Pantographs in EMUs: Why More Than One is Necessary

The term pantograph is often used in railway terminology to refer to a device that collects electric current from overhead lines for electric trains. The number of pantographs on a train can vary based on the train's configuration, which in turn depends on the number of coaches and specific operating conditions. This article delves into how many pantographs are typically used in 12 and 15 coach local trains and provides further insight into the role and necessity of multiple pantographs in electric multiple unit (EMU) trains.

Configuration of Pantographs in Local Trains

For local trains, the standard configuration typically involves two pantographs. This is seen in both 12 and 15 coach trains. Usually, one pantograph is located at each end of the train. However, the exact number and placement can vary based on specific train designs or operating conditions. In general, the standard practice is to have two pantographs for trains of this size.

12-Car and 15-Car Local Trains

12-Car Train

12-car local trains typically have two pantographs placed at each end of the train. This design ensures a stable and efficient current collection system, crucial for smooth operation.

15-Car Train

A 15-car local train follows a similar configuration with two pantographs located at the ends. Just like the 12-car train, this setup provides optimal power collection for the train's operation.

Pantographs in Electric Multiple Unit Trains

Electric Multiple Unit (EMU) trains are more complex in their pantograph configuration due to the need for rapid acceleration and handling of different load scenarios. EMUs are designed to operate within metropolitan areas, where the need for quick clearance of sections is paramount. Additionally, they must be able to handle heavier loads, which is why more than one pantograph is often utilized.

EMU Pantograph Configuration

The number of pantographs used in an EMU train can vary based on the length of the train and its configuration. Here is a breakdown of pantograph usage in EMU trains of different lengths:

6-car EMU: Typically uses 2 pantographs. 9-car EMU: Uses 3 pantographs. 12-car EMU: Uses 4 pantographs. 15-car EMU: Uses 5 pantographs.

Interestingly, the pantograph configuration follows a mathematical pattern where the number of pantographs is equal to the number of coaches divided by 3, rounded up to the nearest whole number. However, this is not always the case, as demonstrated by some exceptions:

8-car EMU: Uses 2 pantographs. 3-car EMU (MSB-MTMY): Uses 2 pantographs.

These exceptions show that the configuration is not purely based on the equation mentioned above, but rather on the specific design and operational requirements of each train.

Why Multiple Pantographs?

The question naturally arises: why can't EMUs operate with a single pantograph? The answer lies in both technical and logical reasons.

Technical Reason

Technically, it is possible to operate an EMU train with a single pantograph. However, the complexity of the electrical system and the design of DC and AC traction systems dictate that multiple pantographs are used. In some EMUs, particularly those that run on DC traction, there is a device called an inter-vehicular coupler (IVC) which requires three separate thick wires for connection. This makes it challenging to use just one pantograph for the entire train.

Logical Reason

From a logical standpoint, there are safety and operational considerations:

Safety: High voltage contact wires, if run through the entire rake, can pose a significant risk in case of any accident or damage. This could result in electrocution and potential injury to personnel. Security: The need to prevent unauthorized access or tampering with high voltage cables is another reason. This could lead to security breaches and potential damage to railway property.

Despite these challenges, the modern three-phase locomotives and EMUs use a simpler system where only two wires are needed for power transmission between units. This includes a high-tension (HT) cable and a multiple-unit (MU) cable, as demonstrated in the configuration of a WAP 5 locomotive.

Conclusion

In summary, the use of multiple pantographs in EMU trains is a necessity due to both technical constraints and logical reasons. While it is possible to operate with a single pantograph, the current and practical configurations in EMUs typically include two or more pantographs to ensure safe and efficient train operations. For 12 and 15 coach local trains, the standard practice is to have two pantographs. This article aims to provide a comprehensive understanding of pantograph usage in both local and EMU trains.

Disclaimer: All images and data have been sourced from publicly available sources, including Google searches and the Indian Rail Info website (IRFCA).