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2.3 Technical structure of the solar inverter
The photovoltaic voltage is adjusted so that the maximum power output of the PV modules is also
achieved with dierent solar irradiation levels and temperatures (MPP-Tracking). These inverters
have quite wide MPP range of suit for variety of PV modules by a variety of manufacturers. Mea-
sures must be taken to ensure that the maximum no- load voltage of 600 V is never exceeded.
Please note that the maximum no-load voltage will occur at the lowest temperatures anticipated.
You will nd more detailed information about temperature dependency in the data sheet for the PV
modules.
The high-quality aluminum casing corresponds to protection degree NEMA 4 (NEMA 3R for wiring
box) and is protected by an anti-corrosion nish. The heat sink on the M series inverters
is designed in such a way that operation of the inverter is possible at ambient temperatures from
-22°F to +113°F (-30°C to +45°C) at full power and optimal eciency for either 240 Vac or 208 Vac
AC grids.
Metal ns designed into the rear side of the inverter chassis are used to dissipate heat and protect
the unit. An internal temperature control protects the interior of the device. In case of high ambient
temperatures, the maximum transferable power is limited.
The solar inverter is controlled by microcontrollers which provide interface communication and the
values and messages on the front-panel display.
AC grid monitoring is done by an independent dedicated micro controller set up to meet the require-
ments of UL 1741,UL1741 SA / IEEE 1547. This enables a connection of the solar inverter to the
in-house grid.
Operator protection requirements are met by electrically isolating the grid from the PV module. The
electrical isolation between the grid and the PV module is equivalent to basic insulation. Maximum
operator protection is ensured by reinforced isolation between the grid, PV modules and accessible
interfaces (display, RS485 interface ). Relevant standards concerning electromagnetic compatibility
(EMC) and safety are fullled.
The solar inverter is functional in grid-parallel operation exclusively. An automatically anti-islanding
function, which was accepted by a certication agency, guarantees secure disconnection in case of
circuit isolation or interruptions in power supply and avoid isolated operation.
The DC arc-fault circuit interrupt (AFCI) is integrated into M4-TL-US,M5-TL-US,M6-TL-US, M8-
TL-US ,and M10-TL-US . It complies the requirement as Type 1 device in UL1699B standard,
series arc faults can be detected.
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