synchronous motor rotor
  • Use the load from the synchronous motor as a starting motor
  • Use an amortisseur winding on the rotor
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8
Q

Egen can also be called:

A

The CEMF

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9
Q

A field-discharge resistor is connected across the field utlizing a synchronizing switch. What type of switch is used?

A

A make before break

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10
Q

The CEMF opposes the supply voltage applied to the stator armature windings by how much degrees?

A

180

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11
Q

Egen can be varied by changing the field excitation. T or F?

A

True

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12
Q

The angle between the centre of a stator pole and the centre of a corresponding rotor pole is called:

A

The torque angle

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13
Q

Describe Pull-out Torque:

A

The value of the load counter-torque required to RIP the rotor out of synchronism.

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14
Q

The overload condition that usually happens when the torque angle exceeds what amount of degrees for SAILENT pole rotors?

A

60-70 degrees

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15
Q

Rated Load on a Synchronous Motors equals what power factor?

A

Unity

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16
Q

What is synchronous reactance?

A

Is the combination of the inductive reactance of the armature and armature reaction.

17
Q

Changing mechanical load on the shaft of the motor has the greatest effect on ________ ________

A

Torque Angle

18
Q

The motor is over excited when the amount of excitation results in a:

A

Leading power factor

19
Q

A Bell Curve represents Field Current vs Power Factor. T or F?

A

True

20
Q

I of the Armature Leads the VResultant angle by 90. T or F?

A

False. It lags VResultant by 90