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VarioTrack
4.3 P
HOTOVOLTAIC GENERATOR
The VarioTrack may accept input voltages between 0 to 150V max. Its operating range as a charger
starts from a value above the battery voltage up to 145V.
If the no-load voltage of the panel is above 60V (in all the temperature range), the whole
solar system must be installed according to protection class II.
4.3.1 Dimensioning
The solar generator is dimensioned to cover an important part or the entire power requirement of the
system. Once the power has been decided upon, it will be distributed among one or more solar
charge regulators, wisely combining the modules among them. These combinations in series and in
parallel must be carried out according to the voltage and current limits of the VarioTrack regulator.
4.3.2 Serial connection (string) of PV modules
To get the optimum voltage, the PV modules shall be connected in series to form a string having the
desired voltage. The optimum operating voltage of the module string (V
the battery voltage. To establish the minimum number of PV modules to be connected in series in
the same string, the max voltage of the battery must be multiplied by 1.2 and divided by the modules
Vmpp voltage.
For example, in a system with a lead-acid battery supporting equalization at 62V: 62*1.2/30.8=2.4.
The result must be rounded up to the highest value (i.e. 3 modules - of 30.8V
example).
The open-circuit voltage of the string must be lower than 145V under any temperature and irradiation
conditions. A 10 to 20% margin is recommended in order to cover these unknowns. To establish the
maximum numbers of the PV modules connected in series in the same string, use the following
formula: 145V/(V
*1.1). (Example: 145/(38*1.1)=3.5). The result must be rounded down to the lowest
oc
value (i.e. 3 modules - of 38V
There should be thus 3 modules in series of the mentioned model for a 48V system as per this example.
The table hereunder gives an idea of the possible arrangements for common panels according to
the number of cells or their type:
36 cell
module
Voc < 25V
U Battery
max. opt.
12V
3
24V
5
48V
5
Beware of the PV module temperature! The above values are for modules under standard test
condition (STC).
4.3.3 Parallel connection of PV module strings
To get the required charging power, 2 or more strings are
usually to be connected in parallel. Each string connected in
parallel shall be composed by the same number of modules
of the same type.
The number of strings connected in parallel depends on the
power of each module. The sum of the power of all the panels
connected to a VarioTrack should not exceed the power that
the VarioTrack can charge, see table to the right.
The number of strings to be connected in parallel must not exceed the maximum power (see table
hereafter) divided by the power of a string and rounded down to the lower value.
12
(PV)
- in series for the above example).
oc
60 cell
module
Voc < 42V
Voc < 50V
max.
opt.
max.
2
1
1
1
3
3
2
2
5
3
3
2
72 cell
96 cell
module
module
Voc < 67V
opt.
max. opt.
1
1
1
2
2
1
2
2
2
Battery
12V
24V
48V
V 4.0
) must always be above
mpp
- in series for the above
mpp
Thin film
module
Voc > 75V
--
0
Number of
1
modules
per string
1
Maximum
recommended power for
the solar generator
VT-40
VT-65
VT-80
625W
1000W
1250W
1250W
2000W
2500W
2500W
4000W
5000W
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