Polyphase system

These systems exhibit three-phase induction or more. They operate on the principle of a rotating magnetic field in alternate-current circuits. The most common example being three phase power. Three phase power is commonly found in industrial applications. Normal household supply consists of a sine wave[?] of alternating polarity[?], with the voltage rising and falling over time. The average power delivered is about 60% of the rated voltage, or about 70 volts for 110 volt supplies.

Alternate current sine wave voltage points, when the field is graphed and analyzed, show a result of a magnetic field that is rotating (thus producing the alternating polarity). When a three-phase voltage completes one full cycle, the magnetic field has rotated through 360°. In a polyphase system several such supplies are overlapped out of phase to smooth out the total voltage. In these systems the total power supplied is over 90% of the rated voltage, which is useful for driving high-power motors.

Nikola Tesla discovered these types of systems.