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Electricity & Electronics > Motor Principles > Flashcards

Motor Principles Flashcards

1
Q

Armature

A

A piece of iron or steel forming the moving part of a magnetic circuit in meters, relays, etc.

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2
Q

Armature Reaction

A

The effect of the armature magnetic field upon the main magnetic field of an electric motor or generator.

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3
Q

Base Speed

A

A motor’s name plate speed.

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4
Q

Capacitor Start Motor

A

A single-phase induction motor that has a capacitor in series with the start winding.

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5
Q

CEMF

A

Abbreviation for counter electromotive force.

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6
Q

Centrifugal Switch

A

A motor mounted switch that disconnects the start winding when the motor reaches approximately 75% of its rated speed.

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7
Q

Code Letters

A

Code on the name plate that signifies the locked rotor current of the motor.

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8
Q

Commutator

A

A ring of copper segments, insulated from each other and connected to the armature winding of a motor or generator.

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9
Q

Cumulative Compound Motor

A

Motors having both shunt and series windings, wound so that the two magnetic fields will combine.

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10
Q

Current Relay

A

A relay that operates at a predetermined value of current. It can be an overcurrent relay, undercurrent relay, or combination of both.

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11
Q

Differential Compound Motor

A

Motors having both shunt and series windings, wound so that the two magnetic fields will oppose each other.

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12
Q

Field

A

A region under some physical influence such as electricity, magnetism, or a combination produced by an electrically charged object, electrons in motion, or a magnetic field.

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13
Q

Field Loss Protection

A

Prevents runaway condition, if the field winding of a motor should open.

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14
Q

Horsepower

A

A unit of power, or the capacity of a mechanism to work. One horsepower equals 746 watts and is equivalent to raising 550 lbs. one foot in one second.

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15
Q

Induction Motor

A

An AC motor that has the primary winding (stator) connected to the power supply. Current is induced into a polyphase secondary or squirrel-cage secondary winding (rotor).

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16
Q

Motor

A

A machine that converts electrical energy into mechanical energy usually by turning a shaft.

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17
Q

NEMA

A

Abbreviation for National Electrical Manufacturers Association.

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18
Q

Permanent Capacitor Motor

A

A capacitor start, capacitor run motor; the start winding and the capacitor are permanently connected in the circuit.

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19
Q

Polyphase Induction Motor

A

A three-phase self-starting motor.

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20
Q

Potential Relay

A

A relay external to the motor that is used in place of a centrifugal switch. The relay coil is connected parallel to the start winding and is energized by an increase in voltage across the start winding as the motor comes up to speed. This opens a NC contact to disconnect the start winding and/or start capacitor.

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21
Q

Reference Speed

A

A set speed depending on applied voltage.

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22
Q

Repulsion Motor

A

A single-phase motor that has the stator winding connected to the source and the rotor winding connected to the commutator. Brushes on the commutator are short-circuited and are placed so that the magnetic axis of the rotor winding is inclined to that of the stator winding. This type of motor has a varying speed characteristic.

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23
Q

RPM

A

Abbreviation for revolutions per minute.

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24
Q

Run-Away

A

Any additive condition to which continued exposure will eventually destroy a device.

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25
Q

Series Motor

A

A motor that has the armature and field windings connected in series.

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26
Q

Shaded Pole

A

A copper ring set into part of the pole piece of a small AC motor to produce the lagging component of a rotating magnetic field for starting purpose.

27
Q

Shaded Pole Motor

A

A single-phase induction motor provided with shading coils that magnetically displace a portion of the field poles to produce a starting torque.

28
Q

Shunt Motor

A

A DC motor that has the field winding and armature winding connected in parallel.

29
Q

Slip

A

The difference in the speed of the rotating field and the rotor of an induction motor.

30
Q

Split Phase/Resistance Start Motor

A

An induction motor with two stator windings, the main or run winding, and the auxiliary or start winding.

31
Q

Squirrel-Cage Rotor

A

A rotor with a squirrel-cage winding (two end rings connected along their circumference with copper or aluminum bars arranged in slots in an iron core.)

32
Q

Stabilized Shunt Motor

A

A shunt-wound motor to which a light series winding has been added to prevent a rise in speed or to reduce the speed when the load is increased.

33
Q

Synchronous Motor

A

An AC motor that operates at a constant speed from no load to full load. Similar to a three-phase AC generator, it has a revolving field that must be excited from a separate DC source.

34
Q

Synchronous Condenser

A

A synchronous motor used for power factor correction.

35
Q

Synchronous Speed

A

The speed at which the field rotates.

36
Q

Thermally Protected

A

A current and temperature responsive device used to protect another device against overheating due to overload.

37
Q

Top Speed

A

The highest safe speed.

38
Q

Torque

A

A rotating or twisting force.

39
Q

Universal Motor

A

A series wound motor designed to develop approximately the same speed and output on DC or a single phase AC of not more than 60 Hz and approximately the same RMS voltage.

40
Q

Windage Losses

A

Heat losses in the windings that must be overcome by any motor or generator.

41
Q

Wound Rotor Motor

A

A motor with three wye connected rotor windings. These windings are connected through slip rings and brushes to an external wye connected speed controller.

42
Q

The fundamental principle of motor action is the…

A

attraction and repulsion of magnetic fields.

43
Q

Three-Finger/ Right Hand Motor Rule

A

Thumb - Points in the direction of the conductor motion
Index Finger - Points in the direction of the field
Middle Finger - Points in the direction of current

44
Q

Stator

A

The stator is the stationary part of the motor. It includes the frame of the motor and the field poles.

45
Q

Armature

A

The armature is the rotating part of the motor. It is wound with many coils of wire embedded in a laminated iron core.

46
Q

Commutator

A

The commutator assembly is composed of pairs of copper segments that are electrically connected to each end of the armature windings.

47
Q

Brushes

A

The brushes provide a means of applying voltage to the commutator while allowing the commutator to rotate.

48
Q

Watts

A

A measure of power.

49
Q

Series Wound Motor

A

The field windings are connected in series with the armature windings.

50
Q

Shunt Would DC Motor

A

The field winding is connected in parallel (shunt) with the armature winding.

51
Q

Cumulative Compound Wound Mmotor

A

When the series winding is connected so that its field adds to the shunt winding field.

52
Q

Differential Compound Motor

A

When the series and shunt windings have opposing fields.

53
Q

Variable Speed Motor

A

The speed of a motor may be altered by varying the current in the field winding or by varying the armature voltage.

54
Q

Series Motor, Variable Speed

A

Speed is usually controlled by a rheostat in series with the armature winding.

55
Q

Rheostat

A

A variable resistor which is used to control current.

56
Q

Shunt Motor, Variable Speed

A

The speed can be controlled by a rheostat in series with the field windings. When the rheostat resistance is increased, the current through the field is decreased.

57
Q

Series DC motors have a ___ starting torque and speed that varies with the load.

A

high

58
Q

Series DC motors can be started without a load. True or false?

A

False, series DC motors must never be started without a load.

59
Q

Shunt Would DC Motor Characteristics

A

Fair starting torque, fairly constant speed, and easy speed control.

60
Q

Series Would DC Motor Characteristics

A

High starting torque, speed varies with the load, and runs away at no load.

61
Q

Cumulative Compound DC Motor Characteristics

A

Excellent starting torque and good constant speed.

62
Q

Differential Compound DC Motor

A

Very poor starting torque and absolutely constant speed.

63
Q

A compound DC motor is a combination of a ___ and ___ motor.

A

series, shunt

Electricity & Electronics (12 decks)

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