HOW DOES A PANTOGRAPH ENSURE CONTINUITY OF CURRENT?

If you watched our video, you’ll know how crucial the horizontal alignment of the collector head is throughout the train’s journey.

Fig: 1 Pantograph mounted on roof of an Electric train
Fig: 1 Pantograph mounted on roof of an Electric train

Trains, with the exception of levitating ones, will always experience vibrations. These vibrations can create slight contact loss between the collector head and overhead line, which affects the continuity of current. Solving this issue of discontinuity is crucial in order to prevent sparks.

Fig: 2a - Pantograph head connected with the OHL
Fig: 2a - Pantograph head connected with the OHL
Fig: 2b- Pantograph head disconnected with the OHL
Fig: 2b- Pantograph head disconnected with the OHL

Passive Suspension System

A balancing rod ensures the horizontal position of the pantograph head at all times during its operation. To compensate for minor vibrations, a plunger and spring arrangements are provided. This arrangement is fixed to the pantograph-head and the horizontal bar and connects the bar of the upper 4 bar linkage. This is called passive suspension. The vibrations push the plunger down and compress the spring. The spring then expands back to its original configuration and pulls the plunger up. The push and pull of the plunger absorbs the vibration of the pantograph head and does not affect the pantograph body. It also allows the pantograph to be more adjustable for the height changes of line as well as to absorb vibrations from the train.

Fig: 3 - Pantograph head mounted over suspension system
Fig: 3 - Pantograph head mounted over suspension system

Two contact stripes of pantograph head

You may be wondering why there are two contact strips slides present on a single pantograph. The voltage of DC OHE is low, carrying high current compared to AC OHE. The area of pantohead depends on the current collection capacity. If the area of conductor is reduced, it leads to excessive heating and potential for burn spots on the carbon strip.

Fig: 4 - Burn spots on the carbon strip
Fig: 4 - Burn spots on the carbon strip

When you divide the strip into two, the current flow from each strip gets reduced, which easily solves our problem. Although a single thick conductor could also do the trick, the above-mentioned method will give the head more stability to stay horizontal as the pneumatic piston pushes it onto the line.

Fig: 5 - Two carbon contact strips
Fig: 5 - Two carbon contact strips

We hope you enjoyed this Lesics members-only Article. Thank you for being part of our team!

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