This calculator sizes a soft starter for a low-voltage AC induction motor based on motor full-load current (FLA), application duty class, and environmental conditions, then verifies the chosen device against three independent sub-tracks: rated current adequacy, AC-53a duty code. This calculator sizes a soft starter for a low-voltage AC induction motor based on motor full-load current (FLA), application duty class, and environmental conditions, then verifies the chosen device against three independent sub-tracks: rated current adequacy, AC-53a duty code. With a soft starter limiting current to 300% FLA: That is a reduction of 245 A — less than half the DOL inrush — on the supply feeder. Voltage dip during motor starting depends on feeder impedance. For a simplified estimate: Given: A nearly 30% voltage dip on a shared busbar is severe — enough to. This is a five-in-one professional toolkit. It covers VFD sizing, soft starter sizing, brake resistor calculation, EMC filter selection, and enclosure selection, all in one place, free, with brand model recommendations from ABB, Siemens, Schneider Electric, Rockwell Automation, and others I've. How to choose a distribution box of the right size for a project based on load current? If you're like most electrical professionals, picking the right distribution box for your project can feel like navigating a maze. In addition to superior starting performance. How to select soft starter capacity In principle, soft starter size should be larger than that of the motor being driven. The rated capacity of the soft starter is usually chosen according to two nominal values, one is corresponding motor power, another is maximum allowable working current of soft.