Proposal and Feasibility Study of the Integrated Diode Synchronous Motor

This paper presents a new type of magnet‐free motor that has concentrated stator windings and rotor coils with a pair of diodes. The most important feature of this motor is that currents in the rotor coils can be generated by utilizing the changes in the spatial second harmonic of the magnetic fields due to the concentrated stator windings, which normally increase motor losses. A prototype of the motor was designed and fabricated, and its basic performance was evaluated. First, using simplified analytic models, we explain the mechanism of inducing currents in the rotor coils by the changes in the spatial second harmonic of the magnetic fields. Second, we compare the torque performance of the proposed motor and that of other types of motors including a magnet motor through finite‐element analyses. The analyzed data show that the proposed motor can possess greater torque/volume ratio than that of the other motors. Finally, using the measured data, we validate the mechanism of inducing currents in the rotor coils, and examine the torque and power characteristics of the motor.     

Dielectric Recovery Characteristics after High‐Frequency Current Interruption in Vacuum Circuit Breaker

When the contacts of circuit breaker are opened just before current zero, the gap between contacts will still be very short. Therefore, it cannot withstand recovery voltage between the contacts. In such a case, multiple reignition is likely to take place. Many investigators had tried to clarify this phenomenon, and many reports have been published. However, high‐frequency current interruption and dielectric recovery characteristics are related to some parameters (value of current, arc time, and so on). In addition, arc phenomenon has also been implicated. Hence, it is difficult to understand this phenomenon accurately. In this paper, we conducted dielectric recovery test and high‐frequency current interruption test. Further, we conducted observation experiment using vacuum chamber in order to investigate the effect of small dc current. At the end, we calculated plasma density in the electrodes after high‐frequency current interruption by considering the result of observation experiment and dielectric recovery test.     

Robust control for a constantly rising temperature system (Hm control approach)

Thermoluminescence dating has attracted the attention of geology and archaeology researchers as a new method. This method requires a heating device to raise the temperature of the specimens at an exact rate. This paper describes the design method of a control system that can achieve this goal. This control system lends to be unstable because of the existence of the parameter perturbation and dead time. In this paper, the perturbation and dead time are treated as perturbations of a nominal plant regarded as a first-order lag time system. Improvement of tracking characteristics in the low-frequency domain and robust stability in the high-frequency domain of the control system are achieved by using the solution of the mixed-sensitivity problem that is a kind of H^∞ control theory. Experiments verify the effectiveness of this method.     

Application of the Integrated Diode Synchronous Motor to Traction Drive Motors

In this study, a traction drive electric motor was designed with a new magnet‐free motor design technique where electromagnets are generated on a rotor by utilizing changes in the spatial second harmonic of the magnetic fields. To apply the proposed technique to electric motor design, balancing the rotor and stator magnetomotive force is important. This paper presents design methods for adjusting the rotor and stator magnetomotive forces. A test motor was designed with these design methods and evaluated using a motor bench. The analytical and measurement data indicated that the proposed motor performed comparably to magnet motors.