Solid State Technology Volume: 3 Issue: Publication Year: 2020 5598

Solid State Technology 
Volume: 63 Issue: 5 
Publication Year: 2020 
5604
Archives Available @ www.solidstatetechnology.us 
Fig. 6. The dependence of the induced electromotive force in two receiving locomotive 
electromagnets versus frequency 
There are three ways to demagnetize materials: electromagnetic, temperature, mechanical. A 
method for demagnetizing rail lashes in a decreasing magnetic field is proposed. The rail lash 
is subjected to magnetization reversal by a magnetic field, the amplitude of which varies with 
decreasing to 0 (Fig. 7), i.e. Н
m0
> Н
m1
>Н
m2
>Н
m3
>Н
m4
…>0. When the induction value is 
zero, the residual induction will tend to 0 [14, 15, 16]. 
H
0
m
H
1
m
H
2
m
H
3
m
H
4
m
H
t
Fig. 7. Temporal characteristic of magnetic field strength 
Intramolecular currents are oriented in a certain way, and their magnetic fields, when 
combined with an external field, change the substance, that is, magnetize. The intrinsic 
macroscopic field is characterized by the vector , which is called the magnetization vector.
The relationship between the three vectors of the magnetic field - induction , intensity
and magnetization , - is written as: 
, (13) 
here 
, - magnetic permeability; 
- magnetic susceptibility. 
Magnetization determines how much magnetic induction in a given medium 
differs 
from magnetic induction in a vacuum
at the same magnetic field strength. All 

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Solid State Technology 
Volume: 63 Issue: 5 
Publication Year: 2020 
5605
Archives Available @ www.solidstatetechnology.us 
substances have magnetic properties [13, 14]. The magnetic permeability for the material of 
the rail lashes is 
. It is variable and depends on the intensity 
, that is 
. Thus, by changing the current in the rail lashes, the induction according to the 
Bio-Savard-Laplace law changes: 
. (14) 
A change in the magnetic induction in the steel of the rails, even at the same current value, is 
initiated not only by the current passing through the conductor, but also inside by the 
molecular currents of the substance surrounding the conductor. Therefore, the material of the 
rails can be magnetized even by changing the Earth's magnetic field [16, 17, 18]. Thus, it is 
possible to demagnetize the material of the rails by acting with an alternating field with a 
decrease in amplitudes. In this case, there are two ways to demagnetize. The first method is to 
decrease the magnitude of the demagnetizing field or to remove the solenoid from the rail 
lash. The second is to reduce the current in the inductor [20].
To automatically reduce the current, turn on the inductance coil and gradually remove it over 
a distance of 0.5 meters within 5 seconds, after which the solenoid is turned off. The residual 
magnetization decreases, that is, the demagnetization occurs along the partial hysteresis 
loops. Moreover, the number of demagnetization periods (cycles) usually reaches from 40 to 
50, and the decrease in amplitude occurs smoothly. With this demagnetization method, 
residual induction in the rail lashes remains. Demagnetization usually occurs to a level that 
does not interfere with the normal operation of railway automation systems.
Limit levels of the residual magnetizing field for rolling stock are accepted no more than H= 
A/m, and induction В=0,06Т. 
Consider the propagation of an alternating electromagnetic field in a massive ferromagnet, 
which is a rail lash [10]. The electromagnetic wave perpendicular to the rail surface changes 
according to the law:
, (15) 
where
-is the demagnetizing field strength on the rail surface at 
; -current 
coordinate of the field propagation; the attenuation coefficient and the phase coefficient equal 
to each other are determined by the expression:
, (16) 
where ν - is the frequency of the demagnetizing field; - relative magnetic permeability ; - 
specific conductivity of the rail material. 
From formula (15) it is seen that the amplitude of the magnetic field decreases according to 
the exponential law. The penetration depth of the electromagnetic wave into the thickness of 
the rail lash is: 
. (17) 
The wavelength, respectively, is: 
. (18) 

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