Technical Specifications Flashcards

A module has Voc = 40 V and a Voc temperature coefficient of -0.30 %/°C. At a record low of -10°C, what is the maximum Voc of a 12-module string?

Answer: 530.4 V

ΔT = -35°C gives a +10.5% increase, so 40 × 1.105 = 44.2 V per module, and 44.2 × 12 = 530.4 V.

Under NEC 690.8, maximum PV source-circuit current is calculated as:

Answer: Isc × 1.25

Maximum circuit current is 125% of the summed parallel module Isc, and a second 125% factor is applied when sizing conductors and OCPD, for 156% overall.

Under NEC 690.12 rapid shutdown, controlled conductors outside the array boundary must be reduced to:

Answer: 30 V within 30 seconds

Outside the array boundary, conductors must drop to 30 V or less within 30 seconds of initiation; inside the boundary the limit is 80 V.

A panel has a 200 A busbar and a 200 A main breaker. Under the NEC 705.12 120% rule, what is the largest PV backfeed breaker allowed at the opposite end of the busbar?

Answer: 40 A

(200 A × 1.2) - 200 A = 40 A.

What does the 'maximum series fuse rating' on a module datasheet specify?

Answer: The largest overcurrent device that can protect the module against reverse current

It is the maximum OCPD rating that keeps reverse fault current from parallel strings within what the module can withstand.

What DC voltage-drop target is commonly recommended in PV design to limit losses?

Answer: Under 2%

Designers commonly target 1-2% DC voltage drop; the NEC sets no mandatory limit, but losses grow quickly above that.

On a bifacial module datasheet, the bifaciality factor is defined as:

Answer: Rear-side efficiency (or Pmax) divided by front-side efficiency

Bifaciality is the ratio of rear to front performance at STC, typically about 70% for PERC, 80% for TOPCon, and 85-90% for HJT.