Passenger trains carry passengers over long distances and are usually long and fast. A growing type of passenger train used for long distances is the high speed rail. These trains can run at speeds up to 500km/hour. To achieve these speeds, a technology called magnetic levitation has been in research and development to be deployed. These trains can be self powered or multiple units of cars or coaches or a combination of locomotives and unpowered coaches. Passenger trains travel between stations or depots where passengers may embark or disembark. These trains operate on fixed schedule and usually get their supply of power from head- end power, which is usually located at the head of a train. The power source, usually a locomotive or generator car, at the front or ‘ head’ provides electricity used for heating, lighting, electrical and other hotel needs. A separate diesel generator located in the train’s head may also be used to supply power to the entire train. Passenger trains consist of the driver, conductor and other staff responsible for the operation and maintenance of the train for the whole duration of the journey. The trains are built with steel on the exterior and the interior built to look like the interior of airplanes, though with more space for ordinary passengers. Passenger trains were first used in the 19th century, powered by coal and steam. Later trains were powered by diesel electric engines. Modern passenger trains which are high speed trains are powered by trains which run purely on electricity, connected to overhead cables. An example of this type of electric propulsion system is the traction motor. A traction motor is an electric motor used for propulsion of a vehicle such as locomotives. Traction motors are used in electrically powered rail vehicles, (electric multiple units) and other electric vehicles such as electric milk flats, elevators, roller coasters, conveyors, trolley buses, vehicles with electric transmission systems such as diesel electric locomotives, electric hybrid vehicles, battery electric vehicles. Traction motors include direct current(DC) and alternating current (AC) motors. Direct current traction motors were used for so many years in electric and diesel electric propulsion of locomotives, but the invention of high powered semiconductors ( thyristors and the IGBT) has now made practical the use of much simpler higher reliability Alternating Current(AC) induction motors known as asynchronous traction motors.