SU1756193A1 - Inductive sensor for automatic locomotive signalling - Google Patents

Abstract

Use: on vehicles in automatic locomotive signaling, as well as in instruments for detecting sleepers and insulating joints with reduced insulation resistance. SUMMARY OF THE INVENTION: Each of two sensor coils 1 (2) located symmetrically with respect to the axis of rail 11. On ferromagnetic cores 7 (8) there are two windings 3,4 (5,6), wound in opposite directions and connected in series with the same ends, Coils The sensors are interconnected according to and in parallel. Due to the symmetry of each coil relative to the electric field of the interferer, the interference voltage at the output of the sensor is absent. 2 Il.

Description

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The invention relates to the field of signaling on vehicles and can be used primarily in automatic locomotive signaling (ALS) as a sensor for inductive communication with rails, as well as in devices for detecting sleepers and insulating joints and reduced insulation resistance,

Known inductive sensor ALS, containing the sensitive element in the form of an inductor with an iron core, oriented in a horizontal plane, and the element of its attachment to the frame of the locomotive above the rail.

A disadvantage of the known inductive sensor is a significant change in the EMF induced in the coil when the sensor is mixed with respect to the rail axis, as well as when metal objects appear under the coil (rail anti-theft liner, reinforced concrete sleepers). As a result, disturbances appear at the input of the locomotive receiver, which can lead to disruption of the system.

The closest in technical essence to the proposed device is an inductive sensor ALS, the sensitive element of which contains two inductive coils with iron cores, installed symmetrically with respect to the axis of the rail and connected in series.

A disadvantage of the known sensor is weak immunity from common mode interference due to the asymmetry of each coil relative to the electric field of the interfering source.

The asymmetry is manifested in the fact that the upper layers of the coil winding are at a higher potential of the electrical field interference with the ground (the body) than the inner ones, which are covered, are shielded by the outer ones. As a result, a potential difference of interference arises between the coil terminals, which affects the signal receiver.

To protect against interference, the receive coils of the ALS must be interrupted into a massive electrostatic screen, which increases the weight and dimensions of the sensor, increases its cost, and makes mounting and sealing more difficult. However, such a screen does not give the desired effect, because, due to the final value of the complex resistance of the screen body to eddy currents, the interference potentials at different points of the screen will be significantly different and this difference will increase with increasing frequency of the interference current. In turn, this potential of the screen induces different potentials on both terminals of the asymmetric coil. Thus, the output of the sensor is present as a disturbance,

due to the potential difference between the terminals of an asymmetrical coil, and interference due to the potential difference between different points of the screen.

Placing each coil of a known sensor in a separate small-sized screen also has no effect, since the spaced screens, like the spaced points in common on both screen coils, are under different potentials.

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The aim of the invention is to improve the noise immunity.

The goal is achieved by the fact that on each ferromagnetic core of the inductive sensor there is an additional winding, the winding direction of which is opposite to the winding direction of the first winding, with which the additional winding is connected in series.

FIG. 1 shows an inductive sensor for a single rail; in fig. 2 is a diagram of connecting an inductive sensor to an ALS input device.

0 An inductive sensor for a single rail contains two inductors 1 and 2 with windings 3-6 and cores 7 and 8. The coils are placed in non-magnetic protective housings 9 and 10 that perform the function

5 electrostatic screens, and installed symmetrically with respect to the axis of the rail 11. Two windings of the same coil are wound in opposite directions and connected in series with the same-named terminals,

0 in fig, 1 to (end) - to, and the other two outputs n (start) - n form the coil output. The outputs of both coils are connected to the receiver 12 signals by two-wire shielded lines 13 and N.

5 The same lines 15 and 16 are used to connect a second rail sensor to the receiver. Inductive sensor works as follows.

The currents flowing in the rail in the windings 3-6 induce an emf. Since the windings connected to opposite sides are connected by the like terminals, the emf induced in them by the useful current. The lines 13 and 14 of the EMF signal are fed to the input of the receiver 12. From the consideration of FIG. 1, it follows that in each pair of one-dimensional turns with the same numbers, counting from the start of winding both windings of the coil, both turns relative to the remote point of space are

equal. For example, both of the first turns of the windings are equally covered by the other turns of their windings. Thus, both windings on a common core are a symmetric system with respect to a remote point in space. Consequently, the potential induced at the terminals of the n - n electric field of the distant source of interference is the same, due to which the common-mode interference does not become symmetrical and there is no interference voltage between the terminals of the n - coil 1 (2).

In order to maintain the relative distance of the coil windings from the source of interference, the coil should be compact.

The symmetry of the system of two windings also exists with respect to the walls of the protective housing; therefore, the potential of interference on the case induces the same potential at both terminals n - n. Due to this, the housing walls can be as close as possible to the windings and make a coil with a screen of small dimensions.

The distance between the coils of the sensor is comparable with the distance to the source of interference, therefore, different potential of interference on the screens and terminals of both coils can be at the same potential on the terminals of one coil. In this case, if both coils of the sensor are connected in parallel, the potential for interference on both outputs of the sensor is the same and there is no symmetrical interference. Therefore, when using a sensor for measurement and control purposes, both sensor coils are connected in parallel.

However, when using the sensor in the ALC, by the condition of monitoring its operability, the coils should be connected in series. To eliminate the possibility of interference in this case, the sensor coils can be connected to the receiver via a galvanic separator (GR) - transformer, optocoupler, etc. - which creates a large attenuation for common mode interference. To fulfill the condition of monitoring the sensor windings, the outputs of the GR connection are consistent.

For example, when transformers (17 in Fig. 2) are used as GRs, their secondary windings are connected in series and connected to the receiver input 12. When one of the sensor winds breaks, its share in the total emf at the output of the block 17 disappears, the signal level at the receiver input 12 decreases and the receiver PBX goes into a barrage state.

To eliminate interference to transformers, Block 17 is enclosed in a continuous screen.

Claims (1)

Invention Formula An inductive sensor for automatic locomotive signaling comprising two coils, the windings of which are placed on ferromagnetic cores mounted above the rail symmetrically about its longitudinal axis, characterized in that, in order to increase the noise immunity, an additional winding is placed on each ferromagnetic core, the winding direction of which is opposite to the winding direction the first winding, with which the additional winding is connected in series. rv U one four "// & / 2 GO Submarine /one