تم الحل ✓
categoryالهندسة الكهربائية
schoolبكالوريوس
event_available2026-07-15
السؤال
Transcribed Image Text:
Problem 1:
An industrial customer with a three-phase, 480 V service entrance is running the following
set of loads:
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Two 15 HP, 89% efficient lathes, 0.79 lagging power factor
One 7 ton heat pump¹ with a COP of 1.9 and a 0.95 lagging power factor
Two electric autoclaves, 30 BTU/h, 98% efficient, 0.97 lagging PF
One 25 kW high-intensity discharge (HID) lighting system, unity PF
If the lighting system is replaced with a T8 fluorescent system with magnetic ballast that
consumes 25% less than the previous system, but introduces a 0.91 leading power factor, by
how much does the service entrance current change? Consider the case when all systems are
fully loaded. Consider the AC load under the new lighting regime.
Use the NFPA 70 to determine the minimum allowed gauge of the service conductors.
Feeder lines are copper, with a 60 °C temperature rating, contained within a raceway with an
ambient temperature of 40 °C. Start with article 310.15; state the specific article(s)/tables
used to determine your answer.
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