All posts by cburada

Analysis of Losses in Brushless Direct Current Motors and Their Influence upon Operation Characteristics

Abstract

Researches regarding the optimum design and construction of brushless direct current motors are very present, owing to their use in small-dimension vehicles (elec-trical scooter, electrical bicycle, motor-scooters, electrical vehicles for disabled passengers). Motors used in two-wheel or four-wheel conveyances are permanent magnet direct current motors, manufactured by brushless technology. The operation, starting and speed control characteristics of the brushless direct current motor designed must correspond to certain conditions of competitiveness and to high exigencies imposed by the complex equipments used in passenger-transport vehicles. The study carried out and the simula-tions presented aim at identifying the important losses in order to reduce them. The widespread use of command electronics associated with power components, in brushless direct current motors supply, enabled the optimization of their operation, with special performances. In this paper there is presented the revised computation relation for iron losses, known in design, by establishing separately the two components: hysteresis losses and eddy-current losses. This way, the efficiency obtained in the design stage gets close to the experimentally established efficiency, the error being less than 2%. images

Indirect Current Control Algorithm Implementation and Validation, for Active Filtering Using Constant Switching Frequency Hysteresis Controllers

Abstract

The aim of this paper is the implementation and the experimental validation of a constant switching fre-quency hysteresis current controller as a part of an active filtering system control algorithm, based on the indirect current control. The classical choices in the literature are the hysteresis current controller and the PI controller both with their corresponding advantages and disadvantages. A solution which achieves the advantages of both classical hysteresis and PI controllers is the constant switching fre-quency hysteresis current controller. This controller can be obtained by combining the hysteresis comparators with the PWM suboptimal modulator. The performances of the ac-tive filtering system based on the indirect current control and the proposed controller are compared with the corre-sponding performances obtained by the same system im-plemented with the well documented PI current controller. The regulator implementation and performance compara-tive study were accomplished on a comprehensive experi-mental active filtering system based on the dSpace DS1103 prototyping board. images

Analysis of the Phaseportrait for the Lü Dynamical System in a Particular Case

Abstract

In the present paper it is started a qualitative analysis of the Lü dynamical system, using the appropiate tools of Hamilton-Poisson geometry and using the software for mathematics MAPLE 15. The Lü’s system arise from electrical engineering networks and it is very known that he has a chaotic behavior. For this reason, the problem of finding the solution of the system could be very difficult. By obtaining of a geometric Hamilton-Poisson structure, we can find such a solution as the intersection of two surfaces, the surfaces equation being given by the Hamiltonian and the Casimir function . Using MAPLE 15, it will be analyzed the phase portrait for two particular simplified versions of the dynamical system associated to the Lü ordinary differential system (a=0, b=c=0 and a=1, b=c=0). Also, we will do a study of the Lyapunov stability of Lü’s system for the particular case (a=1, b=c=0). We obtain that the origin is an unstable equilibrium point for this particular parameter case of the Lü’s model. This fact is confirmed by the numerical simulations. More that, the pictures show that the origin is a non-stable focus, in the first simulation case. Analytical results are accompanied by numerical illustrations. images

Power line Compromising Emanations Analysis

Abstract

The paper presents an innovative method used to analyze the video-compromising signals that computer equipment generates during normal operation. It presents the measurement results achieved for conducted emissions for a commercial laptop using a shielded power source and a commercial transformer as well as conducted emissions generated by a display unit which is connected to a laptop and is alternatively powered by a commercial and a shielded cable. In order to perform these tests, there were selected several graphical images consisting of horizontal bars of various widths to facilitate the detection and evaluation of the compromising video signal level. images

Modeling Three-Phase Short-Circuits for Radial Distribution Systems

Abstract

Monitoring radial distribution systems in short-circuit conditions represents a quite important issue of elec-tric power networks supplied by renewable sources. The method presented in the paper aims to establish in labora-tory conditions, using the similitude criteria, the real value and the duration of a three phase short-circuit current act-ing in renewable sources connected to the electric grids. Since, due to the high values of the short-circuit currents it is difficult to test the operation of the relays in situ, for in-stance in transformer stations or substations, it is manda-tory to test and set using the injection of secondary currents. Consequently, the paper presents the modeling of a real grid, in order to emulate, as accurate as possible. The results of the measurements, reported to the real grid, represent the real ones, existing at the three phase short-circuit level. Therefore, even from the early phase of design, one may choose the breaking equipment, capable to face the condi-tions of dynamic and thermal stability. Since the reporting factors are known, along with the possibility of using the accurate reported value of the real short-circuit current on the model, the tests on model present advantages in relation to the use of the devices of secondary currents injection. The results of the measurements on the model confirm the vi-ability of the last testing method here depicted. images

Continuous Monitoring and SCADA Integration of the Sag of Overhead Electricity Transmission Cables Based on the Measurement of their Slope

Abstract

This paper presents a proposed system for the continuous monitoring of conductor sag values in overhead electricity transmission lines through slope angle measure-ment, by using a mathematical model based on the catenary equation. By measuring the axial angle of the conductor and the slope angle by means of the double axis tilt sensor, the sag value can be calculated in case of cable swings. Using ModBus protocol the value of the tilt sensor can be read by the software application and the calculed sag value is send to SCADA. The results obtained according to the proposed algorithm developed in LabVIEW software environment showed that the system could meet the technical require-ments for measuring conductor sag in electricity transmis-sion lines. images

Disturbance Analysis for Power Systems Based on LabVIEW Real-Time and Reconfigurable FPGA Modules Using Wavelet Transform

Abstract

This paper present a disturbance analysis moni-toring system for the purpose of detection of disturbance analysis using Wavelet Transform (WT). The proposed sys-tem is based on the real-time capabilities of the Real-Time LabVIEW operating system and on a CompactRIO type real-time computer which contains a network of FPGA (Field Programmable Gate Array). The WT is used to ana-lyze the quality of energy and to detect the transient phe-nomena characteristic of the quasi-periodic signals. The system achieves the storage of entries as TDMS (Technical Data Management Streaming) files and Word/Excel type automatic reports automatically sent by email at predefined addresses, contains an OPC UA (Open Platform Communi-cations Unified Architecture) type server for communication with a hierarchically superior SCADA (Supervisory Control And Data Acquisition) type system, performs selective entry of the characteristic parameters into a database, contains a Webserver for Intranet/Internet access, for viewing the measured data, and for system management from any-where, the application is connected to a Cloud-type plat-form. The disturbance analysis monitoring system has been tested using both simulated signals and real signals from a practical experiment. images

Simulation of Idle Running Operating Characteristics for Low-Power Asynchronous Motors

Abstract

The opportunity of this work is backed by the possibility to predetermine the operating characteristics of an asynchronous motor in idle running. This contributes to the realization of a high performance electric drive. An analysis is aimed for low power asynchronous motors used in different types of applications, such as robots, medical equipment and home appliances, transportation systems a.s.o. It is insisted on an advanced mathematical model that provides the best results in simulations and applications [1]. The simulations are important for their quality and preci-sion because they allow us to anticipate the motor behavior and also to establish the errors between the simulation and experimental results. The mathematical model used consid-ered the equations written in the two-axes theory, the rotor quantities being expressed in the fixed stator reference frame. The need for knowledge of qualitative and quantita-tive dynamic behavior related to the field of use determined major investments and extensive research in large laborato-ries. Research on an asynchronous motor with a power of 1.1 kW with variable parameters proved that, between the idle running simulated and experimentally determined val-ues, the errors do not exceed 3.97%. These results authorize the conducted research, providing qualitative and quantita-tive correct simulations for the rated regime. images

Current Aspects in the Conception and Performance of Dispatching Manoeuvres in the National Electric Power Transmission System

Abstract

In this paper, the authors have structured a com-plete algorithm for calculating the self-excitement of the generating groups in the NPS power plants, a phenomenon that can occur in the operative manoeuvres performed in 220 kV, 400 kV and 750 kV electrical networks. This shows how with simple parameter calculations can be evaluated parameter approximate values for long lines switching re-gimes, the safety measures to be taken when manoeuvres are appropriately performed and their sequence in order to avoid dangerous overvoltages that would lead to non-admissible stresses of the energetic equipments. In order to increase the degree of generality of these calculations, the relative size method was used, for which a computational program developed in the Mathcad programming environ-ment was designed. This calculation algorithm was custom-ized for a double-circuit overhead electric line LEA 220 kV case study. Also are presented the practical algorithms for calculating the voltage jump that occurs when connecting and disconnecting the long electric transmission lines from the power system. The overvoltages caused by the switching of these lines are also evaluated. These values must be taken into account by the managerial and operational staff to properly perform and coordinate manoeuvres. For the con-sidered double-circuit overhead power line 220 kV LEA, the calculation algorithms for both no load and under load switching were customized, and two scenarios were studied, namely when the line is not compensated and when the line is compensated by a compensation coil. images

The Resistive Tubular Heater - Mathematical and Simulation Model

Abstract

It is essential to achieve the mathematical model and the simulation when designing complex installations. This allows the analysis of different operating modes and the behavior of the existing system. It enables notification of possible errors and their correction, avoiding additional costs involved for achieving and testing facility in real condi-tions. Some operating modes could be degraded modes. This would be very difficult to replicate or would give rise to a faulty installation. In order to model and simulate a com-plex installation it is, however, need that the components are modeled correctly and to be interpreted correctly the inter-actions between them and the dependency of the parameters on the operating conditions. Because many complex systems incorporate electrical heating tube elements, this paper pro-poses an original mathematical model for a resistive tubular heater. Based on this model it was developed a Matlab-Simulink simulation model. The model has been designed so that it can be easily adapted to various situations, where the heating elements in tube are immersed in liquids or embed-ded in solid materials. The proposed model allows a fast simulation and evaluation of the function of the resistive tubular heater in transient regime or under steady state regime. One challenge was to minimize the parameters which need to be pre-calculated based on physical and con-structive data, in order to enroll them in the prescription blocks of the model. The viability of the presented modeling system was verified both by comparison with a real heating element and by drawing the temperature curves. These curves highlight the fitting in the admitted temperature domain for such an element. images