Abstract of master's work on theme:

"Voltages calculation in the electrical networks, by which resistance spot-welding machines are supplied"

        Introduction

        Resistance spot-welding machines (RSWM) cause serious difficulties when they are supplied by electric energy. They are working in a repeated-short-term mode and creating graphs of the load in the form of alternating rectangular peaks during welding and pauses. RSWM has short (till the several periods) impulses of the current. They are reaching thousands amperes with a low factors of inclusion and utilization. In these cases the main requirement to maintenance department network is a voltage supply, which is practically excluding faulty fusion of contact, i.e. marriage of production.
        The basic problem in RSWM electrosupply is correct calculation of their electric loadings. The network by which RSWM are supplied must correspond to basic requirements: 1) admissible temperature of heating; 2) admissible value of of voltage losses. The second of specified above conditions is rendering main influence on technology and quality of welding and also on electric power charges.

        The urgency of the given development, namely exact method of voltages calculation in the electrical networks, by which RSWM are supplied is caused by quickly growing using of contact electric welding.

        The purpose of work - development of an exact method of definition of a voltage deviation on RSWM clips and a peak current in a network of their feed, which can arise with the set probability.

        Voltages calculation in the electrical networks, by which resistance spot-welding machines are supplied

        It is necessary to calculate function of voltage distribution in the end of a bus duct to determine of voltage losses in a network with RSWM. Therefore it is necessary to execute calculation of voltage losses and peak currents for all variants of simultaneous inclusion RSWM.
        It is offered to count only a site of function of distribution (fig. 1) to reduce amount of calculations, that from the set probability . The least voltage in the end of bus duct corresponds to a case when all n of machines are included simultaneously.
        Probability of this case:
,
        where - inclusion factor of i contact welding machine.
        Process lasts until the condition will be reached:
,
        where k - quantity of steps of distribution function;
        - safety factor, which considers necessity of calculation of a site of distribution function with the certain spare. It is connected by that it is impossible to determine without performance of calculations at what quantity and which included RSWM we will receive the next step of distribution function.
        Further the part of steps of distribution function is necessary to ordering on increase of a voltage up to the most remote from power supply RSWM and to define a voltage on it with probability .

Figure 1 - Voltage distribution function
        For such approach application of specially developed program for definition of currents and voltage of each site of a network is necessary at any quantity connected one, two and three phase machines of different power.
       Initial data for this program are rated power of RSWM , active and reactive specific bus duct resistance and , rated voltage , power factor and distance L from RSWM up to the power supply.
        Calculation is more convenient for executing one of matrix methods. The method of calculation with Ohm`s and Kirchhoff`s laws are used in the program. The algorithm of automatic formation of matrixes of connections П, contours Г, and also matrixes of resistance Z, vector EMF E and vector of current sources is offered.
        The decision of system of the linear equations in a matrix appearance:

        gives a voltage U and currents I of sites of a network.

       Is it presented graphic modeling to network and possible change voltages level on RSWM, which powered from bus-duct on voltage 380 V. Program provides the calculation of the voltages on machine of the resistance contact welding machine (one-, two- and three-phase) under any their connection to bus-duct.

        Conclusions

        The new, theoretically proved method of the definition of loading impulse and of voltage losses with the program of voltages calculation in the electrical networks, by which RSWM are supplied is offered.
        Practical value of work consists that the given method of voltages calculation allows quickly enough and with necessary accuracy to settle an invoice loadings for any types of RSWM and automatic product lines.

        References

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