Investigation of winding cooling enhancement and thermal modelling of large‐power high‐torque‐density direct‐drive PMSM

Large‐power high‐torque‐density direct‐drive permanent magnet synchronous motors (LHDPMSM) are more and more frequently used to drive ball mills, belt conveyors, scraper conveyors, etc. Aiming at the characteristics of large copper loss and high winding temperature rise of the LHDPMSM, an effective winding cooling enhancement technology based on winding overall potting (WOP) is presented. The manufacturing process and cooling principle of WOP is described in detail and compared with the traditional vacuum pressure impregnation (VPI). In order to solve the problem of complex modelling process and long calculation time of LHDPMSM thermal field caused by large volume and asymmetric fluid cooling structure, the lumped parameter thermal network (LPTN) considering both fluid cooling and winding potting is proposed. Then, the cooling capacity of WOP and VPI are compared by LPTN, and the influence of some major cooling system parameters on LHDPMSM temperature rise are also researched. Finally, in order to verify the correctness of the theoretical calculation results, two 450 kW LHDPMSM prototypes adopt WOP and VPI are manufactured, tested and compared. The theoretical and experimental results are highly consistent, which proves the effectiveness of WOP in winding cooling enhancement of LHDPMSM.