Single-phase and three-phase AC squirrel cage induction motors need some type of circuit to initiate a start or stop function. Usually single-phase motors and smaller horsepower three-phase motors can be started with full voltage across the line. However, larger horsepower three-phase motors require reduced voltage starting techniques.
<a href="http://iaeimagazine.org/magazine/category/2012/may2012/">IAEI May-June 2012</a>
SCCRs are required to be marked on industrial control panels and other equipment in accordance with the product standards and theNEC. The SCCR for components typically is determined by testing.