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electrical second year > H-6 Fuses And Breakers > Flashcards

H-6 Fuses And Breakers Flashcards

1
Q

What is overload protection ?

A

overload: A moderate increase in current to an above normal level over a short period time .

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2
Q

What is over current ?

A

overcurrent : A current much larger then normal , momentarily

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3
Q

One advantage and one dis advantage of a fuse

A

Faster , more reliable , Only used once

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4
Q

One advantage and one dis advantage of a breaker

A

resetable, may have poor repeatability

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5
Q

two injurious effects that short current causes

A

mechanical , thermal stress

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6
Q

What determines how much current flows through when a fault occurs

A

IMPEDENCE

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7
Q

A fuse with HRC means

A

HIGH RUPTURING CAPACITY (FAST)

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8
Q

maximum current for plug fuse

A

30 A

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9
Q

Max voltage rating for plug fuse

A

150v to ground

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10
Q

2 other reasons a fuse may open

A

High Ambient temperature , vibrations , poor connection

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11
Q

what do “tamper resisting” plugs do ?

A

Prevent overfusing

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12
Q

Name 2 different style of cartridge fuses

A

Bolt on , ferrile , blade

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13
Q

A fuse is marked with the letter d

A

Marked as TIME DELAY

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14
Q

Example of a fast speed response fuse

A

Electronics - fast

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15
Q

Example of a slow speed response fuse

A

Breakers - motor protection

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16
Q

significance of the voltage rating in fuses

A

Maximum voltage fuse may operate at

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17
Q

significance of continuous current rating in fuses

A

Maximum current fuse may operate at

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18
Q

Significance of interrupting capacity

A

Maximum fault current fuse can handle without destroying itself

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19
Q

A fuse is marked with the letter P

A

Marked as LOW MELTING POINT

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20
Q

Max current ratings for cartridge fuses

A

600A

21
Q

Max voltage ratings for cartridge fuses

A

600V

22
Q

One adv , one disadv of “One Time” and “Renewable” cartridge fuses

A

Used One time ,cant tamper with fuselinks

renewable , can be spiked

23
Q

What is meant by the term code fuse

A

Class H (10 000 AIR)

24
Q

Maximum interrupting rating for code fuses

A

10 000A

25
Q

What is a dual element fuse ?

A

Two elements , protecting against shorts and overloads

26
Q

Cartridge Fuse

A

Ferrule - contacts , knife , bolt on

27
Q

Type C fuses :

A

Rejection Ring must be used

28
Q

Type S fuses :

A

Rejection adapter must be used

29
Q

Standard low voltage ratings for Fuses

A

125v , 250v , 300v , 600v

30
Q

What kinda base does a plug fuse have?

A

Screw Base , Edison Base

31
Q

What does a fuse do?

A

Protects the Conductor in a circuit

32
Q

How does a Bi metallic fuse work ?

A

An insulated tube containing metal strips that melt if too much current passes through ( short circuit )

33
Q

Are type C AND S interchangeable?

A

NON INTERCHANGABLE

34
Q

Proper voltage rating is required …

A

To prevent the arc from re striking.

35
Q

What do the letters HRC mean when refering to a fuse ?

A

High Rupturing Capacity

36
Q

What is the essential difference between HRC1 AND HRC2 fuse ?

A

HRC2 Does not protect against overload , it is used with overload heatres

37
Q

what is a rejection holder?

A

Rejects a standard H fuse

38
Q

Usual interrupting capacity of HRC fuses

A

200 000A

39
Q

What is difference about HRC fuses then cartridge fuses ?

A

Silver links ( lower resistance) , ceramic body , sand filler

40
Q

Are HRC1 AND HRC2 fuses interchangeable ?

A

No

41
Q

Does code let HRC fuses be used instead of cartridge fuses

A

Yes

42
Q

what are HRC1 used for

A

General Purpose Motors

43
Q

HRC2 is used for what?

A

Motor circuits that use seperate overload protection

44
Q

Explain Trip Free

A

The breaker cannot be held ON . It is free to trip.

45
Q

Explain Thermal Trip

A

Trips on bending bi metallic strip ( time delay )

46
Q

Explain Magnetic trip

A

Taps in magnetic Coil

47
Q

Explain Thermal - magnetic trip

A

combination of metal strip and magnetics.

48
Q

what do the letters GFCI mean?

A

Ground fault circuit interrupter

49
Q

If a two pole breaker is not available , it is permissible to use a two single pole breaker?

A

Yes, as long as the poles are together using a tie bar

electrical second year (9 decks)

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