The novel transformer-linked single phase interleaved PFC converter has been proposed in the past. The proposed transformer-linked PFC converter can achieve the miniaturized performance for its scale and weight. As compared with the conventional single phase PFC converter, the core size and the value of the smoothing capacitor in the proposed transformer-linked PFC converter can be reduced by 50% or more. However according to a design, input filter is large compared with conventional interleaved PFC converter. Then, we should analysis ripple of input current. In this paper, the input ripple current of the proposed transformer-linked PFC converter is analytically derived using electrical and magnetic circuits. Furthermore the boost inductor of the conventional interleaved PFC converter is determined where the input current ripple of the conventional method and the proposed method is equal. Finally the operation characteristics and performances of the proposed transformer-linked PFC converter is evaluated and discussed with experimental results.

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We have already proposed anti-slip re-adhesion control based on a disturbance observer and sensor-less vector control. When the control system detects the slip phenomenon, the system generates a torque command to decrease the slip velocity. Hence, this system requires some tuning control parameters based on running test. This paper proposes a new method of the generating torque command for anti-slip re-adhesion control based on slip acceleration. The fine performance of the anti-slip re-adhesion control using the proposed method is confirmed by numerical simulation.

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As computers and factory automation machines become more popular, the stability and reliability of power sources have become an important social issue. It is difficult to completely prevent the instantaneous voltage drop and power failure of power sources. Uninterruptible power supplies (UPSs) are widely used to overcome this problem. This paper proposes a single-phase UPS with small size and improved reliability. The proposed UPS consists of a buck-boost converter, full-bridge inverter without a bulky electrolytic capacitor, and an output LC filter. The buck-boost converter regulates the output voltage to a full-wave rectification waveform. A sinusoidal output voltage can be obtained by the polarity switching of the full-bridge inverter. In this study, the experiments utilize the pilot UPS system and a small film capacitor of 40[µF], and the output power is 500[W]. The experimental results indicate that the proposed UPS supplies stable power to the load under any condition. The instantaneous interruption time of the proposed system is short, at 1[µs] with a semiconductor-type ACSW and the proposed control method. Furthermore, the experimental results confirm the time of 1[ms] when a power failure occurs.

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In order to improve light-load efficiency, a Y-Δ connected three-phase dual active bridge (DAB) galvanically isolated bidirectional dc/dc converter topology is proposed in this paper. All the primary and secondary switches of this converter are operated in a soft-switched manner over the entire operating range, when the secondary to primary voltage gain is kept within approximately 100 ± 14%. In comparison with the conventional Y-Y connected three-phase DAB converter, the stresses of power devices such as transformers, inductors, filters' capacitors, and switches are almost at the same level as that of the conventional converter, and the power devices can be kept at the same size. With space vector analysis of voltage harmonics and inductor current harmonics, it is clear that the 5th and 7th harmonics' reactive current flowing through the inductor is greater than that of the Y-Y connected DAB converter at light-load condition, which makes switches easy to be operated in a soft-switched manner when they turn on. A 5.5kW prototype has been built to verify all the theoretical considerations.

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To reduce the loss due to the ripple current in a multiphase current-reversible chopper, we attempt electromagnetic coupling of an air-core reactor. We deduce the relationships among the amplitude of the ripple current, the duty factor, and the electromagnetic coupling coefficient. We estimate the effect of the electromagnetic coupling when we design a train's energy storage system by using the results of the deduction. We manufacture reactors whose electromagnetic coupling coefficients are 0.93 and 0.60. The manufactured reactors employ a new winding structure that provides an optimal electromagnetic coupling coefficient. The mass of the former type of reactor increases by 4.4%, and that of the latter type of reactor decreases by 17%. Finally, we test the new reactors. When the chopper employs the former type of reactor and operates with equal-phase switching and cumulative coupling, the loss due to the ripple current decreases to 11%. When the chopper employs the latter type of reactor and operates with shift-phase switching and differential coupling, the loss decreases to 31%. From the test, it is found that the deduced relationships agree with the measured values.

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Contactless power transformers have considerable leakage inductance because of the presence of a large air gap between their primary and secondary coils. To eliminate the influence of leakage inductance on the performance, the contactless power transfer system employs power factor compensators. This paper reports on the performance of an LCLC compensator derived using a novel approach. The experiments confirmed that the LCLC compensator can reduce the harmonic components of the currents and improve the power factors in the system connecting to a full-bridge diode rectifier. Then, it is proved that the LCLC compensator has higher transfer efficiency than an LCL compensator.

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The servo system of a surface permanent magnet synchronous motor is operated by current sensors to control the motor torque. However, a current sensor has often offset and gain deviation caused by age-related deterioration and thermal variation. These errors lead to d - q axis current ripple and torque ripple, degrading the performance of the servo system. In order to overcome these problems, a new estimation and compensation method for current measurement errors by using a current simulator is proposed. The method aims to decrease torque ripple caused by both offset and gain deviation during current measurement. Experimental results confirm that the proposed method satisfactorily suppresses current ripple and torque ripple caused by current measurement error.

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Development of a spherical actuator is now necessary but its low torque and narrow rotation range remain problems. In this paper, we propose a new spherical actuator with an outer rotor that can produce higher torque and a wider rotation angle. We confirmed the torque characteristics by employing a 3-D finite element method.

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Closed rotor slots are widely employed in low-power squirrel-cage induction motors with die-cast aluminum cage rotors. Die-cast aluminum cages with closed rotor slots can be manufactured commercially. They help reduce flux pulsation in air gaps and attenuate acoustic noises and surface loss. However, it is difficult to calculate the characteristic of a squirrel cage induction motor with closed rotor slots accurately because the secondary leakage inductance changes greatly with the slip.
In this study, the secondary circuit parameter (secondary leakage inductance and secondary resistance) and torque characteristic as a function of the slip were investigated by FEM analysis. The secondary leakage inductance was calculated using magnetic energy and/or magnetic co-energy of a rotor bar, end-ring, and bridge. The secondary resistance was calculated using Joule loss of the rotor bar and end-ring. Moreover, the torque characteristic was calculated using a Steinmetz motor equivalent circuit with the secondary circuit parameter. The results were compared with the experimental value by using a 4P-0.75kW motor with closed rotor slots. From these analyses, it is seen that the measured values of the secondary circuit parameter and torque characteristic are in good agreement with the values calculated by FEM. It is confirmed that the torque characteristic that is calculated using the Steinmetz motor equivalent circuit with the secondary circuit parameter based on the proposed method is more accurate than the conventional characteristic calculation result because the variation of the secondary circuit parameter is taken into account.

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In this paper, the operation characteristics of a novel LLC-type series resonant converter topology having secondary resonant inductors is presented. Because this converter uses parasitic inductors and realizes high-frequency operation, the size of the converter can be reduced. The operation of both the proposed topology and the conventional one was compared using first harmonic approximation analysis. The results of the analysis revealed that the proposed topology has higher boost capability than the conventional one. Based on the analysis, a 12V, 84A output prototype converter was designed, and it was proven that 2.73kW/l output power density and 95.1% efficiency could be achieved.

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A line-start permanent-magnet synchronous motor (LSPMM) is expected to operate with super-high efficiency, because it can be started as an induction motor and then operated as a permanent magnet synchronous motor. Therefore, in the single-phase LSPMM, high efficiency operation is more possible than in the capacitor motor.
In this paper, an analytical theory based on tensor analysis is proposed for practical performance calculation of a single-phase LSPMM. The general equations for the currents of the single-phase LSPMM are derived from the transient impedance tensor expressed in polyphase symmetrical axes, and the general equation for vibratory and non-vibratory torques is derived from the equations of current.

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In general, negative voltage power supplies have been required for the conventional gate drive circuit of the normally-on type GaN-FET. However, the conventional switched-mode power supply (SMPS) and power conversion system have positive voltage power supplies for controlling active power semiconductor switching devices. In this study, a novel gate drive circuit based on positive voltage power supplies for the normally-on type GaN-FET is proposed and discussed. The proposed gate drive circuit is compared with the conventional gate drive circuit using negative voltage power supplies experimentally. Finally, the effectiveness of the proposed circuit is indicated based on the comparative experimental results.

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This report introduces the research activities in Tsuji laboratory in Saitama University. It is a new laboratory established in March 2012. It deals with motion control and the main targets are tactile sensing and rehabilitation robotics.

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