We determined the natural frequencies of the headlight structure with light emitting diodes (LEDs) for electric locomotive (VL series). We used the ANSYS software system of finite-element analysis for computations. The obtained values of the natural frequencies and the oscillation character of the design on every mode made it possible to determine the design activities that increase the vibration resistance of the design of a headlight.
These factors indicate that it is impossible to realize all the advantages of the LEDs without considering the peculiarities of their application in a particular industry. So, the lighting devices of general industrial use on the LEDs are not applied, for example, in the rail transport.
For this reason, the research and designs aimed at optimizing the construction of lighting devices using the LED light sources are of great importance. At the same time it should be noted that the Russian railways would like to use the LED lamps as a substitute for the exploited ones, i.e. the existing rail lighting devices have to be modernized as the LED light sources with a minimum number of design changes [http://trainclub.ru/view_blog /svetodiody_na_zheleznodorozhnom_transporte/]. The Railways reflect a global world trend, associated with the modernization of signaling devices used on the railways. For example, the transport administration MTA in New York replaced the light sources in the outdoor traffic lights by the LED light sources, without changing the design of the traffic lights.
Several companies that produce searchlights for a locomotive with the LED light sources are known all over the world, among them are the LEDtronic (Canada), Translight Corp (USA), SBF Spezialleuchten GmbH (Germany) and others. In Russia, the front LED searchlight LPB-01 is designed by the Company SMU "RoSAT" (Armavir) and is produced by the plant-producer "Svetodiod ltd." (St. Petersburg). The powerful original LEDs with the white light serve as the light source. A searchlight LPB-01 has a greater board (the light emitting surface) than a frontal lamp with an incandescent lamp, so as a result, to install it, for example, on the electric locomotive EP1M it’s necessary to reconstruct not only a bracket for placing a searchlight in the cab, but also the body of the locomotive cab. This fact increases the cost of modernizing a frontal lamp and does not meet the requirements of the Russian Railways - ensuring a minimum number of the design changes.
A set of regulations with the requirements for locomotive lighting devices is developed with the participation of the Russian Railways. A headlight must provide the nominal axial force of light when achieving the angles of scattering the light beam in the vertical and horizontal planes ~ 3 ° in accordance with Appendix 1 GOST 12.2.056-81. Focusing the searchlight is carried out in this case the following way: a searchlight spaced apart from the screen at 10 m forms a light spot with the diameter of 1000 mm on a flat screen perpendicular to the horizon. The nominal axial force of the light in the center of the light spot should be 6.4 – 9.6·105 cd. The light emitting surface of a circular board of the front lamp with LEDs replacing a reflector should have a diameter 370 mm.
When replacing an elliptical reflector and an incandescent lamp in the existing
design of a headlight [
A searchlight as a light-signal lighting device redistributes the light flow in a small solid angle.
Its diagram of the angular distribution of the light intensity may differ from its own diagram of the light source. In this connection, it is necessary to estimate the number and type of the LEDs installed on the board, replacing an incandescent lamp and an elliptical reflector.
S D2 4 1000
2 4
The area of a circle, lightened by a headlight, on the shield will be flow: F
(degrees). amount: I
Suppose that the design of a searchlight uses 56 LEDs. In this case, one LED has the area 14024.553 mm2 of the lightened circle on the shield. Since a LED generates the light flow in an axially symmetric solid angle (angle of lightening α), each of the 56 LEDs should lighten a circle of diameter D 4 S lightening α on the shield of the circle with a diameter of 1000 mm is equal to α = 2∙θ = 3.6°. The light intensity in this case is equal (for α = 3.6°)
11100 =
= 2 (1 − cos( 2)) 2 (1 − cos( 3.6 2
)) = 3533343.9 cd ≈ 3.5∙106 cd.
The light parameters of an incandescent lamp and the LEDs, as well as the requirements to the light source, regulated by GOST 12.2.056-81 are summarized in Table 1.
The table shows that in order to achieve the light intensity required by the
regulatory documents it is possible to use a smaller number of the LEDs or (and) a
collimator [
The heat is produced in the semiconductor junction of the crystal LED, and the high-power LEDs have the magnitude of the heat, that is sufficient to change the characteristics of the LED light source. The installing armature of the LED made of materials with the high thermal conductivity (typically aluminum alloy) is made for the effective heat dissipation of the LED. The thermal deformation of the structure of the lighting device is capable of changing the diagram of the angular distribution of the light intensity generated by the LEDs. Using the design of a searchlight of a locomotive as light sources indicating LEDs, we can ignore the thermal deformation of the board with the LEDs.
To ensure the required diagram of the angular distribution of the light intensity, we use the matrix (block) system of the light sources arranged on the board (the light emitting surface) of a searchlight in accordance with the interstate standards "Occupational safety of labor standards system. Electric and diesel locomotives with the rail track of 1520 mm. Safety requirements." From the technological considerations the placement of the LEDs on the board evenly on the coaxial circles is most appropriate. The radii of the adjacent circles differ in one value.
As an original model of a headlight of a locomotive weighing 17.438 kg, a model
of a searchlight with an incandescent lamp and an elliptical reflector is used [
Two lugs made of aluminum alloy D16T are welded on the disk. As the LED light source a model of the LED SMD 3528-W produced by the firm CIVILIGHT (Taiwan) is used (Fig. 2), generating the white light and is analogous to the indicator LED of the brand RL50-WH744D, the characteristics of which are used in the calculations. An LED 1 is installed in the special armature, consisting of an aluminum base 2, which is installed in a ceramic conductor 3, centering the lens of the secondary optics 4 (Fig. 2). Fig. 1. – A headlight of a locomotive with the LED light sources and with an incandescent lamp.
Fig. 2. – The LED light source: a - the design of the LED; b – the armature of the LED construction; c - the assembly of the structure of the LED light source. 2. The vibration resistance of the modernized design of a searchlight
The modification of the design of a searchlight results in changing the natural
frequencies of the lighting device, the values of which can lead to the resonance of the
whole structure during the operation of a railway locomotive [
Table 2 summarizes the weights and elastic characteristics of the elements of a searchlight, removed from the construction, and the elements included in the design. Table 2 shows that the weight of the structure of the modernized searchlight is 18.725 kg, i. e. it increased by 1.287 kg or 7.4 %. This fact indicates the possibility of optimizing the design of the board, that can be performed with the holes making it easier and optimizing the number of LEDs. The control of the weight of a searchlight allows you to change the natural frequency of its design, and thus to influence the vibration resistance of a headlight.
To determine the natural frequencies of the modernized design of a searchlight we use the software that runs on the platform of ANSYS Workbench.
The model does not take into account the threaded connections used in the actual design. Fig. 3 shows the layout of a model into finite elements.
Fig. 3 shows the deformation of the design of a searchlight on the first six natural
frequencies of the design. Fig. 4 shows that the aluminum board experiences the
significant deformation at different frequencies, which may occur during the
movement of the locomotive [