Design Principles Flashcards
7 cards from real SE ENGR. practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Design Principles flashcards as text
What is a typical power temperature coefficient (Pmax) for a crystalline silicon module?
Answer: -0.35% to -0.45%/°C
Crystalline silicon modules typically lose about 0.35–0.45% of power for each 1°C rise in cell temperature.
Which conditions define Nominal Operating Cell Temperature (NOCT)?
Answer: 800 W/m², 20°C ambient, 1 m/s wind, open circuit
NOCT is the cell temperature reached at 800 W/m² irradiance, 20°C ambient, and 1 m/s wind with the module open-circuited.
What are Standard Test Conditions (STC) for PV module ratings?
Answer: 1000 W/m², 25°C cell temperature, AM1.5 spectrum
STC is 1000 W/m² irradiance, 25°C cell temperature, and an AM1.5 spectrum.
Under NEC 690.12 rapid shutdown, conductors outside the array boundary must drop to what level within 30 seconds?
Answer: 30 V
Controlled conductors outside the array boundary must be limited to 30 V within 30 seconds of initiation.
Performance ratio (PR) for a PV system is best described as which of the following?
Answer: Actual energy yield divided by the reference yield expected from STC rating and plane-of-array irradiance
PR compares measured final yield with the theoretical yield based on irradiance and nameplate rating, so it captures all system losses.
On a roof with several orientations and partial shading, what is the main design advantage of microinverters?
Answer: Module-level MPPT, so one weak module does not limit the others
Each microinverter tracks its own module's maximum power point, which isolates mismatch and shading losses.
Fire code access pathways on residential PV roofs are typically at least how wide?
Answer: 36 inches
The IFC/IRC generally requires 36-inch-wide access pathways from eave to ridge on residential roofs.