RU2539290C2 - Magnetic friction study device - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: invention relates to electrical equipment and can be used for study of physical nature of so-called magnetic friction and its relation with a magnetic susceptibility of the ferromagnetic placed in the changing external magnetic field. The device for study of magnetic friction contains a magnetised rotating rotor and a motionless stator made from the ferromagnetic substance under study, a polarising coil, a high-frequency transformer, an adjustable DC power supply, an electromagnetic sensor of angular speed of rotor rotation with a counterbalance, a frequency measuring instrument, a control and data processing unit, a broadband low-noise amplifier and a spectrum analyser, a synchronous motor, frequency-regulated AC power supply, a device for measurement of the power consumed by the synchronous motor. The rotating rotor is designed as a symmetric structure with two identical cylindrical poles the gap of which with reference to the cylindrical stator at least by order of two is less than the radius of cylindrical poles of the rotor. Aforesaid elements are interconnected in such a way as pointed out in application materials.

EFFECT: ensuring of possibility of study of magnetic friction in ferromagnets, in particular correlation of magnetic friction and the value of the external magnetic field applied to a ferromagnet.

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Description

The invention relates to the physics of magnetism of ferromagnets and can be used to study the physical nature of the so-called magnetic friction and its relationship with the magnetic susceptibility of a ferromagnet placed in a changing external magnetic field.

Observations in 1919 by G. Barkhausen [1] showed that, with a smooth change in the magnetic field strength, the magnetization of a ferromagnet changes stepwise due to the action of different nature of domain friction. The Barkhausen effect is one of the direct evidence of the domain structure of ferromagnets; it allows one to determine the volume of an individual domain. For most ferromagnets this volume is 10 ^-6 ... 10 ^-9 cm ³ (respectively, the transverse domain size is 0.1 ... 0.01 mm), which indicates that one domain consists of a huge number of atoms and molecules with identically oriented magnetic moments, that is, the domain has a mass many orders of magnitude greater than the mass of an individual molecule or atom of a substance.

It is believed that during the interaction of two magnetized ferromagnets, the magnetic lines of force of one of them (from the north magnetic pole Ν) emerging from the domains enter the domains of the other (the south magnetic pole S) and are “frozen” into the corresponding domains of these ferromagnets located between by the shortest path. When the magnetically interacting magnetized ferromagnets are mutually displaced relative to each other over a certain small range of displacements, the magnetic lines of force respectively lengthen or shorten, which leads to a change in the magnetic resistance of the magnetic circuit, similar to the well-known Ohm's law for a magnetic circuit. Any change in time of magnetic resistance can be detected by technical means based on the Faraday law on electromagnetic induction.

A technical solution is known [2] for detecting fluctuations in magnetic flux during the mutual movement of two magnetized ferromagnets without changing the distance between their magnetic poles. This device consists of two thin-walled cylindrical and coaxially spaced permanent magnets magnetically connected from the ends of the studied ferromagnetic substance, one of which is the rotor, which is rotationally driven by an electric motor, and the other, the stator, is made in the form of a horseshoe-shaped structure of the magnetic circuit on which the inductor is located, forming, together with a capacitor of variable capacity connected to it, an oscillatory circuit tuned to the frequency F = ΩD / 2md, where Ω is the circular frequency of rotation of the cyl a magnetic rotor magnet with a diameter D, m is a certain positive number to be measured, d is the assumed transverse domain size in the ferromagnet used, and the wall thickness h of the cylindrical ends of the magnetic poles is many times smaller than the diameter D, for example, two orders of magnitude, and the ends of the magnetic the rotor and stator poles are located at a small distance s from each other, commensurate with the value of h and forming a magnetic gap. An increase in the D / h ratio in the indicated technical solution is associated with the requirement to reduce the linear velocity dispersion of various points of the ends of thin-walled cylindrical permanent magnets (electromagnets) from the ferromagnetic substance under study in order to obtain a quasimonochromatic oscillatory process in the indicated oscillatory circuit tunable to frequency F.

The same effect of magnetic coupling occurs with any other configuration of the magnetized rotor-stator system [3], for example, in a device with a coaxially mounted cylindrical rotor and a hollow cylindrical stator, inside which the rotor is mounted, so that the cylindrical surfaces of the rotor and stator form a cylindrical magnetic gap constant value. In other words, it is argued that for the rotation of the magnetized rotor-stator system, it is necessary to apply an additional amount of energy compared to the same rotation, but in the absence of magnetization. This device can be taken as the closest technical solution (prototype) of the claimed. This device allows you to study the spectrum of quasiperiodic fluctuations of the magnetic flux due to breakdowns in the bonds of the magnetic domains between the rotor and stator, the gap between which remains constant during rotation of the rotor. The average frequency F of such stalls in the fluctuation spectrum is proportional to the angular velocity of the rotor rotation Ω and the radius R of the rotor, which allows for a given value of the domain size d to find the average value of the number m = dF / ΩR, which determines the average value of the elongation of the magnetic field lines Δp for each pair of domains the rotor-stator system from ε equal to the constant gap between the rotor and the stator to p * = (ε ² + m ² d ² ) ^1/2 . This elongation is Δp = p * -ε, which leads to an increase in the magnetic resistance of the magnetic circuit and, consequently, to excitation in the winding associated with the magnetic circuit of the emf induction at a medium frequency F.

The disadvantage of the prototype is the impossibility of studying magnetic friction in various modes of rotor rotation and identifying the dependence of such friction on the value of the magnetic susceptibility of the ferromagnet χ, which changes with changing magnetic field strength действ acting on the ferromagnet.

These disadvantages of the prototype are eliminated in the claimed technical solution.

The aim of the invention is to enable the study of magnetic friction in ferromagnets, in particular the dependence of magnetic friction on the magnitude of the external magnetic field applied to the ferromagnet.

This goal is achieved in the inventive device for the study of magnetic friction, containing a magnetized rotating rotor and a stationary stator made of the studied ferromagnetic substance, a magnetizing coil connected through a current winding of a high-frequency transformer to an adjustable constant current source, mounted axisymmetrically to the rotor and fixed motionless in the stator body, electromagnetic counterweight of rotor angular rotational speed with counterweight mounted on the axis of rotation of the last and connected through a frequency meter to the first input of the control and information processing unit, for example, to a computer, as well as the secondary winding of a high-frequency transformer connected to the second input of the control and information processing unit through series-connected low-noise amplifier and spectrum analyzer, characterized in that a synchronous motor connected to the axis of rotation of the rotor, connected to a frequency-controlled source of alternating current through a meter output by the synchronous motor of power, the output of the latter is connected to the third input of the control and information processing unit, which is connected to an adjustable DC source by the output, the magnetization bias current of the rotor is transmitted to the fourth input of the control and information processing unit, the additional control output of which is connected to the frequency-controlled input AC source, and the rotating rotor is made in the form of a symmetrical design with two identical cylindrical poles, the clearance of which is no cylindrical stator by at least two orders of magnitude smaller than the radius of cylindrical rotor poles.

Achieving this goal is due to the simultaneous automatic control of the magnetizing current of the rotor and its rotational speed, as well as the automatic processing of information from an adjustable DC source and frequency-tunable AC source, as well as from a device for measuring the power consumed by a synchronous motor using a control and processing unit information based on a comparison of the power consumed by a synchronous motor at a given bias current of the rotor with power the consumption at a given rotor speed in the absence of magnetization of the rotor, provided that the magnetic field strength Η in the magnetic gap is selected proportional to the angular velocity ω of the rotor rotation with the possibility of variation of the proportionality coefficient β of such a connection Η = β ω (the coefficient β is dimensional in units of Ampere ∗ sec / meter).

The invention is illustrated by the accompanying drawings.

In fig. 1 presents a block structural diagram of the device, consisting of the following elements and blocks:

1 - bipolar cylindrical rotor with a symmetrical pole design,

2 - cylindrical bipolar stator,

3 - top cover of the sensor with a bearing,

4 - bottom cover of the sensor with a bearing,

5 - synchronous AC motor,

6 - the axis of rotation of the rotor 1, common to the sensor and built into the stator 2 synchronous AC motor 5,

7 - magnetization coil of the rotor 1, mounted in the body of the stator 2,

8 - insulators of the conclusions of the bias coil 7,

9 - current winding of a high-frequency transformer,

10 - magnetic circuit of a high-frequency transformer (rod or ring),

11 is an adjustable constant current source,

12 - frequency-controlled AC source,

13 is a device for measuring the power consumed by a synchronous motor 5,

14 - electromagnetic sensor of the angular velocity of rotation of the rotor,

15 is a counterweight to the sensor 14,

16 - meter speed shaft 6,

17 - the secondary winding of a high-frequency transformer,

18 is a broadband low noise amplifier,

19 is a spectrum analyzer,

20 - control unit and information processing, for example a personal computer.

In fig. Figure 2 shows plots of the magnetic susceptibility χ of a ferromagnet - curve 21 and its magnetization J as a function of intensity Η of the magnetic field applied to it - curve 22.

In fig. Figure 3 shows graphs of the power Ρ (ω) consumed by a synchronous motor in the absence of magnetization of the rotor — an inclined straight line 23 and magnetization of the rotor in a given range of angular velocities ω of its rotation under the condition Η = β ω, where the dimensional coefficient β is a constant and can vary in depending on the type of the studied ferromagnet - nonmonotonic curve 24.

In fig. Figure 4 gives a visual representation of the nature of the change in the magnetic susceptibility of a ferromagnet with variations in the intensity Η of the external magnetic field.

Consider the action of the claimed device (Fig. 1).

Using control from block 20, the synchronous motor 5 drives the rotor 1 from a frequency-controlled alternating current source 12 without supplying direct current to the magnetization coil 7 (N = 0) from the adjustable direct current source 11. In this case, characteristic 23 is taken (Fig. 3) the dependence of the power Ρ _O (ω) consumed by the synchronous motor 5 in the absence of magnetization of the rotor 1 (H = 0) on the angular speed of rotation of the rotor, measured by the frequency meter 16 when the electromagnetic sensor 14 connected to the axis of rotation 6 is operating, when PIR constant magnitude of the frictional moment M _{TP O,} so that _{Ρ O (ω) = ω Μ} TP O, i.e., this characteristic is a linear function with the proviso that _{Μ TP O = const (ω)} , which usually occurs.

Then, the power P (ω) consumed by the synchronous motor 5 is measured during magnetization of the rotor 1 by the current in the magnetization coil 7 from an adjustable constant current source 11 at various values of the angular speed of rotation of the rotor 1. It is important to indicate that the information control and processing unit 20 implements the condition for a simultaneous change in the current in the magnetization coil 7, i.e., the magnetic field strength Η (ω), and a change in the angular velocity of rotation of the rotor 1 when the condition Η (ω) = β ω is fulfilled, where β is the dimensional constant a, the value of which can be changed.

It is clear that in the presence of magnetic friction associated with the rotation of the magnetized rotor relative to the magnetic pole of the fixed stator while maintaining the magnetic gap between the cylindrical poles of the rotor-stator in both pairs of rotor poles 1, the force of such magnetic friction F _TP (ω) creates a moment of magnetic friction Μ _TP (ω) equal to Μ _TP (ω) = F _TP (ω) R, and then the additional power consumed by the synchronous motor 5 Ρ _TP (ω) = ω Μ _TP (ω) = F _TP (ω) ω R, where ω R = V is the linear velocity of the domains of the ferromagnetic ring 25 of the rotor 1 relative about the bound domains of the ferromagnetic ring 26 of stator 2 (Fig. 5). At V = 0, this power is P _TP (0) = 0, and as V increases, this power is P _TP (0)> 0. The total power Ρ _Σ (ω) consumed by the synchronous motor 5 is equal to the sum Ρ _Σ (ω) = Ρ _O (ω) + Ρ _TP (ω) = ω [M _{TP O} + F _TP (ω) R], and therefore, graph 24 for power Ρ _Σ (ω) is located above the inclined line 23 in Fig. 3, asymptotically approaching it in the initial and final sections (a priori statement).

At the final stage, the dependences Ρ _O (ω) and Ρ _Σ (ω) are compared, which allows one to determine the magnetic friction F _TP (ω) by a simple calculation using the formula F _TP (ω) = [Ρ _Σ (ω) -Ρ _O (ω )] / ω R, where R is the outer radius of the ferromagnetic ring 25 mounted on the poles of the rotor 1 (Fig. 5) with a small gap ε <<< R between the ferromagnetic rings 26 of the rotor-stator system in both identical pairs, like this seen in fig. one.

An a priori assertion about the nonmonotonicity of the characteristic F _TP (ω) with a maximum at the point ω = ω *, for which the magnetic field strength H * created in the magnetic gaps by the magnetization current in the coil 7 and acting on the ferromagnetic material and equal to Η * = β ω *, is the subject of research subject to experimental verification on the basis of the proposed technical solution.

The bias current I from the regulated constant current source 11 creates a magnetic flux Φ in the rotor 1 (indicated by a curved arrow in Fig. 1), which creates an induction B, determined by the area of the stator magnetic pole S, so that Φ = B S. Then the magnetic field strength H, acting on a ferromagnet is equal to Η = Β / µ _O (χ + 1) = Φ / µ _O (χ + 1) S, and the magnetic flux Φ is determined by the magnetization coil design, its number of turns and current I according to well-known electrical formulas, and the area of the magnetic pole of the rotor S = π R h, where h is the width of the magnetic field sa

The reason to consider that the maximum of the function F _TP (ω) corresponds to the magnetic field strength Η * = β ω *, at which the magnetic susceptibility χ of the ferromagnet reaches its maximum value according to the Stoletov curve 21 (Fig. 2), is the idea of the redistribution of the magnetic fluxes of each of magnetic domains of a ferromagnet between a flow exiting the ferromagnet in the form of coupled magnetic fluxes of a group of connected domains and a flux closing for each of the domains inside the body of a ferromagnet, as is graphically represented in fig. four.

The author proposes a model of this process explaining the behavior of a ferromagnet in a magnetic field. In fig. Figure 4 shows the chains of the magnetic domains A, B, C, ... for three different values of the magnetic field strength 0 = 0, H * and H _HAC , the magnetic susceptibility of the ferromagnet for which has the values χ _HF , χ _MAX and χ (H _HAC ) = J, respectively _MAX / μ _O H _HAC for H _HAC > Η *, where J _MAX is the saturation magnetization (Fig. 2), μ _O is the magnetic constant (μ _O = 1.256 ∗ 10 ^-6 G / m).

In the ascending branch of the Stoletov curve at 0≤Η≤H *, the action of an external magnetic field on the ferromagnet increases its ability to magnetize, and in the descending branch of the Stoletov curve, on the contrary, it decreases. This can be explained by the redistribution of the magnetic flux density of each of the magnetic domains of the ferromagnet, oriented along the vector of the external magnetic field, one part of which closes inside the ferromagnet near each of the domains, and the other part forms the magnetic circuit of the group of series-connected domains, creating an external magnetic flux of the magnetized ferromagnet. In this case, each domain is considered as a direct micromagnet with its own magnetic moment, the magnetic lines of force of which are partially closed in the internal circuit, and partially form magnetic bonds with other domains in sequentially arranged chains. In this case, an external magnetic field controls the process of the indicated redistribution of the magnetic fields of domains in ferromagnets.

We denote the total magnetic flux of the domain as σ _O , the part of it that binds into the external magnetic circuit, we will designate as σ ₁ , and its other part forming the internal circuit, we will designate as σ ₂ . Then σ _O = σ ₁ + σ ₂ . The ratio ψ = σ ₁ / σ _O determines the degree of the indicated rearrangement of the magnetic flux of the domain. In a magnetic field with intensity H *, all magnetic field lines of the domain form external magnetic circuits and the value ψ = 1, and for other magnetic field strengths, the value ψ <1, as shown in Fig. four.

From a consideration of the model of the physical explanation of the change in the magnetic susceptibility of a ferromagnet under the CONTROL of an external magnetic field, it can be argued that the magnetic field lines that virtually describe the corresponding partial magnetic fluxes of the domains are really “frozen” into these domains, that is, they are isolated from the magnetic fluxes of other domains, and therefore the magnetic interaction of the domains of the rotor-stator system is represented by the interaction of individual pairs of magnetically coupled domains located respectively on the rotor and the stator with the shortest distance between the domain pairs. Then it becomes clear the effect of magnetic friction, preventing the mutual movement of the rotor relative to the stator without changing the distance between them (without changing the magnitude of the magnetic gap ε). It is also clear that such magnetic coupling, which is disrupted by spasmodic transitions of magnetic bonds between nearby pairs of rotor and stator domains, is associated with the need for additional energy to be used when the rotor moves from the stator in the magnetic gap of electromagnet 1 (Fig. 1).

The presence of stable couplings of pairs of domains of the rotor and stator under the action of magnetization from the coil 7 with direct current and the forced breaking of these bonds during rotation of the rotor, occurring after some extension of the magnetic field lines to a critical value p * = (ε ² + m ² d ² ) ^{1 / 2} > ε, is recorded in the form of excitation of an emf ... s. induction in the secondary winding 17 of the high-frequency transformer due to fluctuations in the magnetic field due to a sudden change in the magnetic resistance of the rotor-stator magnetic circuit and the connection of the magnetization coil 7 with the current winding 9 of the high-frequency transformer with the magnetic circuit 10. After amplification of this emf in the broadband low-noise amplifier 18 and the conversion of the amplified signal in the spectrum analyzer 19, the data are fed to the control and information processing unit 20, which allows you to obtain important additional information about the structure of the studied ferromagnet.

With this representation, the friction force F _TP (ω) really reaches the maximum F _TP * at ω = ω *, at which, according to the above condition Η * = β ω *, the magnetic susceptibility of the ferromagnet reaches the maximum χ _MAX , since ψ = σ ₁ / σ _O = 1, that is, when the magnetic fluxes of the domains exiting the ferromagnet are maximum.

Using the inventive device expands the boundaries of our knowledge of the phenomena occurring in ferromagnets.

Literature

1. Rudyak V.M. The Barkhausen effect, UFN ″, 1970, v. 101, p. 429.

2. Smaller O.F. Magnetoparametric generator, RF patent No. 2359397, publ. in bull. No. 17 dated 06/20/2009.

3. Smaller O.F. A device for measuring the spectrum of the induction signal in a magnetically coupled system, RF patent No. 2467464, publ. in bull. No 32 on 11/20/2012.

Patent Search Data

RU 2467342 C1, 11/20/2012; RU 2451945 C1, 05.27.2012;

RU 2357240 C1, 05.27.2009; RU 2357241 C1, 05.27.2009;

RU 2338216 C1, 11/10/2008; US2009009157 A1, January 8, 2009;

RU 2309527 C1, 10.27.2007; RU 2291546 C1, 01/10/2007;

JP 20011255305 A, 09/21/2001; JP 63180851 A, 07.25.1988.

Claims (1)

A device for studying magnetic friction, containing a magnetized rotating rotor and a fixed stator made of the ferromagnetic substance under study, a magnetizing coil connected through a current winding of a high-frequency transformer to an adjustable constant current source, mounted axisymmetrically to the rotor and fixed motionless in the stator body, an electromagnetic sensor of angular speed of rotation rotor with counterweight mounted on the axis of rotation of the latter and connected through a frequency meter to the first input of the control and information processing unit, for example, to a computer, as well as the secondary winding of a high-frequency transformer connected to the second input of the control and information processing unit via series-connected low-noise amplifier and a spectrum analyzer, characterized in that the rotational axis is connected to it rotor synchronous motor connected to a frequency-controlled source of alternating current through a device for measuring the power consumed by the synchronous motor, output q the latter is connected to the third input of the control and information processing unit, which is connected with an adjustable direct current source with the output, the magnetization bias current of the rotor is transmitted to the fourth input of the information and control unit, the additional control output of which is connected to the input of the frequency-controlled alternating current source, and the rotating rotor is made in the form of a symmetrical design with two identical cylindrical poles, the gap of which relative to the cylindrical stator is not less than m is two orders of magnitude smaller than the radius of the cylindrical poles of the rotor.

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