SU1205087A1 - Method of determining static magnetic characteristics of ferrospecimen and apparatus for accomplishment of same - Google Patents

Abstract

1. A method for determining the static characteristics of ferro samples, including the effect on a ferro sample of an alternating magnetic field, sequentially reducing the frequency of magnetization and recording hysteresis cycles, characterized in that, in order to increase the measurement rate of the static magnetic characteristics of ferro samples, the coercive force will direct current, then for each frequency of the magnetization the dynamic coercive force is determined, and the static characteristic is found at the dawn a hysteresis cycle, for which the deviation of the coercive force from its value at a constant current does not exceed a specified value, while the initial value of the frequency of magnetization I ,,,,. choose from the conditions n.kr d WG where 8 ,. K is the integral estimate of the expenditure of the static and dynamic hysteresis cycles, the coefficient taking into account the shape of the cross section of the ferro sample; form factor EMF measuring winding; relative magnetic permeability and electrical conductivity of ferro sample, respectively; OL is the thickness and volume of the ferrobond, respectively. 2. The method according to claim 1, differing from that with the fact that the coercive force at a direct current is determined by the value of the demagnetizing current at the moment of maximum reversible permeability. 3. A device for determining the static magnetic characteristics of ferro samples containing a pulse generator, a series-connected reverse counter, a digital-to-analog converter, a power amplifier, a magnetizing winding, a reference resistor, a series-connected measuring winding, an integrator, and a recorder. (L

Description

The second information input of which is connected to a reference resistor, as well as a code matching unit, the first information input of which is connected to the output of a reversible counter, characterized in that, in order to reduce the recording time of the static characteristics of ferro samples, a controlled frequency divider, register, counter is entered into it cycles, a test signal generator connected to the magnetizing winding, a coupling capacitor, an extremum control unit and a zero-body whose input is connected to the integrator output, output - with a strobe input of the coincidence of codes, wherein the input control into-

The invention relates to magnetic measurements and is intended to determine the static magnetic characteristics of ferro samples.

The purpose of the invention is to reduce the recording time of the static magnetic characteristics of ferro samples.

The drawing shows a functional diagram of the device for implementing a method for determining the static magnetic characteristics of ferro samples.

The device contains sequentially connected generator 1 impulse. ow, controlled frequency divider 2, reversible counter 3, digital-analog converter 4, amplifier 5, magnetizing winding 6, reference resistor 7, connected in series measuring winding 8, integrator 9 and recorder 10, the second information input of which is connected to the reference resistor 7 and serially connected register 11, block 12 of code matching and counter 13 of cycles, the output of which is connected to the control input of controlled frequency divider 2, and the information inputs of register 11 and block 12 of matching code dineny with input start recorder 10, as well as

The MOS frequency divider is connected to a pulse generator, and the output is connected to the input of a reversible counter, the output of which is connected through a serially connected register, a code matching unit and a cycle counter connected to the control input of a controlled frequency divider, through a separation capacitor to a reference resistor and the output is connected to the inputs of the Register register and Reset of the loop counter; the recorder trigger input is connected to the output of the code match block, and the output of the test signal generator is connected to agnichivayuschey winding.

j

0

a test signal generator 14 connected to the magnetizing winding 6, a coupling capacitor 15, an extremum detection unit 16, connected via a coupling capacitor 15 to the reference resistor 7, and output to the Record Register 11 and Reset Counter inputs 13 cycles, and the zero-body 17, the input of which is connected to the output of the integrator 9, and the output to the gate input of the code matching unit 12.

In the case of dynamic reversal of magnetization of samples at low frequencies, the methodological error of recording (expansion of dynamic hysteresis loops with respect to static ones) is determined by the surface effect. The resulting attenuation of the intensity of the floor in the thickness of the sample is estimated to be equivalent to the intensity equal to the average value of the intensity of the thickness of the samples.

.

(-e

(.one)

where n is l

the intensity of the external gender; coefficient depending on the frequency of bias of the electrical conductivity of the sample material.

Shr-differential magnetic

permeability.

From the expression (1) it follows that at the point of coercive force, where the differential magnetic permeability is maximum, H takes the minimum value, which corresponds to the maximum methodical error of the register | CII.

 Thus, at this point on:; the maximum difference between the registered characteristics and the actual static ones is observed; at the remaining points of the hysteresis cycle, the registration error is obviously less .. Therefore, the degree of approximation of the recorded characteristic to the static one can be estimated from the ratio of its coercive force H to the coercive force on direct current

AND,

where is the registration error.

This allows us to take the registered hysteresis cycles satisfying condition (2) as static with a methodological error in

The method is carried out as follows.

The coercive force of a ferro specimen at a constant current, i.e. in the static magnetization mode, by determining the maximum reversible magnetic permeability. Reversible magnetic permeability of ferro sample

t ,,, о о (3)

. "UH-i- About

where L 15 and U H are increments of magnetic induction and intensity, repeats the nature of the change in differential magnetic permeability and reaches a maximum at the point of coercive force, therefore, the pre-sample to the peak of the sample is demagnetized. The pulses from the pulse generator through the control divider 2 frequencies, the division factor of which is set by the counter 13 cycles maximum, are fed to the input of the reversible counter 3, the state of which is converted by the digital analog converter 4 and the power amplifier 5 to the demagnetizing current in the magnetizing winding 6.

but

.

.

ten

15

12050874

At the same time, an alternating signal from the test signal generator 14 is applied to the magnetizing winding 6, the amplitude of which is much less than the values of the demagnetizing current and does not significantly affect the dynamics of the process. From the reference resistor 7, through a coupling capacitor 15, an alternating voltage is applied, the amplitude of which depends on the magnetic state of the ferro sample. At the moment when the demagnetizing magnetic field reaches the value of the coercive force, the inductance of the magnetizing winding 6 becomes maximum, since the maximum reversible magnetic permeability, and the amplitude of the alternating voltage, is therefore minimal. This moment is fixed by the extremum determination unit 16, which permits the recording of the state of the reversible counter 3 corresponding to the value of the coercive force on the direct current H, to the register 11. In addition, the extremum determination unit 16 clears the state of the counter of 13 cycles, setting the minimum coefficient dividing and thus setting the initial frequency of the magnetization reversal, which is determined by the magnitude of the integral estimate of the divergence of the dynamic hysteresis loops from the static

s

 (four)

Pg - magnetic losses due to eddy currents;

20

25

thirty

35

Where

40

P (- is the hysteresis loss in the static magnetization mode.

In turn, bc is chosen for an order of magnitude of a given registration error S.

Pg is determined by the formula

Pe K, TkV -f -8Xv, (5)

50

Where

K, 5

coefficient taking into account the shape of the cross section of the ferro sample conductivity of the ferrorblast

The shape factor of the EMF of the measuring winding d.V is the thickness and volume of the ferro-resin, respectively;

W Ch51

i is the frequency of magnetization reversal; In „- the amplitude of the magnetic induction,

.a hysteresis loss in static mode

RS 4B ,, - H ,,

(6)

where H is the coercive force at a constant current.

Substituting the expressions (5) and (6). Into (4), determine the initial frequency of the magnetization reversal

. wg

 ()

where - rtJ - relative magnetic permeability.

The value of the magnetizing current is formed similarly to the demagnetization process. In the process of magnetization reversal of the ferro sample, the null organ 17 determines the moments when the magnetic flux reaches zero, at which the 12 codes match block compares the value of the coercive force on the direct current Hj., Recorded in register 11, with the state of the reversible counter 3 corresponding to the value coercive force of the current hysteresis cycle.

If the condition (2) is not fulfilled, the check of which is carried out by the block 12 of coincidence of the codes by eliminating the number of younger digits of the codes being compared depending on the value E, the counter of 13 cycles increases its content by one, thereby increasing 50876

It is the coefficient 4) that divides the patient and, consequently, reduces the frequency of magnetization reversal.

Upon reaching the value of frequency 5 of the reversal, at which the deviation of the coercive force of the current cycle from its value at a constant current does not exceed the specified registration error, block 12 of matching codes turns on the recorder 10, which records the hysteresis cycle corresponding to the characteristic with the error.

In the known technical solution

15 the absence of a quantitative estimate of the methodological error in recording quasistatic characteristics leads to the unjustifiable low frequency of the magnetization reversal (about

20 0.1-0.01 Hz), which reduces the registration rate and complicates the measuring apparatus due to the increased requirements for its sensitivity and stability.

The introduction in the proposed method of quantifying the discrepancies of the characteristics of the current hysteresis cycle of the HCO from its value at a constant current H recorded during quasistatic reversal of the coercive force of the current hysteresis cycle H to uniquely determine the frequency of magnetization reversal that meets the required registration accuracy. This leads in a number of cases to a significant increase in the working frequency of the magnetization reversal (at least in order), which makes it possible to shorten the test time by a factor of 3-5.

VNIIPI Order 8524/48 Circulation 747 Subscription Branch ShSh Patent, Uzhgorod, Proektna St., 4

Claims (3)

1. A method for determining the static characteristics of ferro-samples, including exposure to a ferro-sample of an alternating magnetic field, sequentially reducing the magnetization frequency and registering hysteresis cycles, characterized in that, in order to increase the measurement speed of the static magnetic characteristics of ferro samples, the coercive force at a constant current is preliminarily determined , then, for each bias frequency, the dynamic coercive force is determined, and the static characteristic is found by registering Nome an hysteresis cycle for which the deviation of the coercive force from its value at constant current is less than a predetermined value, the initial value of the magnetic reversal frequency is selected from the condition 'wherein _L 8 - integral estimate differences of static and dynamically and hysteresis cycles; To η - coefficient taking into account the cross-sectional shape of the ferro-sample ·, Ι'φ - coefficient of shape of the EMF of the measuring winding; p, y — relative magnetic permeability and electrical conductivity of the ferro-sample, respectively; 8, V is the thickness and volume of the ferroobrazene, respectively. 2. The method of pop. 1, which differs in that the DC coercive force is determined by the value of the demagnetizing current at the instant of maximum reversible permeability. 3. A device for determining the static magnetic characteristics of ferro samples, containing a pulse generator, a serially connected reverse counter, a digital-to-analog converter, a power amplifier, a magnetizing winding, a reference resistor, a series-connected measuring winding, an integrator and a recorder, the second information input of which is connected to a reference resistor, and also a block matching codes, the first information input of which is connected to the output of the reversible counter, characterized in then, in order to reduce the time of recording the static characteristics of ferro samples, a controlled frequency divider, a register, a cycle counter, a test signal generator connected to a magnetizing winding, an isolation capacitor, an extremum control unit and a zero-organ whose input is connected to the integrator output are introduced into it, and the output is with the gate input of the code matching block, while the input of the controlled frequency divider is connected to the pulse generator, and the output is to the input of the reversible counter, the output of which is through the last the register, the code matching unit, and the cycle counter are connected to the control input of the controlled frequency divider, the input of the extremum determination unit is connected through a dividing capacitor to the reference resistor, and the output to the inputs. Register register and reset of the cycle counter. codes, and the output of the probe signal generator is connected to the magnetizing winding.