The difference between soft starter and frequency converter

Update:10 Nov 2018
Summary:

The soft starter is a novel motor control device that i […]

The soft starter is a novel motor control device that integrates motor soft start, soft stop, light load energy saving and various protection functions. It is called Soft Starter in foreign countries. Its main component is a three-phase parallel thyristor connected in series between the power source and the controlled motor and its electronic control circuit.

Different methods are used to control the conduction angle of the three opposite parallel thyristors, so that the input voltage of the controlled motor changes according to different requirements, and different functions can be realized.

Soft starters and frequency converters are two completely different applications. The inverter is used for speed regulation. The output not only changes the voltage but also changes the frequency. The soft starter is actually a voltage regulator. When the motor starts, the output only changes the voltage and does not change the frequency. The frequency converter has all the soft starter functions, but it is much more expensive than the soft starter and the structure is much more complicated.