封装工艺对电枢热导率影响的实验研究

In order to meet the demand of various driving structures，electric motors for EVs usually have to make a choice between high speed and high torque. To optimize the high efficiency area of EV motors，multiple armature structures are applied to the motors. Compared with armatures used in static electric facilities，the most notable feature of EV motor armature is that they generally need to be varnished with non-metallic materials. However，few models can reasonably predict the axial thermal conductivity of armatures with the casting process. In this paper，9 common armature structures of motor are studied，including hairpin winding，enameled wire，transposition wire，circular litz wire and rectangular litz wire. A test bench for measuring the axial thermal conductivity is established at first，and a mathematical method for compensating the tolerance of the experimental bench is proposed. Then，the axial thermal conductivity differences of 9 armatures before and after varnishing are tested and compared. Finally，based on the machining methods and experimental results of various kinds of armatures，the mathematical model and empirical formula of axial thermal conductivity for "Parallel Winding " and "Twisted Winding" armatures are presented respectively，considering the influence of varnish process.