EMP Electrical Systems & Power Quality 2

Question 1

What is the primary function of a Variable Frequency Drive (VFD) when applied to motor-driven systems?

Accepted Answer

To control motor speed by varying the frequency and voltage of the electrical supply

Answer

To convert DC power to AC power at a fixed output frequency

Answer

To regulate voltage levels in distribution transformers

Answer

To measure power quality parameters in motor branch circuits

Question 2

In a three-phase electrical system, what does 'voltage unbalance' refer to?

Accepted Answer

Unequal voltage magnitudes or phase angle differences among the three phases

Answer

Different power factors measured across the three phases

Answer

Varying frequency detected on different phases of the system

Answer

Unequal reactive power distribution among three-phase loads

Question 3

What is a key benefit of installing electrical sub-metering within a large commercial or industrial facility?

Accepted Answer

It enables identification of energy consumption by individual systems, departments, or equipment

Answer

It eliminates the requirement for utility-grade revenue meters at the service entrance

Answer

It automatically reduces total energy consumption without further operator intervention

Answer

It provides emergency backup power during utility outages

Question 4

What is the primary function of a soft starter connected to an AC motor?

Accepted Answer

To gradually ramp up voltage to the motor during startup, reducing inrush current and mechanical stress

Answer

To eliminate harmonic currents generated by variable speed drives

Answer

To provide uninterruptible backup power during momentary utility outages

Answer

To automatically correct power factor during motor operation

Question 5

Which standard provides the recommended harmonic current and voltage distortion limits for electrical power systems in the United States?

Accepted Answer

IEEE 519 - Recommended Practices for Harmonic Control in Electrical Power Systems

Answer

ASHRAE 90.1 - Energy Standard for Buildings

Answer

NEMA MG-1 - Motors and Generators

Answer

ANSI C84.1 - Voltage Ratings for Electric Power Systems

Question 6

In energy management, what is the primary objective of implementing a load shedding strategy?

Accepted Answer

To reduce peak electrical demand and lower utility demand charges during high-load periods

Answer

To permanently retire and remove outdated electrical equipment from service

Answer

To transfer load between parallel utility feeders during planned maintenance

Answer

To eliminate reactive power penalties on the monthly utility bill

Question 7

Which lighting control technology reduces energy consumption by automatically adjusting artificial light levels based on the amount of available natural daylight?

Accepted Answer

Daylight harvesting controls with photosensors

Answer

Occupancy-based presence sensors

Answer

Time-of-day scheduling controllers

Answer

Demand response relay-based controls