RU2488841C1 - Device for measuring magnetic viscosity of ferromagnetic materials - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: device has series-connected control, computational and display unit, controlled frequency multiphase generator, synchronous motor whose axis is fitted with a ferromagnetic body of revolution made form the analysed ferromagnetic material, placed in the magnetic field of an electromagnet with a magnetising coil, connected to a direct current source from an additional output of the control, computation and display unit. The ferromagnetic body is in form of a solid cylinder which is placed in the magnetic gap of the electromagnet, the length of which is three to five times shorter than the circumference of the ferromagnetic cylinder with its smaller gap relative coaxial-circular poles of the electromagnet, and on top of the ferromagnetic cylinder there is a uniformly wound measuring coil made from a conductor whose ends, which are mounted on the shaft of the synchronous motor in an insulated manner through annular current connectors, are connected to the measuring input of the control, computation and display unit.

EFFECT: high reliability of measurements and broader functional capabilities.

5 dwg

Description

The invention relates to the physics of magnetism and can be used to study the magnetic properties of ferromagnets - their magnetic viscosity and the dependence of magnetic susceptibility on the intensity of an external magnetic field. These characteristics are important for building energy devices.

One of the important properties of ferromagnetic materials is their so-called magnetic viscosity, the magnetic aftereffect is the time lag of the magnetization of a ferromagnet from a change in the magnetic field strength. In the simplest cases, the change in the magnetization ΔJ depending on time t is described by the formula:

$$\Delta J\left(t\right)=\left[J\left(t\right)-J_0\right]=\left[J_{\infty }-J_0\right]\left[\mathrm{one}-\exp \left(-t/\tau \right)\right],(\mathrm{one})$$

where J ₀ and J _∞ are, respectively, the magnetization values immediately after the magnetic field strength H changes at the moment t = 0 and after the establishment of a new equilibrium state, τ is a constant characterizing the process rate and is called the relaxation time constant. The value of m depends on the nature of magnetic viscosity and in various materials can vary from 10 ^-9 seconds to several tens of hours depending on the manufacturing technology of ferromaterials and their structure [1-3].

Known methods and devices for measuring the magnetic viscosity of ferromagnets made in the form of disks or rings rotating relative to the localized magnetic field in which the edge of these disks or rings is located [4-7].

Thus, there is a method of measuring the magnetic viscosity of ferromagnets made in the form of a ring, part of which is placed in the magnetic gap of an electromagnet connected to an adjustable constant current source, and also containing a calculation and indication unit, characterized in that the ferromagnetic ring with a radius R is rotated relative to the magnetic gap an electromagnet of long L with an angular velocity ω, and during the time interval Δt = L / ωR, the values of the magnetic susceptibility of the ferromagnet X (x) inside the magnetic gap of the electro the magnet in the segment 0≤x≤ <L using an electromagnetic sensor, the winding of which is part of the oscillating circuit of a high-frequency generator, for which the electromagnetic sensor is moved along the arc of a circle coaxial with the ferromagnetic ring inside the magnetic gap of the electromagnet, and the measurement of the magnetic susceptibility X (x ) produce in the unit of calculation and indication of the change in frequency in the high-frequency generator, while the value of the constant relaxation τ of the magnetic viscosity of the ferromagnetic ring is determined by ksponentsialno decaying magnetic viscosity distribution X (x) in the area X * ≤X (x) ≤L, wherein X * - coordinate corresponding to the maximum value of the magnetic susceptibility of the test ferromagnet X _MAX, according to the formula τ = (LX *) / ωRln (X MAX / X _MIN ), where X _MIN is the minimum magnetic susceptibility of the ferromagnet at the end of the magnetic gap of the electromagnet at x = L, and the magnetic field in the magnetic gap of the electromagnet is chosen homogeneous and saturating.

According to the specified method, the corresponding measuring device is considered, considered in [7], which can be considered as the closest analogue (prototype) of the claimed technical solution.

A disadvantage of the known prototype is the need to calibrate the device when changing the gap between the magnetic circuit with the magnetic gap of the magnetic sensor with the winding of the measuring oscillating circuit and the test rotating ferromagnetic ring in a localized saturating magnetic field, as well as its relatively low sensitivity to measurements. The reliability of the measurements may be violated due to the radial runout of the rotating disk, in which the distance between the side surface of the ferromagnetic ring and the electromagnetic sensor changes.

These disadvantages of the known device are eliminated in the claimed technical solution.

The objectives of the invention are to increase the reliability of the changes made and expand the functionality of the claimed device, in particular, to assess the uniformity of ferromaterial in its volume.

These goals are achieved in the inventive device for measuring the magnetic viscosity of ferromagnets, containing serially connected control unit, calculation and indication, a multiphase (for example, three-phase) generator with an adjustable frequency, a synchronous motor, on the axis of which is mounted a ferromagnetic body of revolution from the studied ferromaterial, placed in a magnetic field of an electromagnet with a magnetizing winding connected to a source controlled from an additional output of the control unit, calculation and indication direct current, characterized in that the ferromagnetic body is made in the form of a continuous cylinder placed in the magnetic gap of the electromagnet, the length of which in the direction of rotation of the ferromagnetic cylinder is three to five times less than the circumference of the latter with its small gap relative to the coaxially-rounded poles of the electromagnet, and a ferromagnetic cylinder is superimposed on top of it a uniformly wound (for example, turn to turn) measuring winding from a conductor, the ends of which are through ring current collectors, isolated on si synchronous motor, connected to the measuring input of the control unit, calculation and display.

Achieving the goals in the claimed device is explained by the excitation of the emf induction in a winding superimposed on a ferromagnetic cylinder, the value of which is determined by the speed of drawing the ferromaterial in the magnetic gap and the magnetic susceptibility of the ferromaterial in the magnetic gap, which varies with time due to magnetic viscosity, with a variable rotation speed of the ferromagnetic cylinder for a given adjustable magnetic field strength in the magnetic gap, and the possible spread of this value of the emf during the rotation of the ferromagnetic cylinder (at each of its turns) indicates the degree of heterogeneity in the volume of its magnetic susceptibility and (or) magnetic viscosity. The value of the specified emf induction has an extremum of the maximum type at a certain speed of rotation of the ferromaterial in the magnetic gap, the value of which is calculated constant magnetic viscosity of the ferromaterial. Magnetic viscosity is manifested in the time delay of a turn along the magnetic field vector in the magnetic gap of the magnetic moments of the domains of a ferromagnet during its rotation in a magnetic field.

The design of the claimed device is shown in Fig. 1-3, a graph of the dependence of the emf the induction excited in the measuring winding of a ferromagnetic cylinder on the speed of its rotation in a localized magnetic field is shown in Fig. 4, and Fig. 5 shows the famous Stoletov curve.

Figure 1 shows a diagram of the inventive device, consisting of.

1 - an electromagnet with a magnetic gap and rounded poles,

2 - magnetization coils of an electromagnet,

3 - ferromagnetic cylinder from the studied ferromaterial,

4 - axis of rotation of a synchronous motor axisymmetrically fastened to a ferromagnetic cylinder (the corresponding axes are shown deployed at an angle of 90 ° for clarity),

5 - synchronous motor (SD),

6 - multiphase generator (MG), for example, three-phase, with an adjustable oscillation frequency,

7 - control unit, calculation and indication (UVI),

8 - direct current source (IPT) with adjustable bias current,

9 - measuring winding from a conductor uniformly placed on top of a ferromagnetic cylinder, for example, coil to coil,

10 - two ring current collectors for measuring winding 9,

11 - two isolating disks for ring current collectors 10.

Fig. 2 shows a side view of a ferromagnetic cylinder 3 with a measuring winding 9, its axis of rotation 4, on which insulating disks 11 are mounted with ring electrodes 10 to which the ends of the measuring winding are connected. The output of the ring electrodes is connected to the measuring input of the UVI 7 unit.

Figure 3 shows the nature of the winding of the measuring winding 9 using two randomly located turns of it.

Figure 4 shows a graph of the dependence of the emf induction U (ω) in the measuring winding 9 of the magnitude of the angular velocity of rotation ω of the measuring winding without a ferromagnetic cylinder — a dashed straight line and with a ferromagnetic cylinder — a solid curve having an extremum of the maximum type at an angular velocity of rotation ω *.

Figure 5 shows a graph of the dependence of the magnetic susceptibility χ (H) of a ferromagnet on the value of the magnetic field H acting in it - the well-known Stoletov curve. In the region of magnetic saturation (in the para process), the product χ (H) · Н ≈const.

Consider the action of the claimed device.

According to the law on electromagnetic induction, when a single conductor of length b moves with a speed V in a transverse magnetic field with a voltage H, an emf arises in it e ₁ = µ _o HVb where µ _o = 1,256 · 10 ^-6 GN / m is the absolute magnetic permeability of the vacuum. When the measuring winding 9 is tightly wound (turn to turn) with a step of winding δ, n = L / δ of its turns are placed along the length of the magnetic gap L along the direction of movement of the winding. Each coil contains two segments of a conductor of length b each (see Fig. 2), located collinear to the magnetic poles of electromagnet 1, and an emf is excited in them for each of the turns e ₁ = 2µ _o HVb = 2µ _o HqωR, therefore, in the part of the winding of length L, the total value of the emf U (ω) = ne ₁ = 2µ _o HbLωR / δ. For H = const, the emf U (ω) is the linear function of the angular velocity ω of rotation of the ferromagnetic cylinder 3 in the magnetic gap of the electromagnets 1, and the tangent of the angle of the dashed straight line in Fig. 4 relative to the abscissa axis is determined by the magnitude of the magnetic field H in the plane of dislocation of the indicated parts of the measuring winding 9 in magnetic gap (at small distances ξ from the poles of the magnetic gap).

When the ferromagnetic cylinder 3 is rotated in a localized magnetic field inside the gap between the poles of the electromagnet 1, magnetization reversal of certain parts of the ferromaterial occurs, which is carried out, as indicated in (1), with a time delay reflecting the magnetic viscosity of the ferromagnet. This means that the change in the magnetic susceptibility χ (H) also occurs with a time delay according to the expression.

$$\Delta \chi \left(t\right)=\left[\chi {\left(H^{\ast }\right)}_{MAX}-{\chi }_{N\mathrm{BUT}H}\right]\left[\mathrm{one}-\exp \left(-t/\tau \right)\right],(2)$$

assuming that a magnetic field with intensity H * is applied to the ferromagnet, at which the magnetic susceptibility of the ferromagnet reaches its maximum in the steady state, as can be seen on the Stoletov curve (Fig. 5).

It is important to indicate that with increasing magnetic susceptibility from the minimum value corresponding to the initial magnetic susceptibility χ _NACH to the maximum χ (H *) _{MAX, the} magnetic conductivity in the magnetic gap of the electromagnet increases, as if the distance between the poles decreases with the same magnetization current an electromagnet, which leads to an increase in the magnetic field acting on the rotating measuring winding 9 together with a ferromagnetic cylinder. Therefore, in this case, the emf will also grow. induction U (ω) at the ends of the measuring winding.

If the ferromagnetic cylinder with the measuring winding is rotated very quickly, then the magnetic susceptibility will not have time to increase to the maximum value, and therefore the emf induction will decrease with increasing angular velocity. If the angular velocity ω is small, then, according to the Stoletov curve on its descending branch (after the maximum), with a saturating magnetic field, the magnetic susceptibility also becomes small, and the emf induction U (ω) is also reduced. Consequently, when using a saturating magnetic field in the magnetic gap H _us > H *, there exists a certain optimal value of the angular velocity ω * at which the magnetic susceptibility of the ferromagnetic cylinder keeps up with the time a certain differential volume of the ferromagnet covered by the magnetic field dwells Δt = L / ωR (L is the length of the magnetic gap, R is the radius of the ferromagnetic cylinder), reach the maximum value χ (H *) _MAX . This will, in turn, lead to an increase in the emf. induction to a maximum, as can be seen in Fig. 4.

An analysis of the action of a saturating magnetic field on a rotating ferromagnetic cylinder shows that the value of the optimal angular velocity of rotation is ω * = L / еτR. where e = 2.71 is the base of the natural logarithm, whence the sought-after constant relaxation τ of the magnetic viscosity of the ferromagnet was found as τ = L / еω * R

Thus, by varying the frequency of the multiphase generator 6 under control with UVI 7 and for a given value of the magnetization current from the output of the MPT 8 unit (also under control with UVI 7), we can find the value of ω * and calculate the value of the constant magnetic viscosity g of the ferromagnet under study . By the spread of the magnitude of the emf induction in the measuring winding 9 in the process of rotation, one can judge the degree of homogeneity of the ferromagnet. The curve in Fig. 4 can be displayed on the screen of the display, which is part of UVI 7.

Using a combination of the magnetic viscosity properties of ferromagnets, the magnetocaloric effect, and a saturating magnetic field, it is possible to build the so-called thermomagneto-viscous motors that convert the heat of the surrounding environment, for example, the heat of water pools, into mechanical work [8-11]. Therefore, the task of selecting ferromagnets with a certain value of the constant r of magnetic viscosity becomes urgent.

Literature

1. Kronmiiller H. Nachwirkung in Kerromagnetika, B. - [u.a], 1968.

2. Vonsovsky S.V. Magnetism. M., 1971.

3. Mishin D.D. Magnetic materials. M., 1981.

4. Smaller O.F. A device for measuring the magnetic viscosity of ferromagnets. RF patent №2338216, publ. No. 31 of 11/10/2008.

5. Smaller O.F. A method of measuring the magnetic viscosity of ferromaterials. RF patent No. 2357240, publ. No 15 on 05/27/2009.

6. Smaller O.F. Magnetic viscosity meter of ferromagnets. RF patent No. 2357241, publ. No 15 on 05/27/2009.

7. Smaller O.F. A method of measuring the magnetic viscosity of ferromagnets. RF patent No. 2451945, publ. No. 15 dated 05/27/2012 (prototype).

8. Smaller O.F. A method of producing energy and a device for its implementation. RF patent No. 2332778, publ. in bull. No. 24 dated 08/08/2008.

9. Smaller OF. Generator frequency stabilization device. RF patent No. 2368073, publ. in bull. No. 26 dated 09/20/2009.

10. Smaller O.F. Device for automatic control of an electric generator. RF patent No. 2444842, publ. No 7 on 03/10/2012.

11. Smaller OF. A method of producing energy and a device for its implementation. RF patent No. 2452074, publ. No. 15 dated 05/27/2012.

Claims (1)

A device for measuring the magnetic viscosity of ferromagnets, containing a serially connected control unit, calculations and indications, a multiphase (for example, three-phase) generator with an adjustable frequency, a synchronous motor, on the axis of which a ferromagnetic rotation body from the studied ferromaterial is fixed, placed in a magnetic field of an electromagnet with a magnetizing winding connected to a DC source controlled from an additional output of the control unit for computing and indicating, characterized in that The ferromagnetic body is made in the form of a continuous cylinder placed in the magnetic gap of the electromagnet, the length of which is three to five times less than the circumference of the ferromagnetic cylinder with its small gap relative to the coaxially-rounded poles of the electromagnet, and uniformly wound over it on the ferromagnetic cylinder (for example, to the coil) a measuring winding from a conductor, the ends of which through ring current collectors, isolated on the axis of the synchronous motor, are connected to the measuring input of the control unit Ia, computations and display.

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