1. Poor service environment
As the traction motor is installed under the vehicle body, it can withstand the influence of rain, snow and moisture, and the dust raised during locomotive operation is also easy to invade the motor department. In addition, due to the change of season and load, it is often affected by the change of temperature and humidity. Therefore, the motor insulation is easy to be damp and polluted, which has a very adverse impact on its performance and service life. Therefore, the insulation material and insulation structure of traction motor shall have good moisture-proof and dust-proof performance and good ventilation and heat dissipation conditions.
2. The overall dimensions are limited
The traction motor is suspended under the vehicle body, and its installation space is greatly limited. The axial dimension is limited by the gauge and the radial dimension is limited by the diameter of the driving wheel. In order to obtain as much power as possible, the traction motor must be compact in structure, and adopt high-grade insulating materials and conductive and magnetic materials with good performance.
3. Strong action force
When the locomotive runs through the uneven part of the rail, the dynamic action generated by the impact will be transmitted to the traction motor, which will bear great impact and vibration.
4 difficult commutation
The reasons for the difficult commutation of direct and pulse current traction motors are not only affected by the mechanical vibration force, but also electrical reasons. For example, the traction motor is often started and braked, and the current can reach twice the rated current at this time; When the locomotive runs on a long ramp, the motor will be in overcurrent state for a long time; When the locomotive is running at high speed, deep magnetic field weakening is adopted to increase the distortion of air gap magnetic field; The voltage fluctuation of power grid makes the motor terminal voltage rise higher, which will make the commutation of traction motor difficult.
The current of pulse current traction motor is pulsating current. In addition to DC component, there is also a certain AC component. The existence of electromagnetic AC component will make the commutation of motor more difficult, resulting in the increase of commutation spark and even ring fire.
5 uneven load distribution
Another difference between traction motor and ordinary motor is that several traction motors on the same locomotive are connected together both electrically and mechanically. In the aspect of electricity, the motors are connected in parallel; In the mechanical aspect, the motors are coupled with each other through the adhesion between the wheel and the rail. Therefore, due to the different characteristics of traction motors on the same locomotive, different diameters of moving wheels or “idling” and “sliding” of individual wheel sets, it is possible to cause uneven load distribution of motors. Some motors are in overload operation and some motors are in underload operation, so that the locomotive traction can not be brought into full play.
Working characteristics of traction motor
1. Poor service environment