GOST 12635-67

• gost-12635-67.pdf (912.78 KiB)
  ГОСТ 12635-67

GOST 12635−67 of magnetic magnetic high frequency Materials. Test methods in the frequency range from 10 kHz to 1 MHz

GOST 12635−67

Group П99
__________________________________________
* In the index «National standards», 2008
group В89. — Note the manufacturer’s database.

STATE STANDARD OF THE USSR

OF MAGNETIC MAGNETIC HIGH FREQUENCY MATERIALS

Test methods in the frequency range from 10 kHz to 1 MHz

High frequency magnet malleable materials.
Testing methods at the range from 10 kc/s to 1 MS

Date of introduction 1969−01−01

APPROVED by the Committee of standards, measures and measuring instruments under the USSR Council of Ministers 16/II, 1967


This standard applies to high-frequency of magnetic magnetic materials-magnetodielectrics (based on carbonyl iron and aliferov) and ferrites, and establishes methods for determining their magnetic properties when magnetized by an alternating periodic magnetic field in the frequency range from 10 kHz to 1 MHz.

The standard does not specify test methods ferrites with rectangular hysteresis loop, and also test methods in a pulsed mode.

The following shall be the methods definition of magnetic characteristics:

pavement

resonance,

induction,

method beats (only for determination of the temperature coefficient of magnetic permeability).

Characteristics of each method are given in the table, and the list of letter symbols in the formulas table in the Appendix 1.

The choice of method for determining the magnetic characteristics stipulated in the standards and technical documentation of magnetic magnetic materials.

All values after the substitution in the formulas of this standard must be expressed in units of the International system according to GOST 9867−61.

1. GENERAL INSTRUCTIONS

1.1. The selection and preparation of samples for testing.

1.1.1. Samples for testing in the determination of characteristics of ferromagnetic materials should have an annular shape. The ring size should match the sensitivity of the measuring equipment.

1.1.2. Before applying the windings on the ring diameter and thickness must be measured with measurement error no more than ±0,1 mm. for determining the specific loss of the sample, in addition, must be weighed with an error not more than ±0,5%.

1.1.3. The size of the samples calculate the harmonic and average diameters and cross-sectional area by the formula:

, (1)

, (2)

a) for samples of rectangular cross section:

, (3)

b) for samples with cores of aliferov, the shape of which is depicted in hell.1:

. (4)

Damn.1. Form sample with cores of anciferov

Form sample with cores of anciferov

Damn.1


Characteristics test methods

________________
* With helical magnetization.

** Depends on the type of meter, frequency and pattern.


Calculation of magnetic characteristics produced by the harmonic diameter . Depending on the required accuracy of measurements and the radial thickness of a sample, characterized by the ratio , harmonic diameter can be replaced by average . A graph of the ratio of average diameter to the harmonic for different relations of the outer diameter to the inner given on features.2.

Damn.2. A graph of the ratio of average diameter to the harmonic relationship of the diameters of the samples

A graph of the ratio of average diameter to the harmonic relationship of the diameters of the samples

Damn.2

The relative error determine the mean and harmonic diameters of the sample calculated by the formula:

, (5)

. (6)

1.1.4. The relative error in determining the cross sectional area of the sample calculated by the formula:

a) for samples of rectangular cross section:

, (7)

b) for the samples, the shape of which is depicted in hell.1:

. (8)

If sample sizes correspond to the dimensions given in GOST 8763−58, when measured , and with an error not exceeding 0.1 mm, the highest relative error of determination is in the range from 0.2 to 1%, from 1% to 3%, and 2 to 7%.

1.1.5. The choice of the brand of wire for winding, wound on the sample, depends on the type of defined characteristics (magnetic permeability, loss angle, and temperature coefficient of magnetic permeability, etc.) and type of test material. In determining the loss tangent and loss factors of the cores made of carbonyl iron, aliferov and ferrites with low magnetic permeability, with low losses at frequencies over 300 kHz, to the coil resistance of the sample was slightly changed with the change of frequency, it is necessary to perform the winding of the stranded wire (Litz wire) stamps, LASO 12х0,07, LASO 21х0,05. For frequencies up to 300 kHz coil is allowed to perform solid-core copper wire with a diameter of not more than 0.25 mm.

Note. With helical magnetization in order to avoid damage to the insulation of the windings on the sample after measuring its geometric dimensions and the weighting applied to the layer of insulating material (PTFE tape, capacitor paper) with a thickness of about 0.1 mm, and on top of this layer — the coil with the desired number of turns.

1.1.6. Before testing the sample was subjected to demagnetization through the winding fed by current with frequency of 50 Hz with gradually decreasing amplitude. The initial amplitude of the demagnetizing field should exceed the coercivity of the material is not less than 50 times. The minimum amplitude of the demagnetizing field must not exceed the lowest value of field strength in which make measurements of the magnetic characteristics.

The exposure time of the samples after demagnetization before the beginning of measurements of magnetic characteristics is established depending on the type of material and its magnetic permeability. Magnetodielectric based on carbonyl iron exposure after demagnetization are not subjected to aliferov the exposure time should be 10 min For the manganese-zinc ferrite brand NM exposure time should be 24 hours, for Nickel-zinc ferrites brand NN — no less than 3 hours.

In particularly important cases measurements it is recommended to demagnetize ferrites: 150ВЧ, 100ВЧ, 50ВЧ2, 30ВЧ2 and 20ВЧ heating to a temperature above the Curie point.

1.2. Measurement conditions and equipment.

1.2.1. Testing of samples was carried out at an ambient temperature of 298±10 °K (25 °C±10 ° C), relative humidity up to 80% and atmospheric pressure 100000±4000 n/m(750±30 mm Hg.St.).

In determining magnetic properties of materials with temperature coefficients and more than 1·101/deg, it is necessary to introduce amendments calculated by the formula:

, (9)

, (10)

where and  — material characteristics defined at 25 °C.

1.2.2. For testing of magnetic magnetic materials in the frequency range from 10 kHz to 1 MHz, use the following measuring equipment:

a) bridges (Appendix 2);

b) gauges q;

C) ammeter, milliammeter and microammeter (Annex 3);

d) voltmeters and millivoltmeters (Annex 4).

1.2.3. As a measuring apparatus for measuring characteristics of magnetic magnetic materials bridge method allowed the use of overhead installations, made by any schemes or assembled from separate elements, but providing the ability to measure the values given in the table.

2. METHODS OF DETERMINING MAGNETIC CHARACTERISTICS

2.1. Bridge method

2.1.1. When the bridged method definitions listed in the table of characteristics measure the inductance or mutual inductance and resistance of the magnetizing device with an annular core of ferromagnetic material under test, and calculate the magnetic characteristics by appropriate formulas.

2.1.2. For magnetization used a multiturn winding. The number of turns of the multiturn winding choose depending on the brand of the test material, specimen dimensions, the required magnetic field strength and the limits of the measurement equipment to determine the inductance by the formula:

, (11)

where is the coil inductance with the sample.

2.1.3. When testing on the bridge of mutual inductance of the sample must be applied to the two windings, operated by double wire. Counting the number of double coils is produced according to the formula:

, (12)

where is the mutual inductance between the windings of the sample (depends on the limits of the equipment for measuring mutual inductance).

2.1.4. When testing the winding or magnetizing device of the test specimen attached to the bridge and balance it with the adjustable elements under the given normative documents suitable ferromagnetic material values of magnetic field intensity and frequency. From the equilibrium equations of the bridge to determine the inductance or mutual inductance between the windings of the sample and the resistance of the sample. After the introduction of the necessary amendments calculate the magnetic permeability and the loss tangent of the sample material.

2.1.5. Loss factor the hysteresis is determined by measurement of the loss tangent at two values of magnetic field strength and one frequency in the range of linear dependence of dissipation on the magnetic field.

2.1.6. The ratio of the frequency of losses (including eddy currents) is determined by measurement of the loss tangent at two or three frequencies and with the same value of the magnetic eld in the region of linear dependence of loss tangent on frequency.

It is recommended for samples of carbonyl iron testing in the frequency range from 100 kHz to 1 MHz, for samples of aluminum alloy is from 100 to 300 kHz.

2.1.7. The coefficient of additional losses 1·10is determined as the difference between the loss tangent of the material and the sum of the tangents of the loss angle on the hysteresis and frequency.

2.1.8. The coefficient of additional losses, materials with a low value (about 1·10) is determined using a bridge circuit with mutual inductance, measuring the loss tangent of the sample at two frequencies at the same value of magnetic field intensity, and on the basis of these two measurements determine the component of loss tangent independent of frequency. Subtracting from the obtained value , due to losses in the hysteresis, determine the coefficient of additional losses.

2.1.9. Reversible magnetic permeability is determined, applying to the sample an additional winding of the magnetization with direct current, which consistently include adjusting the rheostat, the ammeter for measuring the DC current , the inductor and the power source.

The number of turns of the coil calculated by the formula:

. (13)

2.1.10. Specific loss of material is determined by measuring the resistance loss of the sample by the bridge and measuring the current in the magnetizing winding of the sample.

2.1.11. Temperature coefficients of magnetic permeability and loss tangent determined by the change of the inductance and the resistance of the sample with the magnetizer when you change its temperature. For the determination of 0.5·101/deg and 2·101/deg, you can use any bridge circuit for measurement of inductance and resistance with an accuracy higher than 1% and thermokarstic, allowing you to create a certain temperature in a specified interval with an error of less than 0.5 degrees. To determine (0,02−0,5)·101/grad to apply the method of beating described lower

E.

2.1.12. The magnetic field in the test ring sample count by the formulas:

(14)

or

,

where  — peak value of the magnetizing current in the winding of the sample.

With sinusoidal current waveform of 1.41 .

For cores with a ratio of from 1.4 to 2.5 difference in the values of the field intensity calculated for the harmonic and the average diameters ranged from 1 to 7%.

2.1.13. The amperage measured by the ammeter (Milli — or microammeter) or determine by measuring with a voltmeter (millivoltmeter) the voltage drop across the resistance retreactive. As betrachtung resistance should take is the reactive component which does not exceed 10% of the total resistance. The parameters of the measuring device should not affect the equilibrium condition of the bridge.

The presence of self-capacitance of the windings of the sample and the active current component due to losses in the sample, making the error and the determination of the magnetizing current in the winding. Therefore, the value of the magnetizing current in the winding should be calculated according to the formula:

. (15)

2.1.14. Self-capacitance if the magnetic permeability of the sample is not dependent on frequency, is determined by measuring the inductance at two frequencies (at which the magnetic permeability is constant) and the same current strength in the coil sample and calculated by the formula:

. (16)

If the magnetic permeability of the material varies with frequency, the self-capacitance is determined by applying the same winding as in the test sample, a core of the same size of non-ferromagnetic and non-metallic material. Inductance measurements are also produced at two frequencies-and self-capacitance calculated by the formula 16.

2.1.15. The highest relative error of determination calculated by the formula:

. (17)

Current measurement instruments class 0,5; 1,0; 1,5 the error is in the range of from 2 to 6%.

2.1.16. Counting the real component of relative magnetic permeability of the material of the ring sample produced by the formulas:

(18)

or

(19)

(20)

or

, (21)

where the inductance (with the adjustment for self-capacitance) of the coil with the sample.

The inductance is given by:

. (22)

2.1.17. The largest relative error of determining the magnetic permeability is given by:

. (23)

Measurement error includes the error of measurement of inductance caused by an error of the measuring equipment and the uncertainty of the corrections due to the influence of self-capacitance of the winding.

For samples, the permeability of which in the considered frequency range is independent of frequency, with the inductance measurement with an error of not more than 0.5% and a frequency of 0.05% (formula 16) the error in determining the self-capacitance of the winding is not more than 10%. Otherwise, this error can increase to about 20%.

A maximum relative error of determining the magnetic permeability did not exceed 5%, the error of measurement of inductance should be less than 1% and the outer diameter of test specimens should be at least 24 mm.

2.1.18. The error in determining the permeability increases due to the uncertainty of determining the field strength to values in cases where the magnetic permeability of the material depends on the magnetic field strength and is calculated according to the formula:

. (24)

2.1.19. The loss tangent of the material is calculated by the formula:

(25)

or (in the case of multiturn windings)

, (26)

where:

 — resistance losses, ω,

 — the resistance of the coil with the sample (at a given frequency with the adjustment for self-capacitance of the winding) in ohms,

active winding resistance (measured at DC) with adjustment for the effect of skin effect at given frequency, ω.

The value calculated by the formula:

, (27)

where is the resistance of the winding with the sample, measured at a given frequency in ohms.

The resistance value calculate using the measured resistance value by the formula:

, (28)

where is the correction member to effect surface effect.

Coefficient with frequency dependent magnetizing current and brand of wire. Its value, i.e. the ratio of wire resistance at a given frequency to its resistance measured with direct current to Litz wire calculated by the formula:

, (29)

where:

and are the coefficients that depend on (for copper wire 10,65);

 — frequency, MHz;

 — the diameter of individual wire of the Litz wire, mm;

 — the number of wires of the wire;

the diameter of the wire, mm;

 — ratio-dependent .

In Annex 5 shows graphs of the coefficients and from

and from .

2.1.20. The highest relative error of determination of loss tangent calculated by the formula:

. (30)

2.1.21. The absolute error in determining the resistance losses of the sample material is given by:

. (31)

Note. A maximum relative error of determining the tangent of the angle magnetic losses did not exceed 8%, the error of measurement of inductance shall not exceed 1%, the resistance loss — 5% frequency — 2%.

2.1.22. The loss factor for eddy currents when counted according to the formula:

, (32)

where and and  — tangent of angle of losses and resistance losses, respectively, with frequencies and .

2.1.23. The loss factor for hysteresis in calculated by the formula:

, (33)

where and , and the tangents of the angle of losses and resistance losses, respectively, in the magnetic field and .

2.1.24. The coefficient of additional losses 1·10calculated by the formula:

. (34)

The measurements on the bridge of the mutual inductance coefficient additional loss of 1·10(n.2.1.8) calculated by the formula:

, (35)

where:

and the tangents of the loss angle, measured respectively at the frequencies and ;

 — the field strength at which measurements were conducted.

2.1.25. To obtain the values of loss coefficients allowed the use of graphical methods, while the axis of ordinate delay values of loss tangent and x — axis is the frequency or intensity of magnetic field.

The ratio of the frequency of losses is characterized by the tangent of the slope of the straight line expressing the dependence to the x-axis (Fig.3).

Damn.3. A graph of the loss tangent of the material from the frequency

A graph of the loss tangent of the material from the frequency

Damn.3

Loss factor the hysteresis is characterized by the tangent of the slope of the straight line expressing the dependence to the x-axis (Fig.4).

Damn.4. A graph of the loss tangent of the material on the magnetic field

A graph of the loss tangent of the material on the magnetic field

Damn.4

The coefficient of additional losses is graphically expressed by the segment on the ordinate, corresponding with 0 and 0 and the intercept with the extrapolation of direct or .

2.1.26. The largest relative error of determining the rate of frequency of losses (ignoring the error of measurement of frequency) calculated by the formula:

. (36)

The largest relative error of determining the coefficient of hysteresis losses calculated by the formula:

, (37)

where and  — the resistance losses measured, respectively, at field strengths and .

The largest relative error of determination of coefficient of additional losses, calculate the formula (34), expressed by the formula:

. (38)

When determining the factor using the bridge of mutual inductance calculation error is produced by the formula:

. (39)

The error of the member calculated by the formula:

, (40)

where:

 — absolute accuracy of capacitance , the balancing resistance of losses (Annex 2), f;

 — the resistance of one arm of the bridge of mutual inductance (see Appendix 2), Ohm;

 — absolute accuracy of magnetic field intensity, a/m.

2.1.27. In order for the error of determination of loss coefficients (especially when the values of 1·101/Hz, 1·10m/a, 1·10) did not exceed 20%, the error of the resistance measurement should be not more than 1% (see table).

To reduce the error of determining the rate of frequency of losses (especially when its numerical value is of the order of 1·101/Hz) determination must be carried out at frequencies and differing from each other not less than three times.

To reduce the error of determining the rate of hysteresis loss (especially when its numerical value is of the order of 1·10m/a) a determination shall be made in the intensities of the magnetic field , and differing from each other not less than three

times.

2.1.28. Specific losses in the material on the basis of the measurement results of bridge method calculated by the formula:

. (41)

2.1.29. The largest relative error of determination of specific losses calculated by the formula:

. (42)

If you measure the current the instrument class 1.5, the drag losses with the error not higher than 5% (see table) and weigh the sample with an error of not more than 0.5%, will not exceed 10%.

2.1.30. Calculation of temperature coefficient of magnetic permeability produced by the formula:

, (43)

where: and  — the real components of the relative complex magnetic permeability of the test sample, respectively, at temperatures of and , calculate on the basis of measurements of the inductance at temperatures and ;

 — the same, at a temperature of 25 °C

.

2.1.31. The highest relative error of determination of temperature coefficient of magnetic permeability calculated by the formula:

. (44)

For materials with a temperature coefficient which varies depending on the temperature range the greatest temperature range should not exceed 30 deg. Given the fact that the error did not exceed 20% (see table), the value should not be less than 0.5·101/deg and the temperature measurement error shall not exceed 0.5 degrees.

2.1.32. The temperature coefficient of the tangent of the loss angle calculated by the formula:

, (45)

where:

and resistance losses of the coil with the sample, respectively, at temperatures and ohms;

and  — inductance coil with the sample, respectively, at temperatures and GBV.

When counting it is necessary to consider the difference of wire resistance of winding at a given temperature from its value at normal temperature , taking into account that:

. (46)

2.1.33. The largest relative error of the temperature coefficient of the tangent of the loss angle calculated by the formula:

. (47)

In range of temperature 30 deg, measurement error temperature is not more than 0.5 deg and the resistance measurement with an error not exceeding 1% of the maximum error of the determination of the temperature coefficient of the tangent of the loss angle (at 2·101/deg) is not more than 30%.

2.2. Resonance method

2.2.1. Resonance method definitions listed in the table of values is in the measurement using the measuring q (cometra) inductance and q-factor of the magnetizing device with an annular core of ferromagnetic material under test, and subsequent calculation of the magnetic characteristics by appropriate formulas.

As the magnetizing device can be used as multiturn and single-turn winding (single-turn frame, coaxial holder, high frequency Permeameter). Methods of determining magnetic characteristics of single-turn in the magnetization similar to those described in GOST 12636−67 «Materials of magnetic magnetic high frequency. Test methods at frequencies from 1 to 200 MHz».

2.2.2. The number of windings of the sample is given by (11). In this case, the inductance of the test specimen with helical winding are according to the formula:

, (48)

where is the capacitance of the capacitor of the resonant circuit cometra, f.

2.2.3. When tested sample with multiturn windings after the connection of the winding to the terminals cometra to set the desired frequency and an adjustable capacitance of the resonant circuit to achieve the maximum deflection of the pointer of the scale merit. Then determine the inductance and the quality factor of the sample, which calculates the permeability and the loss tangent of the sample (with the winding).

2.2.4. To determine the temperature coefficients of magnetic permeability and loss tangent of the material measured inductance and q-factor of the sample temperature in high-frequency Permeameter (p.2.2.1) or in a magnetizing device placed in thermokarstic at two or more temperatures within the specified range.

2.2.5. In multiturn winding of counting the relative magnetic permeability of a ring sample produced by the formula (18) or (19).

2.2.6. The relative error of inductance using cometra determined by the formula:

. (49)

If the error cometra frequency does not exceed ±1% and the error in the calibration of the scale capacity is in the range of from 1 to 4% (depending on the capacity value), the largest error in the measurement of inductance will be 3−6% and the real component of relative magnetic permeability is not more than 10%.

2.2.7. The loss tangent of the sample material calculated by the formula:

, (50)

where is the quality factor of the coil with the sample (counted directly on the scale q cometra).

Member due to the winding parameters (p.2.1.19).

2.2.8. The relative error of determining the tangent of the magnetic losses calculated by the formula:

. (51)

If the measurement error of the quality factor with kumera does not exceed 10%, the highest relative error of determination of the tangent of the angle magnetic losses will not exceed 30%.

2.2.9. Calculation of temperature coefficient of magnetic permeability produced by the formula (43) taking into account formulas (18), (22) and (48).

The highest relative error of determination calculated by the formula:

. (52)

where and is the capacitance at resonance, corresponding to temperatures and , f.

Note. When the error temperature is not more than ±0.5 degrees, the interval of its change is 30 deg and the error of the calibration of the scale capacity cometra from 1 to 4% for the determination of the temperature coefficient of magnetic permeability with an error of not more than 20%, must be at least 5·101/deg.

2.2.10. The count value produced by the formula:

, (53)

where and  — q corresponding to the temperatures and .

2.2.11. The highest relative error of determination calculated by the formula:

. (54)

When the error temperature is not more than ±0.5 degrees, the interval of its change is 30 deg and the error of the calibration of the scale q cometra ±10% to determine the temperature coefficient of the tangent of the loss angle with an error not exceeding 30%, the value must be at least 1·101/deg.

2.3. Induction

2.3.1. Induction method definitions listed in the table of values is to measure the magnetizing current in the primary winding of the sample, the EMF, induced in its secondary winding, power (loss of sample) and subsequent calculation of the magnetic characteristics by appropriate formulas.

2.3.2. The amount of current flowing through the primary (magnetizing) winding sample, is measured by an ammeter (Fig.5) or determined using a voltmeter and beseeching resistance (Fig.6).

Damn.5. The strength of the current flowing in the primary (magnetizing) winding in a sample measured by the ammeter

Damn.5

Damn.6. The strength of the current flowing in the primary (magnetizing) winding in a sample, determined by the voltmeter and retreactive resistance

Damn.6

Note. In Annex 3 the list of relevant ammeters, milliammeter and microammeter and their main technical characteristics.

2.3.3. For calculating the maximum value of magnetic induction measurement of the EMF, induced in the secondary winding of the specimen, shall be measured by the voltmeters average or RMS values (with a known shape factor ).

If the shape of the curve is the EMF, induced in the secondary winding of the specimen, a sine wave can be applied to any voltmeter (current, amplitude or average values), for the given range of frequencies.

Note. In Appendix 4 the list of devices and their main technical characteristics.

2.3.4. To determine the dependence of losses in the samples of the amplitude value of magnetic induction or magnetic field applied battleroy method in accordance with the scheme depicted in hell.7. This scheme also allows to determine the dynamic curve of magnetization.

Damn.7. The scheme of determining the dependency of the losses in the samples of the amplitude value of magnetic induction or magnetic field strength. Battleroy method

Damn.7

2.3.5. On the sample above the insulation needs to be applied to the two windings — magnetization and measurement. The measuring winding is applied to a uniformly distributed or concentrated in one place. On top of the measurement winding of the magnetizing coil is applied uniformly throughout the circumference of the sample.

The number of turns of the measuring coil calculated by the formula:

, (55)

where and is the voltage on the secondary winding of the sample V.

The number of turns of the magnetizing winding is calculated by the formula:

. (56)

2.3.6. To determine the dynamic magnetization curve of the material of the test sample to its windings included in the circuit in accordance with the scheme of the devil.5 or 6.

Consistently setting the required values (from smallest to largest) of the magnetic field (proportional to the current in the magnetizing coil) and measuring the corresponding EMF, induced in the measuring winding of the sample, determine the dynamic magnetization curve of the sample material.

2.3.7. If you want to determine the dynamic curve of magnetization and loss measurements produced by the scheme of the devil.7.

Sequentially setting values of the magnetic field (the strength of the current in the magnetizing coil) or magnetic induction (EMF, induced in the measuring winding) and measuring the corresponding values of the power (wattmeter), get the dependence of the losses in the sample on the magnetic field or magnetic induction.

2.3.8. Magnetic field intensity (maximum value) calculated by the formula:

. (57)

2.3.9. The error of determination of magnetic field intensity is in the range of from 2 to 6% depending on the class of the measuring device.

2.3.10. The maximum value of the magnetic induction calculated by the formula:

. (58)

2.3.11. The largest relative error in determining the magnetic induction calculated by the formula:

. (59)

Note. If the largest relative error in determining the cross sectional area will be from 2 to 7%, the frequency accuracy (most generators without resonators) 2% voltage measurement error of 3−5%, the accuracy of determining the shape factor of the curve of secondary E. D. S. — about 3%, the largest relative error in determining the magnetic induction is in the range from 10 to 15%.

2.3.12. Based on the obtained values of the magnetic induction and magnetic field can be built dynamic magnetization curves of the form:

, , ,

, , .

According to the same data can be obtained the dependence of relative amplitude of magnetic permeability on intensity of magnetic field , compute according to the formula:

. (60)

2.3.13. The greatest error in determining the relative amplitude of magnetic permeability when the accuracies of the measurements and indicated in the claims.2.3.9 and 2.3.11, is in the range from 10 to 20%.

2.3.14. Calculation of specific losses in the sample material produced according to the formula:

, (61)

where:

power measured by the wattmeter, W;

 — resistance of secondary winding, ohms:

,

 — the resistance of the parallel windings of the wattmeter, Ohm;

 — resistance of voltmeter in ohms.

At high resistance and (when ) a correction member can be neglected.

2.3.15. The largest relative error of determination of specific losses calculated by the formula:

. (62)

When mass measurement with an error no greater than 0.5%, the application of wattmeters with an uncertainty of measurement power not more than 15% and voltmeters class 2,5 the greatest measurement error of specific losses will be 30%.

2.4. Method beat

2.4.1. The beating method is used to determine the temperature coefficient of magnetic permeability when a small numerical value (±20·101/deg).

Such temperature coefficient of magnetic permeability have, for example, magnetodielectric based on carbonyl iron, ferrites with low magnetic permeability (20 RF).

2.4.2. Temperature coefficient of magnetic permeability determined by the oscillator to change frequency due to changes under the influence of temperature of the inductance coil with core of the material included in the circuit of the measuring generator.

Using an electronic oscilloscope to compare the differential frequency obtained by mixing the oscillations of the two high-frequency generators (main and measurement), with the frequency of the generator of sound frequencies.

2.4.3. A block diagram, which carry out measurement by the method of the beats depicted in hell.8.

Damn.8. Block diagram of measurement «beta (1)» method of beating

Damn.8

High frequency unit allows to obtain voltage, frequency of which is proportional to the measured ratio . This unit includes two high-frequency generator: measurement and basic, a mixer and a low-frequency amplifier.

2.4.4. Frequency of the generator is selected equal to the desired frequency of testing. Due to the high requirements of generators in relation to the stability of their frequency, the main generator must have a quartz crystal resonator. To improve frequency stability of the measuring and base generator, they must be thermostatically, so that fluctuations in the temperature inside the thermostat does not exceed ±0.5 degrees. The variable capacitor of the measuring oscillator should have low temperature coefficient (10·101/deg).

Generator of sound frequencies should give the opportunity to produce the reference frequency accurate to 1 Hz for a frequency change of not more than 5 Hz for 1 h.

2.4.5. Depending on the frequency of the (quartz) generator, the permeability of the material of the test specimen and the limits of change of the capacitance of the capacitor included in the circuit of the measuring generator, count the number of windings of the sample according to the formulas (11) and (48).

If the test is carried out at temperatures above 373 °K, the wire for winding shall have enamel insulation.

2.4.6. Before measurement, the sample coil is dried at a temperature of 373 °K for 1 h (in a separate tank or in the same thermocrete, which make measurements). If the measurement is made not immediately after drying, before measurements, the samples shall be stored in a desiccator.

2.4.7. The test piece with a coil included in the circuit of the measuring capacitor. If you want to define in a wide range of temperatures, the measurements should start with low temperatures.

Setting on the sound generator frequency, lying in the middle of its range, the capacitance change of measuring capacitor generator achieve stop Lissajous figures on the oscilloscope screen. This means that the difference frequency (the measuring and base generators) is equal to the frequency of the sound generator. The value of the difference frequency measured at each fixed temperature, installed in thermocrete.

If you choose the differential frequency so that the capacity of the resonant circuit, which includes the sample to be tested, consistent with the increase of the difference frequency, it is positive in the case when the temperature increases there is an increase of the difference frequency, and Vice versa.

2.4.8. Temperature coefficient of magnetic permeability calculated by the formula:

, (63)

where:

and  — values of the difference frequencies, respectively, in the temperature and counted on the scale of the generator of sound frequency, Hz;


the frequency of the generator in Hz.

2.4.9. The highest relative error of determination calculated by the formula:

. (64)

Absolute error of measurement of the difference frequency at the output of the plant for determination should not exceed 10 Hz.

Note. With an error of temperature measurement in thermocrete not more than 0,5 deg and the temperature range of 30 deg, the greatest relative error of determination does not exceed 20%.

APPENDIX 1. A LIST of basic letter symbols used in the formulas of this standard

ANNEX 1 GOST 12635−67

APPENDIX 2. The characteristics of the equipment used in the testing of samples of magnetic magnetic materials bridge method

ANNEX 2 to GOST 12635−67

APPENDIX 3. The LIST of ammeters, milliammeter and microammeter and their essential characteristics are

ANNEX 3 to GOST 12635−67

ANNEX 4. The LIST of voltmeters and millivoltmeters and their essential characteristics are

4 APPLICATION to GOST 12635−67

APPENDIX 5. GRAPHS of coefficients N, G, and K and K example of calculation («omega») for wire brand LASO 12х0,07

ANNEX 5 GOST 12635−67

GRAPHICS
coefficients , and (damn.1, 2 and 3)
and example of calculation for wire brand LASO 12х0,07

Damn.1

Damn.2

Damn.3