Diagnosing power transformers faults
Jawad Faiz
Reza Heydarabadi
Russian Electrical Engineering 12/2015; 85(12):785-793. DOI: 10.3103/S1068371214120207
ABSTRACT
In this paper, faults in power transformers are categorized into two internal and external faults. The reasons for faults in the transformers are proposed and different faults diagnosis techniques in general and detailed manners are introduced and discussed. Some of these techniques are conventional and generally analytical; and some are novel based on wavelet transform and expert systems. Since numerical techniques in magnetic field analysis have been widely applied in recent years, they can be also used as precise and efficient methods for faults diagnosis of power transformers. The finite element method as a powerful and precise numerical technique is considered here which can also locate the fault position. Initial results in this topic are presented in this paper.
Article
Linear synchronous electromagnetic machines for low-frequency impact technologies
L. A. Neiman
V. Yu. Neiman
Russian Electrical Engineering 12/2015; 85(12):752-756. DOI: 10.3103/S1068371214120098
ABSTRACT
The trend is considered toward development and application of various linear electromagnetic impact machine designs wherein the reciprocal motion of the plunger (armature) is timed with the frequency of the voltage pulses fed to the motor winding (coil) or a system of such coils from a mains-frequency power source. Based on the differences found between the methods of regulating the forced mechanical vibration regimes of the plunger, an analysis is made of the advantages and shortcomings of the operating cycles of synchronous machines built mainly around single- and double-coil designs. Novel electromagnetic synchronous machine designs are presented, along with their operating cycle control methods providing for a necessary sequence of alternation of the voltage half-waves applied to the coils, which make it possible to reduce the current pulse amplitude and the effect of the operation of the impact-type electric drive on the supply circuit. New technical solutions are suggested for improvement of the adjustment accuracy and stability of the forced vibration regime, which improves the performance characteristics and operating conditions of machines.
Analytical calculations of the induced electromagnetic field in the rectangle cross section slab with the use of the grid equivalent circuits
A. I. Inkin
A. I. Aliferov
A. V. Blank
Russian Electrical Engineering 12/2015; 85(12):765-768. DOI: 10.3103/S1068371214120062
ABSTRACT
Typical multiport cells are considered as basic elements to synthesize grid equivalent circuits of induction heating units with a longitudinal magnetic field. The two-dimensional electromagnetic field of the induction unit is divided into elementary rectangular cells. Each cell corresponds to a multiport consisting of five branches connected in one node. Multiport branch resistances are determined by the integral dependence between the magnetic flux and vector magnetic potential. The magnetic flux components are an analog of current in cells, and the cell boundary magnetic voltages are a voltage analog. Methods of circuit theory, as well as circuit simulation software, can be applied to calculate the grid equivalent circuit.
A SIMPLE ANALYTICAL APPROACH FOR THE ANALYSIS OF A SELF-EXCITED INDUCTION GENERATOR FEEDING AN INDUCTION MOTOR
Authors:
Professor Dr. Ibrahim A. M. Abdel-Halim, FIET
Dr. Mahmoud A. Al-Ahmar
Dr. Mohammed E. Elfaraskoury
Abstract:
This paper presents a simple and direct analytical method for the analysis of a system composed of a self-excited induction generator (SEIG) feeding an induction motor (IM). In the method presented, results are obtained for different operating conditions of the SEIG/IM system. The presented analytical approach was verified by comparing the results obtained from it, at different operating conditions, with previously published results obtained numerically, with the induction motor considered as equivalent to a static R-L load. The two sets of results were found to be almost identical.
An Efficient Functional Test Generation Method For Processors Using Genetic Algorithms
Ján Hudec1 / Elena Gramatová1
1Faculty of Informatics and Information Technologies of the Slovak University of Technology Ilkovičova 2, 842 16 Bratislava, Slovakia
© Faculty of Electrical Engineering and Information Technology, Slovak University of Technology. This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License. (CC BY-NC-ND 3.0)
Citation Information: Journal of Electrical Engineering. Volume 66, Issue 4, Pages 185–193, ISSN (Online) 1339-309X, DOI: 10.2478/jee-2015-0031, September 2015
Publication History
Received:
2014-09-16
Published Online:
2015-09-19
Abstract
The paper presents a new functional test generation method for processors testing based on genetic algorithms and evolutionary strategies. The tests are generated over an instruction set architecture and a processor description. Such functional tests belong to the software-oriented testing. Quality of the tests is evaluated by code coverage of the processor description using simulation. The presented test generation method uses VHDL models of processors and the professional simulator ModelSim. The rules, parameters and fitness functions were defined for various genetic algorithms used in automatic test generation. Functionality and effectiveness were evaluated using the RISC type processor DP32.
Keywords: processor; testing; functional test; test generation; genetic algorithm; evolutionary strategy