煤矿低压开关相敏保护器设计

摘要

针对煤矿供电系统保护中短路故障过流和电动机起动过流判别问题,设计了基于STM32芯片定时器信号输入捕获功能的相敏保护器.通过实验分析,得到异步电动机起动的功率因数判别值为0.4 ～0.5.硬件电路将系统电压和电流信号相位关系转换为方波,输入定时器引脚,定时器对方波相邻边沿进行捕获,获得电压和电流信号相位差的电平持续时间,从而得到系统功率因数.经测试,保护器能准确测量系统的功率因数,利用判别值实现短路故障和电动机正常起动的判别.%In order to solve the over-current discriminate problem between the short circuit fault and motor starting in coal mine power supply system protection,designed a phase-sensitive detection protector based on the function of signal input capture in the timer of the STM32 chip.Through the experiment and analysis,the power factor discriminate value of asynchronous motor starting was set 0.4 ～ 0.5.The phase relationship of system voltage and current input to the timer pin as square wave converted by hardware circuit.The timer capture the adjacent edge of square wave get level last time,acquire the level duration of the phase difference between voltage and current signals,obtained the system power factor.Tested by the experiment,the protector can accurately measure the power factor of system and use discriminate value realizes the discretion of short circuit fault and the normal starting of motor.