140DDO15310 仁怀县
电流型工作原理是整流电路将电网来的交流电转换成直流电;再经三相桥式逆变电路转变为频率可调的交流电,供给推进电动机,电流型变频器的直流中间环节,采用大电感滤波。
电压型变频器与电流型变频器同属于交一直一交变频器,也由整流器、滤波器、逆变器三部分组成。工作原理也是整流电路将电网来的交流电转换成直流电;再经三相桥式逆变电路转变为频率可调的交流电,供给推进电动机,电压型变频器的直流中间环节采用大电容。
软启动的电压由零慢慢提升到额定电压,这样电机在启动过程中的启动电流,就由过去过载冲击电流不可控制变成为可控制。并且可根据需要调节启动电流的大小。电机启动的全过程都不存在冲击转矩,而是平滑的启动运行。
软启动器(soft starter)是一种集电机软起动、软停车、多种保护功能于一体的新颖电机控制装置,国外称为Soft Starter。它的主要构成是串接于电源与被控电机之间的三相反并联晶闸管及其电子控制电路。运用不同的方法,控制三相反并联晶闸管的导通角,使被控电机的输入电压按不同的要求而变化,就可实现不同的功能。软起动器和变频器是两种不同用途的产品。变频器是用于需要调速的地方,其输出不但改变电压而且同时改变频率;软起动器实际上是个调压器,用于电机起动时,输出只改变电压并没有改变频率。变频器具备所有软起动器功能,但它的价格比软起动器贵得多,结构也复杂得多。电动机软起动器是运用串接于电源与被控电机之间的软启动器,控制其内部晶闸管的导通角,使电机输入电压从零以预设函数关系逐渐上升,直至启动结束,赋予电机全电压,即为软启动,在软起动过程中,电机起动转矩逐渐增加,转速也逐渐增加。
软启器采用三相反并联晶闸管作为调压器,将其接入电源和电动机定子之间。这种电路如三相全控桥式整流电路。使用软启动器启动电动机时,晶闸管的输出电压逐渐增加,电动机逐渐加速,直到晶闸管全导通,电动机工作在额定电压的机械特性上,实现平滑启动,降低启动电流,避免启动过流跳闸。待电机达到额定转速时,启动过程结束,软启动器自动用旁路接触器取代已完成任务的晶闸管,为电动机正常运转提供额 定电压,以降低晶闸管的热损耗,延长软启动器的使用寿命,其工作效率,又使电网避免了谐波污染。软启动器同时还提供软停车功能,软停车与软启动过程相反,电压逐渐降低,转速逐渐下降到零,避免自由停车引起的转矩冲击。
HP OMNIBOOK XE3 13.3" LAPTOP LCD DISPLAY LG LP133X7
HP InfiniBand Dual Port 380299-B21
HP E4208C SCSI DISK MODULE HP 75000 SERIES C
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