The switched reluctance motor (SRM) has generated considerable attention because of its lack of magnets and lower cost structure compared to the permanent magnet synchronous motor (PMSM) structure. In addition, SRM can achieve high speed rotation because of its simple structure and high robustness. However, SRM has lower torque density than that of PMSM. To increase the torque density in SRM, a grain-oriented electrical steel sheet (GO) can be applied as the stator and rotor materials. The magnetic characteristics of GO fluctuate depending on the angle between the rolling direction and magnetic flux direction. In a previous research, it was confirmed that three kinds of torques are output when the stator and rotor materials use GO. In this paper, three kinds of torques are explained, and a design concept of an SRM using GO is proposed. In addition, the static and dynamic torque characteristics of the proposed SRM are verified by simulation and experiment.

This paper presents a novel current-fed step-up DC-DC converter that is suitable for the front-end high-frequency link DC-DC converter (DC-X) in a grid-tied inverter of a fuel cell interface. The proposed DC-DC converter features the snubberless zero current soft-switching (ZCS) commutation with high-frequency switching by adopting quasi-resonance and parallel load resonance; the multi resonance while minimizing the number of additional circuit components. The switch-mode transitions of the proposed DC-DC converter are explained in detail for revealing the principle of snubberless ZCS due the multi resonance. In order to analysis the proposed DC-DC converter more precisely, a time-domain analysis is employed to examine the high-order harmonics in the three-level stepwise voltage of the quasi-resonant high frequency inverter, which is superior to a conventional sinusoidal AC analysis. The effectiveness of the proposed converter and the analytical strategy is demonstrated by comparing the theoretical and simulation results, after which the feasibility is verified by experiment of a 1 MHz-55 W class prototype with Gallium Nitride (GaN) high-electron-mobility-transistor (HEMT).

We propose a new bias torque function control (B-TFC) method for electric vehicles (EVs) for starting on uphill roads and confirm its effectiveness by simulations and experiments. In the simulation, we developed a new model for accurate behavior of the evaluation system. We compared three kinds of slip suppression control methods, namely without TFC, with TFC (conventional), and the B-TFC. In the case of the B-TFC method, an EV carrying one person can start moving on a 1° wet uphill road without rolling backward. In the simulation using the developed model, the torque is suppressed and fluctuates between the command and bias torques. Then, the vehicle speed at 3s is 1.7m/s, which is the highest among the compared methods. The experimental results therefore agree with the simulations and the developed simulation model reproduces the experimental trends with high accuracy. We confirm that the proposed B-TFC method improves acceleration and slip suppression performances.

Application of large synchronous motors started in the early 90; currently the synchronous motors (SMs) are being phased out and replaced with getting old, and they are being replaced with larger capacity motors which are installed on the existing motor-mount basement. These larger capacity motors require higher magnetic flux than the conventional motors, which leads to the problem of magnetic saturation in the SMs. It is time consuming to find suitable parameters related to flux for each motor using the conventional SM control method. In this paper, a method to improve the adjustment of flux parameters using a simplified matrix table is introduced.

In this study, the authors propose a simple method for estimating stray capacitance of toroidal inductors. The proposed method calculates the total stray capacitance of a toroidal inductor based on the stray capacitance between the winding and the core, calculated by considering the insulation (plastic case and plastic molding) that contains the magnetic core. The frequency characteristics of the toroidal inductor can be calculated by substituting the calculated stray capacitance in the analytical model of the inductor, which takes into account the frequency dependence of the complex magnetic permeability of the magnetic material. In order to evaluate the proposed method, toroidal inductors were fabricated based on carbonyl iron dust, amorphous and nanocrystalline magnetic cores. Comparison between measured and calculated impedances clarify that the proposed method can calculate the stray capacitance of toroidal inductors with practical accuracy.

This study proposes a matrix converter (MC) control method capable of power decoupling (PD) for a single-phase input isolated AC-DC converter. The proposed converter can also be fed by a three-phase source without any additional components. The PD circuit shares its capacitors with the input filters and its switches with the MC, and absorbs the source power ripple to supply a constant DC voltage for the load. Moreover, the MC control method achieves a sinusoidal source current, a high output frequency, and soft switching. Additionally, the feedback control to compensate for the DC output voltage error is applied. The proposed method is evaluated experimentally.

This paper presents an energy saving driving method for freight railway considering measured running resistance and motor efficiency while cruising, which is the most common running state of freight trains. This paper proposes a combination of constant-speed and coasting driving operations, which is expected to reduce energy consumption in terms of running resistance and motor efficiency.

First, we discuss the basic theory of an energy saving driving method and the practical driving operation of cruising for freight railway. Then, we estimate running resistance using train monitor data and motor efficiency using a type test result. Considering the running resistance and motor efficiency, we discuss a driving strategy that conserves energy while cruising. After that, we confirm the energy consumption and driving maneuverability by running tests on several candidates of the energy saving driving methods. We also establish an energy simulation method by reproducing the running test. Finally, we show the validity of the proposed energy saving driving method using the energy simulation.

Authors have proposed the stepped multiple-frequency step radar modulation. The radar modulation also has been demonstrated for various applications through the verification experiments. Narrowband signals are transmitted and received in time division in the modulation. The high range resolution corresponding to the transmission bandwidth is obtained by synthesizing the received signals. That is why the radar modulation enables us achieve both a long-range performance and a high range resolution by a low hardware load. In recent years, 5GHz bandwidth has been allocated to millimeter-wave radar in 79GHz band. In addition, 8GHz bandwidth in 90GHz band tends to be allocated for detecting foreign object debris on runways in the world. In this paper, the parameter studies on the multiple-frequency step radar for the detection of small objects in background clutter environments are conducted. The parameter study results show that the stepped multiple-frequency step radar can achieve centimeter range resolution using some tens to hundreds of MHz A/D converters, which significantly mitigates the effect of the background clutter. Evaluation results indicated that the stepped multiple-frequency step radar has the potential for detecting small objects in background clutter environments.

This paper presents a new technique for carrier harmonics utilization for field excitations and its experimental demonstration. The system is composed of a permanent magnet rotor structure with a wound-field and concentrated winding stator. An induction coil with a series connected capacitor and a field coil with a rectifier are installed on the rotor. The resonance frequency of the LCR series circuit is set to the carrier frequency. Experiments are conducted and the test results are demonstrated along with the driving characteristics.