Influence of massive ferromagnetic shaft on the distribution of electromagnetic field and magnetising current for two- and four-pole induction motors at frequencies of 50 and 200 Hz

Abstract

In this study, the authors aimed to analyse the influence of massive ferromagnetic shaft on the distribution of the electromagnetic field and to evaluate the magnetising current from the mains. To achieve this, they used motors powered by 50 and 200 Hz. They also used both numerical two-dimensional (2D) and 3D field-circuit methods as well as an analytical method based on the results of field analysis. This modified analytical method is based on the magnetisation characteristics of the shaft's material. According to the results, there was a significant impact of shaft's saturation on the machine with one pair of poles in the form of a significant increase in the amplitude of induction in the rotor yoke, which resulted in an increase in the magnetising component of the current drawn by the motor from the grid. This phenomenon was found to increase, in particular, when using non-magnetic shafts. In the case of machines with two pairs of poles, this effect was found to be much smaller than that of one pair of poles. They verified the results experimentally by comparing the calculated and measured magnetising currents.