
System Protection 265
PROBLEMS
Problem 10.1: Determine the time-delay fuse rating for a 3-phase, 208V,
5-hp motor branch circuit in the engine room, which has an ambient air
temperature of 55°C. Assume the motor efciency of 92% and power
factor 80%.
Problem 10.2: The 4.76 kV circuit breaker in Table10.4 can be used for a
rated fault current interruption of 41 kA at rated 4.76 kV
LL
system voltage.
Determine the range of system voltage and interruption current it can be
used for.
Problem 10.3: Determine the continuous current rating and the rms fault
current interruption rating of circuit breaker or fuse on both sides of a
300kVA, 600V∆/208VY ...