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Vol. 26 (2023 year), No. 4, DOI: 10.21443/1560-9278-2023-26-4

Petrov A. R., Gracheva E. I., Valtchev S.
Study of technical parameters of magnetic starters and switches installed in workshop networks

The study of technical parameters of low-voltage switching devices of Russian production – magnetic starters PML and switches RE19 has been carried out. The problem of evaluating energy efficiency of operation of magnetic starters and switches installed in in-plant power supply systems has been presented. The main destabilizing factors significantly affecting the technical characteristics of switching devices with voltage up to 1 kV have been given. Reliability of functioning of the investigated devices, first of all, depends on the degree of wear of switching contacts. The dependences of the heating temperature of the contact areas of switching devices on the loading coefficient have been studied. It has been revealed that with the increase of loading of devices in the range from 1,0 to 2,0Inom the temperature of contacts and contact areas is within the permissible limits in accordance with the requirements of GOST 403-73. The main factors influencing the resistance of contact connections – current flowing through the contacts, their dimensions and heating temperature – have been shown. According to the results of theoretical and experimental studies approximating functions of dependences of resistance of contacts and contact connections of switching devices on rated current have been developed and errors of the calculated method of contact resistance estimation have been determined. The developed dependencies can be used to determine the equivalent resistance of networks of in-plant power supply when estimating the level of power losses, which will increase the reliability of the results obtained.

(in Russian, стр.11, fig. 5, tables. 4, ref 25, AdobePDF, AdobePDF 0 Kb)

Vol. 27 (2024 year), No. 4, DOI: 10.21443/1560-9278-2024-27-4

Petrov A. R., Gracheva E. I., Miftakhova N. K.
Improvement of the methodology for assessing power losses in in-plant power grids

To improve the reliability of calculations of electric power losses in low-voltage electric networks, it is necessary to take into account the influence of the main parameters of electrical equipment. In the course of the study, a structural diagram and an algorithm for determining the equivalent resistance of the section of the shop network have been proposed; the main factors determining the equivalent resistance of the circuit (resistance of low-voltage switching devices, heating temperature of conductors, ambient temperature, equipment load factor) have been identified; graphical dependencies of the change in the equivalent resistance of the radial and trunk sections of the circuit on the mean square equipment load factor and the heating temperature of conductors have been shown. The total error in estimating the equivalent resistance when calculating without taking into account the main studied parameters of equipment for radial, trunk and mixed circuits is 40 % or more. The error in the results of calculations without taking into account the resistance of contact connections of switching devices can reach 80 %. The obtained dependencies of the equivalent resistance on the main parameters of the equipment are recommended for use to improve the reliability of estimating electric power losses in intra-plant electric networks.

(in Russian, стр.10, fig. 4, tables. 4, ref 17, AdobePDF, AdobePDF 0 Kb)