1, frequency aspects:
The output frequency of the soft starter is fixed to the power frequency and the frequency is not adjustable. The frequency converter is adjustable for the output frequency.
2 、 voltage aspect:
The soft starter controls the output voltage by controlling the turn-on angle of the thyristor (or other power electronic component), and the output voltage is slowly increased from 0V to the rated voltage. The voltage of the converter is adjustable.
3 、 motor speed:
The soft starter can not adjust the motor speed; the frequency converter can adjust the motor to run at any speed.