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Installation and Operation Manual (Rev E)
4.5
AC Wiring
The SGI series of inverters must be connected to the grid with three phase conductors and the
appropriate AC grounding conductors. No neutral conductor is required for the inverter to
operate. However, some utilities or jurisdictions may require that a neutral connection be made
from the onsite electrical service directly to the inverter's transformer in order to meet their
effective grounding requirements. Therefore, the installer may land a neutral conductor or a set
of neutral conductors directly on the neutral terminal of the inverter's integrated transformer.
The inverters are designed with a routing path through the inverter enclosure and a means for
connecting these conductors to accommodate this requirement.
Each SGI inverter includes an integrated AC breaker that serves as the connection point for the
AC phase wiring to the onsite electrical service or grid connection. The integrated breaker will
have different ratings depending on the inverter model.
Model
SGI 225-480VAC
SGI 250-480VAC
SGI 266-480VAC
SGI 300-480VAC
SGI 500-480VAC
SGI 500PE-480VAC
Table 4.6 – Factory Included AC Breaker Minimum Specifications
If the onsite electrical service connection is designed with an overcurrent protection device
(OCPD), it must be dedicated to the PV system and must be adequately rated for the current
delivered by the inverter as required by NEC 690. See NEC 690, NEC 705 and NEC 240 for
guidance on sizing the building OCPD. The table below summarizes the inverter's required
ampere rating for nominal 125% rated OCPDs; these ratings may change depending on the
interconnect design and whether or not 100% rated OCPDs are used.
Table 4.7 – Nominal 125% Rated Building Backfeed OCPD Ampere Ratings
The grid impedance value at the connection point should be as low as possible to avoid an
increase of the AC voltage to non-permissible values while the inverter feeds power to the grid.
Designing for less than 1% AC phase-to-phase voltage rise is recommended. Minimizing wiring
impedance also results in higher system efficiency.
DOCR-060371
Ampere Rating
400A
400A
400A
400A
800A
800A
Model
SGI 225-480VAC
SGI 250-480VAC
SGI 266-480VAC
SGI 300-480VAC
SGI 500-480VAC
SGI 500PE-480VAC
Interrupt Rating
100% Rated
25 kAIC
35 kAIC
35 kAIC
35 kAIC
65 kAIC
65 kAIC
Ampere Rating
350A
400A
400A
450A
800A
800A
SGI Series Inverters
No
No
No
Yes
No
No
25
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