Salient-pole permanent magnet synchronous motors have been widely used in industrial applications for their high efficiency. To control these motors, knowledge of rotor position and velocity are necessary and expensive sensors have been used to detect these signals. Although many sensorless control algorithms have been developed for cylindrical permanent magnet motors, they cannot be applied for salient-pole machines without any approximation because of the complicated mathematical model, and this may lead to unstable problems. To solve this problem, new extended electromotive force models for synchronous motors have been proposed in this paper. The proposed models have a simple structure integrating position information both in the magnet and in the inductance into one extended electromotive force term. Using these models, no approximation is necessary. Experimental results show that the proposed model and method are valid.
A single-phase AC power control circuit generates many harmonic components in the input current and the output voltage and current. These harmonics may cause various problems in the utility's distribution and a load equipment connected to the AC power control circuit. In this paper, as a reduction method of these harmonics, we propose a compound PWM AC power control circuit system which has greater reduction effect of these harmonics as compared with the conventional PWM control system. In this proposed circuit system, the reduction effect of harmonics is quantitatively clarified by the numerical calculations. Furthermore, the design method of the appropriate constant values of a LC filter inserted to reduce the input current harmonics is described. The reduction effect for the LC product of the filter in this system is also investigated. These simulation results are verified by the experiments.
Many private railways and municipal railways in Japan use the Automatic Train Control (ATC) system as their train protection system. This system has the function to transmit the permitted speed, determined by the position of the preceding train, through the track circuit and indicate that speed in the driving cab and the function to apply brakes according to the permitted speed. Since this system applies brakes in several stages until the train reaches a halt, the application and release of brakes at each speed stage causes a loss and it is impossible to shorten the headway between two trains. We have developed a new system where the ground equipment transmits the stopping point only and the train is controlled autonomously based on the stopping point information. This system, called D-ATC hereafter, enables shorter train headways than the existing ATC with multi-stage braking. A prototype of this system was build and tested using an actual train in order to judge whether its commercial use is possible. This paper describes the proposal of D-ATC and results of the test runs.
This paper proposes a novel high performance vector control system of AC motors using a low switching frequency (2kHz) PWM voltage source inverter with an output LC filter. Excellent high speed response characteristics of the LC filter output voltage have been realized using a novel deadbeat control algorithm. Experimental results have shown that the response of the current controller is similar to the response without the LC filter. In addition, it has been confirmed by simulation that errors of the LC filter constants within ±10% can be permitted.
This paper proposes new vector controllers in the D-module for controlling current of three-phase systems, which have no vector-rotators in current control loop. Conventional standard vector controller controls current of three-phase systems in rotational reference frame and a couple of vector rotators are indispensable in the loop. Vector rotators that perform sinusoidal operations on current must be realized in discrete-time manner, and sampling of current for the discrete-time processing restricts attainable bandwidth of the current control loop. Broader bandwidth of the loop is desired for both quick response and disturbance suppression. The proposed vector controllers in the D-module are so simple that no vector rotators in the loop are required, and can be realized in continuous-time manner due to its simplicity. Furthermore, under the same bandwidth of the current loop, the proposed one can show the equivalent performance to conventional standard vector controller having vector-rotators in the loop. These features allow broader bandwidth of the loop and better current control performance than the conventional vector controller. Two new vector controllers in the D-module are presented and their usefulness is examined and confirmed through numerical experiments.
In this paper, we propose a boundary structure for improving performances of Single-sided Linear Induction Motors (SLIMs). In such machines, solid-plate conductors and back irons are usually used for secondary stators throughout operating regions. However, to take account of deformation due to thermal expansions, secondary stators are constructed from some sections of limited length. Therefore, a propulsive force characteristic declines when the primary armature crosses the boundary between secondary sections. In this study, by adopting a three-dimensional finite element method, detailed phenomena at the boundary between secondary sections have been clarified from the viewpoint of propulsive force and secondary current distributions. Besides the validity of calculated results is verified by the measured results. Further, to suppress the aggravation of characteristic caused by the secondary structural transition, we connect the secondary sections electrically. Finally, the propulsive force characteristic has been improved in spite of the existence of the boundary.
In the paper, I study some effects of the rotor skew in a 3-phase cage induction motor using 3-D finite element analysis. At first, the calculation method of the equivalent circuit parameters by the results of the analysis is proposed and variations of the parameters by rotor skew are calculated. The harmonic secondary copper loss, which is a part of the stray losses, is calculated at each skew ratio. The calculation method of the iron loss is proposed and the effects of rotor skew about the harmonic iron loss are clarified. The reduction of the magnetic vibration force by rotor skew is understood quantitatively by the analysis. The following results are obtained. X1 and X2 which are T-type equivalent circuit parameters are increased and Xm is decreased by rotor skew. The harmonic secondary copper loss is reduced but harmonic iron loss is increased by rotor skew. The harmonic flux by the rotor slot pulsation are reduced by rotor skew in proportion to the skew coefficient but magnetic vibration force are not reduced in proportion to it, because the distribution of the flux density toward the axial direction is not uniformity by the axial direction flux made by the circular direction bar current, and many harmonic flux with different phase each other are overlapped at the air gap.
This paper deals with a feasible power loss analysis simulator which can actually estimate the power losses of switching mode power converters using IGBTs. The power loss analysis simulator proposed newly is based upon the feasible measured switching power loss data tables and v-i characteristics data tables of power semiconductor power devices; IGBT and diodes. The effectiveness of practical simulation technique, which can discuss power loss evaluations for three phase PWM inverter, is confirmed from the viewpoints of the newly proposed simulation and experimental results.
It is required to use the DC current sensor in the photovoltaic system which is controlled by the maximum power point tracking. To eliminate this expensive sensor, this paper shows how to estimate DC output current of PV array by using the main capacitor voltage and on-duration of the main semiconductor switch in high frequency link type inverter. The experimental data show the proposed technique is helpful to practical use.