Motor Current Signature Analysis in Predictive Maintenance

The aim of this paper is to draw attention to the possibilities offered by spectral analysis of current and voltage in the predictive maintenance of the electric motor. Motor Circuit analysis (MCA) and Motor Current Signature analysis (MCSA) are innovative and non-invasive methods that enable diagnostics and assessment of the condition of the electric motor. The main advantage of the method is that the test is carried out during the normal motor operation, without downtime. All motor defects can be detected at the earliest stage. This enable planning the overhaul according to the condition which can make significant savings. Advanced MCSA analysers enable diagnostics of electric motors that are powered either via a soft starter, frequency inverter or directly from mains. So, it is possible in a simple and reliable way make an condition assessment of frequency inverters. In addition, it is possible to detect faults of driven machine, like misalignment, imbalance, blade faults, belts, bearings issues etc. Theoretical basis and tests that are carried out are explained in the pape

Increasing the Reliability and Availability of the Electric Motor Using Combined Static and Dynamic Diagnostics

The aim of this paper is to point out the importance of early diagnostics and assessment of the condition of the electric motor in increasing the reliability and availability of the plant. Electric motors are unavoidable elements in every production process. As the complexity of the process increases, the number of electric motors involved in it increases. By increasing the number of electric motors, the possibility of cancelling and interrupting production increases. It is therefore very important to monitor the situation and detect defects at an early stage so that timely repair or replacement can be planned, without affecting the production process. Modern diagnostic methods that can be used both during the operation of the electric motor, and with the dismounted and dismantled electric motor are presented in the paper. With good organization and testing schedule and a combination of static and dynamic diagnostic methods, the reliability and availability of the plant can be significantly increased. With increased reliability and availability, a reduction in maintenance costs is achieved. In this article, some examples from the author’s practice are given, when serious engine defects were discovered. These cases confirm the value of predictive testing to increase reliability of electric motor

ANALYSIS OF BUSINESS ENVIRONMENT USING THE MULTI-CRITERIA APPROACH – CASE OF BALKAN’S TRANSITION ECONOMIES

Due to the lack of their own financial resources, attracting the foreign direct investment (FDI) isthe main prerequisite for transitional economies in order to increase production and employment, sothat they can ensure the long term sustainable economic growth. In addition, the foreign directinvestment is an important instrument for the economy restructuring, based on market principles.However, achieving this goal is not simple at all. In order to attract foreign investors, it is necessaryto create a favorable business environment in transition countries, which requires a number ofeconomic, institutional, political and other reforms. The aim of this paper is to point out the mainfactors attracting foreign direct investment and, by using the multi-criteria approach, to rank theBalkan’s transition economies depending on the preferences of investors taking into account certaincomponents of the business environment

Genotypic variability of morphological characteristics of English oak (Quercus robur L) acorn

This paper deals with the acorn morphology (length, diameter and mass) analyzed in seventeen English oak genotypes (Quercus robur L)from the English Oak Clonal Seed Orchard Banov Brod (Srem,Vojvodina). The highest values of acorn mass and length were measured in genotype 5. The largest diameters were measured in genotypes 6 and 21. Genotype 35 had the lowest acorn mass, length and diameter. The results from this study should serve as guidelines for the selection of trees yielding fruits possessing the desirable morphological characteristics

Entrepreneurial Framework Conditions for the SME Development in Serbia

The SME development in Serbia, like in the most of the Western Balkans countries, shows a significant improvement. Serbia has adopted the SME development policy which is in accordance with the EU policies and is actively engaged on improvement of the business environment in order to foster the SME further expansion. It has moved from the phase of formulating policy and defining strategic objectives to implementing policy, particularly in the field of start-ups, provision of business services and dissemination of information. Analysis of the current framework conditions for the SME sector, and its role and significance, demonstrate considerable enhancements in transition period. However, SMEs in Serbia still face numerous problems, that this sector encounters in its business operating. The analysis of business environment for SMEs in Serbia has been performed through consideration of poll survey Global Entrepreneurship Monitor (GEM) as well as annual reports „SME Policy Index 2007” and „SME Policy Index 2009” which show realized progress in application of the European Charter for Small Enterprises in the Western Balkans with special emphasis on Serbia. The most important findings in the paper suggest that, despite realized progress, business environment in Serbia is still under-stimulating for SMEs development due to certain limitations of legal, procedural and financial nature, whereby defined recommendations for improvement of framework for business operating of SMEs in Serbia have been formulated

HYBRID GPS/SINS SYSTEM - AN OVERVIEW

This paper describes a hybrid navigation system consisting of an integrated GPS/INS system. The integration of the navigation systems has been performed to improve the accuracy of the navigation parameters and it is a current trend in the world. The need for continuous navigation, during the change of position of the GPS receiver, during the closing time of the GPS receiving antenna, and during the appearance of interference, has imposed a solution that is achieved by the integration of GPS / INS. The role of SINS, which is part of the integrated GPS / INS navigation system, is to determine the navigation parameters at intervals between two adjacent measurements of GPS receivers, i.e., at times when there is no GPS navigation information for any reason. In this way, GPS and INS, when used together, complement and correct each other, significantly increasing the reliability and accuracy of the hybrid navigation system

AUTOMATIC GENERATION OF THE PLC PROGRAMS FOR THE SEQUENTIAL CONTROL OF PNEUMATIC ACTUATORS

Nowadays, programmable logic controllers (PLC) are widely used in many automated systems, especially for the control of various actuators. The most common PLC programming is performed by either using a ladder diagram or a structured text. The paper presents the automatic generation of PLC programs for the purpose of sequentially controlling pneumatic actuators. In this paper, the pneumatic actuators are supplied and controlled by 5/2-way as well as 5/3-way bistable pneumatic valves with electric activation. The valve type depends on the number of positions in which the actuator should come, and the position sensors are used for detecting its movement. The characteristic encoding of the movement of actuators, position sensors and control commands is performed. The advantages of the automatic generation of the PLC commands and the entire program described in this paper are illustrated in a real example

Acute kidney damage in pregnancy: Etiopathogenesis, diagnostics and basic principles of treatment

© 2020, University of Kragujevac, Faculty of Science. All rights reserved. Acute kidney damage associated with pregnancy occurs in 1/20.000 pregnancies. In developing countries, the main cause of the development of acute kidney damage is septic abortion, and preeclampsia in the developed countries of the world. Preeclamp-sia is defined as newly developed hypertension, proteinuria and swelling in pregnant women after the 20th week of gestation. It occurs due to disorders in the development of placenta and sys-temic disorders of the function of the endothelium of the mother. It is treated with methyldopa, magnesium sulfate and timely deliv-ery. Urgent delivery is indicated if the age of gestation is ≥ 34 weeks. HELLP syndrome is a difficult form of preeclampsia. Its main characteristics are decreased platelet count, microangio-pathic hemolysis anemia, increased concentration of aminotrans-ferase in the serum and acute kidney damage. Severe HELLP syndrome is treated with emergency delivery, antihypertensives, magnesium sulfate, and in some cases plasmapheresis and hemo-dialysis. Acute fatty liver in pregnancy occurs because of decreased activity of the LCHAD enzyme of the fetus. Due to the reduced beta oxidation of fatty acids in the hepatocytes of the fetus, long chain fatty acids that cause damage to the mother's hepato-cytes are released. Swansea criteria are used for diagnosis, and the difficult form of the disease is treated with plasmapheresis and extracorporeal liver support. Atypical HUS is due to a reduced protein activity that regulates the activity of the alternative pathway of the complement system. Its main features are thrombocy-topenia, microangiopathic hemolytic anemia and acute kidney damage. It is treated with plasmapheresis, and in case of resistance with eculizumab. Thrombotic thrombocytopenic purpura is due to decreased activity of the ADAMTS13 enzyme. It is char-acterized by thrombocytopenia, microangiopathic hemolytic ane-mia, high temperature, nervous system disorders and acute kidney damage. It is treated with plasmapheresis, and severe form of disease with corticosteroids and azathioprine. Early detection and timely treatment of acute kidney damage provides a good outcome for the mother and fetus