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Third Year > Elecrical Safety > Flashcards

Flashcards in Elecrical Safety Deck (13)
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1
Q

Electric arch temperatures

A

-typically reach 3500 degrees C

2
Q

Approach distance

A

-7m from power lines when working or operating machinery.

3
Q

Circuit Breakers

A
  • open the circuit they are protecting in the event of a short circuit or high current level overload.
  • basic types of faults are high energy, short circuit faults and longer duration overload faults.
4
Q

Different types of circuit breakers

A
  • single pole, single phase (house hold)
  • three phase auxillary (welders and grinders)
  • motor (on the MCC in industry)
5
Q

Interrupter Rating vs. Fuse Rating

A
  • fuses are rated by: voltage rating, current and amp rating, interrupting rating and blow characteristics.
  • interrupting rating is the maximum current the breaker can safety interrupt without failure.
6
Q

Stop buttons

A

-always wired closed

7
Q

Types of fuses

A
  • fast acting which blow instantly and rapidly when their current rating and blow characteristics are exceeded.
  • Time delay which have thermal delay fusible links and also instant blowing links for high level faults.
8
Q

Ampacity

A

-the allowable current carrying capacity of a wire or cable assembly

9
Q

Thermal overload relays

A
  • emulating the temperature of the motor windings that they protect
  • two kinds are bimetallic and melting alloy
10
Q

Bimetallic relays

A

-use a heater element to detect the amount of current flowing. When the current exceeds it, the heater causes the element to bend.

11
Q

Melting Alloy Relay

A

-use a pot filled with a low temp melting alloy fastened to the current carrying bar to sense the temp of the motor windings. When the temp exceeds the alloy melts

12
Q

Conventional Flow vs. Electron flow

A

-conventional is positive to negation and electron is negative to positive

13
Q

Line voltage tolerance

A

+- 5%