Monte Carlo Analysis of Circulating Currents in Random-Wound Electrical Machines

Abstract

Electrical machines with stranded random windings often suffer from considerable circulating current losses. These losses have been poorly studied because of the difficulty and computational cost of modelling stranded windings, and the stochastic nature of the problem due to the uncertain positions of the strands. This paper proposes two methods to model random stranded windings of arbitrary complexity. Firstly, a circuit model considering the entire main flux path is presented, and some practical implementation considerations are discussed. Secondly, a computationally efficient finite element approach based on non-conforming meshing is presented. Finally, a method is proposed to model the random packing process of strands within a slot, without any re-meshing or inductance re-calculation required. The proposed methods are then compared to special no-rotor measurement data of a large number of high-speed induction machines, and a good agreement is observed.

Reduced Basis Finite Element Modeling of Electrical Machines with Multiconductor Windings

“…As Fig. 6(a) reveals, the largest losses can be found near the borders between winding turns, due to the circulating current effects [9]. The error in losses -compared to the reference solution -has been plotted in Fig.…”

“…However, these studies have mostly focused on purely series-connected coils, or idealized Litz wires. By contrast, the scarce research on circulating currents has mostly ignored the proximity effects [9]- [12]. Some brute-force and analytical approaches have also been studied, typically with problems with relatively few conductors [13]- [21].…”

High-Speed Electric Drives: A Step Towards System Design

“…This phenomena is strictly related to the real positions of the strands inside the slot and becomes important when random wound winding are adopted as in this case study. Different works have addressed the evaluation of circulating currents both analytically (essentially based on circuital approach) [31] and FE study [32]. In this work, a FE simulation considering the worst case scenario in terms of conductors distribution within the slot has been carried out in order to estimate the resistance factor (k ac/dc = R ac /R dc ) as function of the frequency.…”

Domain Decomposition Approach for Efficient Time-Domain Finite-Element Computation of Winding Losses in Electrical Machines

“…or ignored the proximity effects altogether [10]- [19]. Some analytical methods have also been studied, along with bruteforce approaches [20]- [23].…”