This study provides a circuit analysis model of a DC brush motor to predict spike surges at mechanical contacts and conducted EMI by considering the behavior of steady arc discharge. The mechanical contacts model comprises multiple variable resistors, constant voltage sources, ideal diodes, and stray capacitances. In the proposed model, spike surges with steady arc could be predicted with 90% accuracy. Moreover, simulated conducted EMI according to CISPR 25 standard is deviated from the measured value at a maximum of 25dB. Therefore, it is demonstrated that the quantitative prediction of conducted EMI requires consideration of a showering arc model at mechanical contacts.
This study proposes a novel active power decoupling (APD) control method focusing on the power generation characteristics of photovoltaic (PV) arrays. Numerous studies have been conducted on the APD method for achieving a long lifetime of a residential PV power generation system. The APD method reduces the power pulsation, which contains twice the utility frequency caused by a single-phase PV inverter. Compared with the passive power decoupling method using electrolytic capacitors, the APD method incurs power conversion loss due to the increase in passive components and power devices. Many studies have considered the efficiency improvement of the APD method, however most of them focus on the power conversion loss of the APD circuit. It is necessary to consider the power conversion efficiency of the power conditioner and the power generation efficiency of the PV array collectively to improve the efficiency of the PV system. Therefore, in this study, a compensation power control for APD circuit focusing on the power generation characteristics of the PV array is proposed, and the validity of the proposed APD control was verified by evaluating the efficiency based on real-time simulation and experimental results of a 1kW power conditioner.
In this paper, a calculation method is proposed for the radial suspension force of a bearingless motor with a surface-mounted permanent magnet (SPM) rotor, a consequent-pole permanent magnet (CPM) rotor, and a homopolar permanent rotor (HPM). The radial suspension forces are calculated mathematically and analytically using the airgap flux density. It was confirmed that the proposed radial force equations are practical to calculate the suspension force based on the airgap flux density. The CPM bearingless motor and bearingless AC HPM have salient pole rotors that interact with the 2-pole Magnetomotive force (MMF) to generate 6- and 10-pole components. As a result, the radial suspension force of the CPM bearingless motor is generated by 8- and 6-pole, and 8- and 10-pole magnetic flux, whereas the bearingless AC HPM produces the radial suspension force by DC and 2-pole components. The shaft torque, the suspension force, and efficiency were also compared for SPM, CPM bearingless motors, and bearingless AC HPM. Consequently, the torque value of the CPM bearingless motor is quite close to SPM bearingless motor. Moreover, the suspension force of the CPM bearingless motor is quite close to bearingless AC HPM.
The reduction of the leakage magnetic field is a critical problem in achieving the realization of a dynamic wireless power transfer system for battery electric vehicles. In particular, besides the leakage magnetic field of the fundamental component, the harmonic components must also be suppressed. In Japan, the regulation values of the leakage magnetic field are set according to the Radio Law. Accordingly, two methods have been proposed to reduce the harmonic components of the leakage magnetic field: a control method and a circuit method. In the control method, an inverter and rectifier are controlled using a phase shift that can reduce a specific order component. In the circuit method, an LCC circuit with low-pass filter characteristics has been investigated for each of the transmitter and receiver coils has been studied. In this paper, we compare the control method and the circuit method using the same coil and verify how the efficiency and the harmonic components of the current change with respect to the conventional square wave drive.
A dual-winding reluctance motor (DWRM) comprises a stator with armature and field windings, which have different numbers of poles, and a reluctance rotor. This study analyzes the performance of a line-start DWRM that operates under a commercial power grid. To adjust the flux linkage during operation, changeover switches were provided to the stator windings in the analyzed DWRM. The steady-state and transient performances of the DWRM were simulated using a finite element analysis and supported by experiments on a small-scale prototype machine. By applying the winding changeover switch, the DWRM could perform well under the operating mode of both the induction motor and the synchronous motor.
Tracking of an attachment plug of power supply cord is one of the main causes of fire accidents originating from electric equipment. Some anti-tracking attachment plugs and circuit breakers with a function of tracking detection are commercially available, but the number of fire accidents does not decrease. In this paper, as a preliminary stage to establish a more reliable fire prevention system from tracking of attachment plugs, development of tracking is evaluated based on results of surface observation, leakage current, temperature and resistance. It is suggested that phenomena during tracking inception and fire ignition of attachment plugs could be separated into four stages. The timing of tracking detection is also discussed.
The WPT is an additional system compared to the conventional contact power supply. Therefore, the volume and efficiency decrease because of increase in the number of conversion stages. This study focuses on design issues specific to small-capacity high-frequency wireless transformers based on the amount of conductors and clarify the appropriate distribution of coil and core considering volume and losses.
A single-delta bridge-cell converter (hereinafter referred to as an SDBC converter) is a prospective power converter for a static synchronous compensator (STATCOM). The authors have proposed a dc/3ϕ power converter using the SDBC converter and a medium-frequency single-phase transformer with an operating frequency of 150Hz; this converter can exchange a maximum active power of 37% of the rated reactive power with three-phase ac mains supply without increasing the voltage and current ratings of the SDBC converter. In particular, the negative-sequence reactive power control is a challenging task because of the high magnetizing inductance of the transformer. To achieve the negative-sequence reactive power control, a single-phase transformer with low magnetizing inductance is applied to the converter at the expense of the exchangable active and reactive power. The relationship of the magnetizing inductance, active power, and reactive power is revealed in this paper, and the operation of the converter under low magnetizing inductance is experimentally verified by employing a downscaled 110-V, 7-kVA model.
SiC MOSFETs are expected to be applied to wide temperature and high frequency applications. This letter focuses on the temperature dependency of switching delay, which determines the effective dead time of SiC MOSFET. If the case temperature of the test target SiC MOSFET increases (Test-A), its effective dead time is reduced owing to the temperature characteristics of its gate threshold voltage. In constrast, if the case temperature of SiC MOSFET and that of CMOS Gate Driver IC increase simultaneously (Test-B), the effective dead time reduction at high temperature is decreased because the switching delay increment in turn-on for Test-A is larger than that in turn-off.