Electrical & Mechanical Concepts Flashcards

What is the purpose of anti-islanding protection in a grid-tied PV inverter?

Answer: Shut down the inverter if the grid de-energizes

Anti-islanding protection disconnects the inverter from an energized output if the utility grid fails, protecting line workers.

What is the formula for calculating voltage drop across a conductor?

Answer: Vd = I × R

Voltage drop equals current (I) multiplied by the conductor resistance (R) per Ohm's Law.

Which wire gauge has a larger cross-sectional area: 10 AWG or 6 AWG?

Answer: 6 AWG

In the AWG system, lower numbers indicate larger wire diameters and greater cross-sectional area.

What happens to PV module Voc as cell temperature increases?

Answer: Voc decreases

Voc has a negative temperature coefficient, so it decreases as module temperature rises.

A residential PV system uses USE-2 cable on the roof. What does USE-2 indicate?

Answer: Underground Service Entrance, dual-rated for sunlight resistance

USE-2 is a dual-rated cable suitable for underground service entrances and also rated for direct sunlight exposure, common in PV source circuits.

What is the role of a combiner box in a large PV array?

Answer: Combine multiple source circuit outputs into a single output circuit

A combiner box aggregates the output of multiple PV source circuits (strings) into one output circuit feeding the inverter.

What is the primary reason for limiting PV system DC voltage to 600 V in residential applications per the NEC?

Answer: Listed equipment and wiring methods are readily available for ≤600 V systems

600 V is a common threshold in NEC Article 690 because widely available listed components, connectors, and wiring are rated for this voltage.