The influence of the winding and the meridian section of the core on the magnetic moment of the electromagnet

Abstract

The problem arising in the design of DC electromagnets, which is associated with the limitation of the application of the known methods for calculating the magnetic moment of an electromagnet, is described. The influence of the nonuniformity of the external magnetic field of the magnetizing coil on the magnetic moment of an electromagnet is analyzed to determine the limits of applicability of the assumption of uniformity of the external magnetic field. For this purpose, an iterative algorithm was used to numerically solve the integral equation for the surface density of fictitious magnetic charges on the surfaces of cylindrical elements of the core, considering the nonuniformity of the external magnetic field. It is established that the main cause of the discrepancy between the magnetic moment of the core of the electromagnet and the core, located in a uniform magnetic field, is the degree of nonuniformity of the external magnetic field of the coil, as well as the section of the magnetization curve, which corresponds the strength of the resulting magnetic field for the dominant part of the core. It is indicated that the region of application of the assumption of uniformity of the external magnetic field is limited by a relative core length and level of an external field. The influence of the shape of the meridian section of the core on the magnetic moment of the electromagnet is investigated. For core with washers, an iterative algorithm was used with a partitioning of the core medium into both cylindrical and ring elements to account for the additional edge effect due to the presence of washers. The results of the calculation have shown that their presence makes a significant contribution to the magnetic moment of the electromagnet, sometimes giving growth twice, and the level of contribution depends on the position and size of the washers, as well as on which section of the magnetization curve is the strength of the resulting magnetic field for most of the core in the absence of washers. It is shown that with increasing washer radius and a decrease of the distance from the washer to the ends the magnetic moment of the electromagnet increases, which is more pronounced for short cores and less pronounced for long cores .