Spot welding machines (RSWM) are widely used in industry, and they accounted for more than 40% of all welded joints. RSWM high power, working in the repetitive short-time, cause serious difficulties in feeding their electrical energy, because they create graphics load in the form of alternating rectangular peaks during welding and are characterized by short pauses (up to several periods) current pulses, reaching hundreds of amps at low coefficients of inclusion and, consequently, low load factor. In these cases, the basic requirement for backbone network is to shop on the findings of any car included the nominal tension, in order to exclude the lack of penetration of contact, ie spoilage.
The relevance of this development, due to the fact that the rapidly growing use of resistance welding, there is a need to reduce the capital cost of the network supplying the group of welding machines, by developing a more accurate method to calculate the peak current and voltage deviation on the terminals RSWM, because the patched existing techniques based on the approximate calculation of peak currents and voltage fluctuation, which leads to errors and need to choose a power line with a certain margin with inflated capital costs for network itself.
Objective-efficiency power supply system of welding machines, by reducing the capital cost of the network, provided that the required voltage level, by developing a more accurate method of determining the peak currents and losses of tension.
[17] to reduce the volume of calculations suggested that the definition of the limits of the intervals of possible values of peak currents and losses of tension on the boundary (maximum and minimum) distribution functions. Proposed solution for the case of supply of welding machines connected to the busbar unramified. In the method of calculation is provided with current and tension in all the branches for any group of welding machines and inspection of all the options including welding machines with the definition of probability.
To calculate the currents and voltages of all branches of the electrical network used Ohm's law and Kirchhoff. Since the calculation of the distribution function of peak currents and voltage drops definition of currents and tension must be performed repeatedly for different groups included welding machines with different number of phases, capacity, distance from the power source, the algorithm of automatic generation of matrix compounds, circuits, resistors, EMF vector.
The idea of the method of boundary distribution function is that in order to reduce the amount of mortar on the distribution functions for all the welding machines are divided into 7 groups (level) depending on the number of phases and the phases connected to any welding machine:
- Single-phase, connected to the phases of AB; BC; CA - three groups;
- Two-phase, connected to the phases AB, BC; BC, CA; CA, AB - three groups;
- Three-phase ABC.
In calculating the distribution functions will be further considered, not all possible combinations including welding machines, and all possible combinations include a different number of machines of the groups, this would reduce the amount of mortar on the distribution function. When performing calculations for the abscissa limits (maximum and minimum) of the distribution functions of peak current and voltage loss for each combination of the number of machines included in the group calculation is performed twice: for the most powerful welding machines from each group - get the maximum distribution function and for welding machines lowest power - this information is necessary for minimum distribution function.
-All ISS distributed over the phases of the network that sustains them.
- Runs the distribution of ISS for groups depending on the number of phases and on whether the line tension is connected to a welding machine;
- In each group of welders are sorted in ascending power;
- Calculate the distribution function of the number of cars included and it is determined by the number of simultaneous operation of machines, the probability above which no more than a specified maximum likelihood;
- Calculate the peak current and losses of tension for all possible options include welding machines of the formed groups with the total number of machines from one up 
. Moreover, peak currents and losses of tension are calculated for two limiting cases: when the group includes a certain number of welding machines most power and the smallest respectively the maximum and minimum distribution function. The results of calculations (peak current, losses of tension, together with the probability of their occurrence) are stored in the corresponding tracts;
- Perform sorting calculation results in ascending order of peak currents and losses of tension and calculated plots of maximum and minimum distribution functions of these quantities (for the amount included welding machines from 1 to ) subject to stage of the distribution function that corresponds to the case when all the welding machines are disabled;
- The obtained distribution functions are determined by the maximum payment (the minimum and maximum limit distribution function) the value of peak currents and losses of tension. Thus, the proposed method provides a reliable range of the maximum calculated values of peak currents and losses of tension in the network, feeding a group of resistance welding machines with given probability.
In the master's work is expected to improve and test proposed in [17] method. Modification of the algorithm would be that in calculating the areas of distribution functions of peak currents and losses of tension of each group of welding machines to calculate the losses of tension and peak currents will be chosen randomly welding machines, unlike previously proposed a method in which to calculate the boundary of the distribution functions undertook the smallest machines (for the minimum distribution function) or most (maximum distribution function) of power. The legitimacy of such an approach can be proven for a relatively small number of welding machines (16-20) since an increase in the number of welding machines is necessary to consider the large number of options for their simultaneous operation and calculation of time-consuming. In this paper, a comparison between the effectiveness and accuracy of the proposed method with existing guidelines [3] and the methods proposed [2,13-16].
