Code, Standards, and Practices 6 Flashcards
ability to cut off first 1/2 cycle
Current limiting
Interrupting rate
the highest current at rated voltage that a device is identified to interrupt
arc reducing maintenance switch
allows a worker to set a circuit breaker trip unit to ‘no intentional delay’ to reduce the clearing time while the worker is working within an arc-flash boundary
Fuse L
Large
Fuse J
Junior or small
Fuse H
10,000 A interrupting rate
What is the purpus of a motor OCPD
Prevent short circuits and ground faults
Motors are protected by OCPD and
Overloads
What is single phasing
Loosing a any leg on a 3 phase system
What is inrush current
Large amount of current drawn from motor upon start up
Disconnecting switches have?
Ampere ratings
How do overloads protect from to much inrush for to long
Thermal connection will liquify and loose connection
430.6
Ampacity and motor rating determanation
What temp rating are OCPD terminations rated for
75 degree
for a single motor, conductors shall not have an ampacity less than_____ of full load current rating
125%
T/F small conductor rule dose not apply to Motors
True. table 240.4(G)
Where can you find short circuit current ratings in the code
110.10
T/F do transformers have inrush current
True
3 phase transformer current ratings
VA
(voltage x 1.73)
Hazards associated with fault current
Shock, Projectiles, Fire
Fully Rated systems
Circuit breakers are 100% rated for available fault current
Selective coordination
695.3 (C) (3)
Who can deem a selectively coordinated system
Engineer
What breaker trips first on a selectively coordinated system
The breaker closest to the fualt
