Experiment of force‐balanced coil for magnetic energy storage

Higher magnetic field is of great advantage to superconducting magnetic energy storage because it promises a compact device. However, it does not affect the serious problem of huge electromagnetic forces caused by high magnetic fields and large coil current. Electromagnetic stresses, reaching as much as several hundred bars, thus become a major factor in determining whether a large‐size strong magnetic field system can be established. In order to solve this problem, we have proposed the force‐balanced coil (FBC) concept that reduces the huge centering electromagnetic forces by balancing them with the hoop forces caused by the toroidal current. Then we designed and fabricated a small‐size superconducting FBC system to demonstrate the FBC concept. It was successfully excited up to near rated current. It is shown that the FBC system has the potential for simplifying the supporting structures and making the facility compact. © 1999 Scripta Technica, Electr Eng Jpn, 128(3): 82–91, 1999     

Modeling power consumption by electric vehicles and its impact on power demand

Electric vehicles are expected to be one of the means to level the difference between the peak time and off-peak time electric loads. From a global point of view, increasing environmental concerns make us recognize the necessity of replacing conventional gasoline cars by electric vehicles. Due to problems with the efficiency and life time of a battery, it will take time before electric vehicles are in general use. Electric vehicles are used only in specialized small fields. Automobile makers are cooperating to invent advanced batteries for use in electric vehicle. Thus, it is timely to develop appropriate infrastructure standards and technologies to make electric vehicles attractive to consumers. In this paper, we investigate the impact of electric vehicle on electricity demands by assuming analytical models of EV consumption. The charging characteristics of a battery, the running performance, and the practical driving distance of each type of car are used in this analysis. According to the scenario analysis, the simulations clearly presented the impact of EV introduction using the practical day load duration curve for the Tokyo cosmopolitan area. The authors conclude that electric vehicles are effective for load leveling under some sort of market regulations. If there is no regulation in the EV market, power shortage will occur on both nighttime and daytime because of the concentration of the nighttime charge and the quick charge. © 1997 Scripta Technica, Inc. Electr Eng Jpn, 120(4): 40–47, 1997     

Application of a force‐balanced coil to a tokamak device

High field is very favorable for magnetically confined fusion devices such as a tokamak, but electromagnetic force derived from the field becomes a fatal problem. In particular, the largest in‐plane centering force hinders toroidal field coils from operating at higher fields. Variable pitch multihelical coils, which we term force‐balanced coils (FBCs), by which this force is drastically reduced, are proposed for the coil system of tokamaks. FBCs can also provide poloidal flux swing for plasma breakdown and current induction during the ramp‐up phase of the coil current. In this paper, we indicate how to design FBCs for tokamaks. The fusion reactor‐size FBCs are designed and compared with that of the conventional toroidal field coil system. © 1999 Scripta Technica, Electr Eng Jpn, 130(3): 39–48, 2000