|ACTA TECHNICA CSAV|
The paper investigates the starting strategy of a three-phase induction motor drive with one phase out of the supply. It is shown, that three-phase induction motor can be operated successfully in single phasing condition. The starting strategy requires only one phase to be connected with the supply neutral in sinusoidal supply or with the centre tap of the DC voltage source in case of inverter supply. From the mathematical model we can derive both the transient and steady-state starting characteristics of the motor. Experimental results obtained from 1kW laboratory prototype (sinusoidal and inverter supply), confirm the validity of the system.
A mathematical model of Thomson's jumping ring put on a ferromagnetic core together with a field coil is constructed and solved. The coil is fed either by a charged capacitor or by a source sinusoidal voltage. The latter case is analysed to formulate the theory defining the position of the ring in a steady state. A numerical solution of the observed phenomenon is presented.
Simple and intricate behaviour of soils is compared. Three types of soils (sand, loess, clay) and granular silica gel were used in an attempt to model various aspects of soil behaviour. The emphasis was laid on the shear behaviour and one-axial compression. The intricate behaviour is produced by grain crushing. The effect of shear on grain crushing is dealt with. DEM analysis is presently short in explaining the complex behaviour of granular soils.
Paper deals with description of universal controlled structure designed on the second Lyapunov method. Basic properties of this structure are studied from its application in controlled electrical drives and drive's complex point of view. Single properties are verified by modelling by means of programming package MATLAB. At the same time the references to applications realized in area of electrical drives are introduced here.
The paper deals with the analysis of electromagnetic relations on overhead lines at one-line-to-ground fault. The impedance of earth return is examined as well as the distribution of currents and voltages between the earth and ground wire. The knowledge of these quantities is necessary for exploring interaction between the short-circuited line and cables or pipelines running in parallel with the lines. However, this is not included in the presented treatise. Unlike older works it draws on rather exact mathematical model and its computer implementation.
Utility systems must nowadays handle a variety of large 1-phase industrial loads which can have a serious effect on the symmetry of a 3-phase supply system. This paper handles in effect such 1-phase loads so as to be reflected as symmetrical three-phase in order to avoid unbalancing the feeding 3-phase supply. For this purpose, a static wattles device is presented which proves to be practicable for any single-phase load. Additionally, the device is more important when the power-factor of the 1-phase load is equal or near unity.
In this paper an algebraic pole assignment control method using output-feedback have been applied to the design of controllers in a multimachine power system. This method have been employed to improve the dynamic responses of the measurable state variables for a practical power system model -. The responses obtained through a pertinent digital simulation computer program, which shows the dynamic performance of the proposed control method applied in a multimachine power system model.