C.S.P6: Lesson #1- reviewing key OCPD concepts Flashcards
Fuses and circuit breakers are intended to protect conductors and equipment from the effects of potentially harmful ? .
overcurrents
True or false?
Overload current is confined to the normal conductive path provided by the conductors, circuit devices, and loads of the distribution system.
True
Fault current ? the normal conducting path.
flows outside
Because of the ? impedance path, a 3-phase bolted short-circuit condition is typically assumed to be the highest level of fault current.
low
per the Article 100 definition of branch-circuit overcurrent protective device?
A device capable of providing protection for equipment
A device capable of providing protection for service, feeder, and branch circuits
Such devices are provided with interrupting ratings appropriate for the intended use but no less than 5000 amperes.
True or false?
Supplementary overcurrent protective devices are permitted to be used as a substitute for a branch-circuit OCPD or where a branch-circuit OCPD is required (per 240.10).
False
A ? overcurrent protective device is one that clears a fault current in one half cycle or less and reduces the amount of fault current let-through.
current-limiting
True or false?
When fault current is within the current-limiting range of a current-limiting OCPD, the thermal energy and magnetic (mechanical) forces can be greatly reduced. The levels of both thermal energy and magnetic forces are proportional to the square of the fault current that flows.
True
True or false?
A 600-volt or less branch-circuit OCPD can be identified as being current limiting by being marked “current limiting.”
True
true or false?
The voltage rating of the OCPD must be equal to but never greater than the circuit voltage
false
true or false?
A 600-volt AC fuse or circuit breaker is considered to have a 600-volt DC rating, even if it is not marked with a DC voltage rating.
False
True or False?
Branch-circuit fuses do not have to be marked with their ampere rating
False
True or False?
Only standard ampere rated fuses and circuit breakers found in 240.6 are permitted to be used in services, feeders, and branch circuits.
False
True or False?
When the conductor ampacity does not correspond to a standard OCPD ampere rating, the next standard OCPD ampere rating is permitted if that rating does not exceed 800 amperes, and if the conductors are not supplying a circuit with more than one receptacle for cord-and-plug portable loads.
True
True or False?
For motor branch-circuit applications, the motor branch-circuit short-circuit and ground-fault protective device can be located anywhere on the motor branch circuit since fault currents stay within the normal conducting path.
False
