There has always been a need for an electric motor that could be used efficiently in portable solutions and could operate at any frequency from different power sources, or rather at different voltage levels.
The universal motor is for its construction qualities, an engine made up to 3/4 HP power, and on idle show a high speed, requiring the appropriate gear system to prevent this from happening. They can still operate effectively at any frequency, at various voltage levels, and are used in electric shavers, sewing machines, drills, hair dryers, vacuum cleaners, etc. VPS-228
The universal motor was designed for commercial frequencies alternating from 0 to 60 Hz and for voltages from 1.5 to 250 V. It has the rotor in series with the stator coil, the current being driven to the rotor by means of brushes, in a way that when the polarity of the source is switched on, the polarity of the field and the direction of the currents in the armature (rotor) are also inverted, with torque remaining in the same direction.