A traction drive is an electric motor that is used to propel an electric vehicle. Traction motors
are used in electric rail vehicles and other electrically-powered vehicles including elevators, electric milk floats, conveyors
, roller coasters, trolleybuses, and battery electric vehicles. The traction drive replaces the traditional gear and belt systems due to their efficiency, low noise/vibration and simplicity. Traction motors utilize normal force to create usable rotational torque through various fluids. These viscosity traction fluids temporarily change their form from liquid to solid thereby preventing direct metal to metal contact. The rolling motion of a traction motor makes them very efficient and makes them emit low noise compared to the mainstream gear and belt systems. Traction motors with a variable-speed drive (VSD) describes a traction drive with the ability to control the speed of machinery. Many industries operate at varying speeds for different products. When speeds must be pre-selected or need to be set at different ranges, the traction drive variable speed is fit for the task.