Electropneumatic brake (EP) was introduced in the early years of the 20th century in an attempt to overcome the delay in the operation of the pure air brake. Originally designed for meters or meters, electropneumatic brake systems are now common in main passenger railways and in some specialized loading operations. Its main advantage over the air brake is the speed of control and the fast reaction times in the vehicle, which provides instant control of the entire train to the driver. Its speed of operation makes it ideal for automatic train operation (ATO). EP braking is not the same as ECP braking. ECP brakes have recently been introduced in an attempt to overcome the drawbacks of the air brake system in long freight trains.
Even the most modern air brake systems are based on the transmission of an air signal along the brake pipe. This starts from the front of the train and must be sent to all vehicles along the train. There will always be a time lag (called propagation speed) between the reaction of the main vehicle and the reaction of one in the rear. This time span is a considerable moderation in the operation. It causes the braking of the vehicles to occur at different times along the train, so that while some cars are slowing down, others still try to push, without braking, from behind. When released, the front of the train pulls the rear, which still brakes, and causes tension in the couplers. Another drawback is the lack of a gradual release in older systems, a goal difficult to achieve for many years.
The introduction of electric traction and multi-unit control was the spur that eventually produced electrically controlled air brakes. Increased rapid transit operations in cities, with their high volume and frequent stops and starts, meant that rapid response to braking commands and accurate station stop was an essential ingredient for more efficiency. The EP brakes first appeared in the US. UU. They were tried on the New York subway in 1909 and then on the London Underground in 1916.
Brake principles E-P
There are many types of e-p brake systems used today and most of them developed as a "complement" to the original air brake system and as a result incorporated some common principles into their design as follows:
• The e-p brake functions as the service brake while the air brake is retained for emergency use
• The e-p brake does not compromise the "vital" fail-safe characteristics of the air brake.
• The pneumatic brake normally remains in the "Release" position, even when the e-p brake is in "Application" and the same brake cylinders are used.
• E-P brakes are invariably used on multi-unit passenger trains.
• E-P brakes use several train wires to control the electrically operated brake valves in each car.
• The train cables are connected to a "valve" or brake controller in the driver's cab.