Electrical Systems & Power Quality Flashcards
7 cards from real EMP practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Electrical Systems & Power Quality flashcards as text
What is power factor in an electrical system?
Answer: The ratio of real power to apparent power
Power factor is the ratio of real power (kW) to apparent power (kVA), representing how efficiently electrical power is being converted into useful work.
What is the typical minimum acceptable power factor for commercial and industrial facilities before utility penalties apply?
Answer: 0.85
A power factor of 0.85 is generally considered the minimum acceptable threshold, and many utilities impose penalty charges when facility power factors fall below this level.
Which device is most commonly installed to improve power factor in commercial and industrial electrical systems?
Answer: Capacitor bank
Capacitor banks supply reactive power locally at the facility, reducing the reactive power that must be drawn from the utility and thereby improving power factor.
What does Total Harmonic Distortion (THD) measure in an electrical system?
Answer: The ratio of the sum of all harmonic components to the fundamental frequency component
THD quantifies waveform distortion by expressing the cumulative energy of all harmonic frequencies as a ratio relative to the power at the fundamental frequency (60 Hz in the US).
Which of the following is the most common cause of voltage sags in commercial electrical distribution systems?
Answer: Starting of large motors or heavy industrial equipment
Starting large motors causes significant inrush current—often 6 to 10 times the normal running current—which creates a momentary voltage drop (sag) throughout the distribution system.
What is the primary purpose of a power quality analyzer used in energy management?
Answer: To measure and record electrical parameters such as voltage, current, and harmonics to identify power quality issues
A power quality analyzer captures and records electrical parameters—including voltage, current, frequency, harmonic distortion, and power factor—to identify, diagnose, and document power quality problems.
What is a demand charge in utility billing for commercial and industrial customers?
Answer: A charge based on the highest peak power demand recorded during the billing period
A demand charge is a utility fee based on the highest average power demand (kW) recorded during any demand interval (typically 15 or 30 minutes) within the billing period.