BBA Dropper Calculations

In recent years, electrification train industry has made significant progress in Iran. With the advancement of this industry, it is felt to need increase the speed of the lines. At high speeds of the train, maintenance of the stable connection of the current from the contact wire to the pantograph is essential for optimal transmission of power. The interaction between the pantograph and the catenary system is one of the most important issues involved in high-speed of overhead contact line. In order to achieve the best performance of the pantograph and catenary system, accurate calculations of the dropper length are necessary. In order to calculate the dropper length, it is first necessary to make static calculations that it requires a precise mechanical calculation of the overhead contact line to increase the speed of the train.

The main task of droppers is to connect the contact wire and the messenger wire to keep the contact wire parallel with the ground for uniform connection with pantograph so that it allows contact wire to have desired and desirable sag. While the pantograph must not be disconnected from the contact wire, the upward force of the pantograph must not be too high to prevent the rapid wear of the contact wire. The distance between the droppers and their length determines the distribution of uniform elasticity in the catenary system, which requires accurate and complex calculations. In order to perform the dynamic simulation of the interaction between the catenary system-pantograph and verifying the standard EN 50318, accurate calculation of dropper length is necessary. This is another reason for the high importance of dropper length calculations. It looks impossible to get favorable result in dynamic simulation without access to dropper calculations.


Dropper calculations are complex calculations that only few companies in America and European countries are able to do it. Also, mechanical department of Alucast Iran company has succeeded to provide software of dropper calculations that it is valuable for Iran.

Applications and ability of software

- Ability to determine pre-sag of contact wire
- Ability to reduce/increase number of droppers
- Ability to determine the minimum dropper length
- Schematic drawing of the catenary system with a scale in the vertical direction
- Schematic drawing of the catenary system according to the geometric inputs


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