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.
The soft starter is only used in low voltage system, and the liquid resistor starter (cabinet) is commonly used in piezoelectric motor, which is 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.