Pulse relay: principle of operation and basic varieties

The pulse relay was most widely used in the field of railway automation. Such a device commutes its contacts of a network and circuits of different power under loads of a different nature - inductive, capacitive, active, or combinations thereof. Winding relays can be connected to cable or air lines, rail circuits, which have high levels of interference of various types and exposed to lightning.

Pulse relay is used in railway automation systems and networks mainly as a receiver of rail track pulses, 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 appropriate heating.

Let us consider in more detail the design of such a device. The principle of operation of the pulse type relay and the design of the device are based on elements such as a permanent magnet, a coil with an internally mounted armature with movable contacts, four pole tips of the magnetic circuit, and adjusting screws. Anchor is fixed on 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 at a current of 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 as a track relay in rail pulse circuits operating on alternating current. In it inside the case there is a panel with a rectifier from four flint diodes. Such a device has some disadvantages: a large mass and dimensions (more than two kilograms - this is a lot for a protective or regulating device).

Currently, a low-cost relay with a switching contact using a mercury magnetically actuated reed switch (sealed contact) is used as the main relay in railway automation.

The reed switch is a contact spring, which is made 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 likelihood 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.