Version 1.5, Nov 2023

Application Note: Determining the Circuit Breaker Size

Revision History

Version 1.5 November 2023: Footnotes added regarding maximum continuous output for VDE-AR-N 4110 certification

Version 1.4 May 2022: Reference to circuit breaker ratings for India and Israel added

Version 1.3 September 2021: Changes in circuit breaker criteria table

Version 1.2 July 2021: More info added to circuit breaker criteria table

Introduction

Inverters must be protected by over-current protection devices with an exact rating, per model. This document describes how todetermine which over-current protection device to use in three phase commercial installations.
NOTEFor Three Phase Inverters with Synergy Technology in India, use only a circuit breaker device. For selecting a circuit
breaker, refer to https://www.solaredge.com/sites/default/files/se-determining-the-circuit-breaker-ratings-for-threephase-inverters-India.pdf
For Three Phase Inverters with Synergy Technology in Israel, use only a circuit breaker device. For selecting a circuit
breaker, refer to https://www.solaredge.com/sites/default/files/se-determining-the-circuit-breaker-ratings-for-threephase-inverters-Israel.pdf

Using Transformers in Commercial Three Phase Inverter Installations

Using transformers in a commercial installation is optional. In most cases a transformer is used to connect the installation to themedium voltage power grid.
For an example of how to connect a transformer on a medium voltage power grid, refer to:

Medium Voltage Transformer Connection of Commercial Systems, North America
Medium Voltage Transformer Connection of Commercial Systems

The following figure illustrates a typical transformer and commercial three phase inverter installation topology.

Figure 1: Typical transformer and commercial three phase inverter installation topology

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:

Application Note: Determining the Circuit Breaker Size

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Version 1.5, Nov 2023

The transformer should be designed for a typical PV system production profile: high daytime loads with no loads at night.

2The current limiting devices should protect the electrical circuits and the inverters from the excess current created by anoverload, 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 theselection of circuit breakers and fuses at the different hierarchical levels of the installation topology (see Figure 1).
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.

Determining the Size of an Inverter Circuit Breaker

This section explains how to determine the rate of a circuit breaker next to an inverter. For an example of an inverter with a circuit
breaker next to it see Figure 1.

Ensure you have the following parameters before determining the circuit breaker size:
The inverter's maximum continuous output current appears in the data-sheet.

Factor for the installation's country. This factor is dictated by regulation, applicable standards or common practice and is usually
1.25.
To determine the size of an inverter circuit breaker:

1. Multiply the inverter's maximum continuous output current by the factor.
For example, 40A x 1.25= 50A

2. Round up the rated size, as calculated in step 1, to the closest standard circuit breaker size. See Circuit Breaker Criteria table below
for standard sizes suitable for SolarEdge three phase inverters.
NOTE

If the result has a decimal fraction smaller than 0.5 round it down.

3. To ensure that the selected circuit breaker trips as expected, at minimum consider the following:
The circuit breaker rated Voltage and current.

Temperature de-rating due to both close proximity of other circuit breakers and the effect of ambient temperature on thedistribution board.
De-rating due to permanent load.

If the de-rated current of the selected circuit breaker is lower than the maximum output current of the inverter, consider selecting acircuit breaker that is designed for a higher rated current, or reducing the temperature de-rating effect by increasing the distance
between adjacent circuit breakers.
NOTE

Make sure to select cables that are suitable for the environmental conditions, operating Voltage, current and the selectedcircuit breaker.

Three or four pole circuit breakers are required. It is recommended to use a four pole circuit breaker when applicable.

Calculate and verify that the circuit breaker can withstand the expected fault current.
Only use a circuit breaker with tripping characteristic B or C.

Application Note: Determining the Circuit Breaker Size

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Circuit Breaker Specifications

These tables describe criteria for circuit breakers in three phase inverters and three phase inverters with Synergy Technology. For
details about selecting circuit breaker, see the Inverter datasheet.

North America 208L

Maximum continuous output current(per phase)

Recommended circuit breaker

SE14.4KU
SE17.3KUS

40A
48.25A

50A
63A

SE43.2KUS
SE50KUS

120A
139.5A

150A
175A

Inverter

Maximum continuous output current(per phase)

Recommended circuit breaker

SE30KUS
SE33.3KUS
SE40KUS36.25A
40A
48.25A

50A
50A
63A

SE66.6KUS
SE80KUSSE100KUS
SE120KUS

80A
96.5A
120A
145A

100A
125A
150A
200A

Inverter

Maximum continuous output current(per phase)

Recommended circuit breaker

SE12.5K
SE15KUSSE16KUS
SE17K
SE25K
SE27.6K
SE30K
SE33.3K

20A
23AA25.5A
26A
36.25A(1)40A
43.5A(2)48.25A

25A
32A
32A
32A
50A
50A
63A
63A

SE50K
SE55.5K
SE66.6K
SE57K
SE82.8K
SE90K
SE100K

76A
80A
96.5A
120A
120A
130.5A(3)
145A

100A
100A
125A
150A
150A
175A
200A

InverterThree Phase Inverter

Three Phase Inverter with Synergy Technology

North America 480 L-L
Three Phase Inverter

Three Phase Inverter with Synergy Technology

EUROPE AND APAC 380/400 L-L
Three Phase Inverter

Three Phase Inverter with Synergy Technology(1)

For countries that comply with VDE-AR-N 4110 certification, the maximum continuous output current (per phase) is 40A. For details, see the inverter datasheet.

(2)

For countries that comply with VDE-AR-N 4110 certification, the maximum continuous output current (per phase) is 48.25A. For details, see the inverter datasheet.

(3)

For countries that comply with VDE-AR-N 4110 certification, the maximum continuous output current (per phase) is 145A. For details, see the inverter datasheet.

Application Note: Determining the Circuit Breaker Size

Version 1.5, Nov 2023 4EUROPE AND APAC 480 L-L
Maximum continuous output current(per phase)

Recommended circuit breakerSE33.3K
SE40KS

40A
48.25A

50A
63A

SE66.6K
SE80KS
SE100K
SE120K

80A
96.5A
120A
145A

100A
125A
150A
200A

InverterThree Phase Inverter

Three Phase Inverter with Synergy Technology

Application Note: Determining the Circuit Breaker Size