SE Engr. Technical Specifications 4

Question 1

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?

Accepted Answer

530.4 V

Answer

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

Question 2

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

Accepted Answer

Isc × 1.25

Answer

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.

Question 3

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

Accepted Answer

30 V within 30 seconds

Answer

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.

Question 4

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?

Accepted Answer

40 A

Answer

(200 A × 1.2) - 200 A = 40 A.

Question 5

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

Accepted Answer

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

Answer

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

SE Engr. - Solar Energy Engineering Certification Practice Test

SE Engr. - Solar Energy Engineering Certification Practice Test

SE Engr. Technical Specifications 4