软启动器的工作原理：
The working principle of soft starter:
软启动器是一种集电机软起动、软停车、
Soft starter is a kind of soft starting and soft stop for motor,
软启动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。待电机达到额定转数时，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，提高其工作效率，又使电网避免了谐波污染。
The soft starter adopts three-phase anti parallel thyristor as voltage regulator, which is connected between the power supply and the motor stator. This circuit, such as three-phase full controlled bridge rectifier circuit. Start the motor using the soft starter, the thyristor output voltage increases, the motor accelerates gradually until the thyristor wholeconduction motor working in the mechanical properties of rated voltage, to achieve a smooth start, reduce the starting current, avoid starting over-current trip. When the motor reaches the rated speed, the startup process end, soft starter thyristor automatic bypass contactor with substituted completion pipe, provide the rated voltage of the normal operation of the motor, to reduce the heat loss of the thyristor soft starter, prolong the service life, improve the work efficiency, but also to avoid network harmonic pollution.
接线方法是要看软启动器的。一般有一拖一，一拖二，一拖多的也有，就是外围线路比较多了。接线图仅仅参考。
Wiring method is to see the soft starter. Generally there is a drag, a drag two, a drag more, there is more peripheral lines. Wiring diagram is only for reference.
变频器里面的功率模块是IGBT，以适合电动机的频率长时间运行；而软启目前多数用的是可控硅元件，通过设置界面设置启动时间和初始电压等参数，一旦启运完成（到工频）后立即跳开软启回路，旁路接触器吸合，接入工频运行。
The inside of the inverter power module is IGBT, suitable for long time operation of the motor frequency; and the soft start most with the SCR by setting the interface to set the start time and the initial voltage and other parameters, once the completion of shipment immediately after the trip (to power) soft start circuit, bypass contactor, access frequency operation.
软启只在低压系统中这样叫，高压电机目前用的比较多的是液体电阻启动器（柜），俗称“水电阻”。功能几乎一样，但是原理不一样。前者通过可控硅调压限流启动，后者通过电阻调压限流启动。
The soft starter is only used in low voltage system, and the high voltage motor is using liquid resistor starter (cabinet), commonly called "water resistor"". The function is almost the same, but the principle is different. The former is started by thyristor controlled voltage limiting current, and the latter is started by resistance voltage limiting current.
