Figure 2. A simple sine wave with a period of 360° and an amplitude of 1. In single phase power the x-intercepts are 180° from each other. A full period is 360°. A single phase motor has a crest approximately every 16.5 milliseconds giving the motors a tendency to vibrate more, which may contribute to a shortened bearing life.
3800 Series, Single Stage End Suction
80 Series® Engine Driven
Figure 3. Three phase power has three identical sine waves overlapping at an offset of 2π/3 radians or 120°. When one phase reaches an x-intercept or node the next phase is only 30° and approximately 5.6 milliseconds from reaching its crest.
