Electrical & Mechanical Concepts Flashcards

Which type of inverter can operate without a utility grid connection and is used in off-grid PV systems?

Answer: Stand-alone inverter

Stand-alone (off-grid) inverters operate independently of the utility grid, converting DC battery power to AC for loads.

A conductor carrying 25 A is installed in a conduit with three current-carrying conductors. What NEC adjustment factor applies?

Answer: 0.80

NEC Table 310.15(C)(1) requires an 80% (0.80) adjustment factor for 4–6 current-carrying conductors in a raceway.

What is the significance of the Isc rating on a PV module datasheet?

Answer: Current produced under short-circuit conditions at STC

Isc (short-circuit current) is the maximum current a module produces when its output terminals are shorted under STC.

Roof-mounted PV modules must typically have a minimum clearance above the roof surface. What is the primary reason for this requirement?

Answer: Airflow for convective cooling

Clearance beneath modules allows airflow that removes heat, improving module efficiency and longevity.

What does MPPT stand for in the context of solar inverters and charge controllers?

Answer: Maximum Power Point Tracking

MPPT continuously adjusts the operating point of the PV array to extract maximum power as conditions change.

A ground fault protection device (GFPD) in a PV system is designed to detect what condition?

Answer: Unintended current path from the DC circuit to ground

GFPDs detect unintended current flowing from the PV system to ground, which can cause fires or electric shock hazards.

In mechanical terms, what is the dead load on a rooftop PV mounting system?

Answer: Static weight of the array and mounting hardware

Dead load refers to the permanent static weight of the PV modules, racking, and hardware that the roof structure must support.