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Pantographs are used to reduce or enlarge technical drawings and maps, as well as to guide cutting equipment along complicated courses. Pantographs are used by miniature artists to obtain finer detail. The pantograph is spring-loaded, and it pushes a contact shoe up against the contact wire's bottom to draw the electricity required to power the train.
The contact shoe slides along the wire as the train travels, potentially causing standing waves in the wires, which can break the contact and reduce current collection. The pantograph is the link between the overhead contact wire and the electric locomotive's power circuit, which transmits the required power.
A pantograph is an antique mechanism used to transport power from catenary lines in electrical locomotives. It is made up of five linkages that create a parallelogram, each of which is connected by a pin joint to form a revolute pair.
As trains became quicker, the half-pantograph (also referred to as a 'Z'-shaped pantograph) evolved to give a more compact and responsive single-arm design at high speeds. This type of pantograph was invented by Louis Faiveley in 1955. The half-pantograph can be seen on everything from high-speed trains to slow-moving city trams.
For modern electric rail systems, the electric transmission system consists of an upper, weight-carrying wire known as a catenary from which a contact wire is strung. The pantograph is spring-loaded, and it pushes a contact shoe up against the contact wire's bottom to draw the electricity required to power the train. The electrical return is provided by the steel rails of the tracks. The contact shoe slides along the wire as the train travels, potentially causing standing waves in the wires, which can break the contact and reduce current collection. This means that contiguous pantographs are not authorised on some systems.
Trolley poles, which were commonly employed on early streetcar networks, were replaced with pantographs. Trolleybuses, whose freedom of movement and requirement for a two-wire circuit that makes the pantograph impractical, as well as some of the streetcar networks which have frequent sharp turns and require additional freedom of movement in their current collection to ensure unbroken contact, continue to use trolley poles. However, many of these networks are undergoing improvements to support pantograph operation, notably Toronto's.
Pantographs with overhead wires are presently the most common way for modern electric trains to collect current because, while more brittle than a third rail system, they allow for higher voltages.
Pantographs are normally controlled by compressed air from the vehicle's braking system, which is utilised to either lift the unit and hold it against the conductor or lower it when springs are employed to affect the extension. The arm is maintained in the down position by a catch in the second instance to prevent loss of pressure. When using roof-mounted circuit breakers for high-voltage systems, the same air supply is used to "blow out" the electric arc.
A block of graphite is frequently used to ensure contact between a pantograph and an overhead line. While acting as a lubricant, this substance conducts electricity. Because graphite is brittle, it is possible for bits to fall off during operation. Faulty pantographs can seize and rip down overhead wires, creating a two-way feedback loop where bad wires, as well as bad pantographs, can damage each other. You can prevent such a situation by using a pantograph monitoring station. Friction can cause the contact strip to grow red hot at sustained high speeds (over 300 km/h (190 mph), resulting in severe arcing and eventual failure.