SMA SMC 5000 Installation - Manual (Page 53)

SMA Technologie AG Sizing of a Circuit Breaker
Installation Guide SMC50_60-11:SE2006 Page 53
Result:
The nominal current of the circuit breaker is
Inr = 32 A x 0.9 x 0.77 x 1.07 = 23.7 A
The circuit breaker selected for this installation is not suitable due to the fact that the
maximum tolerable current of the circuit breaker is below the maximum current of the
used inverter. It will trip in normal operation.
A solution for this plant would be the installation of the circuit breakers with an 8 mm
gap between each unit. This would result in a reduction coefficient of 0.98 instead of
0.77. This would result in a maximum current of 30 A.
A further solution could be the installation of circuit breakers with a rating of 40 A.
In this case all different aspects have to be evaluated again with respect to this
change. An installation of the circuit breakers in the distribution box without gap be-
tween the units would result in a nominal current of Inr = 40 A x 0.9 x 0.77 x 1.07
= 29.6 A.
SMA recommends the installation described above with a gap between the circuit
breakers.
As well as the thermal rating of the circuit breakers and all other factors as specified
in section „Sizing of a circuit breaker for the AC line of a photovoltaic inverter for
utility interaction” (page 19), of course the applicable DIN VDE standards
a
also
need to be taken into account. The main ones that apply here are:
• DIN VDE 0100 Part 410 and/or the international standard IEC 60364-4-41:1992
• DIN VDE 0100 Part 430 and/or the international standard IEC 364-4-43:1977
and IEC 364-4-473:1977
• DIN VDE 0298 Part 4
a. The standards listed here are standards that apply in Germany. Please note that
other standards apply in other countries. Beside the standards above other stan-
dards may be applicable in special installations.