Innovative protection for DC networks

The range of equipment connected to DC networks is very versatile. Typical loads include,  DC/DC converters, frequency converters and industrial robots. In modern systems, bidirectional power flows occur, for example due to drives capable of feeding back power or energy storage systems. The DC-INDUSTRIE2 system concept specifies increased requirements for overcurrent protection in terms of trip time, selectivity and reliable physical isolation of individual network segments.

Electromechanical circuit breakers are a cost-effective protection solution. Compared to purely electronic or hybrid circuit breakers, they are highly robust, immune to electromagnetic interference and require no additional auxiliary power or parametrisation. E-T-A’s new 8365-T circuit breaker is based on a hydraulic-magnetic tripping principle.

As it contains no electronic components at all, the device is ideal for industrial environments with high levels of electromagnetic interference and harsh operating conditions. It can be reset immediately after an overcurrent trip, allowing the protected load to resume operation. 

The DC-INDUSTRIE2 system concept defines voltage ranges between DC 400 V  and DC 800 V. The 8365-T is the first electromechanical circuit breaker capable of switching single-pole circuits up to DC 400 V and double-pole circuits up to DC 800 V. It covers the voltage ranges defined in the DC-INDUSTRIE2 concept and provides a space-saving, safe and standard-compliant overcurrent protection. 

Short circuit currents in DC networks rise very rapidly and can cause significant thermal and mechanical stress. The 8365-T is available with different characteristic curves and achieves trip times of less than 10 ms. It meets the requirements for quick fault disconnection specified in the system concept, which is a requirement for selective protection coordination in segmented DC networks.

When high-capacity loads are switched on, this typically leads to high inrush current peaks. The 8365-T uses a pulse-delayed characteristic curve that tolerates short-term inrush currents without tripping. This means that, for many applications, no separate pre-charging devices are required, which reduces the system complexity.

The 8365-T is typically used as a backup fuse for DC/DC converters (like our PFA10) and frequency converters, where both overcurrent protection and reliable disconnection are required. In DC lighting systems, LED lights can be separately protected, which simplifies the system architecture. In robotics, the circuit breaker enables selective protection of individual axes and supports maintenance and servicing processes through its isolation function.