NABCEP Electrical & Mechanical Concepts 5

Question 1

What is the purpose of equipotential bonding in a PV array?

Accepted Answer

Connect all metallic parts to the same electrical potential to prevent shock

Answer

Equipotential bonding ensures all metal racking, frames, and enclosures are at the same voltage, eliminating dangerous potential differences.

Question 2

In a transformer, if the primary has 240 turns and the secondary has 60 turns, what is the turns ratio and secondary voltage for a 120 V primary?

Accepted Answer

4:1, 30 V

Answer

Turns ratio = 240/60 = 4:1, so secondary voltage = 120 V ÷ 4 = 30 V.

Question 3

What type of load calculation must be performed before designing a rooftop PV mounting system?

Accepted Answer

Structural load analysis including dead, live, wind, and seismic loads

Answer

A structural load analysis evaluates the roof's ability to support the array's weight plus environmental forces such as wind and snow.

Question 4

What does a negative temperature coefficient of Isc mean for a crystalline silicon PV module?

Accepted Answer

Isc increases slightly as temperature rises

Answer

Crystalline silicon modules have a slightly positive Isc temperature coefficient, meaning current increases marginally with temperature.

Question 5

A 240 V AC, single-phase circuit carries 20 A. What is the apparent power in VA?

Accepted Answer

4,800 VA

Answer

Apparent power (VA) = Voltage × Current = 240 V × 20 A = 4,800 VA.

(NABCEP) North American Board of Certified Energy Practitioners Solar Practice Test