WEG CFW11 Applications Manual page 13

Installation
3 INSTALLATION
3.1 SIZING OF PHOTOVOLTAICS SOLAR MODULES
To install/dimension solar photovoltaic modules must accomplish its 3 main characteristics:
■ Peak Power (W
) Is the maximum measured power that the solar photovoltaic module establishes for the
p
STC condition.
■ Open Circuit Voltage (V
the STC condition.
■ Maximum Power Voltage (V
it will give the maximum output power, for the STC condition.
The Standard Test Conditions (STC) is the values presented were measured by standard tests under radiation
conditions of 1000 W/m² with an air mass (PM) of 1,5 and a cell temperature of 25 ºC.
In the plant where such modules are installed, the climatic conditions may be different, it being necessary to
calculate a new open circuit voltage value for the scaling of the photovoltaic water pumping system. The main
factor that will affect the operation of the system will be the temperature, since the low temperatures will raise
the voltage of the open circuit (V
The equation that considers all variables is complex, as well as knowing the exact values of these variables,
for this reason is presented below a simple equation that approaches the value to reality:
Where:
■ V
: Open circuit voltage of the photovoltaic solar module at the installation local (V);
oc
■ N
: Number of photovoltaic solar modules connected in series;
p
■ V
: Open circuit voltage of photovoltaic solar module in STC condition;
oc (STC)
■ T
: Minimum operating temperature of the module at the operating local (ºC);
minimum
■ T
: Standard panel test temperature, 25 °C;
(STC)
■ β: Temperature Coefficient specified by the photovoltaic solar module data.
With this information calculates the number of solar modules that must be connected in series to operate in
the operating voltage range of the inverter. This serial connection, in turn, shall be replicated in parallel as
many times as necessary to meet the operating power of the system.
The operating voltage of the inverter varies according to the model, being 250-380 Vdc for 220 Vac single
phase and three phase, and 440-750 Vdc for 380-480 Vac models. Particular attention should be given to the
open-circuit voltage (V
higher voltage, this will end up damaging the equipment.
The frequency inverter operates with undervoltage and overvoltage protection, so that if the voltage reaches
these limit values, the inverter will interrupt its operation. Table 3.1 shows the inverter operating voltage
information, as well as the overvoltage and undervoltage limits.
P0296
Number of power
1
phases
Operating
250~380
Voltage (Vdc)
Undervoltage
170
Protection (Vdc)
Overvoltage
400
Protection (Vdc)
Power Supply
Voltage (Vdc)
) is the voltage measured at the terminals of the module when it is uncharged, for
oc
) is a specific value of the voltage which it is multiplied by the output current,
mpp
).
oc
�� = �� ∙ ��
���� ( ������ )
���� ��
), which should not exceed the inverter's overvoltage protection voltage. In case of
oc
Table 3.1 – Voltage levels of the CFW11
200-240 Vac 380 Vac
3 3
250~380 440~750 440~750 440~750 440~750 610~940 610~940 610~940
223 385
400 800
310
∙ (1 + (�� − ��
( ������ )
��������������
400-415 440-460
Vac Vac
3 3
406 446
800 800
540
��
) ∙ )
100
500-525 550-575
480 Vac
Vac Vac
3 3 3
487 530 580
800 1000 1000
710
Solar Pump Drive | 13
600 Vac
3
605
1000