Iec 60404 6 2003

NORME INTERNATIONALE CEI IEC INTERNATIONAL STANDARD 60404 6 Deuxième édition Second edition 2003 06 Matériaux magnétiques – Partie 6 Méthodes de mesure des propriétés magnétiques des matériaux métalli[.]

Eprouvette

The test specimen should have the shape of a ring with a rectangular cross-section, which can be made by a) winding a thin strip or fine wire to form a toroidal core coiled like a watch spring; b) punching, laser cutting, or photochemical machining of ring strips; or c) powder compression and sintering, metal injection molding, or casting.

For powder materials, producing a ring-shaped specimen through metal injection molding or compression (with heating if necessary) should follow the material manufacturer's guidelines to achieve optimal magnetic performance.

For all types of test specimens, it is essential to remove burrs and sharp edges before heat treatment In the case of a material with high permeability, it is preferable to insert the ring-shaped specimen into a two-part annular casing.

Les dimensions du boợtier doivent ờtre telles qu’il s’ajuste parfaitement sans introduire de contrainte dans le matériau de l’éprouvette.

L’anneau doit avoir des dimensions telles que le rapport du diamètre extérieur au diamètre intérieur ne soit pas supérieur à 1,4 et soit, de préférence, inférieur à 1,25.

For solid materials and compressed powder materials, the specimen dimensions—specifically the outer and inner diameters and the ring height—must be measured using properly calibrated measuring instruments These dimensions should be taken at multiple locations on the specimen, with the final values determined as the average of the measurements The cross-sectional area of the specimen must then be calculated accordingly.

A est la section de l’éprouvette, en mètres carrés;

D est le diamètre extérieur de l’éprouvette, en mètres; d est le diamètre intérieur de l’éprouvette, en mètres; h est la hauteur de l’éprouvette, en mètres.

For a stack of sheets or a toroidal wound core, the cross-sectional area of the specimen must be calculated based on the mass, density, and the inner and outer diameter values of the ring The mass and diameters should be measured using properly calibrated instruments The density used must be the conventional density for the material as specified by the manufacturer The cross-sectional area is then determined from these parameters.

LICENSED TO MECON Limited - RANCHI/BANGALORE FOR INTERNAL USE AT THIS LOCATION ONLY, SUPPLIED BY BOOK SUPPLY BUREAU.

The measurements are made on a closed magnetic circuit in the form of a ring test specimen wound with one or two windings.

The test specimen must be a ring with a rectangular cross-section, created by methods such as winding thin strips or wire to form a clock-spring wound toroidal core, punching, laser cutting, or photochemical etching of ring laminations, or by pressing and sintering powders, metal injection molding, or casting.

For powder materials, producing a ring test specimen through metal injection molding or pressing (with heating if needed) must follow the material manufacturer's guidelines to ensure optimal magnetic performance.

Before heat treatment, it is essential to remove burrs and sharp edges from all types of test specimens to ensure accurate results For high permeability materials, enclosing the ring test specimen in a two-part annular case is recommended The case should be precisely dimensioned to fit closely without causing any stress to the test specimen material, maintaining the integrity of the test.

The ring shall have dimensions such that the ratio of the outer to inner diameter shall be no greater than 1,4 and preferably less than 1,25.

For solid and pressed powder materials, the test specimen's dimensions—including outer diameter, inner diameter, and ring height—must be measured using calibrated instruments Measurements should be taken at multiple points on the specimen and averaged to ensure accuracy The cross-sectional area of the test specimen is then calculated based on these averaged dimensions.

A is the cross-sectional area of the test specimen, in square metres;

D is the outer diameter of the test specimen, in metres; d is the inner diameter of the test specimen, in metres; h is the height of the test specimen, in metres.

For a stack of laminations or a toroidal wound core, the cross-sectional area of the test specimen is determined using the mass, density, and the inner and outer diameters of the ring Accurate measurements of mass and diameters must be taken with calibrated instruments, while the density should correspond to the conventional value provided by the manufacturer This method ensures precise calculation of the cross-sectional area, which is essential for evaluating the material's properties.

The mass of the specimen, denoted as \$m\$, is measured in kilograms, while the density of the material, represented by \$\rho\$, is expressed in kilograms per cubic meter These parameters are essential for accurate material analysis and are used exclusively for internal purposes at MECON Limited locations in Ranchi and Bangalore, supplied by Book Supply Bureau.

Pour le calcul de l’intensité du champ magnétique, utiliser la longueur moyenne du circuit magnétique de l’éprouvette déterminée à partir

= 2 m D+ d l π (3) ó lm est la longueur moyenne du circuit magnétique, en mètres.

Si la perte totale spécifique doit être déterminée, alors la masse de l’éprouvette doit être mesurée.

Enroulements

The number of windings and turns depends on the equipment and measurement method used For specific total loss measurements, a magnetizing winding and a secondary winding are typically required In this case, the secondary winding should be wound as close as possible to the specimen to minimize the effect of the flux in the air within the winding All windings must be evenly distributed along the entire length of the specimen.

For measurements at frequencies higher than the current frequencies, it is essential to avoid complications caused by capacitor effects and other related phenomena These issues are detailed and discussed in Appendix A.

It is essential to ensure that the wire insulation is not damaged during the winding process, as this can cause a short circuit in the test specimen An electrical test should be performed using a suitable AC insulation resistance measuring device to verify that there is no direct connection between the winding and the specimen.

When the surface temperature of the test specimen is required, it must be measured by attaching a calibrated non-magnetic thermocouple (such as a type T thermocouple) to the specimen If the specimen is wrapped, a small hole should be made in the wrapping without damaging the specimen material, and the thermocouple must be fixed in contact with the core material If this is not possible, the thermocouple should be attached to the wrapping, and this procedure must be documented in the test report The thermocouple must be connected to a properly calibrated digital voltmeter to measure its output voltage, which can then be converted to the corresponding temperature using the thermocouple calibration tables.

When the temperature of the sample changes over time after magnetization, magnetic property measurements must be conducted either once a predetermined temperature is reached or after an agreed-upon time between the buyer and supplier If measurements are required at elevated temperatures, they can be performed with the sample placed in a suitable furnace to achieve the specified temperature.

A time-dependent second-order magnetic relaxation effect can also alter magnetic properties For the types of materials covered by this standard, this effect is usually masked by temperature changes However, if such magnetic relaxation effects occur, it is important to maintain the specimen at the prescribed magnetic induction or magnetic field intensity for an agreed period before taking the final measurements.

The mass of the test specimen, denoted as $ m $, is measured in kilograms, while the density of the material, represented by $ \rho $, is expressed in kilograms per cubic meter This information is licensed to MECON Limited for internal use at their Ranchi and Bangalore locations, supplied by Book Supply Bureau.

For the calculation of the magnetic field strength, use the mean magnetic path length of the test specimen determined from

( ) m D2+d π l = (3) where lm is the mean magnetic path length of the test specimen, in metres.

If the specific total loss is to be determined, then the mass of the test specimen shall be measured.

The number of windings and turns varies based on the measuring equipment and method used For accurate total loss measurements, both a magnetizing winding and a secondary winding are typically necessary The secondary winding should be wound as close as possible to the test specimen to reduce the impact of air flux within the winding Additionally, all windings must be uniformly distributed along the entire length of the test specimen to ensure precise results.

For measurements at frequencies above power frequencies, care shall be taken to avoid complications related to capacitance and other effects These are introduced and discussed in

During the winding process, it is crucial to prevent damage to the wire insulation to avoid short circuits in the test specimen An electrical inspection using a suitable AC insulation resistance tester should be conducted to verify that there is no direct electrical connection between the winding and the test specimen, ensuring safety and reliability.

To accurately measure the surface temperature of a test specimen, a calibrated non-magnetic thermocouple, such as a type T thermocouple, must be securely attached to the specimen If the specimen is encapsulated, a small hole should be carefully made in the encapsulation without damaging the core material, allowing the thermocouple to contact the core directly If direct contact is not feasible, the thermocouple should be affixed to the encapsulation, and this method must be documented in the test report The thermocouple must then be connected to a calibrated digital voltmeter to measure its output voltage, which corresponds to the temperature based on the thermocouple’s calibration tables.

When the temperature of the test specimen changes over time after magnetization, magnetic property measurements should be conducted either once a predetermined temperature is reached or after a mutually agreed time between the purchaser and supplier For measurements at elevated temperatures, the test specimen can be placed in a suitable oven to achieve the required temperature.

A secondary, smaller time-dependent magnetic relaxation effect can influence the magnetic properties of materials In most cases covered by this standard, temperature variations typically obscure this effect However, if magnetic relaxation becomes noticeable, it is essential to allow the test specimen to remain at the specified magnetic flux density or magnetic field strength for a predetermined period before taking the final measurements This ensures accurate and reliable magnetic property assessment.

5 Mesure de la perméabilité magnétique et de la courbe d’aimantation au moyen de la méthode du voltmètre-ampèremètre

Introduction

Les mesures sont faites en utilisant la méthode du tore normalement aux fréquences de

20 Hz à 200 kHz, la fréquence supérieure étant limitée par la performance de l'instrumentation.

NOTE 1 Lorsque les instruments étalonnés appropriés existent, cette limite supérieure peut être étendue jusqu’à

NOTE 2 Il convient que les mesures en courant continu soient faites selon la méthode du tore décrite dans la

Note 3 outlines the selection of methods for measuring core losses and effective permeability in samples taken from current production These measurements are conducted at high excitation levels and cover a frequency range from nearly direct current up to 10 MHz, and potentially even higher frequencies, as detailed in sections 6.2 and 6.3 of IEC 62044-3.

Appareillage et branchements

L’éprouvette en forme d’anneau doit être entourée par un enroulement d’aimantation, N 1 , et un enroulement secondaire, N 2 (voir 3.2 et Annexe A).

Les appareils doivent être branchés comme indiqué à la Figure 1.

The alternating current source must maintain voltage and frequency variations within ±0.2% of the set value during measurement It should be connected to a true RMS voltmeter or a peak value voltmeter, along with a precision resistor in series with the magnetizing winding N1 on the ring-shaped test specimen, to accurately measure the magnetizing current.

The secondary circuit includes a secondary winding $N_2$ connected in parallel to two voltmeters One voltmeter ($V_2$) measures the true RMS value, while the other ($V_1$) measures the rectified average value and is sometimes calibrated to display values equal to 1.111 times the rectified value.

NOTE lI convient de vérifier la forme de l'onde de la tension secondaire avec un oscilloscope pour s'assurer que seulement la composante fondamentale est présente.

5.2.1 Forme de l’onde de la tension secondaire ou du courant d’aimantation

To obtain comparable measurements, it is essential to agree beforehand that the waveform of the secondary voltage or the magnetizing current must remain sinusoidal with a form factor of 1.111 ± 1% In this case, a non-inductive resistor connected in series with the magnetizing circuit is required.

NOTE 1 Il convient que la constante de temps de la résistance non inductive soit faible pour s'assurer que la forme de l'onde se trouve à l’intérieur de limites spécifiées.

NOTE 2 La résistance non inductive peut être la même résistance que celle utilisée pour la mesure du courant d’aimantation.

NOTE 3 La maỵtrise de la forme de l'onde sinusọdale peut être assurée par des moyens numériques (voir

Aux fréquences dans la gamme 20 Hz à 50 kHz, le facteur de forme de la tension secondaire peut être déterminé en branchant deux voltmètres ayant une impédance élevée (typiquement

A 1 MΩ resistor in parallel with a capacitance ranging from 90 pF to 150 pF is connected across the secondary winding One voltmeter should measure the root mean square (RMS) value of the voltage, while another voltmeter should measure the rectified average value of the secondary voltage The form factor is then calculated by taking the ratio between the RMS value and the rectified average value.

5 Measurement of magnetic permeability and magnetization curve using the voltmeter-ammeter method

The measurements are made using the ring method at frequencies normally from 20 Hz to

200 kHz, the upper frequency being limited by the performance of the instrumentation.

NOTE 1 Where suitable calibrated instruments exist, this upper limit may be extended to 1 MHz.

NOTE 2 DC measurements should be made in accordance with the ring method described in IEC 60404-4.

Section 6.2 and 6.3 of IEC 62044-3 provide a selection of methods for measuring loss and effective permeability of cores used in current production These methods cover high excitation levels and frequencies ranging from nearly direct current (d.c.) up to 10 MHz and beyond, ensuring accurate characterization of core materials across a wide frequency spectrum.

The ring test specimen shall be wound with a magnetizing winding, N 1 , and a secondary winding, N 2 (see 3.2 and Annex A).

The apparatus shall be connected as shown in Figure 1.

The alternating current source must maintain voltage and frequency variations within ±0.2% of the set value during measurement It should be connected in series with a precision resistor and the magnetizing winding N1 on the ring test specimen, using a true RMS or peak reading voltmeter to accurately measure the magnetizing current.

The secondary circuit features a secondary winding $ N_2 $ connected in parallel to two voltmeters One voltmeter, $ V_2 $, measures the true RMS value, while the other, $ V_1 $, measures the average rectified value, often scaled by a factor of 1.111 times the rectified value for accurate readings.

NOTE The waveform of the secondary voltage should be checked with an oscilloscope to ensure that only the fundamental component is present.

5.2.1 Waveform of secondary voltage or magnetizing current

To ensure comparable measurements, it is essential to agree beforehand that either the secondary voltage waveform or the magnetizing current waveform remains sinusoidal with a form factor of 1.111 ± 1% When maintaining the magnetizing current waveform, a non-inductive resistor must be connected in series with the magnetizing circuit.

NOTE 1 The time constant of the non-inductive resistor should be low to ensure that the waveform is within the specified limits.

NOTE 2 The non-inductive resistor can be the same resistor as used for the measurement of the magnetizing current.

NOTE 3 Sinusoidal waveform control may be achieved by digital means (see Annex B).

To determine the form factor of the secondary voltage within the frequency range of 20 Hz to 50 kHz, two high-impedance voltmeters (typically greater than 1 MΩ in parallel with 90 pF to 150 pF) are connected across the secondary winding One voltmeter measures the r.m.s value of the voltage, while the other measures the average rectified value The form factor is calculated by taking the ratio of the r.m.s value to the average rectified value of the secondary voltage.

For optimal power transfer, it may be necessary to optimize the number of turns in the magnetization winding to match the output impedance of the current source This adjustment ensures efficient energy transfer and can be determined through careful analysis of the system's electrical characteristics.

Z est l'impédance de sortie de la source de courant, en ohms; ω est la fréquence angulaire de la sortie de la source de courant, en radians par seconde;

L est l'inductance efficace de l'enroulement d’aimantation de l’éprouvette en forme d’anneau, en henrys, calculée à partir de m r

N 1 est le nombre de tours de l'enroulement d’aimantation;

The cross-sectional area of the specimen, denoted as A, is measured in square meters The magnetic constant, represented by μ₀, equals 4π × 10⁻⁷ henrys per meter The relative permeability of the specimen is indicated by μᵣ Additionally, the average length of the magnetic circuit of the specimen, denoted as lₘ, is measured in meters.

When the relative magnetic permeability is unknown, a preliminary measurement of the magnetic field intensity and magnetic induction, as described in sections 5.3 and 5.4, is required Subsequently, the relative magnetic permeability can be calculated as outlined in section 5.5.

Détermination de l’intensité du champ magnétique

L’intensité du champ magnétique à laquelle la mesure doit être faite est calculée à partir de la relation suivante: m

H est l’intensité du champ magnétique, en ampères par mètre;

N 1 est le nombre de tours de l'enroulement d’aimantation sur l’éprouvette;

I est le courant d’aimantation, en ampères; lm est la longueur moyenne du circuit magnétique, en mètres.

Normally, the amplitude of the magnetic field intensity is determined by measuring the root mean square (RMS) value of the magnetizing current and multiplying it by the square root of 2 For a sinusoidal magnetizing current, this method accurately defines the peak value of the magnetic field intensity In the case of sinusoidal magnetic induction, it provides an equivalent peak value of the magnetic field intensity, which is numerically lower for a given magnetizing current Alternatively, the peak value of the magnetic field can be measured using a peak-value ammeter or voltmeter combined with a precision resistor.

Before measurement, the sample must be carefully demagnetized using a magnetic field intensity at least ten times greater than the coercive field, gradually reducing the magnetization current to zero Demagnetization should be performed at the same frequency or a lower frequency than that used for the measurements.

For optimal power transfer, it is essential to adjust the number of turns in the magnetizing winding to match the output impedance of the power source This optimization ensures maximum efficiency and can be determined through specific calculations.

Z is the output impedance of the power source, in ohms; ω is the angular frequency of the output of the power source, in radians per second;

L is the effective inductance of the magnetizing winding of the ring test specimen, in henrys, calculated from m r

N 1 is the number of turns of the magnetizing winding;

The cross-sectional area of the test specimen, denoted as A, is measured in square metres The magnetic constant, represented by \$\mu_0\$, has a value of \$4 \pi \times 10^{-7}\$ henrys per metre The relative permeability of the test specimen is indicated by \$\mu_r\$ Additionally, the mean magnetic path length of the test specimen, symbolized as \$l_m\$, is measured in metres.

When the relative magnetic permeability is unknown, it is essential to conduct preliminary measurements of the magnetic field strength and magnetic flux density, as outlined in sections 5.3 and 5.4 Subsequently, the relative magnetic permeability can be accurately calculated following the procedure described in section 5.5.

5.3 Determination of magnetic field strength

The magnetic field strength at which the measurement is to be made is calculated from the following relationship: m

H is the magnetic field strength, in amperes per metre;

N 1 is the number of turns of the magnetizing winding on the test specimen;

I is the magnetizing current, in amperes; lm is the mean magnetic path length, in metres.

The amplitude of the magnetic field strength is typically determined by measuring the root mean square (r.m.s.) magnetizing current and multiplying it by the square root of 2, which accurately defines the peak magnetic field strength for sinusoidal magnetizing currents For sinusoidal magnetic flux density, this method provides an equivalent peak magnetic field strength that is numerically lower for the same magnetizing current Alternatively, the peak magnetic field strength can be measured directly using a peak reading ammeter or voltmeter in combination with a precision resistor.

Before measurement, the test specimen must be thoroughly demagnetized by gradually decreasing the magnetizing current from a field strength at least ten times greater than the coercivity down to zero This demagnetization process should be performed at the same or a lower frequency than that used during the measurements to ensure accurate results.

Détermination de l’induction magnétique

La tension secondaire doit être mesurée à l'aide du voltmètre de valeur moyenne V 1 et l’induction magnétique doit être calculée à partir de l'équation suivante:

U 2 est la valeur moyenne redressée de la tension secondaire induite, en volts; f est la fréquence, en hertz;

B$ est la valeur de crête de l’induction magnétique, en teslas;

N 2 est le nombre de tours de l'enroulement secondaire.

Depending on the intensity of the magnetic field and the ratio of the cross-sectional areas of the test specimen and the secondary winding, it may be necessary to correct the magnetic induction to account for the flux in the air gap between the specimen and the secondary winding.

La valeur corrigée, B, de l’induction magnétique est indiquée par la relation suivante:

B′ est la valeur mesurée de l’induction magnétique, en teslas; à0 est la constante magnộtique (= 4 π 10 − 7 henrys par mốtre);

A′ est la section à l’intérieur de l'enroulement secondaire, en mètres carrés;

A est la section de l’éprouvette, en mètres carrés.

Détermination de la perméabilité d’amplitude efficace et de la perméabilité d’amplitude relative

et de la perméabilité d’amplitude relative

Pour les valeurs correspondantes d’intensité du champ magnétique et d’induction magnétique, la perméabilité d’amplitude efficace doit être calculée à partir de la relation suivante:

0 rms a, à à = (9) et la perméabilité d’amplitude relative à partir de:

The parameter \$\mu_0\$ represents the magnetic constant, valued at \$4 \pi \times 10^{-7}\$ henrys per meter The effective amplitude permeability, denoted as \$\mu_{\text{rms}}\$ , corresponds to the root mean square permeability for a sinusoidal magnetic induction Meanwhile, \$\mu_a\$ signifies the relative amplitude permeability associated with a sinusoidal magnetic field intensity.

5.4 Determination of the magnetic flux density

The secondary voltage shall be measured using the average type voltmeter V 1 , and the magnetic flux density shall be calculated from the following equation:

U 2 is the average rectified value of the secondary voltage, in volts; f is the frequency, in hertz;

B$ is the peak magnetic flux density, in teslas;

N 2 is the number of turns of the secondary winding.

Depending on the magnetic field strength and the ratio between the cross-sectional areas of the test specimen and the secondary winding, it is often necessary to correct the magnetic flux density to account for the air flux enclosed between them The corrected magnetic flux density, denoted as \$B\$, is determined using a specific relationship that adjusts for this air gap effect.

B′ is the measured value of magnetic flux density, in teslas; à0 is the magnetic constant ( = 4 π 10 –7 henrys per metre);

H is the magnetic field strength, in amperes per metre;

A′ is the cross-sectional area enclosed by the secondary winding, in square metres;

A is the cross-sectional area of the test specimen, in square metres.

5.5 Determination of the r.m.s amplitude permeability and the relative amplitude permeability

For corresponding values of magnetic field strength and magnetic flux density, the r.m.s. amplitude permeability shall be calculated from the following relationship:

0 rms a, à à = (9) and the relative amplitude permeability from:

0 a à à (10) where à a, rms is the r.m.s amplitude permeability (for sinusoidal magnetic flux density); à a is the relative amplitude permeability (for sinusoidal magnetic field strength); à 0 is the magnetic constant (= 4 π 10 − 7 henrys per metre);

B$ est la valeur de crête de l’induction magnétique, en teslas;

H~ est la valeur efficace de l’intensité du champ magnétique, en ampères par mètre;

H$ est la valeur de crête de l’intensité du champ magnétique, en ampères par mètre.

Détermination de la courbe d’aimantation

The specimen must be carefully demagnetized as described in section 5.3 By gradually increasing the magnetization current, corresponding values of magnetic field intensity and magnetic induction can be obtained, allowing the magnetization curve to be plotted.

6 Mesure de la perte totale spécifique par la méthode du wattmètre

Principe de la mesure

The measurement principle is similar to that described in IEC 60404-2, except that the Epstein frame is replaced by a ring-shaped specimen, and the instrumentation allows measurements at the required frequency The specific total loss measurement must be conducted under sinusoidal magnetic induction conditions For certain specimens, this may require controlling the magnetization current waveform (see Annex B) using analog or digital techniques to ensure the sinusoidal magnetic induction is maintained The devices and specimen windings must be connected as shown in Figure 2.

A selection of measurement methods for total specific loss and amplitude permeability at high excitation levels, covering frequencies from nearly direct current up to 10 MHz and beyond, is provided in sections 6.2 and 6.3 of IEC 62044-3.

The rectified average value of the secondary voltage must be measured using a calibrated average-reading voltmeter The load on the secondary circuit should be kept as low as possible (see Appendix A) Therefore, an electronic voltmeter with a high input impedance is required.

NOTE Des instruments de ce type sont habituellement gradués en valeur moyenne redressée multipliée par 1,111.

A calibrated voltmeter sensitive to RMS values should be used Additionally, the load on the secondary circuit must be kept as low as possible, with an electronic voltmeter being the preferred choice (see Appendix A).

A properly calibrated wattmeter is essential for circuits that may exhibit a low power factor, with a cosine phi (cosφ) value as low as 0.1 Additionally, the input impedance of the voltage circuit should be as high as possible to ensure accurate measurements (refer to Appendix A).

6.1.4 Mesure de la perte totale spécifique

L’éprouvette doit être soigneusement désaimantée comme décrit en 5.3 Le courant dans l’enroulement d’aimantation N 1 doit être augmenté jusqu’à ce que la tension sur le voltmètre

V 1 (indiquant la tension moyenne redressée) corresponde à l’induction magnétique exigée, calculée à partir de l’équation (7).

B$ is the peak magnetic flux density, in teslas;

H~ is the r.m.s value of the magnetic field strength, in amperes per metre;

H$ is the peak value of the magnetic field strength, in amperes per metre.

The test specimen must be carefully demagnetized according to the procedure outlined in section 5.3 By gradually increasing the magnetizing current, precise measurements of magnetic field strength and magnetic flux density can be recorded These values enable the plotting of an accurate magnetization curve, essential for analyzing the magnetic properties of the material.

6 Measurement of specific total loss by the wattmeter method

The principle of measurement is similar to that described in IEC 60404-2 except that the

The Epstein frame is substituted with a ring test specimen, and the instrumentation is designed to perform measurements at the necessary frequency Specific total loss measurements must be conducted under sinusoidal magnetic flux density conditions For certain test specimens, controlling the magnetizing current waveform using analogue or digital methods (as detailed in Annex B) is essential to maintain a sinusoidal magnetic flux density.

The apparatus and the windings of the test specimen shall be connected as shown in Figure 2.

A selection of methods for measuring specific total loss and amplitude permeability at high excitation levels across frequencies from nearly direct current (d.c.) up to 10 MHz and beyond is detailed in sections 6.2 and 6.3 These techniques enable accurate characterization of magnetic materials under varying frequency conditions, essential for optimizing performance in high-frequency applications.

The average rectified value of the secondary voltage shall be measured using a calibrated average type voltmeter The load on the secondary circuit shall be as small as possible (see

Annex A) Consequently an electronic voltmeter with a high input impedance is required.

NOTE Instruments of this type are usually graduated in average rectified value multiplied by 1,111.

A calibrated voltmeter responsive to r.m.s values shall be used Again, the load on the secondary circuit shall be as small as possible, an electronic voltmeter being preferred (see

A calibrated wattmeter suitable for circuits which may have a low power factor (cosφ down to 0,1) The input impedance of the voltage circuit shall be as high as possible (see Annex A).

6.1.4 Measurement of specific total loss

The test specimen must be carefully demagnetized following the procedure outlined in section 5.3 The current in the magnetizing winding N1 should then be gradually increased until the voltage reading on voltmeter V1, which indicates the average rectified voltage, matches the required magnetic flux density determined by equation (7).

The readings from the two voltmeters V1 and V2 must be recorded, and the form factor of the secondary waveform should be calculated and verified according to section 5.2.1 Subsequently, the wattmeter reading must also be documented.

6.1.5 Détermination de la perte totale spécifique

La puissance P m mesurée par le wattmètre comprend la puissance consommée par les instruments du circuit secondaire, qui en première approximation est égale à (1,111U 2 ) 2 / R i puisque la tension secondaire est essentiellement sinusọdale.

Ainsi, la perte totale P c de l’éprouvette doit être calculée selon l’équation suivante:

P c est la perte totale calculée de l’éprouvette, en watts;

P m est la puissance mesurée par le wattmètre, en watts;

N 2 est le nombre de tours de l'enroulement secondaire;

U 2 est la valeur moyenne redressée de la tension secondaire, en volts;

R i est la résistance équivalente combinée des instruments connectés à l'enroulement secondaire, en ohms.

La perte totale spécifique P s doit être obtenue en divisant P c par la masse de l’éprouvette.

P s est la perte totale spécifique de l’éprouvette, en watts par kilogramme; m est la masse de l’éprouvette, en kilogrammes.

7 Mesure des propriétés magnétiques au moyen d’un pont d’impédance numérique

Principe de mesure

Digital impedance bridges, also known as impedance analyzers and LCR measuring devices, are widely used to measure inductance and other technological properties of magnetic components These instruments can determine magnetic properties such as AC inductance permeability and specific total loss, provided certain conditions are met This method assumes that the ring-shaped sample is electrically equivalent to a parallel combination of inductance and resistance AC inductance permeability is calculated from the inductance, while the specific total loss is derived from the resistance.

NOTE 1 Des dispositifs de mesure LCR sont généralement utilisés pour des mesures comparatives seulement.

The readings from voltmeters V1 and V2 are recorded to calculate and verify the form factor of the secondary waveform according to section 5.2.1 Subsequently, the wattmeter reading is also documented to complete the measurement process.

6.1.5 Determination of the specific total loss

The power $ P_m $ measured by the wattmeter includes the power consumed by the instruments in the secondary circuit, which is approximately equal to $\frac{(1.111 U_2)^2}{R_i}$, given that the secondary voltage is essentially sinusoidal.

Thus, the total loss P c of the test specimen shall be calculated in accordance with the equation

P c is the calculated total loss of the test specimen, in watts;

P m is the power measured by the wattmeter, in watts;

N 2 is the number of turns of the secondary winding;

U 2 is the average rectified value of the secondary voltage, in volts;

R i is the combined equivalent resistance of the instruments connected to the secondary winding, in ohms.

The specific total loss P s shall be obtained by dividing P c by the mass of the test specimen.

P s is the specific total loss of the test specimen, in watts per kilogram; m is the mass of the test specimen, in kilograms.

7 Measurement of magnetic properties using a digital impedance bridge

Digital impedance bridges (also known as impedance analyzers and LCR meters) are widely used to measure the inductance and other technological properties of magnetic components.

These instruments are essential for measuring magnetic properties, including a.c inductance permeability and specific total loss, under specific conditions The method relies on the assumption that the ring test specimen behaves electrically like a parallel combination of inductance and resistance From this model, the a.c inductance permeability is calculated based on the inductance, while the specific total loss is derived from the resistance.

NOTE 1 LCR meters are generally used for comparative measurements only.

Note 2: The permeability of inductance in alternating current is determined from the inductive component measured in the impedance of the electrical circuit In this circuit, the magnetic sample is subjected to a sinusoidally varying magnetic induction over time with a zero average value This behavior is represented by the inductive component in parallel with a resistive component.

Tests using this method should be confined to the initial linear region of the magnetization curve, where sinusoidal magnetic induction and magnetic field intensity conditions prevail The specimen must be prepared according to section 3.1 A single winding (N₁) with a sufficient number of turns to maintain sinusoidal magnetic induction should be applied.

Appareillage

L’appareillage d’essai est illustré par la Figure 3 et est constitué des composants indiqués.

Le pont d’impédance numérique étalonné doit avoir la configuration de type à 4 fils Kelvin et doit être configuré pour mesurer l’inductance parallèle (L p ) et la résistance parallèle (R p ).

The output impedance of the signal source must be sufficiently low to ensure a sinusoidal magnetic induction is achieved in the test core Additionally, the bridge should allow compensation to cancel out the impedance of the connecting cables between the instrument and the test specimen.

7.2.2 Ampèremètre de valeur efficace vraie

A true RMS ammeter, properly calibrated, must be used to measure the magnetizing current Alternatively, the magnetizing current can be determined by connecting a precision non-inductive resistor in series with the magnetizing winding and measuring the voltage across it using a calibrated true RMS voltmeter A separate measuring device is not required if the digital impedance measurement instrument includes an internal ammeter or if the accuracy of the signal source setting has been independently verified.

La valeur moyenne redressée de la tension secondaire doit être mesurée à l’aide d’un voltmètre de valeur moyenne étalonné à forte impédance d’entrée (typiquement >1 MΩ en parallèle avec 90 pF à 150 pF).

NOTE Des instruments de ce type sont habituellement gradués en valeur moyenne redressée multipliée par

Un voltmètre étalonné à forte impédance d’entrée (typiquement >1 MΩ en parallèle avec

90 pF à 150 pF) sensible aux valeurs efficaces doit être utilisé.

Mode opératoire

Before measurement, the device must be zeroed according to the manufacturer's instructions to compensate for the impedance of the test cables During high-frequency testing, it is important to eliminate the impedance caused by the winding This can be achieved by connecting the measuring device to a non-magnetic core with the same dimensions as the test specimen and the same number of turns in the winding.

After connecting the specimen to the measurement device, it must be demagnetized using either the device's signal source or an external source Tests should be conducted with progressively increasing magnetization current (magnetic field intensity) or magnetic induction values The relationship between the magnetic field intensity and the magnetization current is described by equation (7).

AC inductance permeability refers to the permeability derived from the inductive component of an electrical circuit's impedance measurement This measurement involves a magnetic test specimen subjected to a sinusoidally varying magnetic flux density with a zero average value over time In this setup, the specimen's behavior is modeled as an inductive component in parallel with a resistive component, allowing accurate determination of its AC permeability.

Testing must be conducted within the initial linear region of the magnetization curve, ensuring sinusoidal magnetic flux density and magnetic field strength conditions The test specimen should be prepared as specified in section 3.1 A single winding (N₁) with an adequate number of turns is applied to maintain the sinusoidal magnetic flux density during the test.

The test apparatus is illustrated in Figure 3 and consists of the components shown.

The calibrated digital impedance bridge must utilize a 4-wire Kelvin configuration designed to accurately measure parallel inductance (L_p) and parallel resistance (R_p) It is essential that the signal source output impedance remains low enough to maintain a sinusoidal magnetic flux density within the test core Additionally, the bridge should possess compensation capabilities to ensure precise and reliable measurements.

(nulling) the impedance of the connecting leads between the instrument and test specimen.

A calibrated true r.m.s ammeter is essential for accurately measuring the magnetizing current Alternatively, the magnetizing current can be determined by placing a non-inductive precision resistor in series with the magnetizing winding and measuring the voltage across it using a calibrated r.m.s voltmeter The need for a separate meter is eliminated if the digital impedance meter includes an internal ammeter or if the signal source's setting accuracy has been independently verified.

The average rectified value of the secondary voltage shall be measured using a high input impedance (typically >1 MΩ in parallel with 90 pF to 150 pF) calibrated average type voltmeter.

NOTE Instruments of this type are usually graduated in average rectified value multiplied by 1,111.

A calibrated high input impedance (typically >1 MΩ in parallel with 90 pF to 150 pF) voltmeter responsive to r.m.s values shall be used.

Before measurement, the meter must be nulled following the manufacturer’s instructions to compensate for the test leads' impedance When conducting high-frequency tests, it is important to eliminate the impedance caused by the winding This can be achieved by connecting the meter to a non-magnetic core that matches the test specimen in dimensions and has the same number of winding turns.

After connecting the test specimen to the meter, it must be demagnetized using the meter’s signal source or an external source Testing should then be performed by gradually increasing the magnetizing current or magnetic flux density The correlation between magnetic field strength and magnetizing current is described by equation (7).

The relationship between magnetic induction and the induced voltage in the winding is described by equation (8) To accurately determine the form factor of the induced voltage in the winding, it is essential to use the voltage measurements obtained from voltmeters V1 and V2.

Les inductances et les résistances mesurées doivent être enregistrées manuellement ou par des moyens électroniques.

It is not always possible to obtain the exact required value of magnetizing current or induction using numerically controlled instruments In such cases, data interpolation becomes necessary and is permitted for this method.

Détermination de la perméabilité relative d’inductance en courant alternatif

La perméabilité relative d’inductance en courant alternatif de l’éprouvette est alors calculée à partir de

= (13) ó à p est la permộabilitộ relative d’inductance en courant alternatif;

L p est l'inductance en parallèle mesurée, en henrys; lm est la longueur moyenne du circuit magnétique de l’éprouvette, en mètres;

N 1 est le nombre de tours de l'enroulement;

A est la section de l’éprouvette, en mètres carrés; à0 est la constante magnộtique (= 4 π 10 –7 henrys par mốtre).

Détermination de la perte totale spécifique

La perte totale spécifique peut être calculée à partir de la résistance en parallèle comme suit:

P s est la perte totale spécifique de l’éprouvette, en watts par kilogramme;

U 2 est la valeur moyenne redressée de la tension secondaire, en volts; m est la masse de l’éprouvette, en kilogrammes;

R p est la résistance en parallèle, en ohms;

R w est la résistance de l'enroulement, en ohms (voir également l'Annexe A).

8 Mesure des propriétés magnétiques au moyen de méthodes numériques

Introduction

Measurements are conducted using the toroid method, with the upper frequency limit constrained by the performance of the voltage measurement device and the frequency response of the precision non-inductive resistor connected in series with the magnetizing winding to determine the magnetizing current.

The relationship between magnetic flux density and the voltage induced in the winding is described by equation (8) The form factor of the induced voltage is determined using readings from voltmeters V1 and V2 Additionally, the measured inductances and resistances are recorded either manually or electronically to ensure accurate data collection.

Achieving the precise magnetizing current or flux density with digitally controlled instruments is not always feasible In such cases, data interpolation becomes essential and is allowed by this method to ensure accurate results.

7.4 Determination of the relative a.c inductance permeability

The relative a.c inductance permeability of the test specimen is then calculated from

L p l à (13) where à p is the relative a.c inductance permeability;

L p is the measured parallel inductance, in henrys; lm is the mean magnetic path length of the test specimen, in metres;

N 1 is the number of turns of the winding;

A is the cross-sectional area of the test specimen, in square metres; à0 is the magnetic constant (= 4 π 10 –7 henrys per metre).

7.5 Determination of the specific total loss

The specific total loss can be calculated from the parallel resistance as follows:

P s is the specific total loss of the test specimen, in watts per kilogram;

U 2 is the average rectified value of the secondary voltage, in volts; m is the mass of the test specimen, in kilograms;

R p is the parallel resistance, in ohms;

R w is the resistance of the winding, in ohms (see also Annex A).

8 Measurement of magnetic properties using digital methods

The measurements are conducted using the ring method, with the upper frequency constrained by the capabilities of the voltage measuring device and the frequency response of the non-inductive precision resistor connected in series with the magnetizing winding to accurately determine the magnetizing current.

Appareils et branchements

Les enroulements de l’éprouvette en forme d’anneau doivent être connectés comme indiqué à la Figure 4.

The alternating current source must maintain voltage and frequency variations within ±0.2% of the set value during measurement It should be connected in series with the magnetizing winding N1 on the ring-shaped test specimen and a precision non-inductive resistor, which is linked to an analog-to-digital voltage converter (A/D), V1.

Le circuit secondaire comporte un enroulement secondaire N 2 connecté à un convertisseur de tension analogique/numérique, V 2

The resolution of the analog-to-digital voltage converter must be adequate to ensure accurate measurements Additionally, the sampling rate of the measurement equipment should provide a sufficient number of samples per signal period It is essential that each pair of values is sampled simultaneously to maintain data integrity, as detailed in publications on digital signal processing.

Forme de l’onde du courant d’aimantation

To obtain comparable measurements, it is essential to agree beforehand that the waveform of the secondary voltage or the magnetizing current must remain sinusoidal, with a form factor of 1.111 ± 1%.

To generate a high-quality secondary voltage or magnetizing current waveform, it is essential to optimize the number of turns in the magnetizing winding to match the output impedance of the power source This optimization can be achieved by applying the conditions outlined in equations (4) and (5).

Enroulement d’aimantation

Les prescriptions de 3.2 et l’Annexe A doivent être respectées.

Détermination de l’intensité du champ magnétique

L’intensité du champ magnétique à laquelle la mesure doit être faite est calculée à partir de la relation suivante:

H(t) est l’intensité du champ magnétique à un instant t, en ampères par mètre;

U1(t) represents the voltage at a given time t across the precision non-inductive resistor used to determine the magnetizing current, measured in volts Additionally, lm denotes the average length of the magnetic circuit, expressed in meters.

R est la résistance de la résistance de précision non inductive en série avec l’enroulement d’aimantation pour déterminer le courant d’aimantation, en ohms.

Avec les valeurs discrètes pour la tension U 1 , l’intensité du champ magnétique est calculée comme suit:

The windings of the ring test specimen shall be connected as shown in Figure 4.

The alternating current source must maintain voltage and frequency variations within ±0.2% of the set value during measurement It should be connected in series with the magnetizing winding N1 on the ring test specimen, along with a non-inductive precision resistor A calibrated voltage analog-to-digital converter is used across the resistor to ensure accurate measurement.

The secondary circuit comprises a secondary winding N 2 connected to a voltage analogue/digital converter, V 2

The voltage analogue-to-digital converter must have adequate resolution to ensure accurate measurements Additionally, the measuring equipment's sampling rate should be high enough to capture a sufficient number of samples per signal period It is essential that each pair of values is sampled simultaneously to maintain data integrity, as detailed in digital signal processing literature.

To ensure comparable measurements, it is essential to agree beforehand that either the secondary voltage waveform or the magnetizing current waveform will be maintained as sinusoidal, with a form factor of 1.111 ± 1% This agreement guarantees consistency and accuracy in the measurement process.

To achieve an optimal waveform of the secondary voltage or magnetizing current, it is essential to adjust the number of turns in the magnetizing winding to align with the power source's output impedance This optimization can be accurately determined using the conditions outlined in equations (4) and (5).

The requirements of 3.2 and Annex A shall be met.

8.5 Determination of the magnetic field strength

The magnetic field strength at which the measurement is to be made is calculated from the following relationship:

H(t) is the magnetic field strength at a time t, in amperes per metre;

U 1 (t) is the voltage at a time t across the non-inductive precision resistor to determine the magnetizing current, in volts; lm is the mean magnetic path length, in metres;

R is the resistance of the non-inductive precision resistor in series with the magnetizing winding to determine the magnetizing current, in ohms.

With the discrete values for voltage U 1 , the magnetic field strength is calculated as follows:

LICENSED TO MECON Limited - RANCHI/BANGALORE FOR INTERNAL USE AT THIS LOCATION ONLY, SUPPLIED BY BOOK SUPPLY BUREAU. ó

H i est la valeur discrète de l’intensité du champ magnétique, en ampères par mètre;

U 1 i est la valeur discrète de la tension à travers la résistance de précision non inductive pour déterminer le courant d’aimantation, en volts.

Détermination de l’induction magnétique

La tension secondaire doit être mesurée en utilisant un convertisseur de tension analogique/numérique et l’induction magnétique doit être calculée à partir de l’équation suivante:

B(t) est l’induction magnétique à un instant t, en teslas;

N 2 est le nombre de tours de l'enroulement secondaire;

U 2 (t) est la tension secondaire à un instant t, en volts;

K est tel que la moyenne de temps de B(t) est zéro.

Détermination de la perméabilité relative en courant alternatif

Pour des valeurs correspondantes de l’intensité du champ magnétique et de l’induction, la perméabilité magnétique relative en courant alternatif doit être calculée à partir de la relation suivante:

0 a à à = (18) ó àa est la permộabilitộ relative en courant alternatif; à0 est la constante magnộtique (4 à 10 –7 henrys par mốtre);

Bˆ est la valeur de crête de l’induction magnétique, en teslas;

Hˆ est la valeur de crête de l’intensité du champ magnétique, en ampères par mètre.

Détermination de la courbe d’aimantation en courant alternatif

The specimen must be carefully demagnetized By gradually increasing the magnetization current, corresponding values of the maximum magnetic field intensity and maximum magnetic induction can be obtained, allowing the plotting of an alternating current magnetization curve.

Test specimen

The test specimen must be a ring with a rectangular cross-section, created by methods such as winding thin strips or wire to form a clock-spring wound toroidal core, punching, laser cutting, or photochemical etching of ring laminations, or by pressing and sintering powders, metal injection molding, or casting.

For powder materials, producing a ring test specimen through metal injection molding or pressing (with heating if needed) must follow the material manufacturer's guidelines to ensure optimal magnetic performance.

Before heat treatment, it is essential to remove burrs and sharp edges from all types of test specimens to ensure accurate results For high permeability materials, enclosing the ring test specimen in a two-part annular case is recommended The case should be precisely dimensioned to fit closely without causing any stress to the test specimen material, maintaining the integrity of the test.

The ring shall have dimensions such that the ratio of the outer to inner diameter shall be no greater than 1,4 and preferably less than 1,25.

For solid and pressed powder materials, the test specimen's dimensions—including the outer diameter, inner diameter, and ring height—must be measured using calibrated instruments These measurements should be taken at multiple points on the specimen and averaged to ensure accuracy The cross-sectional area of the test specimen is then calculated based on these averaged dimensions.

D is the outer diameter of the test specimen, in metres; d is the inner diameter of the test specimen, in metres; h is the height of the test specimen, in metres.

To determine the cross-sectional area of a stack of laminations or a toroidal wound core, it is essential to calculate it using the mass, density, and the inner and outer diameters of the ring Accurate measurements of mass and diameters must be taken with calibrated instruments, while the density should reflect the conventional value provided by the manufacturer The cross-sectional area can then be derived from these measurements.

The mass of the specimen, denoted as \$m\$, is measured in kilograms, while \$\rho\$ represents the material's density, expressed in kilograms per cubic meter These parameters are essential for accurate material analysis and testing.

Pour le calcul de l’intensité du champ magnétique, utiliser la longueur moyenne du circuit magnétique de l’éprouvette déterminée à partir

= 2 m D+ d l π (3) ó lm est la longueur moyenne du circuit magnétique, en mètres.

Si la perte totale spécifique doit être déterminée, alors la masse de l’éprouvette doit être mesurée.

The number of turns and windings depends on the equipment and measurement method used For specific total loss measurements, a magnetizing winding and a secondary winding are typically required In this case, the secondary winding should be placed as close as possible to the specimen to minimize the effect of air flux within the winding All windings must be uniformly distributed along the entire length of the specimen.

For measurements at frequencies higher than those of the current, it is essential to avoid complications arising from capacitor effects and other influences These issues are presented and discussed in Appendix A.

It is essential to ensure that the wire insulation remains undamaged during the winding process to prevent short circuits in the test specimen An electrical check should be conducted using a suitable alternating current insulation resistance measuring device to confirm that there is no direct connection between the winding and the test specimen.

To accurately measure the surface temperature of a specimen, a calibrated non-magnetic thermocouple, such as a type T thermocouple, should be attached to the specimen If the specimen is wrapped, a small hole must be created in the wrapping without damaging the specimen material, ensuring the thermocouple is in contact with the core material If direct contact is not feasible, the thermocouple should be affixed to the wrapping, and this procedure must be documented in the test report The thermocouple should be connected to a calibrated digital voltmeter to measure its output voltage, which can then be correlated to the corresponding temperature using the thermocouple calibration tables.

When the temperature of the sample changes over time after magnetization, magnetic property measurements should be conducted either when a predetermined temperature is reached or after an agreed-upon time between the buyer and the supplier For high-temperature measurements, the sample can be placed in a suitable furnace to achieve the required temperature.

A time-dependent second-order magnetic relaxation effect can alter magnetic properties For materials covered by this standard, this effect is typically obscured by temperature changes However, if such magnetic relaxation effects occur, it is essential to maintain the specimen at the prescribed magnetic induction or field intensity for an agreed period before taking final measurements.

This document is licensed to MECON Limited for internal use at the Ranchi and Bangalore locations, and it has been supplied by the Book Supply Bureau In this context, the mass of the test specimen is denoted by $ m $ and is measured in kilograms, while the density of the material is represented by $ \rho $ and is expressed in kilograms per cubic meter.

For the calculation of the magnetic field strength, use the mean magnetic path length of the test specimen determined from

( ) m D2+d π l = (3) where lm is the mean magnetic path length of the test specimen, in metres.

If the specific total loss is to be determined, then the mass of the test specimen shall be measured.

Windings

The number of windings and turns is determined by the measuring equipment and method used For accurate total loss measurements, both a magnetizing and a secondary winding are typically necessary It is essential that the secondary winding is placed as close as possible to the test specimen to reduce the influence of air flux Additionally, all windings must be uniformly distributed along the entire length of the test specimen.

For measurements at frequencies above power frequencies, care shall be taken to avoid complications related to capacitance and other effects These are introduced and discussed in

It is crucial to protect the wire insulation from damage during the winding process to prevent short circuits in the test specimen An electrical check using an appropriate a.c insulation resistance measuring device must be conducted to confirm that there is no direct connection between the winding and the test specimen.

To measure the surface temperature of a test specimen, a calibrated non-magnetic thermocouple, such as a type T thermocouple, should be securely attached If the specimen is encapsulated, a small hole must be created in the encapsulation without damaging the specimen, allowing the thermocouple to contact the core material If direct contact is not feasible, the thermocouple can be affixed to the encapsulation, and this method should be documented in the test report The thermocouple must be connected to a calibrated digital voltmeter to measure its output voltage, which can then be correlated to temperature using the thermocouple's calibration tables.

When the temperature of a test specimen changes over time after magnetization, magnetic property measurements should be conducted once a mutually agreed temperature is achieved or after a specified time between the purchaser and supplier For measurements at elevated temperatures, the test specimen should be placed in an appropriate oven to attain the desired temperature.

A secondary time-dependent magnetic relaxation effect can influence the magnetic properties of certain materials Typically, this effect is overshadowed by temperature variations However, if these magnetic relaxation effects are noticeable, it is essential to allow the test specimen to stabilize at the specified magnetic flux density or magnetic field strength for a predetermined duration before conducting the final measurements.

5 Mesure de la perméabilité magnétique et de la courbe d’aimantation au moyen de la méthode du voltmètre-ampèremètre

Les mesures sont faites en utilisant la méthode du tore normalement aux fréquences de

20 Hz à 200 kHz, la fréquence supérieure étant limitée par la performance de l'instrumentation.

NOTE 1 Lorsque les instruments étalonnés appropriés existent, cette limite supérieure peut être étendue jusqu’à

NOTE 2 Il convient que les mesures en courant continu soient faites selon la méthode du tore décrite dans la

Section 6.2 and 6.3 of IEC 62044-3 provide a selection of methods for measuring losses and effective permeability of cores taken from ongoing production, under high excitation levels and frequencies ranging from direct current to 10 MHz and beyond.

L’éprouvette en forme d’anneau doit être entourée par un enroulement d’aimantation, N 1 , et un enroulement secondaire, N 2 (voir 3.2 et Annexe A).

Les appareils doivent être branchés comme indiqué à la Figure 1.

The alternating current source must exhibit a voltage and frequency variation at its output not exceeding ±0.2% of the adjusted value during measurement It should be connected to a true RMS voltmeter or a peak value voltmeter, along with a precision resistor in series with the magnetizing winding N1 on the ring-shaped specimen, to measure the magnetizing current.

The secondary circuit includes a secondary winding N2 connected to two voltmeters in parallel One voltmeter (V2) measures the true effective value, while the other (V1) measures the rectified average value, which is sometimes calibrated to display values equal to 1.111 times the rectified value.

NOTE lI convient de vérifier la forme de l'onde de la tension secondaire avec un oscilloscope pour s'assurer que seulement la composante fondamentale est présente.

5.2.1 Forme de l’onde de la tension secondaire ou du courant d’aimantation

To obtain comparable measurements, it is essential to agree beforehand that the waveform of the secondary voltage or the magnetizing current must remain sinusoidal with a form factor of 1.111 ± 1% In this scenario, a non-inductive resistor connected in series to the magnetizing circuit is required.

NOTE 1 Il convient que la constante de temps de la résistance non inductive soit faible pour s'assurer que la forme de l'onde se trouve à l’intérieur de limites spécifiées.

NOTE 2 La résistance non inductive peut être la même résistance que celle utilisée pour la mesure du courant d’aimantation.

NOTE 3 La maỵtrise de la forme de l'onde sinusọdale peut être assurée par des moyens numériques (voir

Aux fréquences dans la gamme 20 Hz à 50 kHz, le facteur de forme de la tension secondaire peut être déterminé en branchant deux voltmètres ayant une impédance élevée (typiquement

A 1 MΩ resistor in parallel with a capacitance of 90 pF to 150 pF is connected across the secondary winding One voltmeter should measure the effective value of the voltage, while another should measure the average rectified value of the secondary voltage The form factor is then calculated as the ratio of the effective value to the average rectified value.

5 Measurement of magnetic permeability and magnetization curve using the voltmeter-ammeter method

The measurements are made using the ring method at frequencies normally from 20 Hz to

200 kHz, the upper frequency being limited by the performance of the instrumentation.

NOTE 1 Where suitable calibrated instruments exist, this upper limit may be extended to 1 MHz.

NOTE 2 DC measurements should be made in accordance with the ring method described in IEC 60404-4.

A variety of methods for measuring loss and effective permeability of cores from current production are outlined in sections 6.2 and 6.3 of IEC 62044-3, applicable at high excitation levels and across frequencies from nearly direct current (d.c.) to 10 MHz and beyond.

Apparatus and connections

The ring test specimen shall be wound with a magnetizing winding, N 1 , and a secondary winding, N 2 (see 3.2 and Annex A).

The apparatus shall be connected as shown in Figure 1.

The alternating current source must maintain a voltage and frequency variation at its output within ±0.2% of the adjusted value during measurement It should be connected to a true RMS or peak reading voltmeter, along with a precision resistor, in series with the magnetizing winding N1 on the ring test specimen to accurately measure the magnetizing current.

The secondary circuit features a secondary winding N2 linked to two parallel voltmeters One voltmeter (V2) measures the true root mean square (r.m.s.) value, while the other voltmeter (V1) measures the average rectified value, which is occasionally scaled to 1.111 times the rectified value.

NOTE The waveform of the secondary voltage should be checked with an oscilloscope to ensure that only the fundamental component is present.

5.2.1 Waveform of secondary voltage or magnetizing current

To ensure consistent measurements, it is essential to agree beforehand on maintaining either the secondary voltage waveform or the magnetizing current waveform as sinusoidal, with a form factor of 1.111 ± 1% If the magnetizing current waveform is chosen, a non-inductive resistor must be connected in series with the magnetizing circuit.

NOTE 1 The time constant of the non-inductive resistor should be low to ensure that the waveform is within the specified limits.

NOTE 2 The non-inductive resistor can be the same resistor as used for the measurement of the magnetizing current.

NOTE 3 Sinusoidal waveform control may be achieved by digital means (see Annex B).

To determine the form factor of the secondary voltage at frequencies between 20 Hz and 50 kHz, connect two high-impedance voltmeters (typically >1 MΩ in parallel with 90 pF to 150 pF) across the secondary winding One voltmeter measures the r.m.s value of the voltage, while the other measures the average rectified value The form factor is calculated as the ratio of the r.m.s value to the average rectified value.

For optimal power transfer, it may be necessary to adjust the number of turns in the excitation winding to match the output impedance of the current source This adjustment can be determined from the relevant calculations.

Z est l'impédance de sortie de la source de courant, en ohms; ω est la fréquence angulaire de la sortie de la source de courant, en radians par seconde;

L est l'inductance efficace de l'enroulement d’aimantation de l’éprouvette en forme d’anneau, en henrys, calculée à partir de m r

The section area of the specimen, denoted as A, is measured in square meters The magnetic constant, represented as μ₀, equals $4 \pi \times 10^{-7}$ henries per meter The relative permeability of the specimen is indicated as μᵣ Additionally, lm refers to the average length of the magnetic circuit of the specimen, expressed in meters.

When the relative magnetic permeability is unknown, a preliminary measurement of the magnetic field intensity and magnetic induction, as outlined in sections 5.3 and 5.4, may be required, along with the calculation of the relative magnetic permeability as described in section 5.5.

5.3 Détermination de l’intensité du champ magnétique

L’intensité du champ magnétique à laquelle la mesure doit être faite est calculée à partir de la relation suivante: m

N 1 est le nombre de tours de l'enroulement d’aimantation sur l’éprouvette;

I est le courant d’aimantation, en ampères; lm est la longueur moyenne du circuit magnétique, en mètres.

The amplitude of the magnetic field intensity is typically determined by measuring the effective value of the magnetizing current and multiplying it by the square root of 2 For a sinusoidal magnetizing current, this establishes the correct peak value of the magnetic field intensity In the case of sinusoidal magnetic induction, it defines an equivalent peak value of the magnetic field intensity, which is numerically lower for a given magnetizing current Alternatively, the peak value of the magnetic field can be measured using a peak value ammeter or a peak value voltmeter along with a precision resistor.

Before measurement, the test tube must be carefully demagnetized at a field intensity value no less than ten times the coercive field, gradually reducing the corresponding magnetization current to zero Demagnetization should be performed at the same frequency or at a lower frequency than that used for the measurements.

To achieve optimal power transfer, it is essential to adjust the number of turns in the magnetizing winding to align with the output impedance of the power source This optimization can be determined through specific calculations.

Z is the output impedance of the power source, in ohms; ω is the angular frequency of the output of the power source, in radians per second;

L is the effective inductance of the magnetizing winding of the ring test specimen, in henrys, calculated from m r

The cross-sectional area of the test specimen is denoted as A, measured in square metres The magnetic constant, represented as à 0, is equal to $4 \pi \times 10^{-7}$ henrys per metre The relative permeability of the test specimen is indicated by à r, while lm refers to the mean magnetic path length of the specimen, measured in metres.

In cases where the relative magnetic permeability is unknown, it is essential to first measure the magnetic field strength and magnetic flux density as outlined in sections 5.3 and 5.4 Subsequently, the relative magnetic permeability can be calculated following the guidelines provided in section 5.5.

Tiêu đề	Partie 6: Methods of Measurement of the Magnetic Properties of Magnetically Soft Metallic and Powder Materials at Frequencies in the Range 20 Hz to 200 kHz
Trường học	Not specified
Chuyên ngành	Electrical engineering
Thể loại	International Standard
Năm xuất bản	2003

Định dạng
Số trang	54
Dung lượng	760,64 KB