The most influential factor involved in electrical engineering right from the beginning to the end is "The Power Factor". This may be defined in another way as the COEFFICIENT OF THE VOLT AMPERES. The phase advancing winding may be fed either through a separate supply or through primary or through the secondary terminals. The supply through the secondary terminals may be named as feed back. In that case, the system is said to be a self-contained system, doing (improving its input) some work at the cost of small amount of energy consumed in the phase advancing winding.