Studer NEXT3 - 5.3.1 Sizing of AC protective devices

Studer Innotec SA
next3
Technical user manual V1.3 © Studer-Innotec SA 35
Example of connection for AC loads
5.3.1 Sizing of AC protective devices
The source must be connected to the input terminals marked "AC-Source" with sufficient wire cross-
section, depending on the power output of the source, and protected by a protection device of the
appropriate rating. In any case it must be maximum 80A per nx3.
For people safety, we recommend using residual current devices (RCD) for loads at the output of the
nx3. Take care of the earthing and neutral system for proper operation of the RCD. In any case, AC
distribution must comply to the local standards and regulations, and generally, be realised through
a distribution panel in an enclosure.
For cables protection, no downstream protective device is formally required if cross-sections of cable
used for distribution satisfy to regulatory requirements for the largest rated output current listed on the
nameplate of the next3. The next3 is protected against overload and short-circuit and will stop in
those cases. When connected to a source, the upstream protection must stop short-circuits currents
from the grid/genset.
Insulation tests
At commissioning of an electrical system, insulations tests are performed on the
wiring (in some countries, depending on local regulation). It is performed applying
high voltages on the cables and measuring the leakage current. This must be done
without the next3 in the loop. Overvoltage surge protections included in the next3
will invalidate the tests.
Insulation between circuits and the ground is tested in factory for every next3 unit
manufactured according to the device IEC/EN 62109 and IEC/EN 62477 safety
standards.