Search the digital library catalog

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: 25
Full text (6,72 MB)

Abstract: Mountain regions are important producers of organic food. For them, reliable decision making regarding business planning necessitates different critical support methods. KARSIM 1.0 (DSM) is a methodology based on an integrated deterministic simulation system application for decision-making support, consisting of 74 deterministic production simulation models. DSM enables different types of cost and financial feasibility calculations for organic production and food processing. KARSIM 1.0 was used to simulate three specific business alternatives for mountain organic farms. (Alternative 1: spelt grain, fruit cider, wine and brandy, plum brandy, calves meat and sheep-soft cheese production, Alternative 2: spelt flour, pear and apple juice, plum brandy, veal and sheep's milk, Alternative 3: spelt grain, dried fruit, calves, soft and hard sheep cheese). Simulation model results were compared using two multi-objective analysis methods: the analytical hierarchical process (Expert Choice Decision Support System software) and DEX-i method. the results showed the bigest multi-objective decision evaluation for alternative 2 (Expert Choice = 0.361 and DEX-i evaluation = excellent). We can conclude that the combination of a deterministic cost simulation model and multi-criteria decision analysis present an acceptable decision support tool for mountain organic farms; however, further research is desirable.
Keywords: simulation modeling, KARSIM 1.0, MCDA, DEXži, analytical hierarchical process, mountain organic farms
Published in DKUM: 05.06.2012; Views: 2345; Downloads: 139
Link to full text