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Planning the Installation
975-0320-01-01 2–3
PV Array Voltage and MPPT Requirements
MPPT operational
window
The MPPT software maximizes the output energy of solar arrays as long as the
operating voltage is within the MPPT operational window. Ensure that the PV
array used in the system operates within the MPPT operational window.
Effects of array voltages outside of the MPPT operational window are shown in
Table 2-1.
Voltage
requirements
The maximum power point voltage of a string connected to the GT Inverter should
preferably be above 240 Vdc. If it is less than 240 Vdc, the inverter continues to
operate, but it regulates the PV voltage to 240 V. Because the array is not
operating at its maximum power point, this may result in lower than expected
energy harvest. If V
oc
is below 240 Vdc, the inverter remains off-line and does not
deliver power.
The open circuit voltage of the array under normal conditions should be above
240 Vdc.
The short circuit current (I
sc
) rating of the array at any temperature must not
exceed the I
sc
rating of the inverter. For maximum solar energy harvest, it is
recommended that the effective power output of the array be matched with the
input power capacity of the inverter.
WARNING: Shock hazard
Whenever a PV array is exposed to sunlight, a shock hazard exists at the output wires or
exposed terminals. To reduce the risk of shock during installation, cover the array with an
opaque (dark) material before making any connections, and always test for voltage before
touching exposed wiring or devices.
Table 2-1
MPPT Operational Window
Voltage Effect of Array Voltage Inverter Mode
V
oc
< 240 Vdc Inverter not operating. Off-line
V
MPP
< 240 Vdc
(V
oc
> 240 Vdc)
Operating voltage shifts to 240 Vdc; the array is not at its
maximum power point.
On-line (low power)
V
MPP
240 to 550 Vdc Maximum harvest of solar energy. On-line (MPPT window)
V
MPP
550 to 600 Vdc Does not allow maximum harvest of solar energy. On-line (power derating)
V
MPP
> 600 Vdc
(or V
oc
> 600 Vdc)
Inverter stops delivering power and shuts down. Inverter
may be damaged.
Off-line (shutdown)
CAUTION: Equipment damage
To prevent damage to the inverter, the array voltage must never exceed 600 V
oc
(open
circuit voltage) under any condition.