JP2016133355A - Iron loss measuring method and iron loss measuring apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for accurately measuring an amplitude of a current flowing through a coil having a soft magnetic material core, and a relative phase difference of the current flowing through the coil to end-to-end voltage of the coil, thereby accurately measuring iron loss.SOLUTION: Provided is an iron loss measuring method for measuring iron loss of a measurement target sample 7 by using a voltage measurement circuit 1, a current detection element 3 and a current measurement circuit 2, which includes: a preparation step of storing frequency characteristics of impedance magnitude of the current detection element, and frequency characteristics of a relative measurement phase difference for the current detection element and the current measurement circuit with respect to the voltage measurement circuit; a first measurement step of applying periodic signals to a series circuit comprising the measurement target sample 7 and the current detection element, measuring end-to-end voltage and current of the measurement target sample and decomposing the measured voltage and current into frequency components; a second measurement step of correcting an amplitude of the current flowing through the measurement target sample for each frequency component and correcting the relative phase difference of the current to the end-to-end voltage for each frequency component, by using the data stored in the preparation step; and a third measurement step of calculating the iron loss.SELECTED DRAWING: Figure 6

Description

  The present invention relates to an iron loss measuring method and an iron loss measuring apparatus for a coil component having a soft magnetic material as an iron core.

  Soft magnetic materials are widely used as iron cores for coil parts such as motors, transformers, and inductors. In recent years, with the trend of power saving, these coil components are strongly required to reduce the iron loss, which is the power loss of the iron core. In order to develop and manufacture a material with reduced iron loss, it is strongly desired to provide an iron loss measuring device that measures iron loss more accurately.

  A general iron loss measuring apparatus has a voltage measuring circuit and a current measuring circuit including a shunt resistor or a current sensor. When performing measurement, form a series circuit in which a coil component as a device under test and a shunt resistor or current sensor are connected in series, apply a periodic signal from the external signal generator to both ends of the series circuit, The voltage across the coil component and the voltage across the shunt resistor or current sensor are measured for at least one cycle. Measurement is performed at time intervals sufficiently shorter than the cycle. The current flowing through the series circuit is calculated from the voltage across the shunt resistor or current sensor, and the product of the voltage across the coil component and the current is integrated for one cycle time, and divided by the time of one cycle. Calculate a certain iron loss.

Japanese Patent Publication No. 6-60913

  However, in the above measurement, if the shunt resistor is used, the first problem that the amplitude of the current flowing through the coil component cannot be measured accurately and the relative phase difference between the voltage across the coil component and the current flowing through the coil component is There is a second problem that it cannot be measured accurately.

  The first problem is that the shunt resistor has not only a direct current resistance value but also a parasitic reactance composed of a parasitic capacitance and a parasitic inductance. When a shunt resistor having a small direct current resistance value is used, The impact will increase. On the other hand, in order to maintain a good waveform of the applied signal and to reduce heat generation, it is desirable that the DC resistance value of the shunt resistor is small, especially when measuring high current coil components related to automobiles. Is desirable to be small. Therefore, the first problem becomes a big problem when measuring a coil component for a large current.

  The second problem becomes a big problem in the case of a high power factor. As a technique for solving the second problem, there is a technique called deskew, which has been used for a long time to correct the delay time of a measurement signal between channels of an oscilloscope, and has recently been used in some power meters. However, since the frequency phase characteristic of the current measurement circuit including the shunt resistor or the current sensor is not a straight line, the deskew cannot accurately remove the relative measurement phase error for the entire frequency range.

  For the reasons as described above, the conventional iron loss measuring apparatus cannot accurately measure the iron loss due to the first and second problems.

  The present invention accurately measures the amplitude of the current flowing in the coil component whose core is a soft magnetic material and the relative phase difference of the current flowing in the coil component with respect to the voltage across the coil component, and accurately measures the iron loss of the coil component. An object of the present invention is to provide an iron loss measuring apparatus.

In order to achieve the above object, the iron loss measurement method and apparatus of the present invention execute a preparation process and a measurement process.
In the preparation step, the frequency reference and the frequency phase characteristic of the magnitude of the impedance are measured by an impedance measuring device different from the iron loss measuring device of the present invention such as an impedance analyzer whose traceability is guaranteed in advance, and a stored reference sample is prepared. The frequency characteristics of the accurate impedance magnitude of the current detection element and the frequency characteristics of the accurate relative measurement phase error of the current measurement circuit including the current detection element with respect to the voltage measurement circuit are measured and stored in advance. Keep it.

  In the measurement process, a periodic signal is applied to a series circuit in which the sample to be measured and the current detection element are connected in series, and the voltage across the sample to be measured and the voltage across the current detection element are measured and stored in the preparation process. The accurate amplitude of the current flowing in the sample to be measured is calculated using the frequency characteristic of the magnitude of the accurate impedance of the current detecting element. In addition, using the frequency characteristic of the accurate relative measurement phase error of the current measurement circuit including the current detection element for the voltage measurement circuit stored in the preparation process, the current flows to the measurement sample with respect to the voltage across the measurement sample. Corrects the relative phase difference of the current, calculates the correct relative phase difference, and corrects the current flowing in the correct sample to be measured, the correct voltage across the sample to be measured, and the sample to be measured with respect to the correct voltage across the sample to be measured. The iron loss of the coil component is obtained from the relative phase difference of the flowing current.

  The frequency characteristics of the accurate impedance magnitude of the current detection element stored in the preparation step for one current detection element and the accurate relative measurement phase error of the current measurement circuit including the current detection element with respect to the voltage measurement circuit The frequency characteristics can be used repeatedly as long as they are the same current detection element. Therefore, if the same current detection element is used, it is possible to execute the measurement process for different samples to be measured without a preparation process. However, when there is a possibility that the characteristics of the current detection element may change, it is desirable to perform a preparation process as appropriate.

  The iron loss measuring apparatus to which the present invention is applied has a voltage measuring circuit, a current measuring circuit, a shunt resistor or current sensor, and a control calculation unit. The control calculation unit includes a storage unit that stores the frequency characteristic of the magnitude of the impedance of the current detection element and the frequency characteristic of the relative measurement phase error of the current detection element and the current measurement circuit with respect to the voltage measurement circuit. The control calculation unit controls each unit to execute a measurement process, and performs a measurement process for measuring the iron loss of the sample to be measured. Furthermore, the control calculation unit may control each unit to execute the preparation process.

  According to the present invention, the accuracy of iron loss measurement of a sample to be measured using a soft magnetic material as an iron core is improved.

FIG. 1 is a block diagram showing a schematic configuration of a general iron loss measuring apparatus. FIG. 2 is a diagram illustrating the influence of the relative measurement phase error on the iron loss value. FIG. 3 is a diagram illustrating frequency phase characteristics of a voltage measurement circuit and a current measurement circuit including a shunt resistor, which are assumed for conventional deskewing. (A) shows two characteristics, and (B) and (C) show two characteristics. A technique for matching two characteristics is shown. FIG. 4 is a diagram for explaining the problem of deskew, in which (A) shows two characteristics, and (B) and (C) show a technique for matching the two characteristics. FIG. 5 is a block diagram showing a schematic configuration of an iron loss measuring apparatus using a current sensor instead of a shunt resistor. FIG. 6 is a flowchart illustrating processing executed by the iron loss measuring apparatus according to the embodiment to measure the iron loss of a coil component that is a sample to be measured. FIG. 7 is a diagram illustrating a state of the iron loss measuring apparatus according to the embodiment when the second preparation step is executed. FIG. 8 is a diagram showing the relationship between the frequency phase characteristics of the reference sample measured in the first preparation process and the frequency characteristics of α (ω) and β (ω) calculated in the second preparation process. The horizontal axis represents the linear scale. FIG. FIG. 9 is a diagram showing the relationship between the frequency phase characteristics of the reference sample measured in the first preparation process and the frequency characteristics of α (ω) and β (ω) calculated in the second preparation process. It is the figure drawn, (A) shows the whole frequency range, (B) has expanded and shown a part of frequency range. FIG. 10 is a diagram illustrating the frequency characteristic Δφ (ω) of the relative measurement phase error calculated in the second preparation step and the frequency characteristic | Z _s (ω) | of the magnitude of the impedance of the shunt resistor. Δφ (ω) and (B) indicate | Z _s (ω) |. Drawing 11 is a figure showing the state of the iron loss measuring device of an embodiment at the time of performing the 1st measurement process. FIG. 12 shows the frequency characteristic θ ′ _std (ω) of the phase difference of the fundamental wave obtained when the reference sample used in the preparation process is the measurement object in the embodiment, and the frequency phase measured in the first preparation process. It is a figure which shows difference (DELTA) (theta) _std ((omega)) with characteristic (theta) _std ((omega)). FIG. 13 is obtained by dividing the amplitude of the fundamental wave of the voltage across the sample obtained when the reference sample used in the preparation process is the measurement object in the embodiment by the amplitude of the fundamental wave of the current flowing through the sample. is the magnitude of the frequency characteristic of the impedance of the sample | Z _'std (ω) | and the magnitude of the frequency characteristic of the impedance measured in the first preparation step | Z _std (ω) | and the difference | ΔZ _std (ω) It is a figure which shows |. FIG. 14 is a diagram illustrating a state of the iron loss measuring apparatus according to the embodiment when measuring a coil component having a secondary winding.

Before describing the iron loss measuring apparatus of the embodiment, a general iron loss measuring technique will be described.
In general, a power meter or a power analyzer is used to measure the iron loss of the coil component. A method of measuring the iron loss of the coil component using these conventional measuring devices will be described.

FIG. 1 is a block diagram showing a schematic configuration of a general iron loss measuring apparatus.
The iron loss measuring device 10 includes a voltage measuring circuit 1, a current measuring circuit 2, a shunt resistor 3, a control calculation unit 4, and a display device 5. The control calculation unit 4 is formed from, for example, a CPU, a ROM, a RAM, and the like.

  The voltage measurement circuit 1 includes an amplifier 11, an A / D converter (converter) 12, and a storage device 13. The current measurement circuit 2 includes an amplifier 21, an A / D converter (converter) 22, and a storage device 23.

When performing measurement, the external signal generator 6, the coil component 7 to be measured, and the shunt resistor 3 are connected as shown in the figure, and a periodic signal with an angular frequency ω ₀ is output from the external signal generator 6. And applied to the coil component 7. At this time, the voltage measurement circuit 1 measures the voltage V _L (t) across the coil component 7 for at least one period (period T ₀ = 2π / ω ₀ ) and converts it into a digital signal by the A / D converter 12. And stored in the storage device 13. The current measurement circuit 2 measures the voltage V _s (t) across the shunt resistor 3 for at least one cycle, converts it into a digital signal by the A / D converter 22, and stores it in the storage device 23. (t) is a function of time t. As described above, the voltage measurement circuit 1 and the current measurement circuit 2 hold V _L (t) and V _s (t) as discrete data, respectively. The control calculation unit 4 controls the voltage measurement circuit 1 and the current measurement circuit 2 and performs data processing such as numerical calculation using discrete data held in the storage devices 13 and 23. The display device 5 displays the result of the data processing.

V _s (t) is converted into a current I _L (t) flowing through the coil component 7 by the following equation (1) using the (direct current) resistance value R _s of the shunt resistor 3.

And the iron loss _Pc which is the power loss of the coil component 7 is calculated by numerical integration according to the following equation (2).

However, the value of the iron loss obtained by this conventional measuring method has the following two problems, and it cannot be said that the iron loss is accurately measured.
The first problem is that the amplitude of the current I _L (t) flowing through the coil component 7 cannot be measured accurately.

The shunt resistor 3 is not composed only of the DC resistance value R _s, but always has the parasitic reactance X _s composed of the parasitic capacitance C _s and the parasitic inductance L _s, and thus the impedance of the shunt resistor 3 Z _s is expressed by the following equation (3).

The shunt resistor 3 is provided for measuring the current I _L (t) flowing through the coil component 7, and the resistance value R _s of the shunt resistor 3 is an originally unnecessary load when viewed from the external signal generator 6. is there. In particular, when the periodic signal output from the external signal generator 6 is a square wave, the applied signal deteriorates such that the current flowing through the coil component 7 does not become a triangular wave unless the resistance value R _s is small. Further, the heat generated by power loss in the shunt resistor 3, since it also causes variation in the resistance value R _s themselves the shunt resistor 3, the resistance value R _s may be detected across the voltage V _s of the shunt resistor 3 (t) is It is desirable to use the smallest possible range. In particular, the coil component 7 used for automobiles and the like is for a large current, and the power loss at the shunt resistor 3 increases.

On the other hand, the parasitic capacitance and parasitic inductance of the shunt resistor 3 is of the shunt resistor 3 specific, since it has been intentionally added, in order to reduce the parasitic reactance X _s is limited.

For the above reason, it is desirable to reduce the DC resistance value R _s of the shunt resistor 3. As a result, the ratio of the parasitic reactance X _{s to} the DC resistance value R _{s in} the impedance Z _s of the shunt resistor 3 increases. In particular, when the angular frequency ω _{0 of the} periodic signal output from the external signal generator 6 is increased, the ratio is further increased.

For example, when a certain shunt resistor 3 is regarded as equivalent to a series circuit having a resistance value R _s = 100 [mΩ] and a parasitic inductance L _s = 10 [nH], reactance is obtained at a frequency ω ₀ / 2π = 100 [kHz]. X _s is 6.3 [mΩ]. At the frequency ω ₀ / 2π = 1 [MHz], X _s becomes 63 [mΩ]. As the angular frequency ω _{0 of the} periodic signal output from the external signal generator 6 increases, the reactance X _s further increases, and the voltage V _s (t) across the shunt resistor 3 is expressed as a coil component using equation (1). Conversion to the current I _L (t) flowing through 7 is not accurate.

The second problem is that the relative phase difference between the voltage V _L (t) across the coil component 7 and the current I _L (t) flowing through the coil component 7 cannot be measured accurately.

When the both-ends voltage V _L (t) of the coil component 7 and the current I _L (t) flowing through the coil component 7 are expressed by Fourier series assuming that there is no DC component, the following equations (4) and (5) are obtained. In Equations (4) and (5), V _Lk and I _Lk are the amplitudes (k: natural number) of k-order harmonics of angular frequency ω ₀ of V _L (t) and I _L (t), respectively, and θ _k is is the angular frequency ω relative phase difference k-th harmonic of ₀ I _L (t) for V _L (t).

When these are substituted into equation (2), the iron loss P _c is expressed by the following equation (6).

From this equation (6), in order to accurately determine the iron loss P _c , the angular frequency ω ₀ , the amplitude V _{Lk of} the voltage across the coil component 7 with respect to the k-order harmonic kω ₀ , the current flowing through the coil component 7 It can be seen that it is important to accurately measure the amplitude I _Lk and the relative phase difference θ _k thereof.

However, in the conventional measurement method, this relative phase difference θ _k is deviated from θ _k to be originally measured, resulting in a relative measurement phase error Δφ _k , and the current I _L (t) flowing through the coil component 7 is expressed by Equation (5). However, it is known that the following expression (7) is obtained.

The reason why the relative phase measurement error Δφ _k occurs is that there is always a difference in the delay time of the measurement signal between the voltage measurement circuit 1 and the current measurement circuit 2 including the shunt resistor 3.
Therefore, the iron loss in this case is represented not by the equation (6) but by P _c ′ in the following equation (8).

Here, in order to see the effect of the relative measurement phase error Δφ _k on the value of the iron loss, the iron loss error ΔP _c is defined by the following equation (9). In order to simplify the description, Equation (9) describes only a specific angular frequency ω _x (k = x) component.

FIG. 2 is a diagram illustrating the influence of the relative measurement phase error on the iron loss value. In FIG. 2, using formula (9), the iron loss error when the power factor angle θ _x is changed in the range of 89.1 [deg] to 89.7 [deg] and the relative measurement phase error Δφ _x is ± 0.2 [deg]. The result of obtaining ΔP _c is shown. From this figure, it can be seen how the relative measurement phase error Δφ _x affects the iron loss value. For example, if a high power factor angle of the power factor angle theta _x of the object to be measured is 89.7 [deg], only relative measured phase error [Delta] [phi _x occurs ± 0.1 [deg], the iron loss error [Delta] P _c 33.3% It will also become.

Therefore, if the relative measurement phase error Δφ _k is not removed by any method, the relative phase difference θ _k between the voltage V _L (t) across the coil component 7 and the amplitude I _L (t) of the current flowing through the coil component 7 is accurate. It can be seen that the iron loss _Pc cannot be measured accurately.

As a method of removing this relative measurement phase error Δφ _k , there is a method called deskew that has been used for a long time to correct the delay time of the measurement signal between channels of the oscilloscope, and in recent years it has also been used for some power meters. Yes.

Deskew is a method of removing relative measurement phase errors by correcting two characteristics so as to match. However, even if this deskew method is used, the relative measurement phase error Δφ _k cannot be removed accurately. Hereinafter, the reason will be described.
First, the principle of removing a relative measurement phase error [Delta] [phi _k in deskew.

  FIG. 3 is a diagram illustrating frequency phase characteristics of a voltage measurement circuit and a current measurement circuit including a shunt resistor, which are assumed for conventional deskewing. (A) shows two characteristics, and (B) and (C) show two characteristics. A technique for matching two characteristics is shown.

As shown in FIG. 3A, the deskew is a straight line P and a straight line Q, which are ideal as electrical circuits, in terms of frequency phase characteristics of the voltage measurement circuit 1 and the current measurement circuit 2 including the shunt resistor 3, respectively. Is assumed. In this case, as shown in FIGS. 3B and 3C, the relative measurement phase error Δφ _k before the deskew is the difference between the straight line P and the straight line Q, and is represented by the straight line R. In FIGS. 3A to 3C, the difference between the straight line P and the straight line Q at the angular frequency ω _x is the relative measurement phase error Δφ _x .

The deskew, as is the relative phase difference theta _x specific voltage signal to be input to each of the current measuring circuit 2 at the angular frequency omega _x including a voltage measurement circuit 1 and the shunt resistor 3 and the current signal is 0, or a known In addition, the phase of one (or both) signals is adjusted. In order to simplify the description, in FIGS. 3B and 3C, a case where a signal having a relative phase difference θ _x of 0 is input will be described. In order to correctly measure θ _x = 0, as shown in FIG. 3B, the point A of the straight line Q with respect to the angular frequency ω _x overlaps the point B of the straight line P, or (C ), The frequency phase characteristics of the voltage measurement circuit 1 or the current measurement circuit 2 including the shunt resistor 3 must be corrected so that the point B overlaps the point A.

The above correction is performed as follows. Apart from the straight line P and the straight line Q, a straight line R having an angular frequency ω _x and a phase of Δφ _x expressed by the following equation (10) is created. Next, as shown in FIG. 3B, a straight line R is added to the straight line Q, or correction is performed by subtracting the straight line R from the straight line P as shown in FIG.

In the former case, the voltage V _L (t) remains as in Expression (4), and the phase of the following expression (11) with respect to the phase of each frequency component of the current I _L (t) in Expression (7). In the latter case, the current I _L (t) remains as in the equation (7), and the phase of each frequency component of the voltage V _L (t) in the equation (4) is The phase correction of equation (12) is performed.

In either case, when substituting into the equation (2), the relative measurement phase error Δφ _k is removed, and the iron loss P _c is expressed by the equation (6), which seems to be correct at first glance.

However, as is well known in the field of electrical measurement, the frequency phase characteristics of the voltage measurement circuit 1 and the current measurement circuit 2 can be brought close to an ideal straight line as an electrical circuit, but include a shunt resistor 3. It is impossible to make the frequency phase characteristic of the current measurement circuit 2 an ideal straight line. This is because the shunt resistor 3 is not composed of only the DC resistor R _s as described above, but necessarily has a parasitic reactance X _s composed of a parasitic capacitance C _s and a parasitic inductance L _s . Therefore, it is impossible to accurately remove the relative measured phase error [Delta] [phi _k is deskew.

FIG. 4 is a diagram for explaining the problem of deskew, in which (A) shows two characteristics, and (B) and (C) show a technique for matching the two characteristics.
With reference to FIG. 4, the reason why the relative measurement phase error Δφ _k cannot be accurately removed by deskew will be further described. In FIG. 4, for simplicity of explanation, the frequency phase characteristic of the voltage measurement circuit 1 is a straight line S shown in FIG. 4A, and the frequency phase characteristic of the current measurement circuit 2 including the shunt resistor 3 is broken. Let T be. The relative measurement phase error Δφ _k before the deskew is a difference between the straight line S and the broken line T. Here, it is assumed that the difference between the straight line S and the broken line T at the angular frequency ω _x is the relative measurement phase error Δφ _x .

The deskew in this case will be described with reference to FIGS. 4B and 4C. In deskew, a voltage signal and a current signal having an angular frequency ω _x and a relative phase difference θ _x of 0 are input to the voltage measurement circuit 1 and the current measurement circuit 2 including the shunt resistor 3, respectively. In order to correctly measure θ _x = 0, the point A of the polygonal line T with respect to the angular frequency ω _x overlaps the point B of the straight line S as shown in FIG. As shown in (C), the frequency phase characteristics of the voltage measurement circuit 1 or the current measurement circuit 3 including the shunt resistor 3 are corrected so that the point B overlaps the point A on the contrary.

This correction is performed as follows. As shown in FIG. 4B, apart from the straight line S and the broken line T, a straight line U having an angular frequency ω _x and a phase Δφ _x is formed. Next, the straight line U is added to the broken line T, or correction is performed to subtract the straight line U from the straight line S as shown in FIG. In the former case, the broken line T becomes a broken line V and does not overlap with the straight line S except for the angular frequency ω _x . In the latter case, the straight line S do not overlap the fold line T except straight W becomes, again angular frequency omega _x. Both this, the deskew means that except for the angular frequency omega _x no relative measured phase error [Delta] [phi _k is removed in another angular frequency.

As described above, the deskew can remove the relative measurement phase error at one point of the angular frequency, but cannot accurately remove the relative measurement phase error Δφ _k at the other angular frequencies.
As described above, generally the core loss measurement apparatus has first and second problems, can not accurately measure the iron loss P _C.

In the above example, the example of the iron loss measuring device using the shunt resistor 3 has been described. However, the power meter and the power analyzer use the shunt resistor as a means for detecting the current I _L (t) flowing through the coil component 7. Instead, a current sensor such as a current transformer or a current probe may be used.

FIG. 5 is a block diagram showing a schematic configuration of the iron loss measuring apparatus using the current sensor 16 instead of the shunt resistor.
The iron loss measuring apparatus 10A in FIG. 5 is the same as the iron loss measuring apparatus 10 in FIG. 1 except that the current sensor 16 is used, and a description thereof will be omitted. It is also known that the current measurement circuit 17 including the current sensor 16 does not have an ideal straight line in frequency and phase characteristics. Therefore, in the deskew, the relative measurement phase error Δφ _k cannot be accurately removed, as in the device using the shunt resistor 3 in FIG. In other words, when the current sensor 16 is used, there is the second problem as in the case where the shunt resistor 3 is used, and the iron loss cannot be measured accurately.

The iron loss measuring apparatus according to the embodiment described below can accurately measure the iron loss of a coil component.
The iron loss measuring apparatus according to the embodiment has a similar configuration to the iron loss measuring apparatus 10 in FIG. 1 or the iron loss measuring apparatus 10A in FIG. 5, but the configuration of the control calculation unit 4 is different. Hereinafter, the iron loss measuring apparatus 10 of FIG. 1 having the shunt resistor 3 will be described as an example, but the same applies to the iron loss measuring apparatus 10A of FIG.

In the iron loss measuring apparatus of the embodiment, the measurement frequency is 10 [kHz] to 1 [MHz]. The DC resistance value R _s of the shunt resistor 3 is 100 mΩ. As described above, the control calculation unit 4 is realized by a computer or the like, and controls the voltage measurement circuit 1 and the current measurement circuit 2 and performs data processing such as data storage and numerical calculation. The display device 5 displays the data processing result and information / instruction to the operator.

FIG. 6 is a flowchart illustrating processing executed by the iron loss measuring apparatus according to the embodiment to measure the iron loss of the coil component 7 that is the sample to be measured.
As shown in FIG. 6, the process includes an apparatus setting step S10, a first preparation step S11, a second preparation step S12, a first measurement step S13, a second measurement step S14, and a third measurement step S15. Have. The first preparation step S11 and the second preparation step S12 may be collectively referred to as a preparation step, and the first measurement step S13 to the third measurement step S15 may be collectively referred to as a measurement step.

In the apparatus setting step S10, the iron loss measuring apparatus is set to a state suitable for performing the measurement. If the iron loss measuring apparatus is in a state suitable for measurement, the apparatus setting step S10 need not be performed. As will be described later, when the information acquired in the preparation process is already stored and the measurement process is started without the preparation process, the apparatus setting process S10 is performed. Also in this case, if the iron loss measuring apparatus is in a state suitable for measurement, the apparatus setting step S10 need not be performed. In the preparation step, the frequency characteristic of the magnitude of the impedance of the shunt resistor 3 | Z _s (ω) | and the frequency characteristic of the relative measurement phase error Δφ (ω) of the current measurement circuit including the shunt resistance with respect to the voltage measurement circuit are calculated in advance. And remember. In the measurement process, the coil component, which is an actual sample to be measured, is measured, and correction processing is performed using | Z _s (ω) | and Δφ (ω) stored in the preparation process to determine the iron loss.

Hereinafter, each step will be described in detail.
In the device setting step S10, for each of the voltage measurement circuit 1 and the current measurement circuit 2 that does not include the shunt resistor 3, the frequency amplitude characteristic is adjusted to a known Gaussian characteristic or the maximum flat characteristic, and the frequency phase characteristic is adjusted to a straight line to cut off. The frequency is set to 10 [MHz], which is 10 times the upper limit of the measurement frequency, 1 [MHz].

  As is well known in the field of electrical measurement, if the cut-off frequency is about this level, the voltage measurement value of each of the voltage measurement circuit 1 and the current measurement circuit 2 that does not include the shunt resistor 3 is independent even at the upper limit of the measurement frequency. Is accurate.

In the first preparation step S11, a reference sample in which a resistor (representative resistance value (DC resistance value) R _d = 0.5 [Ω]) and an inductor (representative inductance value L _d = 0.5 [μH]) are connected in series is prepared. Impedance measurement frequency characteristic | Z _std (ω) | and frequency phase characteristic θ _std (ω) are measured with an impedance analyzer such as an impedance analyzer that guarantees traceability. To 100 [MHz], which is 100 times the upper limit of 1 [MHz], and is stored in the storage device. It is recommended that the reference sample resistance and inductor have the lowest possible temperature coefficient. The resistors used in the embodiment have a resistance of 100 [ppm / ° C.] and an inductor of 35 [ppm / ° C.].

FIG. 7 is a diagram illustrating a state of the iron loss measuring apparatus 10 according to the embodiment when the second preparation step S12 is performed.
In 2nd preparation process S12, as shown in FIG. 7, said reference | standard sample 24 is arrange | positioned as a to-be-measured sample of the iron loss measuring apparatus 10 of embodiment. Then, the measurement and calculation described in detail below are repeated from the lower limit 10 [kHz] of the measurement frequency to 100 [MHz] which is 100 times the upper limit, and the frequency characteristic of the magnitude of the impedance of the shunt resistor 3 | Z _s ( ω) | and the frequency characteristic Δφ (ω) of the relative measurement phase error of the current measurement circuit 2 including the shunt resistor 3 with respect to the voltage measurement circuit 1 are obtained and stored.

The second preparation step S12 will be specifically described. And it outputs a sine wave of angular frequency omega _x from the signal generator 6 is applied to the reference sample 24. At this time, the voltage V _std (t) across the reference sample and the voltage V _s (t) across the shunt resistor 3 are captured and stored for at least one cycle. V _std (t) and V _s (t) are expanded by Fourier series, and only the fundamental wave ω _x component expressed by the following equations (13) and (14) is extracted. V _std1 and V _s1 are the amplitudes of the fundamental wave ω _x components of V _std (t) and V _s (t), respectively. Α (ω _x ) and β (ω _x ) are the phases of the fundamental wave ω _x component of V _std (t) and V _s (t), respectively. (ω _x ) indicates a function of the angular frequency ω _x .

First, the impedance magnitude | Z _s (ω _x ) | of the shunt resistor 3 with respect to the angular frequency ω _x is obtained.
Since the magnitude of the impedance | Z _std (ω _x ) | with respect to the angular frequency ω _x of the reference sample 24 is known in the first preparation step, the maximum current I _std1 flowing through the reference sample 24 is the result of the equation (13). From the following equation (15).

Further, _assuming that the unknown impedance of the shunt resistor 3 is | Z _s (ω _x ) |, I _std1 can also be expressed by the following equation (16) from the result of the equation (14).

Therefore, since the right sides of the equations (15) and (16) are equal, the unknown impedance magnitude | Z _s (ω _x ) | of the shunt resistor 3 is obtained from the following equation (17). Can do.

Next, a relative measurement phase error Δφ (ω _x ) with respect to the angular frequency ω _x of the current measurement circuit 2 including the shunt resistor 3 with respect to the voltage measurement circuit 1 is obtained.
The phase of the fundamental wave of the voltage V _s (t) across the shunt resistor 3 with respect to the fundamental wave of the voltage V _std (t) across the reference sample 24, that is, the phase γ of the fundamental wave of the current I _std (t) flowing through the reference sample 24 (ω _x ) can be obtained by the following equation (18) from equations (13) and (14).

Originally, this γ (ω _x ) must match the phase θ _std (ω _x ) with respect to the angular frequency ω _x of the reference sample 24 measured in the first preparation step, but the relative measurement phase error Δφ (ω _x ). Does not match because there is. Accordingly, the relative measurement phase error Δφ (ω _x ) is a phase difference between the phase θ _std (ω _x ) and γ (ω _x ) measured and stored in the first preparation step, and the following equation (19) Given in.

Actually, if this Δφ (ω _x ) is added to the phase −β (ω _x ) of the fundamental wave of V _s (t) in equation (14) and phase correction is performed, the fundamental wave of V _s (t) The phase is expressed by the following equation (20).

Therefore, the fundamental wave of the phase of V _s (t) with respect to the fundamental wave of V _std (t), i.e., the fundamental wave of the phase of the I _std (t) is expressed by the following equation (21).

Thus, it can be seen that the phase θ _std (ω _x ) of the reference sample 24 measured and stored in the first preparation step coincides with the accurate phase θ _std (ω _x ).

The above measurement and calculation are repeated while changing the frequency from the lower limit of 10 [kHz] to 100 [MHz], which is 100 times the upper limit of 1 [MHz], and the impedance of the shunt resistor 3 is changed. The second preparation step is completed by obtaining and storing the frequency characteristic | Z _s (ω) | and the frequency characteristic Δφ (ω) of the relative measurement phase error.

FIG. 8 is a diagram showing the relationship between the frequency phase characteristic θ _std (ω) of the reference sample 24 measured in the first preparation process and the frequency characteristics of α (ω) and β (ω) calculated in the second preparation process. FIG. 6 is a diagram in which the horizontal axis is drawn with a linear scale.

FIG. 9 shows the frequency phase characteristic θ _std (ω) of the reference sample 24 measured in the first preparation step and the frequency characteristics of α (ω) and β (ω) calculated in the second preparation step, as in FIG. It is a figure which shows a relationship, a horizontal axis is drawn logarithmically so that description of phase correction may be easy to grasp, (A) shows the whole frequency range, (B) shows a part of frequency range enlarged. . FIG. 9B further shows the relationship between γ (ω _x ) and θ _std (ω _x ).

FIG. 10 is a diagram showing the frequency characteristic Δφ (ω) of the relative measurement phase error calculated in the second preparation step and the frequency characteristic | Z _s (ω) | of the magnitude of the impedance of the shunt resistor 3. Indicates Δφ (ω), and (B) indicates | Z _s (ω) |.

  For example, although it is not the calculation of the iron loss described in patent document 1, the method of calculating only the electric current of a to-be-measured object is proposed. According to Patent Document 1, the frequency characteristic or the frequency phase characteristic of the magnitude of the impedance of the shunt resistor 3 is different from that of an iron loss measuring apparatus such as an impedance analyzer in which traceability is ensured as in the case of the reference sample 24. It has been proposed to measure in advance with an impedance measuring instrument. However, in the embodiment, unlike Patent Document 1, the frequency characteristic or the frequency phase characteristic of the magnitude of the impedance of the shunt resistor 3 is not measured in advance by another impedance measuring device. The reason is that since the resistance value of the shunt resistor 3 of the embodiment is as small as 100 [mΩ], even if this is measured by another impedance measuring device, a large measurement error occurs.

  The shunt resistor is an essentially unnecessary load, and it also causes the fluctuation of the resistance value itself due to heat generation due to power loss, so the resistance value is selected as small as possible within the range where the voltage across the shunt resistor can be detected, A material in the range of several tens [mΩ] to several hundreds [mΩ] is generally used. However, these other impedance measuring instruments have very poor measurement accuracy when the impedance magnitude is less than 200 to 300 [mΩ] or more than 4 to 5 [MΩ]. It is known that a large measurement error of 10 [%] and several [deg] in phase occurs. When such a measurement error occurs, as explained in FIG. 2, it can no longer be used for accurate measurement of iron loss. In the example described in the example of Patent Document 1, a shunt resistor having a resistance value of 1 [Ω] is used, and this is because a large shunt resistor having a resistance value is used. It is thought to avoid this.

The preparation process has been described above. As described above, the preparation process does not have to be performed every time the iron loss of the coil component is measured using the iron loss measuring apparatus of the embodiment. During the adjustment of the iron loss measuring device, the frequency characteristic | Z _s (ω) | of the magnitude of the impedance of the shunt resistor 3 and the frequency characteristic Δφ (ω) of the relative measurement phase error are obtained and stored. If you do, you don't have to do it again.

FIG. 11 is a diagram illustrating a state of the iron loss measuring apparatus 10 according to the embodiment when the first measurement step S13 is performed.
Hereinafter, the measurement process will be described with reference to FIG.

In the first measurement step, the coil component 7 that is the object to be measured is arranged as a sample to be measured of the iron loss measuring apparatus 10 of the embodiment, and a series circuit is formed with the shunt resistor 3. A periodic signal having an angular frequency ω ₀ is output from the external signal generator 6 and applied to both ends of the series circuit. As a result, a current corresponding to the periodic signal flows through the coil component 7 and the shunt resistor 3. At this time, the voltage V _L (t) across the coil component 7 and the voltage V _s (t) across the shunt resistor 3 are captured and stored for at least one cycle. V _L (t) and V _s (t) are Fourier-expanded to the 100th harmonics represented by the following equations (22) and (23), respectively. V _Lk and V _sk are the amplitudes of the k-order harmonics of ω ₀ of V _L (t) and V _s (t), respectively, and α (kω ₀ ) and β (kω ₀ ) are V _L (t) and This is the phase of the kth harmonic of ω ₀ of V _s (t). As is well known in the Fourier series, the voltage up to the 100th harmonic is about the 60th order or higher. The voltage V _L (t) across the coil component 7 or the voltage V _s (t) across the shunt resistor 3 is square. This is because even waves can be reproduced.

In the second measurement step, the frequency characteristic of the magnitude of the impedance of the shunt resistor 3 stored in the preparation step is stored as the amplitude V _sk of each frequency component of V _s (t) as expressed by the following equation (24). Dividing by | Z _s (kω ₀ ) |, the amplitude of each frequency component of the current I _L (t) flowing through the coil component 7 is corrected to an accurate amplitude. Further, by adding the frequency characteristic Δφ (kω ₀ ) of the relative measurement phase error stored in the preparation step to the phase β (kω ₀ ) of each frequency component of V _s (t), the current I _L (t ) To correct the phase of each frequency component to obtain an accurate current I _L (t).

If there is no frequency characteristic | Z _s (ω) | corresponding to the angular frequency kω ₀ in the frequency characteristic | Z _s (ω) | stored in the preparation process, the frequency characteristic | Z _s (ω) | Is obtained by interpolation using a linear function. Similar processing is performed for the frequency characteristic Δφ (ω) of the relative measurement phase error when there is no frequency characteristic corresponding to the angular frequency kω ₀ .

In the third measurement step, using the current I _L (t) flowing through the coil component 7 of equation (24) and the voltage V _L (t) across the coil component 7 of equation (22), according to the above equation (2) The iron loss P _c is obtained by numerical integration.

Since the amplitude of the current flowing through the coil component 7 and the relative phase difference of the current flowing through the coil component 7 with respect to the voltage across the coil component 7 can be accurately corrected, the iron loss measuring device of the present invention can accurately The iron loss P _c can be obtained.

  The specific example which proves that the relative phase difference of the electric current which flows into the coil component 7 with respect to the both-ends voltage of the coil component 7 by the iron loss measuring apparatus 10 of embodiment and the amplitude of the electric current which flows into the coil component 7 is correct is shown.

In FIG. 12, the reference sample 24 used in the preparation process is arranged again as a sample to be measured, and a sine wave is output and applied while changing the frequency from 10 [kHz] to 1 [MHz] from the signal generator 6. The current I _L (t (t) flowing in the sample of the equation (24) with respect to the fundamental wave of the both-ends voltage V _L (t) of the sample of the equation (22) obtained when the above measurement process is performed for each frequency. the frequency characteristic of the phase difference of the fundamental wave theta _'std (omega)) of, and the frequency phase characteristics of the reference sample 24 measured in the first preparation step theta _std (omega), the difference Δθ expressed by the following equation (25) _std (ω) is shown. Ideally, this is 0.00 [deg] over the entire frequency, but the frequency phase characteristic θstd (ω of the reference sample 24 measured in the first preparation step with very high accuracy of ± 0.02 [deg] according to the present invention. ) And the relative phase difference of the current flowing through the sample with respect to the voltage across the sample is measured.

FIG. 13 shows the amplitude of the fundamental wave of the both-ends voltage V _L (t) of the sample of Expression (22) obtained when the measurement process is performed for each frequency, as in FIG. The frequency characteristic of the magnitude of the impedance of the sample obtained by dividing by the amplitude of the fundamental wave of the current I _L (t) flowing through the sample | Z ′ _std (ω) | and the reference sample 24 measured in the first preparation step The difference | ΔZ _std (ω) | represented by the following equation (26) with respect to the frequency characteristic | Z _std (ω) | of the magnitude of the impedance is shown. Ideally, this is 0.00 [%] over the entire frequency, but according to the present invention, the magnitude of the impedance of the reference sample 24 measured in the first preparation step with very high accuracy of less than 0.16 [%] at the maximum. frequency characteristic | Z _std (ω) | consistent with, it can be seen that the magnitude of the impedance of the sample, i.e., the current flowing through the sample being measured.

In the description of the above embodiment, the case of measuring the coil component 7 of a single coil has been described, but it is also possible to measure a coil component having a secondary winding (the number of turns N ₂ ).
FIG. 14 is a diagram illustrating a state of the iron loss measuring apparatus according to the embodiment when measuring a coil component having a secondary winding.

As shown in FIG. 14, one terminal of the primary winding of the coil component 26 having the secondary winding is connected to the shunt resistor 3, and the other terminal of the primary winding and the other end of the shunt resistor 3. Then, a periodic signal having an angular frequency ω ₀ is output from the external signal generator 6 and a signal is applied to the primary winding. As a result, a current corresponding to the periodic signal flows through the primary winding and the shunt resistor 3, and a signal is induced in the secondary winding. The voltage measurement circuit 1 measures the voltage across the secondary winding, not the voltage across the primary winding (the number of turns N ₁ ).

  The single-coil coil component 7 shown in the state of FIG. 11 is used to measure iron loss including copper loss of a coil component that cannot be wound with a secondary winding, for example, a packaged inductor component. On the other hand, when measuring the coil component 26 having the secondary winding as shown in FIG. 14, the iron loss not including the copper loss of the primary winding can be measured. There is an advantage that the pure iron loss of the soft magnetic material itself can be measured.

As shown in FIG. 14, in the configuration in which the coil component 26 having the secondary winding is measured, the iron loss P _c is calculated by the following equation (27) instead of the equation (2). However, since the procedure and data processing of the preparation process and the measurement process are the same except for the calculation of the iron loss P _c , detailed description is omitted.

In the embodiment, correction is performed by adding the frequency characteristic Δφ (kω ₀ ) of the relative measurement phase error to the phase β (kω ₀ ) of each frequency component of V _s (t) in Expression (23). 22) Even if the phase α (kω ₀ ) of each frequency component of V _L (t) is corrected by adding Δφ (kω ₀ ), the accuracy of the iron loss P _c obtained by the equation (2) can be improved. There is no effect. However, phase correction in which Δφ (kω ₀ ) is added to the phase α (kω ₀ ) of each frequency component of V _L (t) causes a problem in measured values other than the iron loss P _c . This phase correction is based on V _s (t) measured by the current measurement circuit 2 including the shunt resistor whose frequency phase characteristic is not linear, and V _L (t) measured by the voltage measurement circuit whose frequency phase characteristic is linear. Therefore, the signal waveforms of V _s (t) and V _L (t) are changed to those different from the true signal waveform. Therefore, as in the embodiment, it is desirable to correct by adding the frequency characteristic Δφ (kω ₀ ) of the relative measurement phase error to the phase β (kω ₀ ) of each frequency component of V _s (t). However, if the frequency phase characteristics of the current measurement circuit 2 including the shunt resistor are close to a straight line, phase correction by adding Δφ (kω ₀ ) to the phase α (kω ₀ ) of each frequency component of V _L (t) is also a problem. There is no.

  In the embodiment, the signal acquisition in the preparation process and the measurement process is performed for one period, but is not limited to one period. If as many integer cycles as possible are taken in and one cycle in which the averaging process is performed is taken as a calculation target, the measurement accuracy is further improved.

  Further, in the embodiment, a reference sample in which a resistor and an inductor are connected in series is adopted, but the reference sample is not particularly limited to this element configuration. This is an impedance measuring instrument different from the iron loss measuring device of the present invention, such as an impedance analyzer, whose traceability is guaranteed from the lower limit to the upper limit of 100 times, and has high impedance frequency characteristics and frequency phase characteristics. Any element configuration having an impedance of 0.5 [Ω] to several [Ω] that can be accurately measured is acceptable.

Furthermore, in the embodiment, the case where the shunt resistor is used as the means for detecting the current I _L (t) has been described. However, the present invention is not limited to this, and a current sensor such as a current transformer or a current probe may be used. .
As described above, according to the iron loss measuring apparatus of the present invention, the amplitude of the current flowing through the coil component and the relative phase difference of the current flowing through the coil component with respect to the voltage across the coil component can be accurately corrected. The accurate iron loss of the coil component can be obtained from the current flowing through the accurate coil component, the accurate voltage across the coil component, and the relative phase difference of the current flowing through the coil component with respect to the accurate voltage across the coil component.

1 Voltage measurement circuit 2 Current measurement circuit 3 Shunt resistance (current detection element)
DESCRIPTION OF SYMBOLS 4 Control calculating part 5 Display apparatus 6 Signal generator 7 Sample to be measured 16 Current sensor 24 Reference sample 26 Coil component which has secondary winding

Claims (16)

An iron loss measurement method for measuring iron loss of a sample to be measured using a voltage measurement circuit, a current detection element, and a current measurement circuit,
A preparatory step of storing a frequency characteristic of the magnitude of impedance of the current detection element and a frequency characteristic of a relative measurement phase error of the current detection element and the current measurement circuit with respect to the voltage measurement circuit;
A periodic signal is applied to a series circuit in which the sample to be measured and the element for current detection are connected in series, and the voltage flowing across the sample to be measured is applied to the voltage across the voltage of the sample to be measured by the voltage measuring circuit. And a first measurement step of measuring with the current measurement circuit, and decomposing the voltage across the sample to be measured and the current flowing through the sample to be measured into frequency components;
Using the data stored in the preparation step, the amplitude of the current flowing in the sample to be measured is corrected for each frequency component, and the relative phase difference of the current flowing in the sample to be measured with respect to the voltage across the sample to be measured A second measurement step for correcting each frequency component,
Third measurement step of calculating the iron loss of the sample to be measured using the voltage and the amplitude of the sample to be measured and the current flowing through the sample to be measured in which the relative phase difference with respect to the voltage across the sample is corrected. An iron loss measuring method comprising: The preparation step includes
A first preparatory step of measuring and storing the frequency characteristic and frequency phase characteristic of the magnitude of the impedance of the reference sample;
The voltage across the reference sample is measured by the voltage measurement circuit, the current flowing through the reference sample is measured by the current detection element and the current measurement circuit, and the measurement data stored in the first preparation step is used. Calculating and storing a frequency characteristic of the magnitude of impedance of the current detection element and a frequency characteristic of a relative measurement phase error of the current detection element and the current measurement circuit with respect to the voltage measurement circuit; The iron loss measuring method according to claim 1, comprising: Before performing the first measurement step or the preparation step,
The frequency amplitude characteristics of the voltage measurement circuit and the current measurement circuit are adjusted to a Gaussian characteristic or a maximum flat characteristic, the frequency phase characteristics of the voltage measurement circuit and the current measurement circuit are adjusted to a straight line, and the cutoff frequency is adjusted to the measurement frequency. The iron loss measuring method according to claim 2, further comprising a device setting step of setting the upper limit to 10 times or more of the upper limit.   The iron loss measuring method according to any one of claims 1 to 3, wherein in the second measuring step, the phase of the current flowing through the sample to be measured is corrected so as to match the phase of the voltage across the sample to be measured. .   The iron loss measurement method according to claim 1, wherein the current detection element is a shunt resistor.   The iron loss measurement method according to claim 1, wherein the current detection element is a current sensor resistance.   When the sample to be measured has a primary winding and a secondary winding, in the first measurement step, the periodic signal is applied to the primary winding and the voltage across the secondary winding is measured. The iron loss measuring method according to any one of claims 1 to 6. Frequency characteristics of the magnitude of impedance of the current detection element for measuring the iron loss of the sample to be measured using the voltage measurement circuit, the current detection element, and the current measurement circuit, and the current with respect to the voltage measurement circuit A method of measuring a frequency characteristic of a relative measurement phase error of a detection element and the current measurement circuit,
A first preparatory step of measuring and storing the frequency characteristic and frequency phase characteristic of the magnitude of the impedance of the reference sample;
The voltage across the reference sample is measured by the voltage measurement circuit, the current flowing through the reference sample is measured by the current detection element and the current measurement circuit, and the measurement data stored in the first preparation step is used. And a second preparatory step for calculating a frequency characteristic of the magnitude of the impedance of the current detection element and a frequency characteristic of a relative measurement phase error of the current detection element and the current measurement circuit with respect to the voltage measurement circuit. Method. A voltage measurement circuit for measuring the voltage across the sample to be measured;
A current detection element;
A current measurement circuit for detecting a current flowing in the current detection element;
A control operation unit,
The control calculation unit is
A storage unit that stores a frequency characteristic of an impedance magnitude of the current detection element and a frequency characteristic of a relative measurement phase error of the current detection element and the current measurement circuit with respect to the voltage measurement circuit; Iron loss measuring device. The control calculation unit is
A periodic signal is applied to a series circuit in which the sample to be measured and the element for current detection are connected in series, and the voltage flowing across the sample to be measured is applied to the voltage across the voltage of the sample to be measured by the voltage measuring circuit. And a first measurement step of measuring with the current measurement circuit, and decomposing the voltage across the sample to be measured and the current flowing through the sample to be measured into frequency components;
Using the data stored in the preparation step, the amplitude of the current flowing in the sample to be measured is corrected for each frequency component, and the relative phase difference of the current flowing in the sample to be measured with respect to the voltage across the sample to be measured A second measurement step for correcting each frequency component,
Third measurement step of calculating the iron loss of the sample to be measured using the voltage and the amplitude of the sample to be measured and the current flowing through the sample to be measured in which the relative phase difference with respect to the voltage across the sample is corrected. And the iron loss measuring apparatus of Claim 9 performed. The control calculation unit is
A first preparatory step of measuring and storing the frequency characteristic and frequency phase characteristic of the magnitude of the impedance of the reference sample;
The voltage across the reference sample is measured by the voltage measurement circuit, the current flowing through the reference sample is measured by the current detection element and the current measurement circuit, and the measurement data stored in the first preparation step is used. Calculating and storing a frequency characteristic of the magnitude of impedance of the current detection element and a frequency characteristic of a relative measurement phase error of the current detection element and the current measurement circuit with respect to the voltage measurement circuit; The iron loss measuring device according to claim 10, wherein   11. The voltage measurement circuit and the current measurement circuit each have a frequency amplitude characteristic adjusted to a Gaussian characteristic or a maximum flat characteristic, a frequency phase characteristic adjusted to a straight line, and a cutoff frequency equal to or more than 10 times the upper limit of the measurement frequency. Or the iron loss measuring apparatus of 11. The control calculation unit is
The iron loss measurement according to any one of claims 10 to 12, wherein in the second measurement step, the phase of the current flowing through the sample to be measured is corrected so as to coincide with the phase of the voltage across the sample to be measured. apparatus.   The iron loss measuring apparatus according to claim 9, wherein the current detection element is a shunt resistor.   The iron loss measuring apparatus according to claim 9, wherein the current detection element is a current sensor resistance.   When the sample to be measured has a primary winding and a secondary winding, in the first measurement step, the periodic signal is applied to the primary winding and the voltage across the secondary winding is measured. The iron loss measuring apparatus according to any one of claims 10 to 12.

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