Studer Innotec SA
next3
40 V 1.3 © Studer-Innotec SA next3 Tech manual
5.4 CONNECTING THE PHOTOVOLTAIC GENERATOR
The next3 has an internal solar charge controller made of two independent MPPTs. Each MPPT can
support up to 22Adc of photovoltaic (PV) current in operation. For this reason, each MPPT has 2
inputs and up to 4 strings can be connected to the device. The two inputs of the top (MPPT1) are
connected internally, as well as the two at the bottom (MPPT2). The rated current of the PV
generator can be higher as the next3 limits with electronic control the maximum taken from the
generator in any case. In any case the maximum short-circuit (Isc) current is 27Adc.
The next3 solar input is intended to be connected exclusively to a source like a
photovoltaic generator, excluding any other energy source.
The next3 is designed for PV generators supplying up to 900Vdc. This voltage is
dangerous for human beings.
During the installation or the maintenance of the system, it is mandatory to make
sure that no dangerous voltage may surge in the system. The disconnection device
must be open and secured against any accidental reclosing.
5.4.1
PV string dimensioning
The next3 accept input voltages between 350Vdc and 900Vdc max. It starts operating from
350Vdc (start-up in the morning) and will continue to operate even if the voltage decreases
down to 100Vdc (shut down in the evening, partial shading, etc.). The 350Vdc are necessary
to detect a proper ground insulation of the PV before starting the system.
The nominal power of each MPPT channel is 8kW. The maximum current will be limited to
22Adc and the maximum voltage allowed is 900Vdc. See below the PV input characteristics:
Tests of the efficiency performed by an independent lab showed the following result for the
conversion efficiency from solar to grid:
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