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.
1、频率方面：
1, frequency aspects:
软启动器的输出频率固定为电源频率，频率不可调；变频器是输出频率可调。
The output frequency of the soft starter is fixed as the power frequency and the frequency is not adjustable; the frequency converter is adjustable output frequency.
2、电压方面：
2, voltage aspects:
软启动器通过控制可控硅（或其他电力电子元件）导通角来控制输出电压，其输出电压由0V慢慢升到额定电压；变频器的电压是可调的。
The soft starter controls the output voltage by controlling the turn-on angle of SCR (or other power electronic components), the output voltage rises from 0V to the rated voltage, and the voltage of the converter is adjustable.
3、电机速度方面：
3, motor speed aspects:
软启动器不可调节电机速度；变频器可以调节电机在任何速度运行。
The soft starter can not adjust the motor speed; the frequency converter can adjust the motor running at any speed.
