A magnetic core loss test circuit and test system based on square wave excitation
Patent Information
- Application Number
- CN202522272217.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-10-27
- Publication Date
- 2026-09-25
- Estimated Expiration
- 2035-10-27
AI Technical Summary
该方案虽然物理模型清晰，但存在如下共性不足：其一，装备成本高——高带宽、低失真度的正弦功率源价格昂贵，系统构成复杂，配套测量与隔离链路亦抬升总体成本，难以在中小企业与批量产线普及；其二，可用性与维护性差——大功率线性放大器效率低、体积与散热要求高，参数调试与长期运维门槛大；其三，测试覆盖受限——在高频、高磁通密度条件下维持理想正弦波形与恒定B峰值的难度增大，导致测试效率与一致性受影响
[0008]本实用新型的基于方波激励的磁芯损耗测试电路及测试系统，包括方波激励模块、谐振模块及计算模块，即通过方波激励配合谐振模块构成低成本、结构简洁的测试拓扑，利用谐振效应在较小驱动电压下获得接近目标工况的试验条件，进而计算模块可对所检测到的电压、电流等目标参数进行运算即可准确求取磁芯损耗，从而摆脱对高价正弦功率源与复杂放大链路的依赖，显著降低设备投入与运维门槛；同时频率与试验幅值调节便捷、测试效率高、结果一致性好，能够在高频与较高磁通密度范围内实现对磁芯损耗的有效评估，避免了正弦波功率放大器的使用，以及复杂的补偿电容计算过程。
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Figure CN224803216U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of power electronics technology, and in particular to a magnetic core loss testing circuit and system based on square wave excitation. Background Technology
[0002] In power electronic systems, improving converter efficiency depends on the accurate decomposition and quantification of various system losses. Among them, the core loss of magnetic components (inductors, transformers) accounts for a significant proportion and directly affects material selection, magnetic circuit design and overall energy efficiency optimization.
[0003] Most related technologies employ core loss testing under sinusoidal excitation conditions: a high-power, high-fidelity sinusoidal signal source or power amplifier drives the core under test within the target frequency and magnetic flux density range, and then voltage, current, and phase measurements are used to calculate the loss. While this approach has a clear physical model, it suffers from the following common drawbacks: First, high equipment cost—high-bandwidth, low-distortion sinusoidal power sources are expensive, the system configuration is complex, and the accompanying measurement and isolation links further increase the overall cost, making it difficult to popularize in small and medium-sized enterprises and mass production lines; Second, poor usability and maintainability—high-power linear amplifiers have low efficiency, large size, and high heat dissipation requirements, making parameter tuning and long-term maintenance challenging; Third, limited test coverage—maintaining an ideal sinusoidal waveform and a constant B peak value under high frequency and high magnetic flux density conditions increases the difficulty, affecting test efficiency and consistency.
[0004] Therefore, the relevant technologies need to be improved. Utility Model Content
[0005] The main objective of this invention is to provide a magnetic core loss testing circuit and system based on square wave excitation, so as to at least solve the technical problems mentioned in the related art.
[0006] To achieve the above objectives, the first aspect of this utility model provides a magnetic core loss testing circuit based on square wave excitation, the magnetic core loss testing circuit based on square wave excitation includes a square wave excitation module, a resonance module and a calculation module; The positive terminal of the square wave excitation module is used to be electrically connected to the first end of the magnetic core under test, one end of the resonant module is used to be electrically connected to the second end of the magnetic core under test, and the other end of the resonant module is electrically connected to the negative terminal of the square wave excitation module. The calculation module is used to acquire the detected target parameters and calculate the core loss of the magnetic core under test.
[0007] A second aspect of this utility model provides a magnetic core loss testing system, including a system body and a magnetic core loss testing circuit as described in the first aspect, wherein the magnetic core loss testing circuit is integrated on the system body.
[0008] This invention discloses a magnetic core loss testing circuit and system based on square wave excitation, comprising a square wave excitation module, a resonant module, and a calculation module. The square wave excitation, combined with the resonant module, forms a low-cost, simple test topology. Utilizing the resonant effect, test conditions close to the target operating condition are obtained at a relatively small driving voltage. The calculation module can then accurately calculate the magnetic core loss by operating on the detected voltage, current, and other target parameters. This eliminates the reliance on expensive sinusoidal power sources and complex amplification links, significantly reducing equipment investment and maintenance barriers. Furthermore, the system offers convenient frequency and test amplitude adjustment, high testing efficiency, and good result consistency. It can effectively assess magnetic core loss within a high-frequency and high-flux-density range, avoiding the use of sinusoidal power amplifiers and the complex calculation process of compensation capacitors. Attached Figure Description
[0009] To more clearly illustrate the technical solutions in the embodiments of this utility model or related technologies, the drawings used in the description of the embodiments or related technologies will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0010] Figure 1 A schematic diagram of the circuit connection for a magnetic core loss test circuit based on square wave excitation provided in an embodiment of this application; Figure 2 This is a circuit connection diagram of the square wave excitation module in an embodiment of this application; Figure 3 This is a circuit connection diagram of the square wave excitation module in an embodiment of this application; Figure 4 The results of core loss provided by the manufacturer for the same core under test under different operating temperature conditions and the results of core loss measured using the embodiments of this application. Detailed Implementation
[0011] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.
[0012] It should be noted that related terms such as "first" and "second" can be used to describe various components, but these terms do not limit the component. These terms are only used to distinguish one component from another. For example, without departing from the scope of this utility model, the first component can be referred to as the second component, and the second component can similarly be referred to as the first component. The term "and / or" refers to any one or more combinations of related and descriptive terms.
[0013] Please see Figure 1 This application provides a magnetic core loss test circuit based on square wave excitation. The test circuit includes at least a square wave excitation module 10, a resonant module 40, and a calculation module (not shown in the figure).
[0014] The electrical connections in the test circuit are as follows: the positive terminal of the square wave excitation module 10 is electrically connected to the first end of the magnetic core 30 under test, one end of the resonant module 40 is electrically connected to the second end of the magnetic core 30 under test, and the other end of the resonant module 40 is electrically connected to the negative terminal of the square wave excitation module 10, thereby forming a series circuit of square wave source—line impedance—magnetizing inductance L (equivalent to the primary winding N1 of the magnetic core 30 under test)—resonant capacitor C.
[0015] In an optional embodiment of this application, the test circuit may further include a line impedance module 20, which is electrically connected between the positive terminal of the square wave excitation module 10 and the first end of the magnetic core 30 under test.
[0016] It should be noted that the test object in this embodiment, namely the magnetic core 30 under test, typically includes a primary winding N1 and a secondary winding N2 wound on the same core. The first end of the primary winding N1 is connected to the output terminal of the line impedance module 20, and the second end of the primary winding N1 is connected to one end of the resonant module 40 and one end of the secondary winding N2. The other end of the resonant module 40 is connected to the negative terminal of the square wave excitation module 10 to form a series resonant circuit. The primary winding N1 and the secondary winding N2 have the same number of turns, the same winding direction, and are strongly coupled (coupling coefficient close to 1). The other end of the secondary winding N2 remains open during the test, used only to connect a voltage measurement probe to obtain the sampled voltage V1, and does not carry load current.
[0017] During testing, the square wave excitation module 10 outputs a square wave voltage Vs with a 50% duty cycle at the set test frequency fs, providing an amplitude / frequency adjustable drive source. The line impedance module 20 limits inrush current, suppresses the influence of higher harmonics of the square wave on the resonant branch, isolates the excitation source from the circuit under test, and improves transient stability. The resonant module 40 forms a series resonance with the magnetizing inductance of the core under test, creating an approximately sinusoidal voltage condition with controllable amplitude at the test frequency to achieve the target magnetic flux density and establish a measurement relationship of equal amplitude and opposite phase for V1 and V2. Finally, the calculation module is used to obtain the detected target parameters (e.g., the voltage V1 across the secondary winding N2, the voltage V2 across the resonant module, and the input current of the square wave excitation module 10). ), and calculate the core loss of the magnetic core under test.
[0018] As can be seen, the magnetic core loss test circuit based on square wave excitation in this application embodiment forms a low-cost and simple test topology by combining square wave excitation with line impedance and resonant modules. It utilizes the resonance effect to obtain test conditions close to the target operating condition under a relatively small driving voltage. Then, the calculation module can accurately calculate the magnetic core loss by calculating the detected target parameters such as voltage and current, thereby eliminating the dependence on expensive sinusoidal power sources and complex amplification links, significantly reducing equipment investment and maintenance threshold. At the same time, the frequency and test amplitude are easy to adjust, the test efficiency is high, and the results are consistent. It can effectively evaluate the magnetic core loss in the range of high frequency and high magnetic flux density, avoiding the use of sinusoidal power amplifiers and the complex compensation capacitor calculation process.
[0019] It should be understood that the line impedance module 20 can be: a small-value series resistor (current limiting / damping), an RL series circuit (small inductor + small resistor to suppress high-frequency harmonics and spikes), an RC damping or RCD absorption network (to improve transient stability), a small inductor (choke) unit, or a combination of the above components; its parameters can be set according to the target frequency, allowable surge current, resonant quality factor and source internal resistance, with the principle of limiting the surge current, suppressing high-order harmonics and providing necessary damping without significantly affecting the resonance conditions.
[0020] It should be noted that the core loss test circuit may also include a detection module (not shown in the figure).
[0021] The detection module can be various sampling units (voltage probe, current probe, or shunt) used to detect the voltage V1 across the secondary winding, the voltage V2 across the resonant module, and the input current of the square wave excitation module, and send the data to the calculation module (e.g., a host computer). This can be achieved by directly measuring the current in the connecting wires using a current probe, or by using a shunt to measure the voltage equivalent to obtain the current result.
[0022] Please see Figure 2 and Figure 3 The square wave excitation module 10 includes a DC power supply Vm, a bus filter capacitor Cm, and a square wave output switch module connected in sequence.
[0023] Specifically, the positive terminal of the DC power supply Vm is electrically connected to one end of the bus filter capacitor Cm and one end of the square wave output switch module, while the negative terminal of the DC power supply Vm is electrically connected to the other end of the bus filter capacitor Cm and the other end of the square wave output switch module.
[0024] The square wave excitation module 10 of this application embodiment provides the bus voltage through the DC power supply Vm, and the bus filter capacitor Cm is connected in parallel for voltage regulation / ripple suppression. Under complementary drive and dead-time setting control, the square wave output switch module outputs a square wave voltage Vs with a duty cycle of 50% at the test frequency fs with its midpoint relative to the negative terminal of the bus. The amplitude and frequency are adjustable, which is used to provide stable and low-distortion square wave excitation for the subsequent line impedance module and resonant module.
[0025] exist Figure 2 The square wave output switch module includes a first switch K1, a second switch K2, a third switch K3, and a fourth switch K4.
[0026] Specifically, one end of the first switch K1 is electrically connected to the positive terminal of the DC power supply Vm, one end of the bus filter capacitor Cm, and one end of the third switch K3. The other end of the first switch K1 is electrically connected to one end of the second switch K2 and serves as the first output terminal. The other end of the second switch K2 is simultaneously electrically connected to the negative terminal of the DC power supply Vm, the other end of the bus filter capacitor Cm, and one end of the fourth switch K4. The other end of the fourth switch K4 is electrically connected to the other end of the third switch K3 and serves as the second output terminal. The first and second output terminals are used to operate at the test frequency. The output is a square wave voltage with a duty cycle of 50%.
[0027] Specifically, the square wave output switch module of this application embodiment is composed of a first switch K1, a second switch K2, a third switch K3, and a fourth switch K4, and can be used at a test frequency. The system achieves a bipolar square wave voltage with a 50% duty cycle between the first and second output terminals. Preferably, MOSFETs / SiC MOSFETs are used as K1, K2, K3, and K4, along with gate drive and overcurrent, overtemperature, and undervoltage lockout protection to ensure the adjustability of the square wave amplitude and frequency, and reliable, low-distortion operation of the excitation source.
[0028] exist Figure 3 The square wave output switching module includes a fifth switching transistor K5, a sixth switching transistor K6, a first DC blocking coupling capacitor Cm3, and a second DC blocking coupling capacitor Cm4.
[0029] Specifically, one end of the fifth switch K5 is electrically connected to the positive terminal of the DC power supply Vm, one end of the bus filter capacitor Cm, and one end of the first DC blocking coupling capacitor Cm2. The other end of the fifth switch K5 is electrically connected to one end of the sixth switch K6 and serves as the first output terminal. The other end of the sixth switch K6 is simultaneously electrically connected to the negative terminal of the DC power supply Vm, the other end of the bus filter capacitor Cm, and one end of the second DC blocking coupling capacitor Cm4. The other end of the second DC blocking coupling capacitor Cm4 is electrically connected to the other end of the first DC blocking coupling capacitor Cm3 and serves as the second output terminal. The first and second output terminals are used to operate at the test frequency. The output is a square wave voltage with a duty cycle of 50%.
[0030] The square wave output switch module of this embodiment is constructed using a fifth switch K5, a sixth switch K6, a first DC blocking coupling capacitor Cm3, and a second DC blocking coupling capacitor Cm4. The half-bridge structure (K5, K6) outputs alternating high and low level signals. These alternating signals are interleaved and coupled to the output terminal through the first and second DC blocking coupling capacitors Cm3 and Cm4, thereby achieving a bipolar square wave voltage output with ground reference and a 50% duty cycle, suitable for excitation scenarios requiring high symmetry. Preferably, MOSFETs / SiC MOSFETs are used for K5 and K6, along with gate drive and overcurrent, overtemperature, and undervoltage lockout protection to ensure the adjustability of the square wave amplitude and frequency, and the reliable, low-distortion operation of the excitation source.
[0031] In an optional embodiment of this application, the resonant module 40 is a resonant capacitor C.
[0032] To ensure that the magnetizing inductance L of the magnetic core 30 under test and the resonant capacitor C form a first-order series resonance at the test frequency, the capacitance value must satisfy the following relationship:
[0033] in, This indicates the test frequency of the square wave excitation module 10. The value represents the inductance of the primary winding N1 in the magnetic core 30 under test. From the first-order LC resonant circuit, it can be seen that at resonance, the inductor voltage and capacitor voltage have equal amplitudes and are approximately 180 degrees out of phase. The voltage gain is approximately:
[0034] R includes the resistance of the line impedance unit, other stray resistances of the line, and the equivalent resistance of the magnetic core loss. When the stray resistance is very small, R is mainly determined by the equivalent resistance of the magnetic core loss. Therefore, by reasonably selecting the values of L and C under resonance conditions, a large-amplitude approximate sinusoidal voltage can be obtained across the inductor with a relatively small square wave amplitude, thereby achieving a test condition with a high magnetic flux density B. At the same time, the large gain reduces the influence of the input square wave on the sinusoidal voltage of the inductor to a negligible level.
[0035] In an optional embodiment of this application, the calculation module calculates the core loss of the magnetic core 30 under test according to a calculation formula, which is:
[0036] in, Indicates core loss. This represents the sum of V1 and V2. Indicates the input current. This indicates the period of the test frequency.
[0037] Meanwhile, the magnetic flux density corresponding to the core loss is:
[0038] Please see Figure 3 CH3 represents V1 (secondary-side sampling voltage), and CH4 represents V2 (voltage across the resonant capacitor). It can be seen that the sinusoidal components of V1 and V2 are of equal amplitude and out of phase (≈180°). Since V1 also incorporates the voltage component across the equivalent resistance of the core loss, a step / peak will appear at the instant the square wave flips, changing with the input. CH2 represents V3 = V1 + V2, theoretically retaining only the voltage corresponding to the loss component; CH1 represents the input current I1. Based on this, the calculation module performs calculations within one fundamental frequency period T. and The core loss can be obtained by integration (as shown in the calculation formula).
[0039] Please see Figure 4 Comparative tests were conducted on the same magnetic core at 25℃, 60℃, 80℃, 100℃, 120℃, and 140℃. The deviation between the magnetic core loss data (left side) obtained using the test circuit of this application and the data provided by the manufacturer (right side) was controlled within approximately 10% (better than 8% at most temperature points). The trends of the two sets of data were consistent with the increase in temperature, and no systematic deviation was observed. Given the current lack of a unified standard testing device for magnetic core loss in the industry, these test results demonstrate that the test circuit of this application can achieve measurement accuracy highly consistent with the manufacturer's data without the need for an expensive sinusoidal source, which is sufficient to meet the engineering application requirements for the selection and loss assessment of magnetic components in power electronic converters.
[0040] This application also provides a magnetic core loss testing system, including a system body and a magnetic core loss testing circuit as described in the above embodiments, wherein the magnetic core loss testing circuit is integrated on the system body.
[0041] The magnetic core loss testing circuit and system based on square wave excitation in this application constitute a low-cost and simple test topology by combining square wave excitation with line impedance and resonant modules. By utilizing the resonance effect, test conditions close to the target operating condition can be obtained at a relatively small driving voltage. Then, the calculation module can accurately calculate the magnetic core loss by calculating the detected target parameters such as voltage and current, thereby eliminating the dependence on expensive sinusoidal power sources and complex amplification links, significantly reducing equipment investment and maintenance threshold. At the same time, the frequency and test amplitude are easy to adjust, the test efficiency is high, and the results are consistent. It can effectively evaluate the magnetic core loss in the range of high frequency and high magnetic flux density, avoiding the use of sinusoidal power amplifiers and the complex compensation capacitor calculation process.
[0042] In addition, the magnetic core loss test circuit and test system using the embodiments of this application only need to provide a small amount of active and reactive power. Therefore, a square wave generating circuit with low power and low voltage amplitude can be used, which greatly reduces the cost of the magnetic core loss test device while ensuring high measurement accuracy.
[0043] The specific embodiments of the utility model have been described in detail above, but they are only examples, and the utility model is not limited to the specific embodiments described above. For those skilled in the art, any equivalent modifications or substitutions to the utility model are also within the scope of the utility model. Therefore, all equivalent transformations, modifications, and improvements made without departing from the spirit and principles of the utility model should be covered within the scope of the utility model.
Claims
1. A magnetic core loss testing circuit based on square wave excitation, characterized in that, The magnetic core loss test circuit based on square wave excitation includes a square wave excitation module, a resonance module, and a calculation module; The positive terminal of the square wave excitation module is used to be electrically connected to the first end of the magnetic core under test, one end of the resonant module is used to be electrically connected to the second end of the magnetic core under test, and the other end of the resonant module is electrically connected to the negative terminal of the square wave excitation module. The calculation module is used to acquire the detected target parameters and calculate the core loss of the magnetic core under test.
2. The core loss testing circuit based on square wave excitation as described in claim 1, characterized in that, The magnetic core under test includes a primary winding and a secondary winding; The first end of the primary winding is electrically connected to the output end of the line impedance module, and the second end of the primary winding is simultaneously electrically connected to one end of the resonant module and one end of the secondary winding. The number of turns in the primary winding is equal to the number of turns in the secondary winding.
3. The core loss testing circuit based on square wave excitation as described in claim 2, characterized in that, The target parameters include the voltage V1 across the secondary winding, the voltage V2 across the resonant module, and the input current of the square wave excitation module. .
4. The core loss testing circuit based on square wave excitation as described in claim 3, characterized in that, The calculation module calculates the core loss of the magnetic core under test according to the calculation formula; The calculation formula is as follows: in, Indicates core loss. This represents the sum of V1 and V2. Indicates the input current. This indicates the period of the test frequency.
5. The core loss testing circuit based on square wave excitation as described in claim 4, characterized in that, The resonant module is a resonant capacitor; The capacitance C of the resonant capacitor satisfies the following relationship: in, This indicates the test frequency of the square wave excitation module. This represents the inductance value of the primary winding in the magnetic core under test.
6. The core loss testing circuit based on square wave excitation as described in claim 5, characterized in that, The square wave excitation module includes a DC power supply, a bus filter capacitor, and a square wave output switch module connected in sequence. The positive terminal of the DC power supply is electrically connected to one end of the bus filter capacitor and one end of the square wave output switch module, while the negative terminal of the DC power supply is electrically connected to the other end of the bus filter capacitor and the other end of the square wave output switch module.
7. The core loss testing circuit based on square wave excitation as described in claim 6, characterized in that, The square wave output switch module includes a first switch transistor, a second switch transistor, a third switch transistor, and a fourth switch transistor; One end of the first switch is electrically connected to the positive terminal of the DC power supply, one end of the bus filter capacitor, and one end of the third switch. The other end of the first switch is electrically connected to one end of the second switch and serves as the first output terminal. The other end of the second switch is electrically connected to the negative terminal of the DC power supply, the other end of the bus filter capacitor, and one end of the fourth switch. The other end of the fourth switch is electrically connected to the other end of the third switch and serves as the second output terminal. The first output terminal and the second output terminal are used for testing frequency. The output is a square wave voltage with a duty cycle of 50%.
8. The core loss testing circuit based on square wave excitation as described in claim 6, characterized in that, The square wave output switching module includes a fifth switching transistor, a sixth switching transistor, a first DC blocking coupling capacitor, and a second DC blocking coupling capacitor. One end of the fifth switch is electrically connected to the positive terminal of the DC power supply, one end of the bus filter capacitor, and one end of the first DC blocking coupling capacitor. The other end of the fifth switch is electrically connected to one end of the sixth switch and serves as the first output terminal. The other end of the sixth switch is simultaneously electrically connected to the negative terminal of the DC power supply, the other end of the bus filter capacitor, and one end of the second DC blocking coupling capacitor. The other end of the second DC blocking coupling capacitor is electrically connected to the other end of the first DC blocking coupling capacitor and serves as the second output terminal. The first output terminal and the second output terminal are used for testing frequency. The output is a square wave voltage with a duty cycle of 50%.
9. The core loss testing circuit based on square wave excitation as described in any one of claims 2 to 8, characterized in that, The magnetic core loss test circuit also includes a detection module and a line impedance module. The detection module is used to detect the voltage V1 across the secondary winding, the voltage V2 across the resonant module, and the input current of the square wave excitation module. And send it to the computing module; The line impedance module is electrically connected between the positive terminal of the square wave excitation module and the first end of the magnetic core under test.
10. A magnetic core loss testing system, characterized in that, The system includes a system body and a core loss test circuit as described in any one of claims 1 to 9, wherein the core loss test circuit is integrated on the system body.