The basic difference between soft starters and VFDs is that the VFD is used to achieve control over the motor speed whereas the soft starter is used for reducing the inrush current. Variable frequency drives and soft starters are energy-efficient devices....
Soft starts, or reduced-voltage soft starters (RVSS), are also able to step a motor up gradually, but drives can be programmed to ramp up the motor much more gradually and smoothly, and can operate the motor at less than full speed to decrease wear and tear. Variable speed drives can ...