A magnetic core loss measurement system, method, and medium

Abstract

The application relates to a magnetic core loss measuring system, which comprises a direct current power supply, a magnetizing winding, a frequency modulation capacitor, a switch, a signal acquisition module and a magnetic core loss calculation module, the direct current power supply is connected in parallel at two ends of the magnetizing winding, the switch is located between the direct current power supply and the magnetizing winding, the magnetizing winding is wound on a measured magnetic element, the number of turns of the magnetizing winding is less than that of the measured magnetic element, the frequency modulation capacitor is connected in parallel at two ends of the measured magnetic element, the signal acquisition module is used for measuring and sampling the voltage of the frequency modulation capacitor and the current flowing through the measured magnetic element, the magnetic core loss calculation module calculates the magnetic core loss density according to the sampling data of the signal acquisition module, and draws a magnetic core loss density curve. Compared with the prior art, the application effectively improves the precision of the magnetic core loss measurement under high-frequency conditions.

Description

Technical Field

[0001] This invention belongs to the field of magnetic core loss measurement technology, and in particular relates to a magnetic core loss measurement system, method and medium. Background Technology

[0002] The trend towards miniaturization and high-frequency operation of power electronic power converters has placed higher demands on the power density and efficiency of power devices. The core loss of magnetic components is an important part of the power converter loss. Therefore, accurate measurement of core loss is of great significance for the optimized design of power electronic power converters.

[0003] Existing methods for measuring magnetic core loss can be broadly categorized into thermal and electrical methods. The basic principle of thermal methods is to obtain the loss by measuring the temperature change caused by core loss within a hot chamber. Electrical methods can be divided into two types: the two-winding method and the oscillation method. The two-winding method calculates core loss by measuring the voltage and current of the magnetic element under a sinusoidal voltage injection condition, while the oscillation method calculates core loss by exciting electromagnetic oscillations in the magnetic element through switching and calculating its damping characteristics. Comparing existing core loss measurement technologies, it is clear that thermal methods offer high measurement accuracy but require a high-precision hot chamber, have a long measurement time, and are complex to operate; the two-winding method is simple to implement, but phase errors in voltage and current measurements can cause errors in core loss measurement. Especially for high-frequency magnetic cores, measurement errors caused by phase differences are often not negligible. The oscillation method does not have the phase difference problem in voltage and current measurements, and is simple to operate and has low implementation costs, making it suitable for high-frequency core loss measurement. To eliminate the influence of switching device losses, Chinese patent application 202310636207.7 discloses a magnetic core loss measurement system and method based on switching oscillation, which removes the switching device from the oscillation circuit, effectively improving the measurement accuracy of magnetic core loss. However, under high-frequency conditions (such as MHz), the switching device is difficult to completely cut off the high-frequency oscillation current due to parasitic capacitance, thus causing errors in magnetic core loss measurement. Therefore, it is necessary to design a magnetic core loss measurement method to overcome the difficulties in measuring high-frequency magnetic core loss in existing technologies. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art by providing a magnetic core loss measurement system, method and medium to improve the accuracy of magnetic core loss measurement under high frequency conditions.

[0005] The objective of this invention can be achieved through the following technical solutions:

[0006] A magnetic core loss measurement system includes a DC power supply, a switch, a magnetizing winding, a frequency modulation capacitor, a signal acquisition module, and a magnetic core loss calculation module.

[0007] The DC power supply is connected in parallel across the magnetizing winding. The switch is located between the DC power supply and the magnetizing winding. The magnetizing winding is wound on the magnetic element under test. The number of turns of the magnetizing winding is less than the number of turns of the magnetic element under test. The frequency modulation capacitor is connected in parallel across the magnetic element under test. The signal acquisition module is used to measure and sample the voltage of the frequency modulation capacitor and the current flowing through the magnetic element under test. The core loss calculation module calculates the core loss density based on the sampling data of the signal acquisition module and plots the core loss density curve.

[0008] Furthermore, the signal acquisition module uses an A / D sampling circuit to sample the voltage of the frequency modulation capacitor and the current flowing through the magnetic component under test.

[0009] Furthermore, the signal acquisition module uses a digital oscilloscope to sample the voltage of the frequency modulation capacitor and the current flowing through the magnetic component under test.

[0010] Furthermore, the number of turns in the magnetized winding is 1 to 10 turns.

[0011] Furthermore, the magnetic component under test is an inductor or a transformer.

[0012] The present invention also provides a method for measuring core loss based on the core loss measurement system described above, comprising the following steps:

[0013] S1. Adjust the voltage of the DC power supply to U0, close the switch to charge the magnetic component under test, and open the switch after time t0 to stimulate oscillation.

[0014] S2, the voltage u of the frequency modulation capacitor c and the current i flowing through the magnetic element being measured L Perform measurements and sampling;

[0015] S3. Calculate the core loss density and magnetic flux density amplitude based on the sampling results of step S2, and plot the core loss density curve.

[0016] Furthermore, in step S2, the sampling process is as follows:

[0017] The voltage and current waveforms of high-frequency oscillations were obtained by measurement;

[0018] By sequentially selecting two adjacent periods in the waveform diagram, the i-th peak value U in the voltage oscillation is obtained. peak_i and the (i+1)th peak And the corresponding value I of the current oscillation envelope. peak_i and

[0019] Furthermore, in the core loss density curve, the core loss density P corresponding to the i-th point is...core_loss_i The calculation formula is as follows:

[0020]

[0021] Where V is the volume of the magnetic core of the magnetic element being tested.

[0022] Furthermore, in the core loss density curve, the magnetic flux density amplitude B corresponding to the i-th point is... m_i The calculation formula is as follows:

[0023]

[0024] Where N is the number of turns of the magnetic element under test, ω is the cross-sectional area of ​​the magnetic core of the magnetic element under test, and ψ is the oscillation angular frequency.

[0025] The present invention also provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, can implement the above-described method.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] 1. This invention charges the magnetic element under test by winding a magnetizing coil wound on the core of the magnetic element under test. The number of turns of the magnetizing coil is less than the number of turns of the coil of the magnetic element under test. According to the principle of transformer impedance conversion, the off-state high-frequency impedance converted to the oscillation side by the switch can be increased. This overcomes the problem that the double winding method is greatly affected by the phase difference of voltage and current measurement under high-frequency testing, and the problem that the measurement results are greatly affected by the loss of the switching device when the oscillation method is used to measure the core loss under high-frequency conditions in the existing technology. It can effectively suppress the core loss measurement error caused by the inability of the switch to completely cut off the high-frequency oscillation current, greatly reduce the high-frequency leakage current through the parasitic capacitance of the switch, and effectively improve the measurement accuracy.

[0028] 2. The system structure of this invention is simple and easy to implement, with low equipment cost, and multiple points on the core loss density curve can be obtained in one measurement, which improves measurement efficiency. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the system of the present invention.

[0030] Wherein: 1. DC power supply; 2. Switch; 3. Magnetic component under test; 4. Magnetizing winding; 5. Frequency modulation capacitor; 6. Signal acquisition module; 7. Core loss calculation module; N1 is the number of turns of the magnetizing winding; N2 is the number of turns of the magnetic component under test; u c The voltage across the frequency modulation capacitor; i l The current flowing through the magnetic component being measured;

[0031] Figure 2This is a flowchart of the method of the present invention;

[0032] Figure 3 This is a schematic diagram of the oscillating voltage and oscillating current waveforms;

[0033] Figure 4 The waveforms of high-frequency oscillation current and oscillation voltage at 2MHz are shown.

[0034] Figure 5 This is a schematic diagram of the original oscillation method core loss measurement system.

[0035] Figure 6 This is a schematic diagram of a traditional dual-winding method magnetic core loss measurement system.

[0036] Figure 7 The results are the core loss test results at 2MHz;

[0037] Figure 8 The results are the core loss test results at 10MHz;

[0038] in, Figure 7 and Figure 8 The horizontal axis represents the magnetic flux density amplitude, and the vertical axis represents the core loss density. Detailed Implementation

[0039] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0040] Example:

[0041] This embodiment provides a magnetic core loss measurement system, such as Figure 1As shown, 1. DC power supply; 2. Switch; 3. Magnetic element under test; 4. Magnetizing winding; 5. Frequency modulation capacitor; 6. Signal acquisition module; 7. Core loss calculation module; DC power supply 1 is connected to both ends of magnetizing winding 4, and switch 2 is located between DC power supply 1 and magnetizing winding 4. Magnetizing winding 4 is wound on the magnetic element under test 3 and is used to magnetize the magnetic element under test 3. The number of turns of the coil of magnetizing winding 4 is N1, with a typical value of 1 to 10 turns, which is much smaller than the number of turns of the coil of the magnetic element under test 3 N2. The impedance of switch 2 seen from the magnetic element under test can be effectively amplified to (N2 / N1)2 times the actual value. Therefore, magnetizing winding 4 can suppress the core loss measurement error caused by switch 2's inability to completely cut off the high-frequency oscillation current by increasing the off-state high-frequency impedance of switch 2 referred to the oscillation side. One end of switch 2 is connected to DC power supply 1, and the other end is connected to magnetizing winding 4. When switch 2 is closed, DC power supply 1 magnetizes the magnetic component 3 under test through magnetizing winding 4. When switch 2 is open, high-frequency electromagnetic oscillation is generated between the magnetic component 3 under test and frequency modulation capacitor 5. Frequency modulation capacitor 5 is connected in parallel across the magnetic component 3 under test to adjust the target frequency for core loss testing. A capacitor with a small equivalent series resistance is selected for frequency modulation capacitor 5. Signal acquisition module 6 uses a current probe and a voltage probe to measure the current i flowing through the magnetic component 3 under test. L And the voltage u of the frequency modulation capacitor 5 c Measurements are performed, and sampling is conducted using an A / D sampling circuit or a digital oscilloscope. The core loss calculation module 7 calculates the core loss density based on the sampling data from the signal acquisition module 6 and plots the core loss density curve. The core loss density curve is the relationship curve between the core loss density and the magnetic flux density amplitude. The core loss density is the core loss per unit volume.

[0042] The magnetic component 3 under test is an inductor or transformer. When measuring the core loss density of the magnetic component 3 based on the above system, if... Figure 2 As shown, it includes the following steps:

[0043] S1. Charge the magnetic component under test: Adjust the voltage of DC power supply 1 to U0, close switch 2 to charge the magnetic component under test 3, and after time t0, open switch 2 to stimulate oscillation.

[0044] S2, Oscillation Test: The voltage u of the frequency modulation capacitor 5... c and the current i flowing through the magnetic element 3 under test L Perform measurements and sampling;

[0045] In step S2, the sampling process is as follows:

[0046] The voltage and current waveforms of high-frequency oscillations are obtained by measurement, such as... Figure 3 As shown;

[0047] By sequentially selecting two adjacent periods in the waveform diagram, the i-th peak value U in the voltage oscillation is obtained. peak_i and the (i+1)th peak And the corresponding value I of the current oscillation envelope. peak_i and

[0048] S3. Data Processing: Calculate the core loss density and magnetic flux density amplitude based on the sampling results of step S2, and plot the core loss density curve.

[0049] The core loss density P corresponding to the i-th point core_loss_i and magnetic flux density amplitude V m_i The calculation formula is as follows:

[0050]

[0051]

[0052] Where i is the volume of the magnetic core of the tested magnetic element, N is the number of turns of the tested magnetic element, A is the cross-sectional area of ​​the magnetic core of the tested magnetic element, and ω is the oscillation angular frequency.

[0053] To verify the effectiveness of this invention, the core loss measurement system and method proposed in this invention were compared with the previous oscillation method measurement system and method (Chinese Patent Application 202310636207.7 discloses a core loss measurement system and method based on switching oscillation, the system structure of which is as follows). Figure 5 (as shown) and the traditional two-winding method measurement system and method (system structure as shown) Figure 6 The following experiments were conducted for comparison. The main parameters of the magnetic core loss measurement system proposed in this invention are shown in Table 1. During the experiment, two different magnetic components were tested at different frequencies.

[0054] The first magnetic component under test was made of a 76071A7 magnetic core from MAGNETICS wound with enameled wire, with 15 turns and 3 turns in the magnetizing winding. The capacitance of the frequency modulation capacitor was set to 440pF (composed of two 220pF mica capacitors connected in parallel). The test conditions were: DC power supply voltage 50V, switch on-time t0 = 5μs, test temperature 25℃, and frequency 2MHz. Figure 2 The steps involve using a high-frequency current probe and a voltage probe to measure the oscillation current and voltage data at an oscillation frequency of 2MHz, such as... Figure 4 As shown.

[0055] The second magnetic component under test was made of a 67 toroidal core (model 5967001801) from Fair-Rite wound with enameled wire, with 5 turns and 1 turn in the magnetizing winding. The frequency modulation capacitor was set to 440pF (composed of two 220pF mica capacitors connected in parallel). The test conditions were: DC power supply voltage 30V, second switch on-time t0 = 5µs, test temperature 25℃, and frequency 10MHz. The test procedure is as follows: Figure 2 Finally, formulas (1) and (2) are used to calculate the core loss density and magnetic flux density amplitude of the two tested magnetic components, and the core loss density curve is plotted.

[0056] Table 1 Parameters of the magnetic core loss measurement system of the present invention

[0057] Adjustable DC power supply 0-60V DC capacitor 820μF film capacitor switch A bidirectional turn-off switch is formed by two MOSFETs connected in reverse series. Frequency modulation capacitor mica capacitors

[0058] The core loss density curve plotted at 2MHz is shown below. Figure 7 As shown, the test results of the traditional double-winding method and the method of the present invention are consistent, while the test results of the oscillation method before the improvement are significantly larger, which verifies the effectiveness of the method of the present invention.

[0059] The core loss density curve plotted at 10MHz is as follows: Figure 8 As shown, it can be seen that the traditional double-winding method deviates significantly from the method proposed in this invention. Experimental results show that as the frequency increases, the accuracy of the method proposed in this invention is higher than that of the traditional double-winding method.

[0060] If the above methods are implemented as software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this invention, or the part that contributes to the prior art, or a part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0061] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A method for measuring magnetic core loss, implemented based on a magnetic core loss measurement system, characterized in that, The magnetic core loss measurement system includes a DC power supply (1), a switch (2), a magnetizing winding (4), a frequency modulation capacitor (5), a signal acquisition module (6), and a magnetic core loss calculation module (7). The DC power supply (1) is connected in parallel across the magnetizing winding (4). The switch (2) is located between the DC power supply (1) and the magnetizing winding (4). The magnetizing winding (4) is wound on the magnetic element under test (3). The number of turns of the magnetizing winding (4) is less than the number of turns of the magnetic element under test (3). The frequency modulation capacitor (5) is connected in parallel across the magnetic element under test (3). The signal acquisition module (6) is used to measure and sample the voltage of the frequency modulation capacitor (5) and the current flowing through the magnetic element under test (3). The magnetic core loss calculation module (7) calculates the magnetic core loss density based on the sampling data of the signal acquisition module (6) and plots the magnetic core loss density curve. The method for measuring magnetic core loss includes the following steps: S1. Adjust the voltage of the DC power supply (1) to When the switch (2) is closed, the magnetic component (3) under test is energized. After a certain time... Disconnect the switch (2) to trigger oscillation; S2, voltage of frequency modulation capacitor (5) and the current flowing through the magnetic element (3) being measured Perform measurements and sampling; S3. Calculate the core loss density and magnetic flux density amplitude based on the sampling results of step S2, and plot the core loss density curve.

2. The method for measuring core loss according to claim 1, characterized in that, The signal acquisition module (6) uses an A / D sampling circuit to sample the voltage of the frequency modulation capacitor (5) and the current flowing through the magnetic element (3) under test.

3. The method for measuring core loss according to claim 1, characterized in that, The signal acquisition module (6) uses a digital oscilloscope to sample the voltage of the frequency modulation capacitor (5) and the current flowing through the magnetic element (3) under test.

4. The method for measuring core loss according to claim 1, characterized in that, The number of coil turns of the magnetized winding (4) is 1 to 10 turns.

5. The method for measuring core loss according to claim 1, characterized in that, The magnetic component under test (3) is an inductor or a transformer.

6. The method for measuring core loss according to claim 1, characterized in that, In step S2, the sampling process is as follows: The voltage and current waveforms of high-frequency oscillations were obtained by measurement; By sequentially selecting two adjacent periods in the waveform diagram, the first period of voltage oscillation is obtained. Peak and the Peak And the corresponding value of the current oscillation envelope. and .

7. The method for measuring core loss according to claim 6, characterized in that, In the core loss density curve, the first The core loss density corresponding to each point The calculation formula is as follows: in, The volume of the magnetic core of the magnetic component being tested is given.

8. The method for measuring core loss according to claim 6, characterized in that, In the core loss density curve, the first The magnetic flux density amplitude corresponding to each point The calculation formula is as follows: in, The number of turns of the magnetic component being tested. The cross-sectional area of ​​the magnetic core of the magnetic component being tested is... ω is the oscillation angular frequency.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the program is executed by the processor, it implements the method as described in claim 1.

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