A PWM method has been applied to a high capacity six phase current source inverter system in order to obtain sinusoidal output voltage and current. In this system, the three-phase coupling reactor is connected between the inverter output and an induction motor used as a load. Then the reactor eliminates harmonic components included in the inverter output current except 12κ±1(κ=1, 2, 3, …)th order.
As a result, the distortion factor of the inverter output current decreases. But the resonant circuit is composed of the capacitance of filter capacitor and the induction motor leakage inductance. Then the resonance current is superimposed on the induction motor phase currents. To solve this problem, the optimal PWM pattern is derived, so that the resonant current becoms very small.
The order of the resonant frequency component of the induction motor phase current depend on the inverter frequency. Then total inverter frequency range is divided into several areas. The optimal PWM pattern is derived in each area. As a result, the use of each optimal PWM pattern allows us to drive the induction motor, over a wide range of speed, under the condition of small distortion factor of phase currents.

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This paper proposes a beam search based FMS scheduling system where the evaluation function is adaptively selected throughout the scheduling period by utilizing a fuzzy inference based procedure. The proposed procedure is specially designed for dynamic production environments, where the conditions change frequently. In the proposed method, the performance of beam search with different evaluation functions is studied with varying production conditions. Environmental variables are then used to detect those environment changes, as input to the fuzzy inference system. The fuzzy inference will thereupon attribute preference levels to the evaluation functions, according to their adequacy to the current environment. The scheduling is made using partitioned combination of the evaluation functions. In order to verify the validity of the proposed method, an application to FMS scheduling is presented.

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In a three phase AC power system where multiple currents harmonics can occur, the total current harmonics becomes the vector sum of the currents harmonics generated from each. So if the initial phase angle of the current harmonics can be controlled, it is possible to suppress the total current harmonics slightly by the cancellation of each current harmonics on a per system basis.
What these authors propose are to provide a phase shifter for each three phase AC power system that is subject to multiple current harmonics generation, then, by controlling the current harmonics's initial phase angle at the ideal value, to cancel the current harmonics and restrain the total current harmonics. As far as these authors know, no paper examining the details of a current harmonics restraint system through phase control has been published. We therefore conducted a theoretical analysis and simulation regarding feeders 2, 3, and 4. This is to report that the results showed that, using multiple variable control, it is possible through arithmetic controls to actualize phase angles for each feeder's phase shifter where the total current harmonics becomes minimal.

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This paper presents two definitions of a saturated salient-pole synchronous machine turn ratio between the d-axis and the field circuit, which can clarify the physical relationship between the leakage reactances and the leakage flux.
The definitions are derived from two-dimensional finite elements and based on an assumption that the total leakage flux of the machine consists of the armature leakage component which flows only in the stator, the field leakage component which flows only in the rotor and the gap leakage component which flows across the gap and stems from the difference in the space distribution between d-axis and field winding. The values of the two defined turn ratios vary according to the magnetic saturation. One definition is based on the first order harmonics of the gap flux density space distribution. It clarifies the relationship between the armature leakage reactance and the armature leakage component of the leakage flux. The other definition is based on the amount of gap flux. It clarifies the relationship between the field leakage reactance and the field leakage component of the leakage flux.
The results of reactance analyses show the validity of these two definitions.

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Superconducting Magnetic Energy Storage (SMES) is very promising for the future power storage system because of fast response, low loss and high efficiency. Strong magnetic field is very favorable for SMES because it promises a compact device. However, the huge electromagnetic forces caused by strong magnetic fields and coil current becomes a serious problem. We propose the Force-balanced Coil (FBC) concept for the SMES which drastically reduces the huge centering forces by balancing it with the hoop forces induced by the toroidal current. Superconductor stress, length, maximum field and stored energy were surveyed. The results were compared with the toroidal type configuration and ordinary helical type one, It is shown that Force-balanced Coil is more compact than the others in view point of electromagnetic force and per-unit length stored energy of the superconductor and has a potential for simplifying the supporting structure, making the facility compact.

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This paper proposes a configuration for transformerless connected compensators consisting of voltage source inverters with parallel and series connected capacitors. The behavior of transmission lines and power flow control with reactive series compensators are described. After presentation of the circuits and configurations their mode of operation is shown in more details using an example which is representative for practical applications.

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The torsional vibration is often initiated by the momentary impact which occurs when a load is connected to a motor by several mechanical coupling parts. An industrial motor drive system is typically represented as a two-mass plant. To suppress the vibration generated in the two-mass plant, many control methods have been developed for practical use. In this paper, the authors propose a simple vibration suppression strategy which employs two variable parameters consisting of resonance ratio and damping factor along with a state feedback approach. The control performance, resulting in excellent vibration suppression even for small resonant ratio, is verified by simulations and experiments.

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It is demonstrated that the rotor design of multi-flux barrier synchronous reluctance motors can be optimized in terms of a key geometric parameters, i.e., the optimum number of flux barrier and the ratio of the flux barrier width to the iron rib width so as to obtain maximum torque production. The results indicate the 6-layer flux-barrier rotor is optimum design considering practical use. An experimental motor has been fabricated and the results of measurements of the motor parameters prove the validity of the rotor design optimization.

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One of authors developed PM vernier motor which has high torque at very slow speed so that it can be used for socalled direct drive systems, and its construction, principle and control scheme were already presented. However, a rotary encoder having high resolution for detecting the rotor position was required in the control scheme, which is very expensive. So the authors developed a variable reluctance type N-speed synchro having large number for N, which is inexpensive because of its very simple construction. It consists of stator and rotor cores punched slots. However, nothing is put into the rotor slots, because both exciting and output windings are put into the stator slots.
In the present paper, detailed explanation of construction and principle of the VR synchro is given at first and it is shown by the experimental result that three phase sinusoidal voltages of 32 cycle per revolution can be obtained. Then, it is described that demodulated output voltages of the VR N-speed synchro can be directly used for current phase commands of the PM vernier motor, which makes the control scheme very simple and inexpensive. The measured speed response characteristics for the four-quadrant drive showed very good performance.

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This paper proposes a hybrid active filter for damping of harmonic resonance in industrial power systems. The hybrid active filter consists of a small-rated active filter and a 5th-turned passive filter. The active filter is controlled to behave as a variable resistor by adjusting a feedback gain which changes from a negative to positive value. The negative resistance cancels a positive resistor inherent in the passive filter, so that the hybrid active filter acts as an ideal passive filter with infinite quality factor. This results in a significant improvement of harmonic damping accompanied by harmonic mitigation, compared with the passive filter used alone. Moreover, the active filter acts as a positive resistor to prevent an excessive harmonic current from flowing into the passive filter. Experimental results obtained from a 20-kW laboratory model verify the viability and effectiveness of the hybrid active filter proposed in this paper.

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The present paper examines a permanent-split-capacitor type single-phase induction motor that does not contain a rotor. The stator of this motor is capable of generating an elliptical magnetic field inside the housing by exciting 2-stator windings, a main winding and an auxiliary winding. Magnetic field shape can be varied by changing the value of the capacitor in series with the auxiliary winding. The stator of this motor is referred to as a single-phase magnetic field generator, and the electrical and magnetic characteristics of the generator were investigated. An expression was derived for determining of the magnetic field based on the magnetic circuit of the generator. The derived equation was applied to calculate the Lissajous elliptical magnetic field produced in a prototype magnetic field generator. The calculated results were in good agreement with those obtained experimentally using an oscilloscope to generate the Lissajous patterns. In addition, the calculated value of the magnetic flux density was in good agreement with that measured experimentally using a Gauss meter. Information on a new magnetic barrel finishing machine was obtained from the results of the experiments, and used to manufacture the new machine. This machine has succeeded in finishing various metals with complex shapes.

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A shaft generator system supplies electrical power required in a ship by using a part of the power produced by the main engine. Since the speed of the main engine can vary over a wide range, an externally commutated thyristor inverter, which has high reliability, is generally used to produce ac power with constant voltage and frequency.
In this paper, a set of system equations, by which the total harmonic distortion of the output voltage, for example, can be estimated, is derived first. The effects of leading angle of the inverter and the reactance of ac reactor located in the output-side of the inverter on the system performances and the operation limit of the system are then clarified. Moreover, a way of taking the system losses into account is proposed to obtain precise calculation results. Finally, the apparent power for the synchronous condenser to provide reactive power in the system is discussed.

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This paper presents the research trends of linear drive systems. The analysis is based on the investigation database by the Japan Information Center of Science and Technology (JICST), from Jan. 1995 to Dec. 1996. As the results we confirm the increase on the study of linear synchronous motor for application to FA machines in the world.

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