{"id":2026,"date":"2026-08-20T15:38:20","date_gmt":"2026-08-20T07:38:20","guid":{"rendered":"https:\/\/jutrion.com\/?p=2026"},"modified":"2026-08-20T15:38:24","modified_gmt":"2026-08-20T07:38:24","slug":"dimensionamento-de-disjuntor-cc-solar","status":"publish","type":"post","link":"https:\/\/jutrion.com\/pt\/solar-dc-circuit-breaker-sizing\/","title":{"rendered":"Dimensionamento de Disjuntor CC Solar: String, Sa\u00edda do Combinador e Sele\u00e7\u00e3o entre MCB e MCCB"},"content":{"rendered":"\n
\n

Fast Sizing Answer<\/h2>\n<\/blockquote>\n\n\n\n

Size a solar DC circuit breaker at its actual position on the one-line diagram. Use cold-corrected string Voc<\/sub> for voltage, module Isc<\/sub> multiplied by the parallel-string count and the project\u2019s required factor for current, then confirm cable protection, DC breaking capacity, pole wiring and enclosure derating. Choose an MCB or MCCB only after those duties are known.<\/p>\n\n\n\n

The same PV array can require a 20 A device at one string and a 100 A device at the combiner output. Both devices see approximately the same string voltage, but they do not carry the same current or protect the same conductor. That is why a request such as \u201c1000 V DC solar breaker\u201d is not ready for model selection.<\/p>\n\n\n\n

The first question is not What breaker size?<\/em> It is Where is the breaker, and what can feed a fault at that point?<\/strong><\/p>\n\n\n\n

\n

Place the Breaker on the PV Protection Map<\/h2>\n<\/blockquote>\n\n\n\n
\"\"
Solar PV DC protection map showing string, combiner output and inverter input breaker positions<\/em><\/code><\/figcaption><\/figure>\n\n\n\n

A solar array is a chain of electrically different circuits. Mark the proposed breaker before opening a catalogue:<\/p>\n\n\n\n

PV string \u2192 string combiner input \u2192 combined DC output \u2192 inverter DC input<\/strong><\/p>\n\n\n\n

Moving one position to the right changes the current path. Modules in series raise voltage. Compatible strings in parallel raise current. A breaker at an individual input normally carries one string; a breaker at the common output carries all strings connected to that output.<\/p>\n\n\n\n

Position<\/th>Current through the device<\/th>Main duty to establish<\/th>Usual shortlist<\/th><\/tr><\/thead>
Individual string<\/td>One string<\/td>Reverse-current protection and string isolation<\/td>gPV fuse or PV-rated DC MCB where the design permits<\/td><\/tr>
Combiner output<\/td>Sum of the parallel strings<\/td>Combined feeder and output-cable protection<\/td>PV-rated DC MCB, DC MCCB or switch-disconnector with separate protection<\/td><\/tr>
Inverter DC input<\/td>Current assigned to that inverter input or MPPT path<\/td>Equipment isolation and coordinated protection<\/td>Breaker or switch-disconnector specified by the system design<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n

The table deliberately says \u201cshortlist.\u201d A circuit breaker is not automatically required at every position. A string may use gPV fuses; an inverter may already include a suitable DC isolator; an output may need isolation while overcurrent protection is provided elsewhere. Define the missing function before choosing the device.<\/p>\n\n\n\n

The article on solar combiner-box sizing<\/a> explains how MPPT grouping determines which strings may share an output. Complete that architecture decision first. A breaker cannot correct strings that should never have been paralleled.<\/p>\n\n\n\n

\n

Establish the Current Window, Not Just a Minimum Ampere Rating<\/h2>\n<\/blockquote>\n\n\n\n
\"\"
Solar DC circuit breaker current sizing from five parallel strings to a 100 amp candidate<\/em><\/code><\/figcaption><\/figure>\n\n\n\n

The current calculation has two sides. The breaker must carry the design current under the installed conditions, but it must not be so large that the protected cable or connected equipment is left outside its limits.<\/p>\n\n\n\n

For matched PV strings:<\/p>\n\n\n\n

Isc,path<\/sub> = Np<\/sub> \u00d7 Isc,module<\/sub><\/strong><\/p>\n\n\n\n

where:<\/p>\n\n\n\n