Safe Use Of The Photovoltaic Modules; Protection Devices; Cable Cross-Section; Parallel Connection Of Several Variotracks - Studer VarioTrack VT-40 User Manual

For example, in a 48V system with strings composed of 3 in-series modules of 260W connected to
model VT-65: 4000 / 780=5.1 => 5 strings (3900W) can be put in parallel.
These strings of 3 modules in series may become 6 when connected to model VT-80.
These strings of 3 modules in series may become 3 when connected to model VT-40.
If the maximum currents mentioned in chap. 4.3.3.1 are respected, the PV generator can be over-
dimensioned in order to get the required charging power even when solar irradiation is lower. In this
case, a part of the energy will be lost when the solar irradiation is higher.
Note: the VarioTrack has a current limit. The maximum power of the VarioTrack depends on the
charging phase voltage of the battery.
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 35A for model VT-40, 60A for model VT-65 and 75A for model VT-80.
Note: the National Electrical Code (NEC) in force in the United States requires a limit of the
solar generator current <= 0.8 x rated current of the solar regulator. Thus in order to comply
with NEC, the maximum current for the solar generator is 32A for the VarioTrack model VT-40,
52A for the VT-65 and 64A for the VT-80.
In any case, the VarioTrack will limit the charging current (battery) to its rated current, i.e. 40A for
model VT-40, 65A for model VT-65 and 80A for model VT-80.

4.3.4 Safe use of the photovoltaic modules

The VarioTrack is meant for PV generators supplying up to 150Vdc. 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 VarioTrack
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. 4.7).

4.3.6 Cable cross-section

The connection cable cross-section must be chosen according to the short-circuit current of the PV
generator and the local installation rules. For VT-65 and VT-80, a 25mm
recommended, terminals (M6) must be tightened at a torque of 5 Nm. For the VT-40, a 10mm
section is recommended, terminals (M5) must be tightened at a torque of 5 Nm.
All connection cables as well as the PV cables must be mounted using cable restraints in order to
avoid any pulling on the connection.

4.3.7 Parallel connection of several VarioTracks

As many VarioTrack as necessary could be connected in parallel on the same battery bank
according to the battery capacity. Each will have its own independent solar generator and is
connected with its own disconnection and protection device to the battery.
Up to 15 VarioTrack could be synchronized and interconnected to the same communication bus
(see chap. 4.8) on a single system. Beyond these 15 units, any additional unit will not be
interconnected and thus their battery cycles will work independently.
Manuel utilisateur V 4.0
Studer Innotec SA
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