There are many considerations for selecting the suitable transformer and its associated
current limiting devices such as circuit breakers and fuses. The considerations must
include at least the following:
The transformer should be designed for a typical PV system production profile:
high daytime loads with no loads at night.
The current limiting devices should protect the electrical circuits and the
inverters from the excess current created by an overload, or a short circuit. If a
short circuit or other overcurrent occurs, the current limiting devices should
block the current flow to the circuit, thus preventing damage to the electrical
circuits and the inverters.
The circuit breakers and the fuses should comply with the transformer
manufacturer recommendations and with the relevant sections in standards
such as IEC 60909, IEC 60364, UL 508A and NEC 2017.
Some manufacturers provide detailed information about the transformer short
circuit calculation procedure, and its effect on the selection of circuit breakers
and fuses at the different hierarchical levels of the installation topology (see
Figure 43
).
For an example of a calculation, refer to:
Guidelines on the Short Circuit Current Rating for Industrial Control Panels
Short-circuit current rating (SCCR) of industrial control panels
To ensure that the circuit breaker and fuses trip as expected, follow their
manufacturers' recommendations, especially with respect to the various de-
rating considerations.
NOTE
Transformer procurement, installation, maintenance and support are the
responsibility of the installer. Damage to the inverter due to incorrect
transformer installation, or use of a transformer that is incompatible with the
SolarEdge system will render the SolarEdge warranty invalid.
NOTE
Transformer procurement, installation, maintenance and support are the
responsibility of the installer. Damage to the inverter due to incorrect
transformer installation, or use of a transformer that is incompatible with the
SolarEdge system will render the SolarEdge warranty invalid.
Appendix G: Determining the Circuit Breaker Size 99
Three Phase System Installation Guide MAN-01-00057-4.1
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