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Abstract: The paper deals with the dynamics of a resistance spot welding system. At the core of this system is a transformer, which is powered on the primary side by a pulse-width modulated inverter and has a full-wave output rectifier on the secondary side that provides a direct welding current. The entire system is nonlinear, due to magnetic hysteresis and electronics. The electronics prevent the current from flowing in all parts of the welding transformer at separate time intervals during the voltage supply period; therefore, not all the parameters affect the dynamic of currents and voltages all the time so the system is also time-variant. To design a high-performance welding system and to predict the maximum possible welding current at a specific load, it is necessary to know the welding and primary currents. The leakage inductances of the system can reduce the maximum welding current significantly at higher frequencies and the same load. There are several methods to determine these currents, each with its drawbacks. Measurements are time-consuming, using professional software is expensive and requires time to learn and free open-source software has many limitations and does not guarantee the correctness of the results. The article presents a new, fourth option—a theoretical derivation of analytical expressions that facilitate straightforward and rapid calculation of the welding and primary currents of the resistance spot welding system with symmetrical secondary branches. The derivation of the mathematical expressions is based on the equivalent circuits that describe the system in different operating states. The results of the numerical simulations confirmed the derived expressions completely.
Keywords: DC–DC converters, pulse width modulation (PWM), welding transformers, center-tapped transformers, full-wave rectifier, resistance spot welding (RSW), leakage inductance, analytical modeling, time-variant system, equivalent circuit
Published in DKUM: 08.08.2024; Views: 77; Downloads: 17
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Abstract: Background/Purpose: An effective financial system should increase the efficiency of economic activities. This study provides evidence regarding the importance of financial development for agricultural growth in Ukraine. Methodology: We used non-integrated and integral indicators, time series and regression analysis to investigate the link between the financial development and agricultural growth. Results: The results based on integral indicators shows that the financial development does not affect agricultural growth in Ukraine. The study based on non-integrated indicators, which characterizes various aspects of the financial system’s banking component and agricultural growth, provided a significant link between the financial system and agriculture growth. The regression models revealed if bank deposits to GDP (%) increases the value added per worker in agriculture increases exponentially. The results of the study indicate that, agriculture is more sensitive to lending changes than the vast majority of other sectors of the economy. The increasing lending of one UAH (Ukrainian hryvnia) resulted in retail turnover growth of 1.62 UAH, while agricultural gross output, growth was UAH 5.06. Conclusion: Our results reveal a positive relationship between financial system’s banking component and agriculture growth in Ukraine. The results indicate the necessity for continued research into further developing universal methodological approaches of appraising the nexus of the financial system’s banking component on agriculture growth in general as well separate farm groups. The results of our study has important implications on policy making authorities efforts to stimulate agricultural growth by improving the efficiency of the financial system’s banking component.
Keywords: agricultural growth, the integral indicator of the agricultural growth, the integral indicator of the financial development, time series analysis, regression analysis, financial system
Published in DKUM: 04.05.2018; Views: 1477; Downloads: 397
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Abstract: V diplomskem delu sem predstavila optimiranje dobavne verige v podjetju EUREL Poljčane. Prvi del diplomskega dela predstavlja teoretična izhodišča, ki se nanašajo na uvajanje t.i. vitke proizvodnje, metode za uvajanje vitke proizvodnje ter principe vitkih podjetij. Opisala in opredelila sem pojem upravljanje dobavne verige, vrste dobavnih verig, globalne dobavne verige, optimiranje dobavne verige, model integracije dobavne verige, ovire pri njihovi integraciji, ključne procese v njej ter opredelila bodoče trende in usmeritve na področju optimiranja dobavnih verig. V empiričnem delu sem predstavila podjetje B/S/H Hišni aparati, osnovne podatke o podjetju, kratek zgodovinski oris podjetja, proizvodni program ter politiko in strategijo podjetja. Praktični del diplomskega dela se nanaša na optimiranje dobavne verige v podjetju EUREL Poljčane. Ta del je pravzaprav raziskovalno delo, saj je bil projekt izveden pilotno in je predstavljal osnovo za izvedbo nadaljnjih projektov optimiranja dobavnih verig vseh dobaviteljev v žarišču. Pri projektu so sodelovali tudi zunanji strokovnjaki, ki so nas usmerjali pri izvajanju različnih analiz: mapa/zemljevid vrednostnega toka, analiza vrednostnega toka, design vrednostnega toka. Izdelane analize so nam služile kot osnova za izdelavo akcijskega načrta, plana implementacije ter za dejansko implementacijo bodočega stanja. Zadnji korak optimiranja dobavne verige zajema kontrolno fazo, ki je namenjena prikazu in ovrednotenju rezultatov. Rezultati oz. koristi, ki izhajajo iz implementiranih izboljšav, se partnersko delijo med ključne udeležence dobavne verige.
Keywords: Upravljanje dobavne verige, vitka proizvodnja, mapa vrednostnega toka, analiza vrednostnega toka, design vrednostnega toka, Toyotin proizvodni sistem, Just in Time, Jidoka (neodvisen, samoupraven, avtonomen), Kaizen (aktivnosti nenehnega izboljševanja), tok proizvodnje, Pull-System (material je "povlečen" na delovno mesto), Outsourcing (zunanje izvajanje dejavnosti), Lead Time (časovna perioda med prejemom naročila odjemalca in dobavo končnega proizvoda odjemalcu), MRP-Material Requirements Planning (p
Published in DKUM: 25.05.2010; Views: 6328; Downloads: 565
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