Design of n -Layer Flat Wire Winding in Permanent Magnet Machine for Electric Vehicles

In the traditional $2{k}$ -layer ( ${k} =1$ , 2, $3, \ldots $ ) flat wire winding, the number of turns per phase is limited to be even number. It makes the performance pairing between the vehicle and its electric machines difficult, including the dc bus voltage and the torque-speed curve. In this article, the general design method of n-layer ( ${n} =1$ , 2, $3, \ldots $ ) flat wire winding is analyzed for permanent magnet (PM) machines applied in electric vehicles (EVs), including the design of basic connection unit, the elementary branch, and the parallel branch. Apart from the design of even-layer winding, i.e., ${n} = 2{k}$ , the number of winding layers can also be designed as an odd number, i.e., ${n} = 2{k}-1$ , in the proposed design method, which can lower the pairing difficulty between the required torque-speed curve and the dc bus voltage. In addition, compared with the existing even layer design method, the proposed flat wire winding design method can reduce the manufacturing cost by using less flat wire pin types. The proposed design method can support the design of both full pitch winding and short pitch winding. The proposed design method is verified by a finite element (FE) analysis by comparatively analyzing five-, six-, seven-, and eight-layer winding machines having both full and short pitch windings. Both six- and seven-layer full pitch winding PM machine prototypes, which are designed based on the n-layer winding layout, are built and tested to validate the proposed flat wire winding design method.