Technical Structure Of The Solar Inverter - Delta SI 5000 Operating And Installation Manual

4.2

Technical structure of the solar inverter

A potential isolation of the solar inverter from the mains grid is achieved through a DC/AC con-
verter with integrated high-frequency transformer. The photovoltaic voltage is adjusted so that the
maximum power output of the PV modules is also achieved with different PV irradiation levels and
temperatures (MPP-Tracking).
The MPP range of the solar inverter is between 150 V and 450 V. This facilitates the use of PV
modules by a variety of manufacturers. Measures must be taken to ensure that the maximum open-
circuit voltage of 540 VDC is never exceeded. Please note that the maximum open-circuit voltage
will occur at the lowest temperatures anticipated. You will find more detailed information about
temperature dependency in the data sheet of the PV modules. The device's power consumption is
kept to a minimum.
The high-quality aluminum casing corresponds to protection class IP65 (water-jet-proof and dust-
proof) and is protected against weathering processes by surface refinement. The cooling charac-
teristic profile is designed so that operation of the inverter is possible with ambient temperatures
from -25°C to +60°C.
A cooling characteristic profile is used for the removal of the power dissipation caused through
the voltage conversion. An internal temperature control protects the device against too high tem-
peratures in the interior of the solar inverter. In case of high ambient temperatures, the maximum
transferable power is limited (see diagram under 6.5).
The solar inverter is controlled by microcontrollers, which also implement interface communication
and the monitoring of values and messages on the display.
Two independent and redundant microcontrollers control the monitoring of the grid, which is consis-
tent with the feed-in directives of VDEW and DIN 0126-1-1 (anti-islanding protection). This enables
an installation of the solar inverter in the in-house mains grid.
Operator protection requirements are met by electrically isolating the mains from the PV module.
The electrical isolation between the mains and the PV module is equivalent to basic insulation.
Maximum operator protection is ensured by reinforced isolation between the mains, PV modules
and accessible interfaces (display, RS485 interface and fan port). Relevant standards concerning
electromagnetic compatibility (EMC) and safety are fulfilled.
The solar inverter is functional in on-grid operation exclusively. An automatically-acting isolation
point, which was accepted by a certification agency, guarantees secure disconnection in case of
circuit isolation or interruptions in power supply and avoids isolated operation.
The equipment provided for the disconnection is a so-called „automatic isolation for in-plant genera-
tion systems of nominal power ≤ 4.6 kVA, with single-phase parallel feed-in over solar inverter into
the mains grid of the public supply".
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