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TRAY’s 4TH Final > Understanding basic AC control equipment 209 > Flashcards

Understanding basic AC control equipment 209 Flashcards

1
Q

The NEMA 7 enclosure is designed for use

A

where flammable gases or vapors may be present

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2
Q

In the ______ mechanism, the hinged armature pivots to the sealed-in position.

A

Clapper

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3
Q

The shading coil reduces which of the following in the armature?

A

Vibration

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4
Q

The minimum potential diference that will cause the armature to seat against the pole faces of a relay coil is called the ____ voltage

A

Seal in

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5
Q

Which of the following is NOT the result of the potential difference across the coil being too great?

A

Reduced magnetic force

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6
Q

When appied to pushbultons, the terms standard duty and heavy duty apply only to the

A

amount of current the pushbutton contacts can carry

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7
Q

A NEMA-type 1B flush-mounted station requires a

A

4 11/6 in. single outlet box

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8
Q

NEMA-type 7-9 pushbutton stations for hazardous locations are suitable for all of the following locations EXCEPT

A

corrosive fumes or liquids

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9
Q

When only one START STOP station is used with several emergency STOP buttons at different
locations, the STOP stations are wired

A

in series

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10
Q

Which of the following are designed for only ac use?

A

Joy-stick operators

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11
Q

The purpose of the actuator in a precision snapswich is

A

transmit force from the outside

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12
Q

The temperalure that develops inside a swich under operating condions depends on al of ti
following EXCEPT the _____ current.

A

pulse

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13
Q

When a remote cable actuator is used, the switch is mounted

A

where space permits

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14
Q

When a plug in swich needs replacing. which is replaced?

A

Only the plug-in portion

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15
Q

When should a mercury swich be replaced?

A

When the mercury strings out or breaks up into pools

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16
Q

A ______ switch is used for changing a control circuit from one sequence to another.

A

Transfer

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17
Q

Plugging switches can operate

A

both A and B

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18
Q

Which kind of swich is clastied according to the kind of liquid or gas being measured?

A

Mechanical Pressure

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19
Q

Capilay tube, direct immersion, and thermostat are kinds ___ of

A

temperature control

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20
Q

Float swiches are used for controlin al of the following EXCEPT

A

temperature-maintaining equipment

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21
Q

Typical time delay relays are normally used in applicalions that

A

do not often need changes in time settings

22
Q

In the multiple circuit timer, each set of timer contacts opens or closes according to

A

its cam setting

23
Q

What type of timer has only two cams?

A

Percentage

24
Q

If a counter is to be operated from an ac source, a _____ must be used with it.

A

rectifier

25
Q

revolution counter is used where a machine cannot be controlled

A

by time

26
Q

The displayed contacts are data.

A

double-make

27
Q

An undercurrent relay functions when the current reaches a(n)

A

lower limit

28
Q

The voltage sensing relay requires a

A

temperature-compensating network

29
Q

The oulput relay of a three phase sequence sensing relay de energizes when the

A

phase relationship is other than A-B-C

30
Q

What is the maximum vollage for a NEMA Class B industrial ac relay?

A

600 V

31
Q

Combustible dusts are Class _____ hazardous material

A

ll

32
Q

All of the flowing are potential sources of ignition EXCEPT

A

aluminum tools dropped on a steel surface

33
Q

Industrial control equipment located in Class 1, Division l areas

A

has all arcing parts immersed under 6 in. of oil

34
Q

In hazardous locations, where the conduit enters an enclosure housing arcing high- temperature equipment, a seal must be within________ in. of the enclosure it isolates.

A

18

35
Q

The main disadvantage of mineral insulated (MI)cable is its

A

tendency to attract moisture

36
Q

Atter the proper speed lip top (PSF) ercut has been set on a synchronous motor control unt,
the setting can be cleared by a signal from the

A

pole slip (SPL) circuit

37
Q

Eight automatic sequence decelerating relays are required in a multispeed starter having ______ speeds

A

8

38
Q

An automatic autotransformer starter for a large induction motor begins by applying _____ line voltage to the motor.

A

less than full

39
Q

Part winding starters are generally used with motors having _____ connected windings.

A

delta

40
Q

The open circuit transition della starter has all of the folwing EXCEPT

A

a set of resistors

41
Q

Size ______starters are the largest size that can be accommodated by MCCs with drawout construction.

A

4

42
Q

The NEMA 12 endosure

A

has gaskets on all doors, cover and bottom plates, and around operating mechanisms

43
Q

Tin plated copper busbars are recommended for use in

A

corrosive environments

44
Q

A location for an MC needs to be all of the following EXCEPT

A

air-conditioned

45
Q

It work is required on the secondary circuis of an MC curent transformer afer they have been energized, the secondaries must be

A

short-circuited

46
Q

The end barriers on 600 V terminal blocks are ______ than those on 300 V blocks.

A

thicker and higher

47
Q

What type of wing terminals should be used where viration poses a threat of breakage

A

Insulated

48
Q

A specialy coaled steel spring is required for connecting

A

aluminum-to-aluminum wire

49
Q

A connector with no mark is for

A

copper conductors only

50
Q

When a panel is assembled, a plastic wiring duct may be

A

used to avoid the problems of laced wire

TRAY’s 4TH Final (7 decks)

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