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Electric Motors > Inclass8Squirrel&Wound > Flashcards

Inclass8Squirrel&Wound Flashcards

1
Q

For the squirrel cage motor, there are no physical electrical connections between the stator and the rotor

A

T

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2
Q

The shorting rings mounted on the rotor shaft transfer power to the load

A

F

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3
Q

The main difference between different types of 3-phase motors is the design of the rotors and rotor windings

A

T

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4
Q

Since an induction motor is an electric motor that uses the principles of mutual induction to develop current and torque in the rotor, it is correct to say that the shorted secondary in the rotor carries the induced secondary current

A

T

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5
Q

A rotor always rotates at exactly the correct speed to induce the current required to develop the torque necessary to drive the load.

A

T

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6
Q

A conducting ring, or shorting ring, is a metal ring used to electrically connect the bars of the squirrel cage rotor at the end of the cage frame.

A

T

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7
Q

The same single standard rotor design for an induction motor can deliver different starting torques and starting currents.

A

F

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8
Q

The squirrel cage bars of a design A motor rotor are placed deep in the iron of the rotor and have low reactance.

A

F

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9
Q

The low reactance of a Design A motor rotor allows for a large current to flow through the bars and a large torque to be developed.

A

T

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10
Q

Motor design B is the most widely used design with normal starting torque and low starting current.

A

T

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11
Q

A design D motor rotor has two conductor bars in each slot, with one above the other.

A

F

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12
Q

The top bar of a design C motor rotor is a high-resistance conductor, while the bottom bar is a high-reactance conductor. This arrangement forces the top bar to carry the most of the current during starting.

A

T

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13
Q

The bars of a design B motor rotor are narrow and are placed deep in the iron, which increases the reactance and lowers the current, while maintaining normal starting torque.

A

T

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14
Q

Because of the high resistance and high slip, design D motors are less efficient than the other designs

A

T

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15
Q

The stator of a wound-rotor motor is different than the stator of a squirrel-cage induction motor.

A

F

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16
Q

Wound-rotor stator windings are not short circuited; they are wye connected, with the free end of each winding connected to a slip ring.

A

F

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17
Q

A pigtail connects the slip rings to the power supply.

A

F

18
Q

Brush material is typically composed of a mixture of carbon and graphite for high-voltage machines and of graphite and metallic powder for low-voltage machines

A

T

19
Q

Resistors used in a wound-rotor motor are often referred to as secondary resistors, because the rotor is the secondary of the motor.

A

T

20
Q

A wound-rotor motor is never started with full resistance in the circuit

A

F

21
Q

Starters for wound-rotor motors use a timer to automatically remove resistance from the rotor circuit.

A

T

22
Q

The rotor windings are marked T1, T2 and T3

A

F

23
Q

THe M1 connection is the outside slip ring, the M2 connection is the middle slip ring, and the M3 connection is close the rotor windings.

A

T

24
Q

The resistance is increased as the motor accelerates in order to shift the point of maximum torque.

A

F

25
Q

The M1 connection is the outside slip ring, the M2 connection is the middle slip ring, and the M3 connection is close to the rotor windings.

A

T

26
Q

The stator______ consist of coils of copper wire placed in slots of 120 electrical degrees apart.
a core - b slots - c windings - d inductors

A

c. windings

27
Q

Motor design ____ is a design with normal starting torque and normal starting current.
a. A b. C c. B d. D

A

a. A

28
Q

Motor Design ____________ has high starting torque and low starting current.
a. D b. B c. A d. C

A

d. C

29
Q

Current flowing through the ___________ in the rotor creates a magnetic field around the bars.
a. wound windings b. shorting bars c. conducting bars
d. conduction coils

A

c. conducting bars

30
Q

The combined magnetic field and the current flow interact to create the motor _________. a. mutual induction b. flux c. slip
d. torque

A

d. torque

31
Q

Design ________ motors are design for a broad variety of applications, such as HVAC applications, providing power for fans and blowers, and in industrial applications providing power for pumps. a. A b. B c. C d. D

A

b. B

32
Q

A(n)_______________ is an extended, flexible connection or a braided copper conductor.
a. coil winding b. pigtail c. leaf spring d. extension cord.

A

b. pigtail

33
Q

A wound rotor motor can be distinguished from a squirrel cage induction motor by the presence of the _________. a. coils of wire in the winding slots instead of the solid conductor bars. b. three slip rings on the shaft
c. external resistance bank. d. all of the above

A

all of the above

34
Q

A wound rotor motor ____________ is a device containing high-wattage resitors that is designed to control the speed of a wound rotor motor and operate in variable speed mode for as long as needed. a. regulator b. starter
c. resistor d. arrestor

A

a. regulator

35
Q

Resistors designed for starting a wound rotor motor can _________ the heat generated during the short time required for starting the motor.
a. deflect b. shunt c. absorb d. dissipate

A

d. dissipate

36
Q

A __________ is a type of regulator.
a. drum switch b. three pole rheostat c. silicon controlled rectifier
d. all of the above

A

d. all of the above

37
Q

A(n) ______ is a sliding contact that rides against a rotating component to provide a connection to a stationary circuit.

A

brush

38
Q

A spring placed behind a brush forces the brush to make contact with the ___________

A

slip ring

39
Q

The ________________ is changed during startup to keep the maximum torque near the actual operating speed throughout the acceleration period.

A

resistance

40
Q

A(n) ____________ is a solid state device used to switch a set of resistors in or out of a wound rotor circuit.

A

Silicon-controlled-rectifier

41
Q

A(n) _______________ is the entire assembly of the brush, brush holder, insulators, and any wiring included in the assembly.

A

brush rigging

Electric Motors (3 decks)

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