Electrical & Mechanical Concepts Flashcards

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

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

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

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?

Answer: 4:1, 30 V

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

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

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

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

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

Answer: Isc increases slightly as temperature rises

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

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

Answer: 4,800 VA

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

What standard torque specification concern applies when installing PV module mounting hardware on racking?

Answer: Under-torquing or over-torquing can cause frame damage or loose connections

Module frames can crack if over-torqued, while under-torqued connections can loosen under wind and thermal cycling.

Which NABCEP competency area requires understanding of wire sizing based on both ampacity and voltage drop?

Answer: System Design

System Design requires selecting conductors that meet both ampacity requirements and allowable voltage drop limits for optimal performance.