Aiming to help bring about a responsible and sustainable society, Fuji Electric provides environmentally friendly products that can most efficiently use energy for social and industrial infrastructure and other various fields. In order to develop products that meet the needs of the market in a timely manner, it is essential to quantify physical phenomena, which form the basis of the functions and performance of products. As a powerful means to that end, we develop and exploit various simulation technologies.
This special issue presents the simulation technologies that support the product development of Fuji Electric.

Along with the recent progress in computational science, simulation technologies have come to be widely used in various phases from R&D to product design. Fuji Electric also takes advantage of device simulation and molecular simulation to improve performance, analyze and estimate electrical characteristics and clarify phenomena at the atomic level of SiC devices. Moreover, we have reduced the cooling fan noise of electrical equipment, analyzed the internal arc discharge of switchgears, and optimized the design of showcases by applying simulation technologies such as electromagnetic noise analysis, acoustic noise analysis, and fluid analysis. With these technologies, we aim to offer high-performance, high-reliability products in short delivery times.

The development of semiconductor devices that use SiC (silicon carbide) based materials has been increasing as a means of achieving further energy savings in power electronic products. SiC trench-type MOSFET are capable of reducing loss even more than conventional planar types. Fuji Electric is implementing simulation based characteristic prediction in order to improve the efficiency of new SiC device development. It is necessary to consider the newly utilized crystalline surface characteristics for the simulation of the trench-type because the characteristics of SiC differ by its crystalline surfaces. We have established a convenient method for incorporating the parameters into the simulation model, which enabled reproduction of actual observations and prediction of performance improvements.

In SiC (silicon carbide) devices, which are wide band-gap semiconductors, bipolar devices are considered beneficial for achieving a high withstand voltage in excess of 13 kV. Fuji Electric has improved prediction accuracy by repeatedly adjusting parameters based on the analysis of differences between simulation predictions and actual results. We implemented withstand voltage characteristic simulations, forward characteristic simulations, and switching characteristic simulations, and then reflected the measured physical property values into the parameters, while also taking into account interface charges and parasitic resistance. As a result, we were able to reproduce with a high level of accuracy the characteristics of actual devices.

Research and development of power semiconductor devices with SiC (silicon carbide) has been very active because of the increasing need for low-loss power electronics equipment. The electrical properties of the SiC-metal-oxide-semiconductor field-effect transistors (SiC-MOSFETs) are affected by charge trapping that is thought to be caused by the atomic level disorder at the interface between the gate oxide and SiC (SiC/SiO₂ interface). In order to analyze the origin of the disorder at the interface, we have been implementing the atomic level analysis using both the X-ray photoelectron spectroscopy and the simulation based on the first principles calculations. As a result, we were able to estimate the chemical state of Si at SiC/SiO₂ interface, as well as its terminated structure via nitrogen when the interface is nitrided.

Molecular simulation is a technology for evaluating the various properties of materials based on their molecular structure by using a computer. It has received attention as a method for speeding up the development of products. Semiconductor modules are being employed to an expanding range of applications such as industrial equipment and electric vehicle. In order to ensure high reliability, importance is placed on the adhesion of materials and resin. Against a backdrop of this, we implemented a study using molecular simulation for analyzing auxiliary agents for improving adhesiveness. We evaluated 2 types of auxiliary adhesion agents and elucidated molecular level mechanisms related to adhesion with aluminum.

The number of products sealed with a thermosetting resin such as semiconductor products has been increasing as the heat resistance and withstand voltage are improved and the size is miniaturized. Currently, structural design for products is being implemented using stress analysis based on CAE analysis in order to ensure reliability in products sealed with a resin. However, this type of analysis cannot predict resin cracks and interfacial peeling between the resin and component materials that cause failure. We have thus established a method for grasping curing behavior of thermosetting resin, a residual stress distribution analysis technology that can be utilized after curing has completed, and an evaluating technology for adhesive interface strength considering the adhering end distance. As a result, we can now construct structural design systems compatible with thermosetting resin sealing, thus enabling us to improve the reliability of products.

Power electronics have been becoming more widely used as core products for achieving energy savings and energy creation. However, power electronics equipment may cause electromagnetic noise interference, such as communication failure and malfunction and damage of electronic equipment. For preventing electromagnetic noise interference caused by conduction noise and radiation noise, Fuji Electric has been developing various simulation-based technologies, including the improvement of the analysis accuracy of electromagnetic noise generated by power electronics equipment to comply with relevant regulations, analysis models from which we can select a simplifi ed or detailed one depending on applications, and applications for power electronics systems in addition to that for single equipment.

The size reduction trend of electric power equipment causes increased heat generation density along with an accompanying need for increased airflow for cooling. In this situation, aerodynamic noise can be the dominant noise source for air-cooled electric equipment. Grasping the noise generation mechanism and the noise reduction by measurements are often difficult, getting physical information through simulation can be an effective approach. In order to achieve noise reduction of equipment, we elucidated the aerodynamic noise generating mechanism by focusing the fan, the main source of noise in air cooling equipment, and estimated noise change caused by cooling structure differences. Simulated sound pressure level and peak frequencies are in good agreement with the measurement. This technology can be applied to understand the noise generation mechanism, and can also be used to structure design.

Switchgear include devices that play an important role in operations such as electric circuit switching and power measuring and monitoring, and IEC standards stipulate safety performance criteria regarding arc discharge (internal arc faults) in switchgear. Fuji Electric has developed an analysis technology for predicting pressure rise and pressure discharge performance during internal arc faults in order to design safe switchgear. By incorporating a pressure loss model in the vicinity of devices that discharge pressure and an arc model derived from the results of actual device testing, we have been able to implement highly accurate analysis. We have developed IEC standard compliant switchgear based on this analysis technology.

More than half of the electric power load in open showcases used in stores such as supermarkets and convenience stores is heat invasion that comes from the front opening of the displays. In order to save energy on the showcases, it is necessary to improve the performance of air curtains that suppress this heat invasion. Air curtain performance changes over time based on the impact of frost formation on the evaporator. Fuji Electric has developed a thermal-fluid simulation technique for elucidating this phenomenon, and based on this technique, we have developed a new air curtain system. Demonstration results achieved improved energy saving of more than 30% compared with conventional systems.

Plastic has excellent electrical insulation properties and is often utilized in various products due to its mechanical properties and characteristics. In order to improve the quality of plastic parts, Fuji Electric has utilized resin flow analysis to elucidate the quality and productivity issues that exist during the early stages of development. Furthermore, we have been reflecting our findings into the design of our products and molds. We have verified ease of assembly in consideration of warping by using the analysis results and a 3D printer, and as a result, we developed parts suitable for automated assembly in a short time. We have also utilized unsteady heat transfer analysis to optimize the temperature control circuit for molds and have significantly reduced the molding cycle. Furthermore, we have been working to estimate the fiber length of fiber-reinforced plastic, and are now able to determine the distribution trends of the fiber length that affects the strength of parts.