Pulse relay is the most widespreadreceived in the field of railway automation. Such a device switches its contacts of a network and circuits of different power under loads of a different nature - inductive, capacitive, active or their combinations. Windings of the relay can be connected to cable or air lines, rail circuits, which have high levels of interference of various kinds and are subject to lightning strikes.
Pulse relay is used in systems and networksrailway automation mainly as a receiver of the impulses of rail chains, which control the rail lines on the sections and stations. In complex and unstable conditions, the main objective of this device is a clear and reliable trouble-free operation in the field of telemechanics and railway automation to ensure the safety of work and train traffic. The pulse relay is also installed in both unheated special relay cabinets and in relay rooms with adequate heating.
Let's consider in more detail the device of suchdevice. The principle of operation of the pulse type relay and the design of the device are based on such elements as a permanent magnet, a coil with an internally mounted armature with movable contacts, four pole tips of the magnetic circuit, adjusting screws. The anchor is fixed to a metal base. The impulse relay of the plug type has a contact system consisting of fixed and movable contacts. Such a system is designed for several tens of millions of switching operations with a current up to several amperes and a voltage of several tens of volts. All parts of the relay are under a transparent cap with a handle.
A small-sized impulse relay is used asTrack relay in rail pulse circuits operating on alternating current. In it inside the case there is a panel with a rectifier of four flint diodes. Such a device has some drawbacks: a large mass and dimensions (more than two kilograms - this is a lot for a protective or regulating device).
Currently, as the main relay in theRailway automation uses an inexpensive relay with a switching contact using a mercury magnetically actuated reed switch (pressurized contact).
The reed switch is a contact spring thatmade of a special magnetic material and placed in a glass ampoule. This ampoule is filled with an inert gas, or it creates a vacuum to reduce the possibility of sparking or corrosion of contacts. A pulse relay with a switchable sealed contact has its positive sides, such as small dimensions, low cost, high speed, easy operation, high reliability. However, there are some drawbacks. For example, such a relay is difficult to apply in winter because of the influence of low temperatures on mercury. Therefore, for such a device, as an impulse relay with reed switch, an additional external heating is required.
