If you ever saw an electric rail engine, then you must observe that the engine takes power from the overhead wires with Pantograph. So the question arises, what is Pantograph?
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Pantograph is a set of articulated arms fixed to the roof of the engine. It unfolds and extends along a vertical axis. The horizontal end piece of the pantograph is called head. This head is fitted with carbon strip. Their number and types depends on the nature and intensity of the current to be transmitted that is AC or DC. These carbon strips along the catenary contact wire thus capturing the electricity required to power the engine’s traction motors.
The catenary is more complex than a simple power cable. It is made up of messenger cables, contact wires, droppers, steady arms and tension devices. All these elements are supported at regular intervals by a series of masts. The catenary’s architecture is designed so that even at high speed, contacy between the catenary contact wire and the pantograph is permanent and uninterrupted.
The cable of the overhead line is so heavy that suspended between two points they do not form straight line but sink due to their weight. For higher speed and in order to get a continuous contact between the catenary and the head of the pantograph, thus avoiding excessive power loss the catenary contact wire must maintained in a horizontal position. It must also be rigid enough to interact in a dynamic way with the pantograph.
The contact wire is supported at regular intervals with droppers. Thanks to these droppers and tensioning loads the contact wire is maintained in horizontal axis with a controlled level of rigidity. These droppers have variable lengths calculated in accordance with several parameters such as the tensioning loads of the contact and messenger wires or their mechanical characteristics.