A high-precision core loss measurement device with multiple input waveforms

Abstract

The present invention proposes a high-precision core loss measurement device with multiple input waveforms. The device includes a periodic square wave voltage generation module, a multi-waveform input generation module and a core loss measurement module. The periodic square wave voltage generation module generates a periodic square wave voltage, and the multi-waveform input generation module generates a variety of common voltage waveforms, and then generates current waveforms of different shapes on the primary winding of the magnetic core to be measured through different switch combinations and switch tube conduction timings. The core loss measurement module uses the inductance in the air-core transformer to partially compensate for the error amplification effect caused by the voltage and current phase angle difference caused by the inductance of the magnetic core to be measured. By calculating the compensation factor, the error caused under any input waveform is reduced to close to 0, thereby achieving high-precision measurement of the core loss. The present invention solves the problem of sensitivity to measurement phase error when measuring core loss using the dual-winding method, and can accurately measure the core loss at high frequencies.

Description

Technical Field

[0001] The invention relates to a magnetic core loss measuring device, in particular to a high-precision magnetic core loss measuring device with multiple input waveforms. Background Art

[0002] Magnetic components play an important role in almost all power electronic applications. Magnetic components are usually the largest and least efficient components in power electronic devices. With the demand for high power density and high efficiency power converters, high-frequency magnetic components such as transformers and inductors become the main targets for optimization. To achieve this goal, the switching frequency of converters is getting higher and higher, which makes core loss an important factor affecting magnetic design and converter efficiency. Therefore, accurate core loss measurement, especially at high frequency, plays an important role in magnetic design and thermal design as well as the exploration of new high-frequency magnetic materials.

[0003] The existing methods for measuring core loss are mainly divided into thermal methods and electrical methods. The basic idea of ​​the thermal method is to place the wound core in a thermal isolation chamber and measure the temperature difference between the inlet and outlet coolants. Based on the temperature difference and the coolant flow rate, the heat generated by the core can be calculated. The thermal method is very accurate, but it is time-consuming, has high requirements for the experimental environment, and it is difficult to eliminate winding losses. The electrical method is generally divided into an oscillation method and a double winding method. The oscillation method is to wind the measured core into an inductor, and then connect a capacitor in series so that the inductor and capacitor resonate in series at the measured frequency. When the capacitor resonates in series with the inductor, the quality factor or resistance of the resonant branch can be measured by measuring the voltage amplitude ratio on the capacitor and the resonant branch, thereby measuring the core loss. Although the oscillation method is suitable for high frequencies, it has high matching requirements for the resonant capacitor, it is difficult to eliminate winding losses, and it is limited to sinusoidal excitation. The double winding method winds two windings on the measured core, namely the primary winding and the secondary winding. By measuring the voltage on the secondary winding and the current on the primary winding, integrating the measured voltage and current, and then multiplying by the turns ratio, the core loss can be obtained. The double winding method is simple to implement and can eliminate winding losses, but when the core quality factor is high, the phase angle difference between the measured voltage and current is Close to 90°. However, the oscilloscope sampling resolution, probe mismatch and some parasitic parameters will cause a certain phase error between the measured value of voltage and current and the actual value. The core loss error caused by this phase error will be The error is .and The value is very large, so the core loss error becomes very large. The double winding method is widely used because of its simplicity and ability to eliminate winding loss. A capacitor-compensated core loss measurement method (201911196878.6) is currently in the patent application. A capacitor is connected in series with the primary winding of the core, so that becomes 0. However, this method has high requirements on the capacitance value. becomes 0, but in actual situations, the capacitance value is difficult to meet the condition exactly, and the capacitor compensation phase can only be applied to sinusoidal excitation. Therefore, a measurement device is needed to overcome the defects of the prior art and achieve high-precision measurement of core loss at high frequencies. Summary of the invention

[0004] The purpose of the present invention is to solve the problem of sensitivity to measurement phase error when measuring core loss using a dual-winding method, overcome the defects of the prior art, and propose a high-precision core loss measurement device with multiple input waveforms.

[0005] The purpose of the present invention is achieved by at least one of the following technical solutions.

[0006] A high-precision magnetic core loss measuring device with multiple input waveforms, comprising a periodic square wave voltage generating module, a multiple waveform input generating module and a magnetic core loss measuring module;

[0007] The periodic square wave voltage generating module is connected in parallel with the magnetic core loss measuring module; one end of the multi-waveform input generating module is grounded, and the other end is connected with the magnetic core loss measuring module;

[0008] The periodic square wave voltage generation module generates a periodic square wave voltage, and the multi-waveform input generation module generates a variety of voltage waveforms. Through different switch combinations and switch tube conduction timings, current waveforms of different shapes are generated on the primary winding of the magnetic core to be measured in the core loss measurement module; the core loss measurement module uses the inductance in the air-core transformer to partially compensate for the error amplification effect caused by the voltage and current phase angle difference caused by the inductance of the magnetic core to be measured. By calculating the compensation factor, the error caused under any input waveform is reduced to close to 0 (minimum), thereby realizing the measurement of core loss.

[0009] Furthermore, the periodic square wave voltage generation module includes a first DC voltage source and four fully controlled switch tubes;

[0010] In the periodic square wave voltage generating module, the first fully-controlled switch tube and the second fully-controlled switch tube are connected in series and then connected in parallel with the first DC voltage source, the third fully-controlled switch tube and the fourth fully-controlled switch tube are connected in series and then also connected in parallel with the first DC voltage source, and the first DC voltage source, the first fully-controlled switch tube, the second fully-controlled switch tube, the third fully-controlled switch tube and the fourth fully-controlled switch tube together form a single-phase voltage-type full-bridge inverter;

[0011] A port is led out from the middle of the connection line between the first fully-controlled switch tube and the second fully-controlled switch tube, and a port is led out from the middle of the connection line between the third fully-controlled switch tube and the fourth fully-controlled switch tube. These two ports constitute the output port of the periodic square wave voltage generation module, which is connected to the core loss measurement module;

[0012] The driving signals of the first fully-controlled switch tube and the second fully-controlled switch tube are complementary, the driving signals of the third fully-controlled switch tube and the fourth fully-controlled switch tube are complementary, the first fully-controlled switch tube and the fourth fully-controlled switch tube are turned on at the same time, and the second fully-controlled switch tube and the third fully-controlled switch tube are turned on at the same time, and the DC voltage generated by the first DC voltage source is converted into a periodic square wave voltage and output to the core loss measurement module.

[0013] Further, the multi-waveform input generation module includes a second DC voltage source, a third DC voltage source, a fourth DC voltage source, a fifth fully-controlled switch tube, a sixth fully-controlled switch tube, a seventh fully-controlled switch tube and an eighth fully-controlled switch tube;

[0014] The negative poles of the second DC voltage source, the third DC voltage source and the fourth DC voltage source are grounded together; the second DC voltage source is connected in series with the fifth fully-controlled switching tube and the sixth fully-controlled switching tube to form a branch, the third DC voltage source is connected in series with the seventh fully-controlled switching tube to form a branch, and the fourth DC voltage source is connected in series with the eighth fully-controlled switching tube to form a branch. These three branches are connected in parallel, and one end of the parallel connection is grounded, which is the negative pole of the three DC voltage sources; the other end of the parallel connection is connected to the core loss measurement module.

[0015] Furthermore, the core loss measurement module uses the inductance in the air-core transformer to partially compensate for the error amplification effect caused by the voltage and current phase angle difference caused by the inductance of the core to be measured. By calculating the compensation factor, the error caused by the oscilloscope sampling resolution, probe mismatch and parasitic parameters under any input waveform is reduced to close to 0 (minimum), thereby realizing the measurement of core loss.

[0016] The magnetic core loss measurement module includes a magnetic core to be measured, an air-core transformer, an inductor, a capacitor, a first single-pole double-position switch and a second single-pole double-position switch;

[0017] In the core loss measurement module, the magnetic core to be tested is connected in series with the air-core transformer. After the series connection, the inductance and resistance of the whole are equivalent to and ;

[0018] In the first single-pole double-position switch, the first first moving end is connected to the connection point of the inductor and the capacitor, the first second moving end is grounded, and the first fixed end is connected to the primary winding of the magnetic core to be tested;

[0019] In the second single-pole double-position switch, the second first movable end is connected to the capacitor, the second second movable end is connected to the multi-waveform input generation module, and the second fixed end is connected to the primary coil of the air-core transformer;

[0020] When the first single-pole double-position switch is turned to the first first moving end and the second single-pole double-position switch is turned to the second first moving end, the entirety of the magnetic core to be tested and the air-core transformer connected in series with the inductor and capacitor forms a T-type network, also called an LCL filtering circuit.

[0021] Furthermore, in the core loss measurement module, the secondary winding of the magnetic core to be measured is open-circuited, and the secondary coil of the air-core transformer is open-circuited.

[0022] Furthermore, the LCL filter circuit in the core loss measurement module filters the higher harmonics in the periodic square wave voltage, so that the current flowing through the primary winding of the magnetic core to be measured is a sine wave;

[0023] The ratio of the current nth harmonic amplitude to the current fundamental amplitude on the primary winding of the magnetic core to be measured is:

[0024] ;

[0025] in, , , , , , is the actual capacitance value of the capacitor in the LCL filter circuit, is the inductance value of the inductor, is the capacitance value of the capacitor, is the fundamental frequency, is the fundamental angular frequency, is the amplitude of the nth harmonic of the primary winding current of the magnetic core to be measured, is the fundamental amplitude of the primary winding current of the magnetic core to be measured.

[0026] Furthermore, in order to ensure that the harmonic content of the current on the primary winding of the magnetic core to be tested is less than 0.05, the actual capacitance value is selected. With equivalent inductance When the current harmonic content of the primary winding of the magnetic core to be tested is less than 0.05, the ratio of the third harmonic amplitude of the current on the primary winding of the magnetic core to be tested to the current fundamental amplitude needs to be verified. If the ratio is less than 0.05, it is considered that the current harmonic content of the primary winding of the magnetic core to be tested is less than 0.05.

[0027] when , When one of them is 1 and the other is greater than 1, the current harmonic content is less than 0.05.

[0028] Furthermore, by turning the switch to different positions and switching the tube at different timings, different forms of current waveforms are generated on the primary winding of the magnetic core to be tested, thereby measuring the magnetic core loss, as follows:

[0029] When the first single-pole double-position switch is turned to the first first moving end and the second single-pole double-position switch is turned to the second first moving end, the whole of the magnetic core to be tested and the air-core transformer connected in series with the inductor and the capacitor forms an LCL filter circuit, which filters the high-order harmonics in the periodic square wave voltage, so that the current flowing through the primary winding of the magnetic core to be tested is a sine wave;

[0030] When the first single-pole double-position switch is turned to the first second movable end and the second single-pole double-position switch is turned to the second second movable end, by controlling the voltage amplitudes of the second DC voltage source, the third DC voltage source, and the fourth DC voltage source, and the conduction timing of the fifth fully-controlled switch tube, the sixth fully-controlled switch tube, the seventh fully-controlled switch tube, and the eighth fully-controlled switch tube, step voltages of different waveforms are generated on the primary winding of the magnetic core to be tested, thereby generating triangular wave currents and trapezoidal wave currents of different shapes on the primary winding of the magnetic core to be tested;

[0031] When it is necessary to generate a triangular wave current on the primary winding of the magnetic core to be tested, the voltage value of the second DC voltage source is set to 0, the fifth fully-controlled switch tube and the seventh fully-controlled switch tube are turned on at the same time, the sixth fully-controlled switch tube and the eighth fully-controlled switch tube are turned on at the same time, the driving signals of the seventh fully-controlled switch tube and the eighth fully-controlled switch tube are complementary, and a second-order step wave voltage is generated at the second second moving end of the second single-pole double-set switch, that is, a triangular wave current is generated on the primary winding of the magnetic core to be tested; the voltage values ​​of the third DC voltage source and the fourth DC voltage source are changed, the slope of the triangular wave current is changed, the duty cycle of the driving signal of the seventh fully-controlled switch tube is changed, and the shape of the triangular wave current is changed;

[0032] When it is necessary to generate a trapezoidal wave current on the primary winding of the magnetic core to be tested, the waveform is generated in three stages. In the first stage, the voltage value of the third DC voltage source is set to a positive value, the seventh fully-controlled switch tube is turned on, and the other switches are turned off; in the second stage, the voltage value of the second DC voltage source is set to 0, the fifth fully-controlled switch tube and the sixth fully-controlled switch tube are turned on, and the other switches are turned off; in the third stage, the voltage value of the fourth DC voltage source is set to a negative value, the eighth fully-controlled switch tube is turned on, and the other switches are turned off; at this time, a three-step ladder wave voltage will be generated at the second second moving end of the second single-pole double-position switch, that is, a trapezoidal wave current is generated on the primary winding of the magnetic core to be tested; changing the voltage values ​​of the third DC voltage source and the fourth DC voltage source changes the slope of the trapezoidal wave current, changes the on-time of the seventh fully-controlled switch tube and the eighth fully-controlled switch tube, and changes the shape of the trapezoidal wave current.

[0033] Furthermore, the physical quantity to be measured in the core loss measurement module is the open circuit voltage of the secondary winding of the core to be measured. , Open circuit voltage of secondary coil of air core transformer And the current flowing through the primary winding of the magnetic core to be tested ;

[0034] Core loss The calculation formula is:

[0035] ;

[0036] in, N 1. N 2 are the primary winding turns and the secondary winding turns of the magnetic core to be tested, N 3. N 4 are the primary coil turns and secondary coil turns of the air-core transformer, k is the compensation factor;

[0037] The current flowing through the primary winding of the magnetic core to be tested After adding a phase angle perturbation, we get ; Compensation factor k The details are as follows:

[0038] ;

[0039] in, is the current flowing through the primary winding of the magnetic core to be tested Add a phase angle disturbance to the current.

[0040] Furthermore, the magnetic flux density on the magnetic core to be measured is:

[0041] ;

[0042] in, A is the cross-sectional area of ​​the magnetic circuit of the magnetic core to be tested;

[0043] The compensating inductor in the core loss measurement module uses the inductance of an air-core transformer, which has no core loss.

[0044] Compared with the prior art, the present invention has the following advantages and technical effects:

[0045] 1. The present invention generates common current waveforms such as triangular waves and step waves on the primary winding of the magnetic core to be tested simply and at low cost by combining a DC voltage source with a switch tube, and generates a sinusoidal current waveform with low harmonic content by LCL filtering. Therefore, the present invention can measure the core loss of the magnetic core under common excitation.

[0046] 2. The present invention uses the inductance of an air-core transformer to partially compensate for the error amplification effect caused by the voltage and current phase angle difference caused by the inductance of the magnetic core to be measured. By calculating the compensation factor, the errors caused by the oscilloscope sampling resolution, probe mismatch and some parasitic parameters under any input waveform can be reduced to close to 0, thereby solving the problem of sensitivity to measurement phase error when measuring magnetic core loss by the dual-winding method, and being able to accurately measure the magnetic core loss at high frequencies. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 is a circuit diagram of a high-precision magnetic core loss measurement device with multiple input waveforms in an embodiment of the present invention;

[0048] Figure 2 is a diagram of the third harmonic content of the current on the primary winding of the magnetic core in the LCL filter circuit in an embodiment of the present invention;

[0049] Figure 3 1 is a schematic diagram of the core loss measurement principle in an embodiment of the present invention. DETAILED DESCRIPTION

[0050] The specific implementation of the invention is further described below in conjunction with the accompanying drawings, but the implementation and protection of the invention are not limited thereto.

[0051] Example:

[0052] A high-precision core loss measurement device with multiple input waveforms, such as Figure 1 As shown, it includes a periodic square wave voltage generating module, a multi-waveform input generating module and a core loss measuring module;

[0053] The periodic square wave voltage generating module is connected in parallel with the magnetic core loss measuring module; one end of the multi-waveform input generating module is grounded, and the other end is connected with the magnetic core loss measuring module;

[0054] The periodic square wave voltage generation module generates a periodic square wave voltage, and the multi-waveform input generation module generates a variety of voltage waveforms. Through different switch combinations and switch tube conduction timings, sinusoidal, triangular or step current waveforms of different shapes are generated on the primary winding of the magnetic core to be measured in the core loss measurement module; the core loss measurement module uses the inductance in the air-core transformer to partially compensate for the error amplification effect caused by the voltage and current phase angle difference caused by the inductance of the magnetic core to be measured. By calculating the compensation factor, the errors caused by the oscilloscope sampling resolution, probe mismatch and parasitic parameters under any input waveform are reduced to close to 0, thereby achieving high-precision measurement of the core loss.

[0055] Furthermore, the secondary winding of the magnetic core to be tested is open-circuited, and the secondary coil of the air-core transformer is open-circuited.

[0056] Furthermore, the periodic square wave voltage generation module includes a first DC voltage source V1 and four fully controlled switch tubes;

[0057] In the periodic square wave voltage generating module, the first fully-controlled switch tube Q1 and the second fully-controlled switch tube Q2 are connected in series and then connected in parallel with the first DC voltage source V1, the third fully-controlled switch tube Q3 and the fourth fully-controlled switch tube Q4 are connected in series and then also connected in parallel with the first DC voltage source V1, and the first DC voltage source V1, the first fully-controlled switch tube Q1, the second fully-controlled switch tube Q2, the third fully-controlled switch tube Q3 and the fourth fully-controlled switch tube Q4 together form a single-phase voltage-type full-bridge inverter;

[0058] A port is led out from the middle of the connection line between the first fully-controlled switch tube Q1 and the second fully-controlled switch tube Q2, and a port is led out from the middle of the connection line between the third fully-controlled switch tube Q3 and the fourth fully-controlled switch tube Q4. These two ports constitute the output port of the periodic square wave voltage generation module, which is connected to the core loss measurement module;

[0059] The driving signals of the first fully-controlled switch tube Q1 and the second fully-controlled switch tube Q2 are complementary, and the driving signals of the third fully-controlled switch tube Q3 and the fourth fully-controlled switch tube Q4 are complementary. The first fully-controlled switch tube Q1 and the fourth fully-controlled switch tube Q4 are turned on at the same time, and the second fully-controlled switch tube Q2 and the third fully-controlled switch tube Q3 are turned on at the same time, and the DC voltage generated by the first DC voltage source V1 is converted into a periodic square wave voltage and output to the core loss measurement module.

[0060] Further, the multi-waveform input generation module includes a second DC voltage source V2, a third DC voltage source V3, a fourth DC voltage source V4, a fifth fully-controlled switch tube Q5, a sixth fully-controlled switch tube Q6, a seventh fully-controlled switch tube Q7 and an eighth fully-controlled switch tube Q8;

[0061] The negative poles of the second DC voltage source V2, the third DC voltage source V3, and the fourth DC voltage source V4 are grounded together; the second DC voltage source V2 is connected in series with the fifth fully-controlled switch tube Q5 and the sixth fully-controlled switch tube Q6 to form a branch, the third DC voltage source V3 is connected in series with the seventh fully-controlled switch tube Q7 to form a branch, and the fourth DC voltage source V4 is connected in series with the eighth fully-controlled switch tube Q8 to form a branch. These three branches are connected in parallel, and one end of the parallel connection is grounded, which is the negative pole of the three DC voltage sources; the other end of the parallel connection is connected to the core loss measurement module.

[0062] Furthermore, the core loss measurement module includes a magnetic core to be tested, an air-core transformer, an inductor L f , capacitor C f , a first single-pole double-position switch S1 and a second single-pole double-position switch S2;

[0063] In the core loss measurement module, the magnetic core to be tested is connected in series with the air-core transformer. After the series connection, the inductance and resistance of the whole are equivalent to and ;

[0064] In the first single-pole double-position switch S1, the first first moving end 1 and the inductor L f and capacitor C f The first and second moving ends 2 are connected to the connection point, the first fixed end is connected to the primary winding of the magnetic core to be tested;

[0065] In the second single-pole double-position switch S2, the second first moving end 3 and the capacitor C f The second moving end 4 is connected to the multi-waveform input generation module, and the second fixed end is connected to the primary coil of the air-core transformer.

[0066] When the first single-pole double-position switch S1 is turned to the first first moving terminal 1, and the second single-pole double-position switch S2 is turned to the second first moving terminal 3, the whole of the magnetic core to be tested and the air-core transformer in series and the inductance L f and capacitor C f It forms a T-type network, also called an LCL filter circuit.

[0067] Furthermore, the LCL filter circuit in the core loss measurement module filters the higher harmonics in the periodic square wave voltage, so that the current flowing through the primary winding of the magnetic core to be measured is a sine wave;

[0068] The ratio of the current nth harmonic amplitude to the current fundamental amplitude on the primary winding of the magnetic core to be measured is:

[0069] ;

[0070] in, , , , , , is the actual capacitance value of the capacitor in the LCL filter circuit, is the fundamental frequency, is the fundamental angular frequency, is the amplitude of the nth harmonic of the primary winding current of the magnetic core to be measured, is the fundamental amplitude of the primary winding current of the magnetic core to be measured.

[0071] Furthermore, the core loss measurement module allows actual capacitance values With equivalent inductance Impedance value deviation, no need , , that is, you can , When it is not 1, it can still ensure that the current harmonic content on the primary winding of the magnetic core to be tested is less than 0.05 within a certain range;

[0072] In order to ensure that the harmonic content of the current on the primary winding of the magnetic core to be tested is less than 0.05, the actual capacitance value is selected. With equivalent inductance When the ratio of the third harmonic amplitude of the current on the primary winding of the magnetic core to be tested to the fundamental amplitude of the current needs to be verified. If its value is less than 0.05, it can be considered that the harmonic content of the current on the primary winding of the magnetic core to be tested is less than 0.05. , When one of them is 1 and the other is greater than 1, the current harmonic content can be reduced to less than 0.05.

[0073] In one embodiment, taking the third harmonic as an example, Figure 2 As shown, Figure 2 Figure a in the figure is When the third harmonic content of current is relationship, Figure 2 Figure b in the figure is When the third harmonic content of current is relationship.

[0074] Figure 3 This is the core loss measurement principle diagram. Figure 3 As shown, the leakage inductance of the magnetic core to be tested on the primary and secondary sides are , The equivalent resistance of the winding loss is , , magnetizing inductance and iron loss resistance are , The leakage inductance of the air-core transformer on the primary and secondary sides are , The equivalent resistance of the winding loss is , , the inductance is .

[0075] Furthermore, by turning the switch to different positions and switching the tube at different timings, different forms of current waveforms can be generated on the primary winding of the magnetic core to be tested, thereby measuring the core loss under common conditions, as follows:

[0076] When the first single-pole double-position switch S1 is turned to the first first moving terminal 1 and the second single-pole double-position switch S2 is turned to the second first moving terminal 3, the whole of the magnetic core to be tested and the air-core transformer in series and the inductance L f and capacitor C f The LCL filter circuit is formed to filter the high-order harmonics in the periodic square wave voltage, so that the current flowing through the primary winding of the magnetic core to be tested is a sine wave;

[0077] When the first single-pole double-position switch S1 is connected to the first second movable terminal 2 and the second single-pole double-position switch S2 is connected to the second second movable terminal 4, by controlling the voltage amplitudes of the second DC voltage source V2, the third DC voltage source V3, and the fourth DC voltage source V4 and the conduction timing of the switch tubes Q5-Q8, step voltages of different waveforms can be generated on the primary winding of the magnetic core to be tested, thereby generating triangular wave currents and trapezoidal wave currents of different shapes on the primary winding of the magnetic core to be tested;

[0078] When it is necessary to generate a triangular wave current on the primary winding of the magnetic core to be tested, the voltage value of the second DC voltage source V2 is set to 0, the fifth fully-controlled switch tube Q5 and the seventh fully-controlled switch tube Q7 are turned on at the same time, the sixth fully-controlled switch tube Q6 and the eighth fully-controlled switch tube Q8 are turned on at the same time, and the driving signals of the seventh fully-controlled switch tube Q7 and the eighth fully-controlled switch tube Q8 are complementary, so that a second-order step wave voltage can be generated at the moving end 4 of the second single-pole double-position switch S2, that is, a triangular wave current is generated on the primary winding of the magnetic core to be tested; changing the voltage values ​​of the third DC voltage source V3 and the fourth DC voltage source V4 can change the slope of the triangular wave current, and changing the duty cycle of the driving signal of the seventh fully-controlled switch tube Q7 can change the shape of the triangular wave current;

[0079] When it is necessary to generate a trapezoidal wave current on the primary winding of the magnetic core to be tested, the waveform is generated in three stages. In the first stage, the voltage value of the third DC voltage source V3 is set to a positive value, the seventh fully controlled switch tube Q7 is turned on, and the other switches are turned off; in the second stage, the voltage value of the second DC voltage source V2 is set to 0, the fifth fully controlled switch tube Q5 and the sixth fully controlled switch tube Q6 are turned on, and the other switches are turned off; in the third stage, the voltage value of the fourth DC voltage source V4 is set to a negative value, the eighth fully controlled switch tube Q8 is turned on, and the other switches are turned off. At this time, a three-step ladder wave voltage is generated at the second second moving end (4) of the second single-pole double-position switch S2, that is, a trapezoidal wave current is generated on the primary winding of the magnetic core to be tested; changing the voltage values ​​of the third DC voltage source V3 and the fourth DC voltage source V4 can change the slope of the trapezoidal wave current, and changing the conduction time of the seventh fully controlled switch tube Q7 and the eighth fully controlled switch tube Q8 can change the shape of the trapezoidal wave current.

[0080] Furthermore, the physical quantity to be measured in the core loss measurement module is the open circuit voltage of the secondary winding of the core to be measured. , Open circuit voltage of secondary coil of air core transformer And the current flowing through the primary winding of the magnetic core to be tested ;

[0081] Core loss The calculation formula is:

[0082] ;

[0083] in, N 1. N 2 are the primary winding turns and the secondary winding turns of the magnetic core to be tested, N 3. N 4 are the primary coil turns and secondary coil turns of the air-core transformer, k is the compensation factor;

[0084] Use the de-skew function of the oscilloscope or a computer program in the later data processing to obtain the current flowing through the primary winding of the magnetic core to be tested. After adding a small phase angle perturbation, we get In one embodiment, this phase angle perturbation is selected to be Adding a 1° phase angle to the waveform, the compensation factor k The details are as follows:

[0085] ;

[0086] in, is the current flowing through the primary winding of the magnetic core to be tested Add a phase angle disturbance to the current.

[0087] Furthermore, the magnetic flux density on the magnetic core to be measured is:

[0088] ;

[0089] in, A is the cross-sectional area of ​​the magnetic circuit of the magnetic core to be tested;

[0090] The compensating inductor in the core loss measurement module uses the inductance of an air-core transformer, which has no core loss.

[0091] In one embodiment, in order to illustrate the effectiveness of the present invention, sinusoidal excitation is used as an example, but it is not limited to this. The physical quantity to be measured is the open circuit voltage of the secondary winding of the magnetic core to be measured. , Open circuit voltage of secondary coil of air core transformer And the current flowing through the primary winding of the magnetic core to be tested Assumptions ,in is the phase angle between the voltage and current on the primary winding of the magnetic core to be measured. Assume that the oscilloscope sampling resolution, probe mismatch and some parasitic parameters cause a phase angle error in the current measurement. According to the principle of measuring core loss by double winding method, we have The same calculation is done on the air-core transformer, and we have . Take the compensation factor , then .because It cannot be measured directly, so other methods are needed to obtain the compensation factor. The current flowing through the primary winding of the magnetic core to be tested Add a small phase angle perturbation , assuming that the current is ,but , we can obtain . Phase Angle Perturbation The addition process can be done by using the de-skew function of an oscilloscope or by processing the data using a computer program. When the oscilloscope sampling resolution, probe mismatch and some parasitic parameters cause the voltage measurement to have phase angle error, and All are voltage measurements, and the voltage phase angle error can be eliminated through the de-skew function. The same is true for other waveform processing.

[0092] In one embodiment, a simulation example is used to illustrate the effectiveness of the present invention. Assume that the loss of a magnetic core is to be measured at 100kHz under sinusoidal excitation. Figure 1 The first single-pole double-position switch S1 in the circuit is connected to the first first movable terminal 1, and the second single-pole double-position switch S2 is connected to the second first movable terminal 3. The voltage of the DC voltage source V1 is 20V. , , , , , , , , . Using Simulink to simulate, the harmonic content of the current flowing through the primary winding of the magnetic core to be tested is 1.73%, which is less than 5% and is a relatively standard sine wave. At this time, the simulation results show that the core loss is 1.2103W. Assuming that the oscilloscope sampling resolution, probe mismatch and some parasitic parameters cause the current measurement to lag by 50 nanoseconds, that is, The core loss obtained by the double winding method is 1.09W, which is 9.94% different from the actual loss. The core loss obtained by the device of the present invention is 1.2113W, which is 0.08% different from the actual loss. It can be seen that the loss accuracy measured by the present invention is significantly higher than that of the double winding method.

[0093] The preferred embodiments of the present invention disclosed above are only used to help explain the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to the specific implementation methods described. Obviously, many modifications and changes can be made according to the content of this specification. This specification selects and specifically describes these examples in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well.

Claims

1. A high-precision core loss measurement device with multiple input waveforms, characterized in that: It includes a periodic square wave voltage generation module, a multi-waveform input generation module and a core loss measurement module; The periodic square wave voltage generating module is connected in parallel with the magnetic core loss measuring module; one end of the multi-waveform input generating module is grounded, and the other end is connected with the magnetic core loss measuring module; The periodic square wave voltage generation module generates a periodic square wave voltage, and the multi-waveform input generation module generates a variety of voltage waveforms. Through different switch combinations and switch tube conduction timings, current waveforms of different shapes are generated on the primary winding of the magnetic core to be measured in the magnetic core loss measurement module; the magnetic core loss measurement module uses the inductance in the air-core transformer to partially compensate for the error amplification effect caused by the voltage and current phase angle difference caused by the inductance of the magnetic core to be measured. By calculating the compensation factor, the error caused by any input waveform is reduced to achieve the measurement of the magnetic core loss; The multi-waveform input generation module includes a second DC voltage source V2, a third DC voltage source V3, a fourth DC voltage source V4, a fifth fully-controlled switch tube Q5, a sixth fully-controlled switch tube Q6, a seventh fully-controlled switch tube Q7 and an eighth fully-controlled switch tube Q8; The negative poles of the second DC voltage source V2, the third DC voltage source V3, and the fourth DC voltage source V4 are grounded together; the second DC voltage source V2 is connected in series with the fifth fully-controlled switch tube Q5 and the sixth fully-controlled switch tube Q6 to form a branch, the third DC voltage source V3 is connected in series with the seventh fully-controlled switch tube Q7 to form a branch, and the fourth DC voltage source V4 is connected in series with the eighth fully-controlled switch tube Q8 to form a branch. These three branches are connected in parallel, one end of the parallel connection is grounded, which is the negative pole of the three DC voltage sources, and the other end of the parallel connection is connected to the core loss measurement module.

2. The high-precision core loss measurement device with multiple input waveforms according to claim 1, characterized in that: The periodic square wave voltage generation module includes a first DC voltage source V1 and four fully controlled switch tubes; In the periodic square wave voltage generating module, the first fully-controlled switch tube Q1 and the second fully-controlled switch tube Q2 are connected in series and then connected in parallel with the first DC voltage source V1, the third fully-controlled switch tube Q3 and the fourth fully-controlled switch tube Q4 are connected in series and then also connected in parallel with the first DC voltage source V1, and the first DC voltage source V1, the first fully-controlled switch tube Q1, the second fully-controlled switch tube Q2, the third fully-controlled switch tube Q3 and the fourth fully-controlled switch tube Q4 together form a single-phase voltage-type full-bridge inverter; A port is led out from the middle of the connection line between the first fully-controlled switch tube Q1 and the second fully-controlled switch tube Q2, and a port is led out from the middle of the connection line between the third fully-controlled switch tube Q3 and the fourth fully-controlled switch tube Q4. These two ports constitute the output port of the periodic square wave voltage generation module, which is connected to the core loss measurement module; The driving signals of the first fully-controlled switch tube Q1 and the second fully-controlled switch tube Q2 are complementary, and the driving signals of the third fully-controlled switch tube Q3 and the fourth fully-controlled switch tube Q4 are complementary. The first fully-controlled switch tube Q1 and the fourth fully-controlled switch tube Q4 are turned on at the same time, and the second fully-controlled switch tube Q2 and the third fully-controlled switch tube Q3 are turned on at the same time, and the DC voltage generated by the first DC voltage source V1 is converted into a periodic square wave voltage and output to the core loss measurement module.

3. The high-precision core loss measurement device with multiple input waveforms according to claim 1, characterized in that: The core loss measurement module uses the inductance in the air-core transformer to partially compensate for the error amplification effect caused by the voltage and current phase angle difference caused by the inductance of the core to be measured. By calculating the compensation factor, the errors caused by the oscilloscope sampling resolution, probe mismatch and parasitic parameters under any input waveform are reduced to a minimum, thus realizing the measurement of core loss. The core loss measurement module includes the magnetic core to be tested, air-core transformer, inductor L f ,capacitance C f , a first single-pole double-position switch S1 and a second single-pole double-position switch S2; In the core loss measurement module, the magnetic core to be tested is connected in series with the air-core transformer. After the series connection, the inductance and resistance of the whole are equivalent to and ; In the first single-pole double-position switch S1, the first first moving end (1) and the inductor L f and capacitor C f The first and second moving ends (2) are connected to the connection point, the first fixed end is connected to the primary winding of the magnetic core to be tested; In the second single-pole double-position switch S2, the second first moving end (3) and the capacitor C f The second moving end (4) is connected to the multi-waveform input generation module, and the second fixed end is connected to the primary coil of the air-core transformer; When the first single-pole double-position switch S1 is switched to the first first movable end (1), and the second single-pole double-position switch S2 is switched to the second first movable end (3), the entirety of the magnetic core to be tested and the air-core transformer in series is connected to the inductor L f and capacitor C f Form a T-shaped network.

4. The high-precision core loss measurement device with multiple input waveforms according to claim 3 is characterized in that: In the core loss measurement module, the secondary winding of the magnetic core to be measured is open-circuited, and the secondary coil of the air-core transformer is open-circuited.

5. The high-precision core loss measurement device with multiple input waveforms according to claim 3, characterized in that: The LCL filter circuit in the core loss measurement module filters the high-order harmonics in the periodic square wave voltage, making the current flowing through the primary winding of the magnetic core to be measured a sine wave; The ratio of the current nth harmonic amplitude to the current fundamental amplitude on the primary winding of the magnetic core to be measured is: ； in, , , , , , is the actual capacitance value of the capacitor in the LCL filter circuit, is the fundamental frequency, is the fundamental angular frequency, is the amplitude of the nth harmonic of the primary winding current of the magnetic core to be measured, is the fundamental amplitude of the primary winding current of the magnetic core to be tested; When selecting the actual capacitance value With equivalent inductance When the ratio of the third harmonic amplitude of the current on the primary winding of the magnetic core to be tested to the current fundamental amplitude is calculated, if the ratio is less than 0.05, it is considered that the current harmonic content on the primary winding of the magnetic core to be tested is less than 0.05; when , When one of them is 1 and the other is greater than 1, the current harmonic content is less than 0.

05.

6. The high-precision core loss measurement device with multiple input waveforms according to claim 3, characterized in that: By turning the switch to different positions and different timings of the switch tube, different current waveforms are generated on the primary winding of the magnetic core to be tested, as follows: When the first single-pole double-position switch S1 is switched to the first first moving end (1) and the second single-pole double-position switch S2 is switched to the second first moving end (3), the entirety of the magnetic core to be tested and the air-core transformer in series is connected to the inductor L f and capacitor C f The LCL filter circuit is formed to filter the high-order harmonics in the periodic square wave voltage, so that the current flowing through the primary winding of the magnetic core to be tested is a sine wave; When the first single-pole double-position switch S1 is connected to the first second movable terminal (2) and the second single-pole double-position switch S2 is connected to the second second movable terminal (4), by controlling the voltage amplitudes of the second DC voltage source V2, the third DC voltage source V3 and the fourth DC voltage source V4, and the conduction timing of the fifth fully-controlled switch tube Q5, the sixth fully-controlled switch tube Q6, the seventh fully-controlled switch tube Q7 and the eighth fully-controlled switch tube Q8, step voltages of different waveforms are generated on the primary winding of the magnetic core to be tested, thereby generating triangular wave currents and trapezoidal wave currents of different shapes on the primary winding of the magnetic core to be tested; When it is necessary to generate a triangular wave current on the primary winding of the magnetic core to be tested, the voltage value of the second DC voltage source V2 is set to 0, the fifth fully-controlled switch tube Q5 and the seventh fully-controlled switch tube Q7 are turned on at the same time, the sixth fully-controlled switch tube Q6 and the eighth fully-controlled switch tube Q8 are turned on at the same time, the driving signals of the seventh fully-controlled switch tube Q7 and the eighth fully-controlled switch tube Q8 are complementary, and a second-order step wave voltage is generated at the second second moving end (4) of the second single-pole double-position switch S2, that is, a triangular wave current is generated on the primary winding of the magnetic core to be tested; the voltage values ​​of the third DC voltage source V3 and the fourth DC voltage source V4 are changed, the slope of the triangular wave current is changed, the duty cycle of the driving signal of the seventh fully-controlled switch tube Q7 is changed, and the shape of the triangular wave current is changed; When it is necessary to generate a trapezoidal wave current on the primary winding of the magnetic core to be tested, the waveform is generated in three stages. In the first stage, the voltage value of the third DC voltage source V3 is set to a positive value, the seventh fully-controlled switch tube Q7 is turned on, and the other switches are turned off; in the second stage, the voltage value of the second DC voltage source V2 is set to 0, the fifth fully-controlled switch tube Q5 and the sixth fully-controlled switch tube Q6 are turned on, and the other switches are turned off; in the third stage, the voltage value of the fourth DC voltage source V4 is set to a negative value, the eighth fully-controlled switch tube Q8 is turned on, and the other switches are turned off; at this time, a three-step ladder wave voltage is generated at the second second moving end (4) of the second single-pole double-position switch S2, that is, a trapezoidal wave current is generated on the primary winding of the magnetic core to be tested; by changing the voltage values ​​of the third DC voltage source V3 and the fourth DC voltage source V4, the slope of the trapezoidal wave current is changed, the conduction time of the seventh fully-controlled switch tube Q7 and the eighth fully-controlled switch tube Q8 is changed, and the shape of the trapezoidal wave current is changed.

7. The high-precision core loss measurement device with multiple input waveforms according to claim 3, characterized in that: The physical quantity that needs to be measured in the core loss measurement module is the open circuit voltage of the secondary winding of the magnetic core to be measured. , Open circuit voltage of secondary coil of air core transformer And the current flowing through the primary winding of the magnetic core to be tested ; Core loss The calculation formula is: ； in, N 1. N 2 are the primary winding turns and the secondary winding turns of the magnetic core to be tested, N 3. N 4 are the primary coil turns and secondary coil turns of the air-core transformer, k is the compensation factor; The current flowing through the primary winding of the magnetic core to be tested After adding a phase angle perturbation, we get ; Compensation factor k The details are as follows: ； in, is the current flowing through the primary winding of the magnetic core to be tested Add a phase angle disturbance to the current.

8. The high-precision core loss measurement device with multiple input waveforms according to claim 7, characterized in that: The magnetic flux density on the magnetic core to be measured is: ； in, A is the cross-sectional area of ​​the magnetic circuit of the magnetic core to be tested; The compensating inductor in the core loss measurement module uses the inductance of an air-core transformer, which has no core loss.

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