One Step Ahead! Fuji Electric's Fundamental Technologies

We provide an overview of our latest fundamental technologies that enhance our product development capabilities.

Current Interruption Technology

Studying interruption technology assuming various circumstances in various locations.

Interruption technology is a technology that interrupts electric current, and it is employed in switch gears and breakers, which are used in power plants, substations, factories, buildings, households, and other facilities where electricity is needed. Users can select the most suitable product from among gas breakers and vacuum breakers according to the voltage and expected abnormal current values for daily switching operations and interruptions resulting from lightning strikes.

During this interruption, arc discharge (high-temperature plasma) occurs between electrodes. Accurately understanding the behavior of this arc discharge helps us to develop an optimal interruption structure. The interruption of short-circuit currents from lightning strikes, which are millions of amperes in strength, is particularly difficult to understand. This phenomenon may or may not happen once in the 10 to 20 years that make up a product lifetime, and arc discharge also occurs just for an instant: 1/100th of a second. It also generates great optical and thermal energy with a few thousand to a few million times the electric power of the arc discharge generated from daily switching operations. It is extremely difficult to accurately measure and understand arc discharge because the temperature of the discharging electrodes instantaneously increases up to about 10,000 degrees centigrade and the pressure to the level above 10 bars.

The model machine demonstrates arc discharge behavior.

Arc discharge behavior can be verified by taking photos every tenth of a second. These photos show that the arc travels from right to left.


We developed a technology that enables accurate understanding of the behavior of arc discharge.

The behavior of arc discharge was previously estimated based on the waveforms obtained through current meters and voltage meters, in combination with past experience. Measurement of the arc plasma temperature via the analysis of light emitted from the arc discharge as well as measurement of the temperature of hot gas (high-temperature gas) generated by arc using a thermocouple, a type of temperature sensor, were not previously possible because of the weakness of electrical signals. Therefore, we developed a special technique for eliminating noise, thus enabling the temperature to be measured. Accordingly, we combined the obtained experimental data with the information we acquired by applying a more sophisticated type of simulation technology, and as a result, we have been able to grasp the behavior with high accuracy.

In the experiment, the phenomenon obtained through the simulation is checked for consistency between the prediction and the result.

Voices of developers

Continuously developing new technologies

This accurate understanding of the behavior of arc discharge allowed us to further accelerate the development of technologies that can meet customer needs, such as the further miniaturization of equipment, shorter interruption time, and interruption of DC power systems. We are applying our interruption technology to our other products for purposes such as improving the safety of distribution boards. We have also begun developing new interruption methods using semiconductor devices.

Interruption technologies have been evolving through understanding of physical phenomena, development of prediction technologies, and suggestions for improvement technologies backed by these efforts. It is a great pleasure to finally reach our target performance after overcoming many challenges. This is such rewarding work.

Electronics and Mechatronics Research Department, Application Technology Research Center, Advanced Technology Laboratory, Corporate R&D Headquarters

The article and the affiliations are at the time of coverage.