SMA SUNNY BOY 8000-US, Руководство по установке

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SMA Solar Technology AG
Installation Guide SB50US-80US-IUS094030 95
PV String Fuse Sizing
In any electrical system, fuses are used to protect wiring and equipment from excessive currents that
can cause damage, heating or in extreme cases even fire. If the fuse rating is too small it could open
during normal operation. If the fuse rating is too large, it cannot provide the needed protection. In PV
systems, the minimum and maximum size of the series fuse is determined by the electrical ratings of
the PV module as well as by UL and National Electrical Code (NEC) requirements. Be sure to consult
with your PV module manufacturer for appropriate PV string fuse ratings.
The minimum size of fuses and wiring are calculated using the Short Circuit Current Rating (Isc) of the
PV module. The NEC requires that all fuses and wiring be sized for a minimum of 1.56 times the Isc
of the PV module used in the system. The proper size PV string fuse is determined by calculating 1.56
x Isc (of the PV module) and then rounding up to the next standard fuse size.
DC Disconnect Requirements
NEC 690.15-18 allows the use of fuse holders as a suitable means of disconnecting PV arrays for
servicing. Additional DC disconnects external to the inverter may be required by the local authority
having jurisdiction.
PV String Fuses
The SMA DC-Disconnect is shipped with 15 A, 600 V DC fuses in the fuse holders. The maximum
string fuse rating for the SMA DC-Disconnect is 20 A. The figure in chapter 9.4.2 "Exchanging the PV
String Fuses within the SMA DC-Disconnect" (page 94) shows the string fuse holders and their
corresponding terminals.
If the Isc of the PV module equals 6.9 A DC, then the PV string fuse size is determined by
1.56 x 6.9 = 10.76. The next standard fuse size would be a 12 A, 600 V DC fuse.
CAUTION!
The string fuse size must not be greater than the maximum fuse size rating of the PV module
as provided on the PV module manufacturers data sheet. If no maximum fuse size is
indicated, please contact the PV module manufacturer!
WARNING!
Never remove a fuse while it is under load. Electrical arcing and damage to the fuse holder
will occur if a fuse is removed under load.