微机保护装置液晶显示启动回路故障分析

为消除微机保护装置液晶显示屏黑屏故障,通过对微机保护装置液晶显示回路进行检查、试验,查明故障原因是液晶显示启动回路无防感应过电压元件,以及继电器和光耦性能不稳定。结合液晶显示电路板原理,提出了在继电器线圈两端反向并联续流二极管,以及更换为性能更稳定的继电器和光耦的改进措施。改造后液晶显示启动回路未再发生故障,液晶显示屏黑屏问题得以解决,保障了保护装置安全运行。

Analysis of Startup Circuit Fault of Liquid Crystal Display in Macro Computer Protection Device

In order to eliminate the black screen fault of liquid crystal display of computer protection device, the circuit of liquid crystal display of protection device is checked and tested. It is found that reasons of the fault are no anti induced overvoltage element in the startup circuit of liquid crystal display and unstable relay and optocoupler performances. Based on the principle of liquid crystal display circuit board, modification measures are proposed including connecting reverse parallel flywheel diode at two ends of the relay coil and changing more stable relay and optocoupler. There is no fault happened again after the modification of liquid crystal display startup circuit, and the black screen problem of liquid crystal display has been solved, which guaranteed the secure operation of protection device.