Safe Use Of The Photovoltaic Modules; Protection Devices; Cable Cross-Section And Connection; Parallel Connection Of Several Variostring - Studer VarioString User Manual

solar irradiation is lower. In this case, a part of the solar energy will be lost when the solar irradiation is
higher because the VarioString will reach its current limit and curtail power output.
The VarioString has a current limit. At any given time, the maximum power of the VarioString
depends on the charging phase voltage of the battery. For example, if the charging phase
is Bulk, and the battery voltage is 50V, the maximum power output is 120A * 50V = 6000VA.
Even if more solar energy is available, the battery charge current will not exceed 120A.
4.3.3.1 Maximum current of the solar generator
The maximum current of the solar generator (sum of the short-circuit currents for all the strings
connected in parallel) is 26A (13A per input).
In any case, the VarioString will limit the charging current (battery) to its rated current of 120A.

4.3.4 Safe use of the photovoltaic modules

The VarioString is meant for PV generators supplying up to 600Vdc (900Vdc in series). This
voltage is dangerous for human beings.
During the installation or the maintenance of the system, it is imperative to make sure that
no dangerous voltage may surge in the system. The disconnection device must be open
and secured against any accidental reclosing.

4.3.5 Protection devices

Wiring protection devices (fuses, circuit breakers) connecting the PV generator to the VarioString
must be installed in accordance with local standards and regulations in force.
The DIN VDE 0100-712 standard prescribes a switching device on all poles between the PV generator
and the charge regulator. This device must be supplied by the installer.
PV modules are often exposed to stormy weather. It is highly recommended to install lightning
protection (see chap. 4.5).

4.3.6 Cable cross-section and connection

The connection cable cross-section must be chosen according to the short-circuit current of the PV
generator and the local installation rules. The Sunclix type PV connectors do not need any special
tools for mounting. They accept cables between 2.5 and 6mm2 (exterior cross section of 5 to 8mm2).
The length of cable to strip to attach the Sunclix connector is 15mm.

4.3.7 Parallel connection of several VarioString

As many VarioString as necessary can be connected in parallel on the same battery bank according
to the battery capacity. Each will have its own independent solar generator (connected in
independent, parallel or series configuration) and include its own disconnection and protection
device to the battery.
Under no circumstances should PV module inputs of several VarioString be put in parallel.
Up to 15 VarioString could be synchronized and interconnected to the same communication bus
(see chap. 4.6) on a single system. Beyond these 15 units, any additional unit will not be
interconnected and thus their battery cycles will work independently.
Solar generators may be of various types and be orientated differently. Each VarioString will adjust
the optimum point of the PV generator independently of the other units connected to the same
battery.
In multi-unit systems (connected to the same communication bus), all VarioStrings must be
connected to the same battery bank.
User manual V 1.0
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