Get more lessons like this at http://www.MathTutorDVD.com Here we learn why 3 Phase Power systems are useful for supplying large blocks of electricity and for supplying power to rotating motors. We learn that when you calculate the total power delivered to a motor over the three phases, the total power is constant even though each phase has a time varying power component. This means that the motor will run more smoothly with less vibration and is why in practice three phase motors are commonly used in industrial equipment.