SMA SUNNY BOY - Manual (Page 44)

Glossary SMA Solar Technology AG
44 SB_SMC-BEN092840 User Manual
String inverter
In string technology, the PV generator is subdivided into individual module surfaces, or "strings", each
of which has an assigned string inverter. This technology reduces system costs while at the same time
making installation a lot simpler and increasing the energy yield and system availability.
Unbalanced load
The difference between the power fed into the grid at the individual phase conductors. In Germany,
it is not permitted to exceed a nominal output of 4.6 kVA (plus 10 % overload, i.e. 5 kVA in total).
Varistor
In the Sunny Boy and Sunny Mini Central, varistors protect the electronics from atmospherically
coupled energy peaks, such as those that can occur in the conductor loop of the PV generator in the
event of nearby lightning strikes. They limit overvoltage by discharging the coupled current to earth.
During operation, varistors are subject to a certain degree of ageing. Varistors which have been in
service for a long time or have already had to discharge overvoltages, are subject to a decrease in
internal resistance and heat up significantly. Thermally monitored varistors recognize this increased
temperature and automatically disconnect from the power circuit. If the protective function of the
varistor is no longer given, the inverter triggers a fault message.