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Electricity & Electronics > AC Motors > Flashcards

AC Motors Flashcards

1
Q

Advantages of AC vs. DC

A

Simpler to construct, rugged, durable, and efficient.

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2
Q

AC Motor Motion

A

The result of the interaction between a rotating magnetic field (stator) and a conductor (rotor) in response to electromagnetic induction.

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3
Q

squirrel cage rotor

A

The bars are connected to each other by a copper or aluminum ring or plate on both ends and are imbedded in a laminated core. .

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4
Q

Stator

A

A stationary part that consists of a steel frame housing which supports the stator (field) windings.

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5
Q

Slip

A

The difference between rotor speed and field speed.

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6
Q

What is the purpose of slip?

A

If the rotor were to rotate as fast as the field, there would be no relative motion. As a result, the rotor must rotate slightly slower than the field.

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7
Q

synchronous speed

A

The speed of the rotating magnetic field of an induction motor.

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8
Q

Motor Ratings

A
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9
Q

Motors can be grouped into one of three broad power ratings:

A

integral horsepower (ihp), fractional horsepower (fhp), and sub fractional horsepower (sfhp)

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10
Q

Voltage Rating

A

The voltage at which the motor may be operated plus or minus 10 percent.

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11
Q

Current Rating

A

Normal running current drawn at rated load, rated voltage, and rated frequency.

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12
Q

Horsepower Rating

A

The number, or fractional part, of a horsepower the motor will produce at rated speed.

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13
Q

RPM or Rated Speed

A

The speed the motor will produce at rated horsepower, voltage and frequency.

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14
Q

Duty Rating

A

The period of time the motor may be operated without overheating. Generally this is continuous.

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15
Q

Temperature rise

A

The amount by which a motor, operating under rated conditions, is hotter than its surroundings.

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16
Q

Temperature (amb)

A

The temperature of the space around the motor.

17
Q

Insulation Class

A

Motor insulation is grouped into classes. The maximum temperature at which a motor should operate depends on the type of insulation used on the motor windings.

18
Q

Service Factor Rating

A

The service factor is a number that can be multiplied by the horsepower rating to determine the maximum continuous horsepower output of the motor.

19
Q

Open Motors Enclosure

A

Enclosures with ventilating openings that allow surrounding air to be forced through the enclosure to cool the motor.

20
Q

Totally Enclosed Motors

A

Motors which do not allow free exchange between surrounding air and air within the enclosures.

21
Q

Single-Phase Induction Motors

A

Without starting assistance the rotor does not move and the motor hums without turning.

22
Q

Split-Phase Motor

A

A type of single-phase induction motor in which the stator is provided with a starting or auxiliary winding (S) and a main or running winding (M). The out-of-phase currents produce the rotating field which is necessary to develop a starting torque.

23
Q

Capacitor-Start Motor

A

A motor that uses a capacitor in series with the start winding that causes the current in that winding to lead the run winding.

24
Q

Single-Value Capacitor Motor

A

A motor that has a run and start winding with a capacitor permanently connected in series with the start or capacitor winding.

25
Q

Two-Value Capacitor Motor

A

A very quiet motor with high starting torque.

26
Q

To reverse the direction of rotation of a split-phase, capacitor-start, single-value capacitor and two-value capacitor motor,…

A

reverse either the start or the run winding connections, NOT BOTH.

27
Q

Does the direction of rotation of a split-phase, capacitor-start, single-value capacitor and two-value capacitor motor change if both connections to power are reversed?

A

No, because both the start and end winding connections are changed together.

28
Q

Repulsion Motor

A

A single-phase AC electric motor that produces high torque and can reverse rotation.

29
Q

Repulsion-Start Induction Motor

A

Starts as a repulsion motor but will run as an induction motor.

30
Q

Shaded Pole Motor

A

A type of single-phase AC electric motor that are known for being simple and reliable. They are used for low starting torque applications and are often used in household applications.

31
Q

Dual Voltage, Single-Phase Motor

A

An electric motor that can operate on two different voltage levels while still only using a single phase power supply.

32
Q

Wound Rotor

A

Rotor wound with insulated windings that are are connected to slip rings mounted on the rotor shaft.

33
Q

Wound-Rotor Induction Motor

A

The rotor of a wound-rotor motor is wound with insulated windings that are wye connected with their open ends being connected to three slip rings.

34
Q

Three-phase motors are either wye or delta connected. True or false?

A

True

Electricity & Electronics (12 decks)

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