Universal electric motors are so called because they are small sized motors, designed for use in mobile or residential appliances. An engine designed for these purposes has its electrical scheme adjusted to work with any type of available voltage. AC motors can be connected directly to the mains.
Because of the way they are constructed, they take advantage of the effect of alternating current to function. They have stator and rotor from an AC motor. It looks a lot like the DC motor because it can work with this type of current as well. It is a low power motor up to 500 watts, widely used in machines such as blenders, waxers, vacuum cleaners, saws and sanders. When the universal motor acquires alternating current, there is a change in the direction of current in the stator coils and wires, but this change will not change the direction of rotation of the motor. It is only permissible to reverse the direction of rotation by modifying the brush connections by the stator coils. In this way, fixed magnetic field reverses its polarity. https://www.mrosupply.com/hydraulics-and-pneumatics/hose-reels/2793461_l-5550-124-x_reelcraft/