Modern Techniques                       
Axle Counter Zp30CA Type

The axle counter is an intelligent element of the centralization equipment of any type, which can take over the function of the track circuit regarding the intimation of the railway vehicle presence on a certain track section without using insulating joints. The operation principle is relatively simple and mainly aims at counting the axles entering the railway track section, as well as those exiting in the controlled area, the comparison of the counting, and in case of coincidence of the entering data with the exiting data the track section is considered available.

Constructive principles
 The Zp30CA type axle counter, supplied by ALCATEL SAL company, uses sensors in the track of SK 30 type and a central unit of EAK 30CA type. The SK 30 sensor, constructively presented in the Figure 1.1. is made of two assemblies Sk 1 and Sk2, both installed on the same track of the railway.Fig. 1.1. Preview of the SK30CA sensors.
Each SK assembly is made, on its turn, of two heads: Transmitter - TX, installed outside the track, and the receiver - Rx, installed inside the track, in opposition with the Tx as in the Figure 1.2.Figure 1.2.
The use of the two assemblies, Sk1 and Sk2, has the motivation of direction discrimination, namely these assemblies provide two balanced signals, of different frequencies, with their help, while the railway vehicle wheel crosses, there it is determined the counting direction.

Electrical principals
Tx coils are supplied with various frequency signals (approximately 30kHz and 29 kHz), and the resulting magnetic fields are coupling around the track with Rx coils, inducing tension in them. Tx / Rx coils are assembled in such a way so the presence of the bandage spout produces deviations of the induced tension phase. The central unit EAK 30CA intimates the deviation of the phase and intercepts its as a detected Fig. 2.1 Signals diagram wheel.
In the following lines, there are presented the shapes of the magnetic fluxes in three characteristic situation:
FIG Without wheela) if the wheel of the railway vehicle is at a distance bigger than 200 mm from the central imaginary line of the contact between the track and the wheel, the lines of the electromagnetic flux perpedincularly meet on the receiving coil under a " &" angle, and the alternative (induced) tension that it is received (induced) is syncronic to the sent signal (Fig. 2.1 Signals diagram).
FIG Wheel at approx. 200 mmb) If the bandage spout is at approximately 200 mm from the central imaginary line of the contact between the track and the wheel, the lines of the electromagnetic flux perpendicularly meet on the receiving coil almost in parallel, and the alternative received (induced) tension is zero, the wheel being detected (see Fig. 2.1. Signals diagram).
c) If the wheel is located on the central imaginary line of the contact between the track and the wheel, the lines of the electromagnetic flux perpendicularly meet on the receiving coil under the "&" angle, and the alternative received (induced) tension is de-phased with 1800 against the transmitted signal (see Fig. 2.1. Signals diagram).

Applications of axle counter
 The system can satisfy the following needs of the railway network:
Station A Station B
a) the control of the current line between two stations without BLA;
Station A Station B
b) the control of the current line between two stations with BLA;
c) the automatic command of a BAT (SAT) equipment from the line without BLA.

Material processed according to 
Axle Counter Manual Zp30CA General Description

eng. Ioan Buciuman

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