In the locomotive or high-speed train used to drive one or a few motor shaft. There are different types of traction motor, such as dc traction motor, ac asynchronous traction motor and synchronous ac traction motor, etc. Dc traction motor, especially the direct current series motor has good control performance and operating characteristics, to adapt to the needs of the locomotive traction characteristics, won a wide range of applications.
       Working principle of the traction motor of the same as the general dc motor, but have a special working conditions: the space size is limited by track and wheel diameter; When the locomotive running through the rail gap and switch to withstand considerable impact vibration; Large and small gear meshing bad when the armature will produce strong torsional vibration; Use in the bad environment, such as rain, snow, grey sand easily invaded. So traction motor has many requirements in the design and structure, such as to make full use of the body's internal space structure is compact, should use insulation materials and magnetic materials, spare parts to have higher mechanical strength and stiffness, the motor needs to have good ventilation cooling conditions and dustproof moistureproof ability, to take special measures to cope with the difficult conditions of "reverse" to reduce the carbon brush of the spark and so on.
       There are two kinds of traction motor suspension. Is a kind of traction motor and shaft connection way of hanging, called axle suspension or half suspension. Using this way of suspension, the impact of the pulley produced by rail gap and switch directly to the traction motor vibration. Suspension is suitable for holding shaft structure locomotive vehicle speed under 120 km/h. The other is a frame suspension (or full suspension). Using this way of hanging fixed suspended on the bogie frame, traction motor in traction motor shaft end and join all kinds of elastic connection between small and big gear components, to reduce the influence of impact vibration. Bearing type suspension is suitable for the structure locomotive vehicle speed higher than 120 kilometers per hour.
　    In traction transformer step-down after silicon rectifier or high power thyristor rectifier dc series power supply for traction motor, and voltage of pulse voltage in traction motor, so the traction motor is called pulse flow traction motor. High power pulse flow "reverse" conditions of traction motor more difficult. In addition, there are some additional loss inside the motor, thus causes the motor temperature rise, therefore, the pulse flow traction motor on the design and construction to take special measures, in order to solve the temperature rise of the "reverse" and two outstanding problems.
Auxiliary motor
       Can use dc motor on electric locomotive auxiliary motor, three-phase ac asynchronous motor is also available. Dc motor was used as auxiliary motor, must by special silicon rectifier power supply. With supplemental three-phase ac asynchronous motor, must be from stationary disguised, frequency conversion device, or special supply of rotary motor three-phase power supply. This special rotating machine called split camera, can put the single phase alternating current into a three-phase alternating current (ac).
Traction generator
       Dedicated to electric drive diesel locomotive, in order to supply traction motor power generator, also called main generator. Traction generator has two kinds of dc and ac. Dc traction generator directly to the dc traction motor power supply. Three-phase alternating current from the ac traction generator after silicon rectifier rectifier to supply power to dc traction motor. Communication is three-phase rectifier circuit, although there is a pulse rectifier voltage, but the pulsating quantity is small, so the traction motor is also known as the general dc motor.

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