Direct Current Less Copper, Fewer Peaks, More Efficiency

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Siemens is launching the first protection and switching products for industrial DC networks with a semiconductor circuit breaker and a semiconductor switching device. This opens up specific savings potential for machine builders and plant designers—in terms of material, energy, and installation complexity.

Frequency converters, robot drives, servo motors, battery storage— anyone designing machines and systems is already working with components that operate internally on a direct current (DC) basis. Nevertheless, the overarching power supply in manufacturing environments is almost exclusively implemented using alternating current (AC). Every conversion costs energy and requires additional components.

"With the increased use of renewable energies, the expanded use of battery storage, and the trend towards DC-based data centers, the topic is now really gaining momentum," explains Andreas Matthe, CEO Electrical Products at Siemens. The idea is not new: about ten years ago, there were initial attempts to replace transformation stages in industrial power supply with direct current networks. At that time, they primarily failed due to a lack of norms and standards. This obstacle has now been largely removed: In May 2026, a specific draft standard for semiconductor circuit breakers, IEC 60947-10, was published—a crucial step for planning reliability.

Regeneration Becomes a System Advantage

For designers of manufacturing facilities, one aspect is particularly interesting: energy recovery. Robot arms that decelerate, elevators that move downward, servo axes in reverse operation—all these processes generate energy that can be directly buffered and reused in a DC intermediate circuit. In an AC network, this involves significant effort. In a DC network with an integrated battery storage, it is inherent to the system.

The figures Siemens cites for typical production environments with robots—based on the DC for Industry project by ODCA—are remarkable: peak power consumption can be reduced by up to 80 percent when direct current technology is combined with energy recovery and storage. This not only lowers operating costs but also reduces the design requirements for the entire power supply.

Another material advantage is added: DC systems eliminate the need for reactive power compensation and require up to 50 percent less copper for wiring and busbars due to smaller cable cross-sections. The elimination of transformers between voltage levels also significantly reduces material and space requirements.

The Centerpiece: Sentron 3QD2

The central product of the new DC portfolio is the semiconductor circuit breaker Sentron 3QD2. It is designed for 1,000 V DC and 250 A—a 2-pole device that combines multiple functions in a compact housing: protection, switching, isolation, monitoring, and energy management.

What fundamentally sets it apart from conventional circuit breakers is the switching speed. Dr. Nico Fritsch, Product Lifecycle Manager at Siemens, explains the underlying physical issue: "In DC networks, there is no zero crossing as in AC that we can use to extinguish the arc. We are dealing with extreme current rises of 200 amperes per microsecond—and we must interrupt them in the shortest time possible through semiconductor technology." The comparison Fritsch uses illustrates the scale: an airbag is considered fast—the Sentron 3QD2 switches 2,000 to 3,000 times faster.

The device's configurability is relevant for designers: The rated current can be adjusted via a digital interface to suit the actual application requirements—for instance, reduced from 250 A to 200 A if the connected load permits. This simplifies device management and avoids unnecessary oversizing.

Another important design feature is bidirectionality: The switch detects the reversal of the energy flow direction and operates in both directions. This is not a comfort function but a system requirement—battery storage and regenerative drives actually reverse the energy flow.

Maintenance-Free and Communication-Capable

Compared to mechanical switching devices, semiconductor technology offers a structural advantage: there are no mechanically wear-prone switching contacts and no contact-related aging. This eliminates a classic, contact-related residual lifespan. The Sentron 3QD2 operates maintenance-free in the switching path—an advantage, especially in hard-to-access installation situations or with high switching cycles.

For service operations, a mechanical disconnect function is nevertheless integrated: In the event of maintenance, the device can be set to the "Off" position and locked with a padlock—standards-compliant and familiar to electricians.

The communication connection is established via a modular interface that is mounted on the side of the DIN rail and seamlessly integrated into Siemens' existing communication portfolio. Alternatively, digital inputs and outputs are available for hardware-based control.

Practical Proof in the Company’s Own Plant

Siemens is the first to use its own switch in its installations: at the new technology campus in Erlangen, the logistics center and the R&D building are partially powered on a DC basis. "The logistics center is a good example, where elevators move up and down, and the recuperation energy can be fed back in," says Matthe. The switch cabinet with a Sentron 3QD2 circuit breaker showcased at the Hannover Messe 2026 is the same one that will later be installed in Erlangen.

The Sentron 3QD2 is complemented by the semiconductor switching device Sirius 3RF5—the first of its kind for DC applications, designed for high-frequency switching of resistive loads. It carries the Siemens EcoTech Label and can be integrated into the low-voltage switchgear Sivacon S8 as well as the busbar trunking systems Sicacon 8PS.

The Sentron 3QD2 is currently in the introduction phase with initial pilot installations; series production as a standard product is planned for the beginning of next year.

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