Abstract: According to the current development trend of pure electric vehicles and the increasing number of pure electric vehicle failures, it aims to strengthen the mastery of the structure and principle of pure electric vehicles by ordinary maintenance personnel. First of all, the article analyzes the control relationship between the high-voltage system of pure electric vehicles, and analyzes the control logic of the high-voltage power-on process of Geely Emgrand EV450 model in detail. According to the mastered logic of high-voltage power-up control, it is mainly divided into five categories: high-voltage interlock disconnection failure, high-voltage contactor adhesion failure, vehicle controller failure, battery management system failure, and motor controller failure. Finally,according to the actual case of Geely Emgrand EV450, it analyzes the possible causes of the failure of the high-voltage system to power. The analysis process is mainly through the owner's description of the fault phenomenon, the recovery of fault phenomenon and the fault code displayed by the fault diagnosis instrument for diagnostic trouble code (DTC) analysis. It is confirmed that it is a vehicle control unit (VCU) power supply failure or VCU's own fault, and then the VCU power line is tested. After testing and analysis, it is confirmed that the cause of the high-voltage failure is +B power supply fuse damage. Therefore, when troubleshooting and analyzing, you not only have a good understanding of high and low voltage electronic control, but also master the control logic between vehicle control unit, battery management system, motor control unit and other systems.In case of failure, you can comprehensively judge the fault range according to the fault phenomenon and fault code.

Key words: Pure electric vehicle; High voltage power-on; Vehicle controller; Motor controller; Fault analysis

摘要： 根据当前纯电动汽车发展趋势以及纯电动汽车故障数量不断增加的现象，旨在加强普 通维修人员对纯电动汽车结构与原理的掌握。文章首先对纯电动汽车高压系统之间控制关系 进行了分析，并对吉利帝豪 EV450 车型整车高压上电流程控制逻辑进行详细分析。根据掌握 的高压上电控制逻辑总结造成高压系统不上电故障的类型，主要分为高压互锁断开故障、高 压接触器粘连故障、整车控制器故障、电池管理系统故障、电机控制器故障五大类。最后根 据吉利帝豪 EV450 实际案例分析造成高压系统不上电故障的可能原因，分析过程主要通过车 主描述故障现象、故障现象复原以及故障诊断仪显示故障码进行故障码（DTC）分析，确认 为整车控制器（VCU）电源故障或 VCU 自身故障，然后对 VCU 电源线路进行测试，经过测 试分析，确认造成高压不上电故障的原因为+B 电源熔丝损坏。因此，故障诊断分析时，不仅 对高低压电控都非常了解，还要掌握整车控制单元、电池管理系统、电机控制单元等系统之 间的控制逻辑，出现故障时，根据故障现象和故障码，综合判断故障范围。

关键词: 纯电动汽车；高压上电；整车控制器；电机控制器；故障分析