EMP Electrical Systems & Power Quality

Question 1

What is power factor in an electrical system?

Accepted Answer

The ratio of real power to apparent power

Answer

Power factor is the ratio of real power (kW) to apparent power (kVA), representing how efficiently electrical power is being converted into useful work.

Question 2

What is the typical minimum acceptable power factor for commercial and industrial facilities before utility penalties apply?

Accepted Answer

0.85

Answer

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.

Question 3

Which device is most commonly installed to improve power factor in commercial and industrial electrical systems?

Accepted Answer

Capacitor bank

Answer

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.

Question 4

What does Total Harmonic Distortion (THD) measure in an electrical system?

Accepted Answer

The ratio of the sum of all harmonic components to the fundamental frequency component

Answer

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).

Question 5

Which of the following is the most common cause of voltage sags in commercial electrical distribution systems?

Accepted Answer

Starting of large motors or heavy industrial equipment

Answer

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.

(EMP) Energy Management Professional Practice Test

(EMP) Energy Management Professional Practice Test

EMP Electrical Systems & Power Quality