Thermal Deformation Analysis of Water Cooling Doubly Salient Brushless DC Generator With Stator Field Winding

Abstract

Thermal deformation changes the length of a variable reluctance machine's air gap; this change has a significant effect on the machine's power density and efficiency. The variable reluctance machine usually has a small air gap, which may cause scrapping failure (due to thermal deformation). Therefore, it is necessary to study the influence of thermal deformation on air gap length in order to avoid scrapping failure and to choose an optimal air gap length. The doubly salient brushless dc (DSBLDC) generator is a variable reluctance machine with stator field winding. Water cooling is the usual method for cooling a DSBLDC generator (as all excitation sources are mounted on the stator). In this paper, a water-cooling DSBLDC generator is employed to analyze thermal deformation. First, the configuration of the DSBLDC generator is introduced and the thermal distribution characteristics of the water-cooling DSBLDC generator are given. Second, the DSBLDC generator is separated into a yoke and pole in order to investigate its thermal deformation. A theoretical calculation model and a three-dimensional finite-element model are then proposed to analyze the thermal deformation. The influence of thermal deformation on the stator, rotor, and air gap length is further analyzed under different temperature distribution conditions. Finally, thermal deformation's influence on output performance is discussed and the calculation and analysis of thermal deformation are verified through experimental results.