This paper proposes a new circuit topology of the three-phase soft switching PWM inverter and PFC converter using IGBT power modules, which has the improved active auxiliary switch and edge resonant bridge leg-commutation-link soft-switching snubber circuit with pulse current regenerative feedback loop as compared with the typical auxiliary resonant pole snubber discussed previously. This three-phase soft switching PWM double converter is more suitable and acceptable for a large capacity uninterruptible power supply, PFC converter, utility-interactive bi-directional converter and so forth. In this paper, the soft switching operation and optimum circuit design of the novel type active auxiliary edge resonant bridge leg commutation link snubber treated here are described for high power applications. Both the main active power switches and the auxiliary active power switches achieve soft switching under the principles of ZVS or ZCS in this three-phase inverter switching. This three-phase soft switching commutation scheme can effectively minimize the switching surge related electromagnetic noise and the switching power losses of the power semiconductor devices; IGBTs and modules used here. This three-phase inverter and rectifier coupled double converter system does not need any sensing circuit and its peripheral logic control circuits to detect the voltage or the current and does not require any unwanted chemical electrolytic capacitor to make the neutral point of the DC power supply voltage source. The performances of this power conditioner are proved on the basis of the experimental and simulation results. Because the power semiconductor switches (IGBT module packages) have the relation of the trade-off in the switching fall time and tail current interval characteristics as well as the conductive saturation voltage characteristics, this three-phase soft-switching PWM double converter can perform to improve actual efficiency in the output power ranges with a trench gate controlled MOS power semiconductor devices which is much more improved to the low saturation voltage. The effectiveness of this is verified from a practical point of view.
We developed a method, which is called the multi nodes technique, that can take into account of the any electrical isolation of conductors using the multi nodes of the electric scalar potentials. The eddy currents in the laminated silicon steel sheets can be calculated using this method without the mesh of the interlaminar air gap. It is quantitatively clarified that the eddy currents in the laminated silicon steel sheets in a permanent magnet-type MRI system have effects on the time variations of the flux distributions.
The unevenness of contact lines is one of the factors that considerably influences on the dynamic characteristics of current collection system. In order to analyze the influence of the contact line unevenness on the fluctuation of the contact force between contact line and pantograph, an instrument was devised to measure the unevenness of contact lines accurately and continuously. The instrument consists of two pairs of laser sensors for the purpose of reducing measurement errors by the vertical vibration of measurement vehicle. This paper describes the measuring method of contact line unevenness, reports some examples of the measurement of real lines, and proposes a method to evaluate the conditions of overhead equipment.
Vibration suppression controls of two-inertia systems have been proposed by many researchers. However, for three-inertia systems, it is difficult to obtain the adequate gains of the PID controller, which suppress the vibration of the speed of the load side. The Coefficient Diagram Method (CDM) that can design the optimum controller’s gains for the 2-inertia systems has been proposed. In this paper, the control method of vibration of multi-inertia systems, such as 3-inertia and 4-inertia systems, based on the CDM is proposed. Especially, the coefficient diagram is used to determine the controller gains. The validity of the proposed method is shown by the computer simulation for both the 3-inertia system and the 4-inertia one. Furthermore experimental results is also presented for the 3-inertia system.
This paper describes an effective way to achieve precise information necessary for systems, such as traction drives, where low-resolution position sensors are commonly used. To solve this problem, the authors propose an estimation scheme called multirate sampling observer, which can estimate the state variables during the interval of two consecutive pulses from such sensors. The authors also propose a novel pole placement method that stabilizes the observer in especially in low speed range. The effectiveness of the observer is verified through various simulations and experiments.
A newly proposed “Active Noise Filter" is implemented to reduce both normal and common mode conducted EMI noise generated by inverter system. The Active Noise Filter detects the conducted noise through high pass filter, controls the EMI noise voltage by feedback loop with operational amplifiers and low-voltage-rated transistors. It does not have any common mode transformers, therefore there is no problem of the iron core saturation. The EMI noise with an inverter system is measured using a line impedance stabilization network (LISN), and it is shown that both normal and common mode noise currents are significantly reduced. Moreover, conducted EMI noise measured at the LISN is reduced by 20 dB in the hundreads kHz of the frequency range. The results explain that the conducted EMI noise can be attenuated without any filter reactors using iron cores which predominantly decide the size of EMI noise filters.
Motion controls in modern servo systems are required to be of high speed and high precision, therefore linear motors are widely introduced into the linear slider system. Direct drive by the linear motor causes the stage to vibrate due to the reaction force arisen from the motion of the stator and the stand. This paper is concerned with the design of a control system for motion control of serial twin sliders driven by linear motors. The control system, consisting of a feedforward controller and a feedback controller, is two degree of freedom control. The feedforward controller is designed to decouple the coupled dynamics of two sliders using an inverse transfer function of the system. On the other hand, the feedback controller has a conventional PID algorithm. Experimental results have shown the high control performance of the control system and the effectiveness of the proposed method.
The improvement of adhesion characteristics is important in electric motor coach. We have already proposed the anti-slip/skid re-adhesion control system based on disturbance observer and sensor-less vector control. The effectiveness of the proposed method has been confirmed by the experiment and the numerical simulation using the tested bogie system of electric motor coach. Then, we apply the proposed method to the actual electric multiple units, which is Series 205-5000. In the experimental results of Series 205-5000, this paper discusses that the proposed anti-slip/skid re-adhesion control system has the desired driving wheel torque response. Moreover, this paper proposes the evaluation method of re-adhesion control test results.
High di/dt switching characteristics of a commercially available silicon carbide schottky barrier diode (SiC-SBD) has been experimentally evaluated in the various di/dt values of 300 A/μs to 2500 A/μs range. Diode voltage waveforms, diode current waveforms, diode stored charges, and diode turn-off losses have been theoretically analyzed. The stored charge and the diode turn-off loss are independent of the forward current value, the di/dt value, and the junction temperature. It is shown that the switching behavior of the SiC-SBD can be expressed a simple variable capacitor, the capacitance of which depends on the reverse bias voltage. The switching characteristics of the SiC-SBD also have been compared to those of a commercially available ultra-fast silicon pn diode (Si-PND). The SiC-SBD has extremely low reverse current and low stored charge compared to those of the Si-PND. The SiC-SBD can reduce the IGBT turn-on loss compared to the Si-PND especially in the high di/dt operation.
A hybrid converter system aims at a large capacity high voltage high efficiency converter system with being free from harmonics in the output. The system can consist of n GTO converters and a single NPC IGBT converter connected series by n+1 output transformers. It is proved that a triple converter system consists of two GTO converters and one IGBT converter is most feasible based on the performance evaluation. Thus, this paper treats a triple converter system in detail. The GTO converters operate in a square-wave switching mode, while the IGBT converter operates in a PWM switching mode. The former produces a base part of the total output voltage. The latter not only produces an additional part of the total output, but offsets the harmonic components generated by the GTO converters. The control strategy for the system is proposed, and the experiments on inverter, rectifier and STATCOM operation are demonstrated. The experimental results verified the validity of the proposed hybrid triple converter configuration and its control strategy.
A single-phase half-bridge Power Factor Correction converter has no common-mode noise theoretically. The output dc capacitor voltages, however, happen to be unbalanced sometimes. In this paper, it is made clear that the unbalanced voltages are principally caused by the asymmetry on the reference signal or the detected current wave. We investigate an improved converter, which has double half-bridge PFC converters in common with two output dc capacitors and should be connected to the single-phase three-wired distribution system. It can output their balanced capacitor voltages even if the reference signal wave has the asymmetry due to the offset in the control circuit. As a result, it can be operated with the lower distortion in source currents, the higher power factor, and the lower ripple in output dc voltage as compared with the conventional converter. Moreover, their output capacitors can be downsized for saving the costs and the maintenances.
This paper proposes an automatic unit number binding method so that a number of logical subsystems are defined in the whole control network for distributed air-conditioners. Each air-conditioner unit starts the proposed algorithm at random timing to allocate its own unit number without any server. Then each outside unit one by one broadcasts the check signal and flows refrigerant gas to the refrigerant circuit between units to make each inside unit discover its piping connection. As a result, a number of logical subsystems are defined in the whole control network. A Petri net model was constructed for verification of our proposed system. For the case of two outside units and three inside units, the reachability to the required states and the deadlock free property were verified. The generalized module-by-module Petri net construction procedure shows applicability to general cases of arbitrary number of units.
In this paper, an automatic design method for PMSM from the only required output characteristics is proposed. In this method, all motor mechanical parameters to realize minimum volume which satisfies a maximum torque, speed, power and losses inputted by user are obtained via control parameters, inductance and magnetic flux. This paper clarified the relationship between an inductance and the motor mechanical parameters, and all mechanical parameters are expressed as a function of the rotor diameter. The output characteristics from the obtained motor mechanical parameters are confirmed by a numerical simulation and Finite Element Method.
Impacts of drift-region thickness of the static induction rectifier on its electrical characteristics were investigated by semiconductor simulations. The decrease of the drift-region thickness, which changes the carrier distribution during the on-state from the pin-like distribution to the BSIT-like one, reduces the stored charge on the anode side. Therefore, as the acceptor dosage in the channel region is decreased, the rectifier having the thin drift region operates with a high switching speed and low forward voltage drop. An oscillation phenomenon in a voltage waveform during the recovery process is related to the drift region thickness.
Vehicles of superconducting maglev system are suspended and driven by superconducting (SC) coils, which have strong magnetic field, and their passenger cabin must be shielded from leakage flux by the SC coils. In order to reduce the leakage flux, we have studied an improved configuration of SC coils, which has small size coils on its end. This configuration can reduce the environmental magnetic field, so that it can strengthen the magnetomotive force of SC coils. This paper describes the characteristics of levitation, guidance and propulsion performance at strengthening the magnetomotive force on the improved configuration of SC coils.
This paper presents a method for determining the optimal maintenance schedule for equipment taking into account both maintenance cost and risk as an implementation of RCM (Reliability Centered Maintenance). In this method, a failure process of equipment is modeled as a probabilistic model, which is used in reliability engineering, and the amount of damages resulting from equipment failure is evaluated using this model. The optimal maintenance interval is determined to minimize the total cost including maintenance cost and the amount of damage suffered from failure. Furthermore, input parameter estimation from the present maintenance interval and the maintenance schedule modification according to the total amount of inspection cost are developed based on the optimal maintenance interval planning function. These propsed functions are implemented as a software tool using Excel.