Focus Shift: Safety on the AC Side
In discussions about the safety and efficiency of photovoltaic systems, the spotlight is usually on the DC side – string distribution, fire switches, surge protection, cable dimensioning.
However, the AC side is facing growing challenges as well, especially when several inverters, storage systems, or charging points are integrated into one common grid.
This is where the AC Box comes in: it performs the central tasks of distribution, protection, and surge suppression in the alternating-current section. In short, it forms the link between generation, storage, and consumption – and is thus a key factor for overall system safety and availability.
Function and Design
An AC Box consolidates the AC outputs of PV inverters, protects the system against overvoltages, and distributes power safely to the grid connection. Depending on the configuration, it may include:
- Surge protection Type 2 or Type 1+2 or Type 1+2+3
- Fuses, circuit breakers, and NH disconnectors
- Busbars and earthing systems
- Terminal blocks or plug connectors
- Optional switching or metering functions
A key element is the robust enclosure – typically made of steel or polycarbonate – designed for indoor or outdoor use. All components are selected and interconnected according to VDE and IEC standards to ensure high electrical and thermal safety.
Customised Solutions Instead of Standard Products
While DC combiner boxes are often produced in series, the AC side is far more variable. Grid type (TN-C, TN-S, TT), feed-in point, number of inverters, and protection concepts differ from project to project.
That’s why specialised manufacturers like Q3 ENERGIE focus on custom engineering and production.
Each AC Box is designed individually – from the current-carrying capacity of the busbars to the arrangement of protection devices. The result is a compact, pre-assembled unit that perfectly matches the electrical parameters and safety requirements of the specific project.
“Especially in the megawatt range or in combined PV and storage systems, the AC Box is not a standard product,” explains Thomas Neumann, Managing Director of Q3 ENERGIE.
“We design each box based on the project’s wiring diagrams and customer requirements – including surge protection, fuses, and switching technology.”
From Concept to Finished Box
The production process follows clearly defined stages:
- Design & planning – based on grid parameters, protection requirements, and the number of inverters.
- Base-plate assembly – installation of busbars, terminals, and protective components.
- Wiring & testing – in accordance with VDE 0100 and IEC 61439.
- Enclosure integration – mechanical assembly, labelling, and final inspection.
The outcome: a tested, ready-to-connect solution that meets both the electrical requirements and the mechanical conditions on site.
Conclusion
The AC Box is far more than just a “junction box” – it is a core safety and switching component of modern energy systems.
In times of growing system complexity – involving PV, battery storage, e-mobility, and backup power – its role becomes increasingly crucial.
With well-thought-out design, certified components, and project-specific engineering, AC Boxes make a vital contribution to operational safety, grid stability, and the long-term reliability of modern energy systems.
