PV Array Sizing for XantrexTM GT30 Grid-Tied Photovoltaic Inverter
For proper operation, the Xantrex GT30 requires two identical photovoltaic subarrays, PV1 and PV2 (same type, number, orientation and electrical
configuration of PV modules) of opposite polarities with respect to earth ground. The negative terminal of monopole PV1 and the positive terminal of
monopole PV2 will be automatically grounded inside the Xantrex GT30.
With any PV inverter, it is critical to properly match the PV array to the inverter. Failure to comply with all of the requirements below will limit the annual
PV system energy harvest, will force the inverter to operate with less-than-optimum conversion efficiencies and will void the product warranty.
Criteria
Value
Notes
Maximum Open Circuit Voltage at Standard PV Module
Test Conditions (STC) per Monopole
375 Vdc
(STC)
Find the open circuit voltage (Voc) at standard test conditions (STC) on the PV module
manufacturer’s data sheet and multiply this number times the number of PV modules to be
connected in series.
Maximum Open Circuit Voltage at the Coldest Historical
Site Temperature
430 Vdc
Find the open circuit voltage (Voc) at standard test conditions (STC) and the temperature
coefficient for open circuit voltage (α Voc) on the PV module manufacturer’s data sheet.
Multiply α Voc times the difference between 25°C and the lowest historical site
temperature. Apply the temperature coefficient to calculate the low temperature Voc and
multiply this number times the number of PV modules to be connected in series. For
example:
With a lowest site temperature of -20°C and α Voc given in mV/°C
Voc -20°C = Voc STC + [(α Voc/1000)  45]
With a lowest site temperature of -20°C and α Voc given in %/°C
Voc -20°C = Voc STC  {1 + [(α Voc/100) 45]}
Maximum Rated Nominal DC Input Power at Standard PV
Module Test Conditions (STC)
35kWdc
(STC)
Find the nominal rated power (Pr) at standard test conditions (STC) on the PV module
manufacturer’s data sheet and multiply this number times the total number of PV modules
to be connected to the Xantrex GT30.
Maximum Array Short Circuit Current at STC
80 Adc
Find the short circuit current (Isc) at standard test conditions (STC) on the PV module
manufacturer's data sheet and multiply this number by the number of strings per monopole
PV1 or PV2 (not PV1 and PV2).
Maximum Number of Series Connected Cells per Monopole
This is an additional string sizing cross-check for single-crystal
and poly-crystalline PV module types only.
600 cells
Find the number of cells per module on the PV module manufacturer’s data sheet and
multiply this number times the number of PV modules to be connected in series.
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All warranty, disclaimer and safety information is contained within the primary documentation received with the unit. Please ensure you are familiar with that information before proceeding.
January 2010 Revision B
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For inclusion with XantrexTM GT30 Grid-Tied Photovoltaic Inverter Planning, Installation and Operation Manual (Part #: 1-153405-01)