ArcFree Technology - Toward a DC Civilization

Generally speaking, when an electric circuit is broken, there is a risk of an electrical arc occurring. However, the electric power infrastructure that's standard in homes today is alternating current (AC), in which the direction of current flow switches 100-120 times per second between plus and minus. Each time this switch happens, any arc is extinguished before it can become a serious spark. This allows, for example, removing plugs from electrical outlets. But a DC power supply has no flipping of current flow, so removing a plug from an outlet can create an arc that generates a lot of sparks—and this in turn can cause fires. To mitigate this fear of sparking, DC plugs are kept below safety thresholds of 12V and 2A, at which arcing will not occur.

Sony CSL is tackling the problem of arcing in DC circuit breaking at voltages above 12V and currents above 2A. We have developed a circuit breaking technology called “ArcFree” that can prevent arcing in circuits operating at, say, 200V and 7A. This eliminates the need to devote space to arc chamber in circuit breakers; reduces erosion of the circuit breaker contacts; and enables components to be made smaller and very long-lasting.


In recent years, due to the desire to arrest global warming, usage of renewable energy has surged. But the power output from renewables is subject to dramatic fluctuation, limiting their usefulness for electric power supply as is. That has spurred a movement toward using rechargeable batteries to temporarily store power and thus stabilize the supply of electricity.

In this setup, the electric power from the rechargeable batteries is DC, which cannot directly supply homes. It must first be converted to AC in order to power home electrical appliances. On the other hand, home electronics such as PCs, tablets, mobile phones and other IT devices have batteries and run off DC. Moreover, some recent models of TVs, fans and air conditioners have also incorporated internal transformers to convert incoming AC power to DC as an energy-saving measure. Appliances with rotating components that operate on DC in this way can use inverters for precise control of RPM to achieve dramatic improvements in space efficiency and energy efficiency.

ArcFree technology makes it possible to store and use renewable energy directly as DC all the way through. This is a more efficient setup. It eliminates the current reverse flow issues that can destabilize AC power grids, as well as the need to synchronize frequency and phase. ArcFree can help bring about the flexibility of autonomous, distributed electric power, enabling the creation of bottom-up electric grids where power is produced and consumed locally.

Sony CSL intends to continue developing this technology and pursuing research toward making high-voltage/high-amperage circuit breaking practical and safe.

ArcFree Technology (English Version) from Sony CSL on Vimeo.