Selective coordination of the emergency system is intended to provide a high level of reliability and continuance of supply needed for systems providing emergency functions.
One of the most basic calculations for any power system, and arguably the least understood and most misrepresented, is the calculation of available fault current.
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>