SU1566314A1 - Method of determining time instability of magnetic permeability of cores - Google Patents

Abstract

The invention relates to magnetic measurements and can be used to predict de-accommodation-induced measurements of the properties of closed cores over time. The core under investigation is remagnetized by a variable field with an increasing amplitude H _M , measuring the amplitude of the intensity of the alternating field H _M1 , which corresponds to the maximum amplitude magnetic permeability. Then, the second harmonic U ₂ is extracted from the total EMF induction signal, the dependence U ₂ = F (H _M ) is determined and the amplitude of the field H _M2 (H _{M2 is} less than H _M1 ) is measured, which corresponds to the maximum of the dependence U ₂ = F (H _M ). Next, the core is magnetized by the field, increasing its amplitude along the ascending sawtooth curve from zero to the found value H _M1 , and the magnetization is repeated until the maximum value U ₂ is measured, which is measured at the point H _M2 . From the ratio of the found value of U ₂ to the total EMF of the induction, a complete relative change in the magnetic permeability on the disaccommodation curve is judged, thus assessing its temporal instability. 3 il.

Description

The invention relates to magnetic measurements and can be used to predict deaccoding induced changes in the properties of closed cores over time.

Predicting the behavior of cores for a multiyear period is of great importance for the optimal design of radio equipment, ensuring the reliability of its operation.

Temporal stability is one of the most important indicators of the quality of standard samples of magnetic properties, intended for the calibration of magnetic measuring installations.

The purpose of the invention is to improve the accuracy and performance of the control.

Figure 1 shows a diagram of the device that implements the method; figure 2 - the spectrum of the natural frequencies of the investigated core; FIG. 3 shows the magnetization timing diagrams of the core under investigation,

In the device (Fig. 1), an ac current meter 2 and a primary toroidal winding 3 covering the core 4 are connected to the alternator 1. A secondary toroidal winding 5 covering the core 4 is connected to the on-off input

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switch 6. A broadband measuring device 7 is connected to one output of switch 6, and a selective measuring device 8 to another output.

The measurements are carried out in fields corresponding to the processes of displacement of domain boundaries, where low-frequency relaxation processes are pronounced. From Fig. 2 it can be seen that the low frequency spectrum is transferred to the second harmonic region with an amplification effect due to the intrinsic nonlinear properties of the ferromagnet. The internal amplification effect is implemented in the method by using a controlled core 4 with windings 3, 5 as an active primary converter (of the ferromodulation type). The source of additional energy is the alternating field produced by the primary winding 3, the magnetizing core 4, while the second harmonic of the magnetic induction Pg induced in the secondary winding 5 carries the information on the constant and infra-frequency components of the magnetic induction B remagnetized core in accordance with the expression

U W, S К (s ,, Нт) Bp, (О where Н is the amplitude of the tension of the Variable gender,

U) is the frequency of the alternating field; K is the proportionality coefficient, which is also the conversion factor in the ferromoduction converter, characterizing the gain efficiency due to the nonlinear properties of the ferromagnet, W.j is the number of turns of the secondary

windings 5) S is the cross-sectional area

core 4.

At the same time, RI is a direct measure of the change in the magnetic properties of the core 4 over time, since the generation of the second harmonic of the magnetic induction not only distorts the shape of the hysteresis loop due to asymmetry, but is also accompanied by the transfer of energy from the first harmonic to the second. Therefore, the magnetic instability can be estimated by the ratio of the second harmonic of the EMF of the magnetic induction to the total EMF of the magnetic induction, which corresponds to the relative change in the magnetic field

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Cementality () on the deaccommodation curve. As can be seen from expression (1), in an alternating field, the temporal magnetic instability of the core 4 is determined not only by the component BJJ, but also by the coefficient K, which linearly depends on the frequency and). Since the residual magnetization B, associated with the prehistory of the sample, does not depend on the floor H, then the dependence U7 f (Km) with the value of B other than zero is determined, it is possible to judge the shape of the curve K f (Hm), and hence the nature of the distribution of the intensity of magnetic instability in a given field region. This distribution is characterized by a maximum in the region of displacement processes, which corresponds to the maximum sensitivity of measurements.

The method is carried out in the following sequence.

The upper limit is determined from the field Ht, corresponding to the maximum amplitude permeability. For this, the core is magnetized by a 4-field variable. By smoothly changing the magnetizing current in accordance with diagram D3 (FIG. 3), the current in the primary winding 3 (FIG. 1) is measured with a current meter 2. At the same time, at the same points of the field, the voltage at the output of the secondary winding 5, proportional to the full induction emf signal (magnetic induction), is measured at the output of the secondary winding 5. For each point of the field, the ratio of the second measured value to the first and the maximum value of the ratio of the magnitudes of the magnitude of the current are found to be proportional to the field Nsc ,.

The field H point is determined for the study of temporal instability. Field H is set according to the maximum dependence of the second harmonic on the amplitude of the field intensity. The core is magnetized by 4 alternating fields of the same frequency. Smoothly changing the current in accordance with D, using a current meter 2, the current in the primary winding 3, proportional to the field strength, is measured, and the voltage at the second harmonic frequency is measured at the same points of the field using a selective device 8 at the same time. i, determine the dependence of the second value on the first and on the maximum dependence of the set value.

LiVac magnetizing current proportional to the field HWl.

(Stabilize the boundaries of the domains. With the -IToft target, the core 4 is magnetized by an alternating field. The magnetizing current in accordance with P1 is changed along a saw-tooth increasing curve from zero to a value corresponding to the Hmi field. When re-magnetized in D along the magnetization at H s using the selective device 8, the amplitude of the second harmonic of the emf of the induction is measured and further magnetization is continued to the field of Im. IT

The maximum temporal relative change in permeability is determined. For this, the stabilized value of the second harmonic U in the field Hm is measured. By switching switch 6, the total magnetic induction signal U is measured in the same field FI and judged by reference to the second harmonic to the sweat signal of magnetic induction

possible temporal change of magnetJ o

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/ w. / m about k1-

permeability (--- --.-), which characterize the temporary instability of the magnetic permeability of the core 4,

Studies have shown that the maximum of the {f (Hm) curve measured by the proposed method is located in the region of displacement processes up to the maximum amplitude magnetic permeability, which confirms the relaxation nature of temporal changes. At the same time, the amplitudes of the second harmonic correlate with the error temporal magnetic instability, obtained by direct measurements of the same core in a known manner.

However, if the instability according to the proposed method was determined within 20 minutes, in the known method it was determined according to the results of observations of the core during half a year. Thus, it provides, with a radical increase in the productivity of the control. At the same time, the dependence of the maximum value of the second harmonic on the frequency of variations is linear.

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It indicates the stability of the readings taken.

Thus, the proposed method makes it possible to artificially stabilize the domain structure of the core and, using the nonlinear properties of a ferromagnet, to obtain, by a single measurement, information on the temporal magnetic instability and to ensure an increase in the measurement accuracy, expressiveness of control and its simplification. In addition, it is possible to determine the distribution of the intensity of magnetic instability in the field of weak fields, which makes it possible to determine the favorable mode of operation of the core in the apparatus (amplitude and frequency of the alternating field). This increases the information content of the control.

Claims (1)

Invention Formula The method of determining the temporal instability of the magnetic permeability of cores, including the effect on the controlled core by an alternating magnetic field and measuring the amplitude magnetic permeability, characterized in that, in order to improve the accuracy and performance of the control, the controlled magnetic core is acted upon by a variable magnetic field with a monotonically increasing amplitude of strength, during this action, the dependence of the amplitude magnetic permeability on the amplitude of the intensity n is recorded belt magnetic field and record the amplitude value of the intensity of the alternating magnetic field corresponding to the maximum amplitude magnetic permeability, then re-act on the core with an alternating magnetic field with a monotonically increasing amplitude of the intensity and record the amplitude of the second harmonic of the EMF of the induction from the amplitude of the intensity of the alternating magnetic field, the registration process of which fixes the amplitude value of the intensity of the alternating magnetic field corresponding to the maximum the maximum of this dependence, after which the controlled core is repeatedly affected by an alternating magnetic field with an amplitude of intensity increasing according to the sawtooth law from zero to a value corresponding to the maximum dependence of the amplitude magnetic permeability on the amplitude of the alternating magnetic field strength, and registering the second harmonic amplitude of the induced emf with the intensity of the alternating magnetic field corresponding to the maximum dependence of the second harmonic of the induced emf on the amplitude of the alternating magnetic field, and the effect of alternating magnetic field a field with an amplitude of intensity increasing according to the saw-tooth law is produced until the amplitude of the second hectare is reached rmoniki EMF induction with the amplitude of the alternating magnetic field intensity corresponding to the maximum dependence of the second harmonic of the EMF induction on the amplitude of the alternating magnetic field, then measuring the amplitude of the second harmonic of the emf of the induction and amplitude of the intensity of the alternating magnetic field corresponding to the maximum dependence of the amplitude of the second harmonic of the emf of induction on the amplitude of the intensity of the alternating magnetic field, and the temporal instability is magnetic controlled permeability of the core is determined from the relationship dn u and v where the temporal instability of the magnetic permeability -, U, Ј, U2 - respectively recorded the amplitude of the second harmonic and the amplitude of the full signal EMF induction. one 1 0 10 20 X W 50 60Г, s O Figz 15 G, MN