Influence of Rotor Geometry on the Circulating Currents of a Delta Connected Electrical Machine 2022-28-0330
The increase in demand of electric vehicles leads to increased concentration towards the performance and stability of the electrical machines used. Compared to other electrical machines, the permanent magnet synchronous machines (PMSMs) are predominantly used in electric vehicles, due to its high efficiency and power density. The permanent magnets are generally placed in different configurations (like V-shaped, U-shaped, etc.), to achieve the required performance characteristics. But these non-linear arrangement of magnets leads to unbalanced flux linkage in the stator windings. This unbalanced flux linkage in different phase windings induces unbalanced back-emf, which results in unbalanced currents (generally termed as circulating currents). In case of star connected machines, these circulating currents are balanced with the help of neutral connection. Whereas these circulating currents are inevitable in delta connected machines, which leads to increased copper losses. This increase in copper losses affects the performance of the machine, rises the heat generation, and may also lead to demagnetization risks. In this paper, with the help of 140kW PMSM, the circulating currents are investigated. Also, a simple and effective method is introduced to reduce the circulating currents to a greater extend.