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ELECTRICMOTORSEXAM > Chapter 11 & 12 - Starting, Braking > Flashcards

Chapter 11 & 12 - Starting, Braking Flashcards

1
Q

Motors typically draw starting current that is about the same as the current required to keep the motor running under load

A

F

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2
Q

The simplest method for starting a motor is to apply the full line voltage across the stator terminals and establish a rotating magnetic field

A

T

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3
Q

Two factors to consider when selecting a motor for full-voltage starting are whether it needs to develop high starting torque or high run efficiency

A

T

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4
Q

Open-circuit transition is preferable to closed-circuit transition because open-circuit transition does not cause a high-current transition surge.

A

F

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5
Q

Autotransformer starting is a slow method of starting, and the heat must dissipate from the resistors.

A

F

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6
Q

In a primary-resistor starting circuit, external resistance is added to and taken away from the motor circuit.

A

T

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7
Q

Starting current is limited by the resistance of the wire in the armature and the field windings during startup with DC reduced-voltage starting

A

T

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8
Q

Although a starting rheostat can also be used to control motor speed, the purpose of a starting rheostat is to increase the voltage during starting.

A

T

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9
Q

In an autotransformer starting circuit, the various windings of the transformer are added to and taken away from the motor circuit to provide reduced voltage when starting.

A

T

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10
Q

A starter using resistors instead of autotransformers looks almost identical to an autotransformer starter.

A

F

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11
Q

Inductors in series act just as resistors in series do, with the source voltage dropped across the inductors (stator and reactors) in series.

A

T

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12
Q

Part-winding starting is usually classified as reduced-voltage starting because of the resulting reduced current and torque.

A

T

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13
Q

The braking method used depends on the application, available power, circuit requirements, cost, and desired results.

A

T

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14
Q

Part-winding starters are typically available in either two- or three-step construction.

A

T

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15
Q

Friction switches are designed to open and close sets of contacts as the shaft speed on the switch varies.

A

F

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15
Q

In friction braking, the braking action is normally applied directly to the shaft.

A

T

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16
Q

A motor cannot be used for plugging if it cannot be reversed at full speed.

A

T

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17
Q

In a circuit where plugging is required only in an emergency, pressing the stop pushbutton de-energizes the forward starter but does not energize the reverse starter.

A

T

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18
Q

The service factor (SF) should be 1.35 or more for plugging applications

A

T

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19
Q

Maintenance of electric brakes is minimal because there are no parts that come in physical contact during braking.

A

T

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20
Q

Electric braking is accomplished by applying an AC voltage to the stationary windings once DC is removed.

A

F

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21
Q

_______________ starting is a method of starting a motor with the full line voltage placed across the terminals.
a. Primary-resistor b. Autotransformer c. Reduced-voltage
d. Full-voltage

A

d. Full-voltage

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22
Q

A __________________ is a control device that uses pushbuttons to energize or de-energize the load connected to it.
a. Magnetic starter b. Soft starter c. Manual contactor
d. Switch

A

c. Manual Contactor

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23
Q

______________ is a condition when a motor is loaded so heavily that the motor shaft cannot turn.
a. Load limit b. Locked rotor c. Torque limit
d. All of the above

A

d. All of the above

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24
Q

A _________________ is an electrically operated switch that includes motor overload protection.
a. magnetic motor starter b. contactor c. manual contactor
d. soft starter

A

a. Magnetic motor starter

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25
Q

Common methods of reduced-voltage starting are primary resistor starting and ______________ starting.
a. Autotransformer b. Part-Winding c. Wye-Delta
d. All of the above

A

d. All of the above

26
Q

__________________ starting is a method of reduced-voltage starting that places resistors in series in the motor power circuit to reduce the voltage to the motor.
a. Autotransformer b. Primary-resistor c. Part-winding
d. Wye-delta

A

b. Primary-resistor

27
Q

________________ starting is a method of reduced-voltage starting that uses a tapped three-phase autotransformer to provide a reduced voltage for starting.
a. Primary-resistor b. Autobot transformer
c. Part-winding d. Autotransformer

A

d. Autotransformer

28
Q

The motor___________ windings must be divide into two or more equal parts for a motor to be started using part-winding starting.
a. Stator b. Rotor c. Armature d. Autotransformer

A

a. Stator

29
Q

A ________________ starter is a motor starter that uses a solid-state device, such as an insulated gate bipolar transistor (IGBT) or silicon-controlled rectifier (SCR), to control motor voltage, current, torque, and speed during acceleration.
a. Electronic b. Solid state c. Electric d. None of the above

A

b. Solid state

30
Q

A(n)_______________ is a device that provides a gradual voltage increase (ramp up) during AC motor starting.
a. Rheostat b. Voltage transducer c. Soft starter d. Controller

A

c. Soft starter

31
Q

To prevent motor damage, reduced-voltage starting must be applied to DC motors larger than about _________________ HP.
a. 1/4 b. 1 c. 5 d. 10

A

b. 1 HP

32
Q

__________________ brakes normally consist of two friction surfaces (shoes or pads) that come in contact with a wheel mounted on the motor shaft.
a. Plug b. Electric c. Friction d. None of the above

A

c. Friction

33
Q

Friction brakes are available in _______________ designs to meet the requirements of almost any application.
a. AC b. DC c. both AC and DC d. magnetic

A

c. both AC and DC

34
Q

Friction brakes are normally controlled by a(n) _______________ that activates the brake shoes.
a. Solenoid b. Switch c. Selector switch d. Release

A

a. Solenoid

35
Q

_______________ is a method of motor braking in which the motor connections are reversed so that the motor develops a counter-torque that acts as a braking force.
a. Plugging b. Reversing c. Switching d. None of the above

A

a. Plugging

36
Q

With plugging, energizing the ______________ adds memory to the circuit and stops the motor.
a. Forward Contactor b. Reversing Starter
c. Overload relay d. Field pole

A

b. Reversing Starter

37
Q

Most single-phase, split-phase, and capacitor-start motors cannot be plugged because their _______________ remove the starting windings when the motor accelerates.
a. Circuit breakers b. Controllers c. Centrifugal switches
d. Run windings

A

c. Centrifugal switches

38
Q

With electric braking, a _______________________ with tapped windings is used to adjust the amount of braking torque applied to the motor.
a. Inductor b. Transformer c. Power supply
d. Decepticon

A

c. Power Supply

39
Q

The _______________ in the control circuit prevents the motor starter and braking contactor from being energized at the same time in electric braking.
a. Interlock system b. Start pushbutton c. Overload Contacts
d. Stop Pushbutton

A

a. Interlock System

40
Q

_____________ braking is a method of motor braking where the braking energy is dissipated as heat in a resistor as a motor is reconnected to act as a generator immediately after it is turned OFF.
a. Kinematic b. Static c. Inertial d. Dynamic

A

d. Dynamic

41
Q

For dynamic braking, the time that the DC current flows in the winding should be controlled by a(n) __________________ relay because the winding can overheat if left ON.
a. Overload b. Time-delay c. Power Dissipating
d. Control

A

b. Time-delay

42
Q

Dynamic braking uses ___________________ to dissipate the heat of braking.
a. Power-capacitors b. Chokes c. Power-resistors
d. Electrolytic-capacitors

A

c. Power-resistors

43
Q

A(n) ________________ is a manual contactor with an added overload protection device.

A

Manual starter

44
Q

The two methods used to switch motors from starting voltage to line voltage include open-circuit transition and _________________ transition.

A

Closed-circuit

45
Q

A starting ________________ or a solid state circuit is used when reduced-voltage starting is applied to DC motors.

A

Rheostat

46
Q

______________________ is a method of reduced-voltage starting that applies voltage to only part of the motor coil windings for starting and then applies power to the remaining coil windings for normal running.

A

Part-Winding-Starting

47
Q

A(n)_______________ starter reduces inrush current compared to the high inrush current produced by across-the-line starters.

A

Solid-State

48
Q

A typical solid-state starting circuit consists of both start and run ______________ connected in the circuit.

A

Silicon-Controlled-Rectifiers*

49
Q

________________ is achieved by increasing the motor voltage in accordance with the setting of the ramp-up control.

A

Full speed*

50
Q

The amount of reduced _________________ , the amount of reduced torque, and the cost of each starting method must be considered when selecting the appropriate starting method.

A

Current

51
Q

The solid-state starting method provides smooth, stepless ________________ in applications such as starting conveyors, compressors, and pumps.

A

Current

52
Q

_________________ is the least expensive reduced-voltage starting method.

A

Full-Voltage-Starting

53
Q

The primary function of a(n) ______________ is to prevent the reversal of the load once the countertorque action of plugging has brought the load to a standstill.

A

Plugging Switch

54
Q

A(n) _______________ may be used in applications where the time needed to decelerate the motor is constant and known.

A

Off-Delay-Timer

55
Q

______________, or DC injection braking, is a method of braking in which a DC voltage is applied to the stator windings of a motor after the AC voltage is removed.

A

Electric braking

56
Q

________________ braking is a method of dynamic braking that reuses the the braking energy to the AC source instead of dissipating the energy as heat.

A

Regenerative

57
Q

Electric braking requires a(n) ________________ at all times.

A

Power source

58
Q

A(n)________________ brake uses unlike magnetic poles that attract each other to provide stopping power to the rotating component.

A

Dynamic

59
Q

Dynamic braking cannot hold a load once it is stopped because there is no ________________ action.

A

Static

60
Q

__________________ brakes are often used along with dynamic braking in applications that require the load to be held.

A

Friction

61
Q

________________ is more expensive than friction braking but less expensive than other braking methods.

A

Electric Braking

62
Q

Dynamic braking cannot brake a motor to a complete stop because the _______________ action decreases as the motor slows.

A

Generator

63
Q

_______________ has the disadvantage of requiring frequent maintenance to inspect and replace the brake shoes.

A

Friction Brakes

ELECTRICMOTORSEXAM (3 decks)

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