Unbalanced magnetic pull in an 18-slot/8-pole dual three-phase machine under different modes of operation

Purpose This paper aims to analyze the emergence and impact of unbalanced magnetic pull (UMP) in an 18-slot/8-pole dual three-phase permanent magnet synchronous machine (DTM) during post fault operation (PFO) and synthetic loading operation (SLO). Understanding UMP in these specific operating modes is important for ensuring mechanical integrity of the electric drive. Design/methodology/approach The authors conducted a series of finite element method (FEM) simulations to investigate UMP under PFO, where only one winding set is active, and SLO, where winding sets are energized in the opposite senses compared to normal operation. They examined the mechanisms leading to UMP and quantitatively assessed its magnitude. Findings The authors' simulations reveal that UMP arises due to interactions between field harmonics with differing spatial orders, specifically the 4th and 5th harmonics during PFO and SLO. The presence of both odd and even harmonics in the machine’s field spectrum is a decisive factor in UMP generation. They found that while UMP increases bearing stress, it does not compromise the mechanical integrity. Research limitations/implications Their analysis is based on FEM simulations and focuses on specific operating modes (PFO and SLO). Future work could explore other slot/pole combinations to generalize the findings. Originality/value This study provides new insights into the behavior of UMP in DTM under non-typical operating modes, contributing to the broader understanding of machine performance and durability.