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变频器制动电路的工作原理-北京雅培华兴科技有限公司

变频器制动电路的工作原理

发布时间:2022-11-15 浏览数:235

当直流电压Ed超过规定值后,取样与比较电路发出指令信号给驱动电路,驱动功率管VT导通,并以IR=Ed/R(R是Rib或Rb)的放电电流放电;反之,当Ed达到预先设定的某一值时,功率管关断,电容器重新进入充电过程,从而达到直流电压上升的目的。异步电动机再生的电能经逆变电路中并联在每个功率管两端的续流二极管全波整流后反馈到直流电路,由于直流电路的能量无法回馈电网,仅靠滤波电容CF1、CF2吸收,此时尽管各部分电路还在继续消耗电能,但CF1、CF2上仍有短时间的电荷堆积,形成“泵生电压”,使直流电压升高,过高的直流电压将损坏部分元件。为避免直流电压过高,当直流电压上升到一定值时,就通过制动电阻将再生的电能消耗掉,同时使直流电压下降,当下降到一定值时就自动切除。对于频繁启动、制动、正反转的设备而言,制动电阻发热严重,应该慎重选择制动电阻的阻值和功率容量。新型的变频器内设置了直流电压自动调节功能,当异步电动机工作于发电状态,使直流电压超过极限值时,变频器将提高制动转矩以防止过电压;当需要使用制动斩波器和制动电阻时,则应关闭此功能,