METHODOLOGY OF DETERMINATION OF THE OF MULTIFREQUENCY MAGNETIC FIELD LEVEL AT WELDER`S WORKING ZONE
The purpose of this work is to develop a methodology for determination of the total level of multifrequency magnetic field (MF) at the working area of welder by studying the dependences of the magnetizing force of its individual harmonic components to the electrical characteristics of the MF source and welding modes. The study was carried out at a wide frequency range of the MF action for the researching of dependences to MF technological parameters of the contact welding machine and the distance to it. An induction magnetic field sensor and a digital recording oscilloscope with a fast Fourier transform function were used for experimental studies of MF magnetizing force and their spectral ranges. Based on the analysis of the obtained MF oscillograms and spectrograms, the shape and magnitude of the MF magnetizing force signals in different frequency ranges were established. Since it is impossible to quantify the overall level for a multifrequency MF with taking into account all the harmonic components of the MF simultaneously, the generalized magnetic field level indicator (MFI) was proposed, which became the basis for its use as a methodology for the assessment of MF impact on human body. The use of the proposed methodology allowed to establish that it is generated MF with harmonic components in the frequency ranges 5-50 and 50-1000 Hz at working area under contact spot welding, which may exceed their maximum allowed levels, leading to the respective increase of MFI level. It was established that any changes in the mode of contact spot welding, compared to the mode of welding with one batch of full-phase pulses of welding current, lead to the increase in MFI with exceeding of maximum allowed level at a distance of 800-1000 mm from the axis of contact welding machine electrodes; modelling of the front and trailing edges of the pulse lead to the reduction of MFI level, while increasing the angle of phase control of the heating mode leads to the increase of MFI level. The proposed methodology can be applied as universal both for hygienic assessment of the electromagnetic environment during arc welding and for other electrical equipment. The developed methodology gives possibility to assess the overall impact of multifrequency MF on human body. It is based on the known laws of electrodynamics using a new generalized indicator - magnetic field level indicator MFI.
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