> 50 or 60 Hz AC, especially 3-phase, makes it really easy to build and operate electric motors, too Three-phase motors are never used in residential settings,

> 50 or 60 Hz AC, especially 3-phase, makes it really easy to build and operate electric motors, too Three-phase motors are never used in residential settings, and most residential motors would be more efficient as brushless DC. There's no need for sinusoidal AC motors any more except in specialized industrial applications.