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Hvac > Unit 18 Application of Motors > Flashcards

Unit 18 Application of Motors Flashcards

1
Q

Is Luis an egg head

True or fals

A

True

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2
Q

Power supply data should include the following information

A

The voltage, the current capacity in amperes, the frequency in hertz (cps), and the phase (single or three).

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3
Q

The voltage range for an electric motor is usually within +or-

A

10%

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4
Q

If an electric motor is rated for 208 V, the maximum allowable voltage would be _____, and the minimum allowable voltage would be _____.

A

228.8 V, 187.2 V.

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5
Q

how a service technician can tell if a compressor motor is drawing the proper amperage when it is running.

A

The technician can take an amperage reading while the motor is operating under load and compare that reading to the FLA on the nameplate. * Also, he must know the operating conditions of the motor.

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6
Q

In the United States, the frequency in cycles per second (cps) at which an AC electric motor operates under normal conditions is

A

60

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7
Q

Three-phase motors are often used in air-conditioning systems in residences.

True or false

A

False

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8
Q

Two types of bearings commonly used on small motors are

A

Sleeve and ball bearings.

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9
Q

An open single-phase motor with a centrifugal starting switch may not be used in

A

An area where explosive gasses exist.

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10
Q

service factor of the motor is a multiplier applied to the motor HP. It indicates how much the motor can run overloaded on a continuous basis w/ out damaging the motor winding

True or false

A

True

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11
Q

How does the insulation factor of a motor affect its use?

A

The insulation type or class (factor) of a motor allows a motor to operate at higher or lower ambient temperatures.

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12
Q

A ______ bearing surface must be used in a vertical shaft motor application.

A

Thrust

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13
Q

Two primary electric motor mount characteristics are

A

Rigid mount and resilient mount (rubber).

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14
Q

NEMA has established standardized motor dimensions. NEMA stands for

A

National Electrical Manufacturers Association.

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15
Q

Two types of motor drives are

A

Belt drive and direct-drive (coupling or mounted to motor shaft).

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16
Q

What is a matched set of belts?

A

A matched set of belts means the belts are exactly the same length.

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17
Q

Name the different types of belts.

A

“A” width belts and “B” width belts. (OR smooth grip and “tractor tire” grip belts)

18
Q

Why must direct-drive couplings be aligned?

A

If direct-drive couplings are out of alignment, vibration will occur, which results in excessive wear.

19
Q

An instrument often used to check the alignment of two shafts is the

A

Dial indicator.

20
Q

Why must resilient-mount motors have a ground strap?

A

If the motor were to have a ground (circuit from the hot line to the frame of the motor), the motor frame would be electrically hot w/ out the ground strap. (By rubber)

21
Q

what is meant by the term rated-load amperage (RLA) as it applies to an compressor motor.

A

RLA is a mathematical calculation used to get UL approval for a compressor motor.

22
Q

SFA

A

Surface factor amperage

23
Q

FLA

A

Full-load amperage

24
Q

RLA

A

Rated-low amperage

24
Q

FLA is the current the motor draws while operating at a _________ at the rated voltage.

A

full-load condition

25
Q

The alternating current frequency used in the U.S. is

A

60 cps

26
Q

CPS

A

Cycle per second

27
Q

If the voltage supplied to the motor is well below the motors rated voltage the current draw will be

A

Higher than it should be.

28
Q

The current a motor will draw at start-up is known as

A

Locked rotor amperage.

29
Q

A sleeve bearing would typically be used in a motor that

A

Operates with a light load and where noise is a factor.

30
Q

A bearing used on the bottom of a motor where the shaft is positioned vertically is called a

A

thrust bearing

31
Q

Roller bearing are normally used with

A

Large motors operating with a heavy load.

32
Q

A direct-drive motor may be connected to the load withe a

A

Coupling

33
Q

The width of a drive belt is classified as

A

“A” or “B” width.

34
Q

Single-phase motors can be wired to operate on three-phase power.

True or false

A

True

35
Q

The approximate FLA for a single-phase, 2 HP motor, operating on 230 V is

A

12 amps

36
Q

The approximate FLA for a 3-phase, 5 HP motor, operating at 400 V is

A

7.6 amps

37
Q

A motor is rated at 230 V. The upper and lower allowable voltage is

A

207 V to 253 V.

38
Q

A loose fitting belt on a belt-driven device will cause

A

Worn pulley grooves.

39
Q

A flexible coupling between the drive and driven device corrects

A

Corrects minor misalignment.

Hvac (29 decks)

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