Method for measuring the DC superposition characteristics of an inductor, system for measuring the DC superposition characteristics of an inductor, and program.

Abstract

DC superposition characteristics can be measured in a short time. [Solution] A measurement step for measuring the inductor voltage, which is the voltage between two endpoints of an inductor, and the inductor current, which is the current flowing through the inductor, when a voltage is applied to the inductor from a single-phase PWM inverter, wherein the inductor current is a superimposed current in which a second current, which is a sine wave with a second frequency, is superimposed on a first current, which is a sawtooth wave with a first frequency; and a calculation step for calculating the DC superimposed characteristics of the inductor based on the inductor voltage and the inductor current.

Description

[Technical Field]

[0001] This invention relates to a method for measuring the DC superposition characteristics of an inductor, a system for measuring the DC superposition characteristics of an inductor, and a program for doing so. [Background technology]

[0002] Even if the alternating current remains constant, an inductor will have a superimposed direct current. As the direct current increases, the permeability decreases and the inductance L decreases. This change in inductance L with respect to the superimposed direct current is called the DC superposition characteristic of the inductor. Hereafter, the DC superposition characteristic of the inductor will simply be referred to as the "DC superposition characteristic". Generally, a common method for measuring DC superposition characteristics involves combining an LCR meter with a DC bias power supply. The AC current output from the LCR meter is superimposed with the DC current output from the DC bias power supply, and this is passed through the inductor (the sample). At this time, the inductance L of the sample is measured using the LCR meter.

[0003] Figure 12 shows an example of a conventional DC superposition characteristic measurement method. The DC bias power supply 901 is DC current I dc Current is passed through inductor 902. Inductor 902 is the sample being measured. A choke coil 903 is connected between the DC bias power supply 901 and inductor 902, so that the current output from the DC bias power supply 901 flows through the choke coil 903 to inductor 902. The choke coil 903 prevents the AC current output from the AC power supply 905 of the LCR meter 904 from flowing into the DC bias power supply 901.

[0004] The AC power supply 905 supplies an AC current of frequency f to the inductor 902 via the coupling capacitor 906. As a result, an AC current superimposed with a DC current flows through the inductor 902. The coupling capacitor 906 prevents the DC current output from the DC bias power supply 901 from flowing into the AC power supply 905.

[0005] The current measuring device 907 measures the alternating current I flowing through the inductor 902. Lis measured. The current measuring device 908 measures the direct current I output from the direct current bias power supply 901 dc is measured. The voltage measuring device 909 measures the alternating current voltage V across both ends of the inductor 902 L is measured. Then, based on these measured values, the effective value I e of the alternating current, the effective value V e of the alternating current voltage, and the phase difference θ between I L and V L are calculated.

[0006] The magnitude |Z| of the impedance of the inductor 902 is calculated by Equation (1).

Equation

[0007] The imaginary part of |Z| is the inductive reactance of the inductor 902. Therefore, the inductance L of the inductor 902 is calculated by Equation (2).

Equation

[0008] By changing the direct current I dc and calculating the inductance L, the DC superposition characteristic, which is the relationship between the direct current I dc and the inductance L, is calculated. FIG. 13 is an example of the DC superposition characteristic showing the relationship between the direct current I dc of the inductor and the inductance L.

Prior Art Documents

Patent Documents

[0009]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0010] However, in conventional DC superposition characteristic measurement methods, as described above, the DC current I dc Since it is necessary to calculate the inductance L while changing the value, the measurement takes time. The object of the present invention is to provide a method for measuring the DC superposition characteristics of an inductor, a system for measuring the DC superposition characteristics of an inductor, and a program that can measure the DC superposition characteristics in a short time. [Means for solving the problem]

[0011] One aspect of the present invention is a method for measuring the DC superposition characteristics of an inductor, comprising: a measurement step of measuring an inductor voltage, which is the voltage between two endpoints of an inductor, and an inductor current, which is the current flowing through the inductor, when a voltage is applied to the inductor from a single-phase PWM inverter, wherein the inductor current is a superimposed current obtained by superimposing a second current, which is a sine wave with a second frequency, onto a first current, which is a sawtooth wave with a first frequency; and a calculation step of calculating the DC superposition characteristics of the inductor based on the inductor voltage and the inductor current, wherein the calculation step comprises a pseudo-DC current calculation substep of calculating a pseudo-DC current based on the component of the inductor current at the second frequency in a section that is sufficiently shorter than the reciprocal of the second frequency; an inductance calculation substep of calculating the inductance corresponding to the pseudo-DC current based on the component of the inductor current at the first frequency in the section; and a DC superposition characteristic calculation substep of calculating the DC superposition characteristics based on the pseudo-DC current and the inductance. [Effects of the Invention]

[0012] According to the present invention, DC superposition characteristics can be measured in a short time. [Brief explanation of the drawing]

[0013] [Figure 1]This diagram shows the configuration of the DC superposition characteristic measurement system 100 according to this embodiment. [Figure 2] This figure shows an example of currents IL(t), I0(t), and Isw(t). [Figure 3] This figure shows an example of voltages VL(t), V0(t), and Vsw(t). [Figure 4] This figure shows the currents IL(t), I0(t), and Isw(t) over a narrower time window. [Figure 5] This figure shows the voltages VL(t), V0(t), and Vsw(t) over a narrower time window. [Figure 6] This figure shows the currents IL(t), I0(t), and Isw(t) over a narrower time window. [Figure 7] This flowchart shows the procedure for measuring the DC superposition characteristics of sample 3 in this embodiment. [Figure 8] This figure shows the currents IL(t), I0(t), and Isw(t) measured or calculated in the first experiment. [Figure 9] This figure shows the DC superposition characteristics of sample 3 calculated in the first experiment. [Figure 10] This figure shows the currents IL(t), I0(t), and Isw(t) measured or calculated in the second experiment. [Figure 11] This figure shows the DC superposition characteristics of sample 3 calculated in the second experiment. [Figure 12] An example of a conventional DC superposition characteristic measurement method is shown. [Figure 13] This is an example of a DC superposition characteristic showing the relationship between the DC current Idc and the inductance L of inductor 102. [Modes for carrying out the invention]

[0014] Embodiments of the present invention will be described in detail below with reference to the drawings. Figure 1 shows the configuration of the DC superposition characteristic measurement system 100 according to this embodiment. The DC superposition characteristic measurement system 100 comprises a single-phase PWM inverter 1, a DC power supply 2, a sample 3, a measuring device 4, a calculation device 5, a filter capacitor 6, and a load resistor 7. The sample 3 is an inductor. The DC superposition characteristic measurement system 100 measures the DC superposition characteristics of sample 3.

[0015] DC power supply 2 is connected to single-phase PWM inverter 1. DC power supply 2 has a DC voltage V dc The single-phase PWM inverter 1 is a single-phase inverter that performs pulse width modulation. The single-phase PWM inverter 1 receives the DC voltage V applied from the DC power supply 2. dc Converts to AC voltage V0. The single-phase PWM inverter 1 has an output frequency f0 and a carrier frequency f sw It performs unipolar modulation.

[0016] The single-phase PWM inverter 1 is connected to the sample 3. An AC voltage is applied to the sample 3 from the single-phase PWM inverter 1. The AC voltage applied to the sample 3 from the single-phase PWM inverter 1 is an AC voltage whose pulse width changes with time. When an AC voltage with a pulse width that changes with time is applied to the sample 3 from the single-phase PWM inverter 1, a current I is applied to the sample 3. L Current I flows. L The frequency is the carrier frequency f sw This is a current in which a sawtooth wave current is superimposed with a sinusoidal current whose frequency is output frequency f0. In this embodiment, the frequency is the carrier frequency f sw Therefore, it is sufficient for a current to flow through sample 3 in which a sawtooth wave current is superimposed with a sinusoidal current whose frequency is output frequency f0, and a single-phase PWM inverter 1 and a DC power supply 2 are not required. Furthermore, the single-phase PWM inverter 1 may operate in bipolar modulation mode instead of unipolar modulation mode.

[0017] The measuring device 4 measures the voltage V between the two endpoints of the sample 3. L and the current I flowing through sample 3 LThe device measures the voltage. The measuring device 4 includes, for example, a secondary winding 41, a differential voltage measuring instrument 42, a current measuring instrument 43, and an oscilloscope 44.

[0018] The secondary winding 41 is wound around the sample 3. The secondary winding 41 is magnetically coupled to the sample 3. The sample 3 and the secondary winding 41 mutually induce each other. The differential voltage measuring instrument 42 measures the voltage V between the two endpoints of the secondary winding 41. L2 Measure the voltage V. L is the voltage V L2 This is calculated using formula (3), which includes the number of turns N1 of the primary winding and the number of turns N2 of the secondary winding 41 of sample 3.

number

[0019] The differential voltage measuring instrument 42 measures the voltage V between the two endpoints of sample 3. L It may also be measured directly. However, in this case, the voltage drop due to the primary winding resistance must be taken into consideration.

[0020] Current measuring instrument 43 measures current I L The current measuring instrument 43 is, for example, a clamp-type current sensor, and measures the current I connected to the sample 3. L By sandwiching the path through which current I flows, L The current measuring instrument 43 is a through-type current sensor and measures the current I connected to the sample 3. L By making the path through which the current flows pass through the hole in the center of the sensor, the current I L You may measure it.

[0021] The oscilloscope 44 receives the voltage V from the differential voltage meter 42 and the current meter 43. L and current I L Obtain the measurement results.

[0022] The calculation unit 5 receives the voltage V from the measuring device 4. L and current I L The measurement results are obtained. The calculation unit 5 calculates the voltage V L and current I LBased on the measurement results, the DC superposition characteristics of sample 3 are calculated. Details of the method for calculating the DC superposition characteristics will be described later. The calculation unit 5 outputs the calculated DC superposition characteristics of sample 3. The calculation unit 5 displays the calculated DC superposition characteristics of sample 3 on a built-in display device, for example. The calculation unit 5 may also output the magnitude of the DC current flowing through sample 3 and its inductance. The calculation unit 5 may record the calculated DC superposition characteristics of sample 3 in its internal memory.

[0023] The filter capacitor 6 is connected in parallel to the load resistor 7, which is connected in series with the sample 3 to the single-phase PWM inverter 1. The capacitance C of the filter capacitor 6 is equal to the inductance L of the sample 3 and the carrier frequency f of the AC voltage applied by the single-phase PWM inverter 1. sw This is determined by the filter capacitor 6 and the sample 3 forming a low-pass filter. Therefore, the cutoff frequency of the low-pass filter is f c Therefore, the capacitance C of the filter capacitor 6 is expressed by equation (4).

number

[0024] Generally, the cutoff frequency f c is approximately f sw The equation is / n (where n is a value between 10 and 20). Therefore, the capacitance C of the filter capacitor 6 is expressed by equation (5).

number

[0025] The resistance R of the load resistor 7 is the maximum inductor current I, which is the maximum current that is desired to flow through sample 3. Lm This is expressed by equation (6) using the maximum AC voltage V0.

number

[0026] In equation (6), α is the modulation rate of the single-phase PWM inverter 1.

[0027] The following explains in detail how the DC superposition characteristics are calculated by the arithmetic unit 5. First, the voltage V L (t) and current I L A Fast Fourier Transform (FFT) is performed on (t) to calculate the components V0(t) and I0(t) of the output frequency f0. Also, the voltage V L (t) and current I L Perform an FFT on (t) and the carrier frequency f sw The above ingredients V sw (t) and I sw Calculate (t). Below, the voltage V0(t) is calculated as voltage V L This is called the low-frequency component of (t), and the voltage V sw (t) with voltage V L This is called the high-frequency component of (t), and the current I0(t) is called the current I L This is called the low-frequency component of (t), and current I sw (t) Current I L This is called the high-frequency component of (t). Figure 2 shows current I L (t), I0(t) and I sw This figure shows an example of (t). Figure 3 shows the voltage V L (t), V0(t) and V sw This figure shows an example of (t).

[0028] Figures 2 and 3 show f sw The current and voltage when =f0×20 are shown. Figure 4 shows the current I over a narrower time interval. L (t), I0(t) and I sw Figure (t) is shown. Figure 5 shows the voltage V over a narrower time interval. L (t), V0(t) and V sw This figure shows (t). Looking at the current I0(t) in Figure 4, the carrier period T sw (=1 / f sw In a section of the same length as ), the change in current I0(t) is I sw Compared to (t), it is small and can be considered as a DC current. Note that the output frequency f0 of the single-phase PWM inverter 1 is, for example, 50Hz or 60Hz, and the carrier frequency fsw The value is f0 × 200 or greater. Therefore, the carrier period T sw In a section of the same length, the current I0(t) can be considered as a DC current. Below, the carrier period T sw A section of the same length as "T sw It is called a "section".

[0029] f sw The larger the ratio of to f0, the larger the carrier period T. sw The current I0(t) in this case can be considered as a DC current. This DC current is called a "pseudo-DC current I pdc They call it that.

[0030] Pseudo DC current I pdc Let's explain how to calculate time τ. n from τ n+1 The nth T up to sw I0(t) and I in the interval sw (t) and V sw Based on (t), pseudo-DC current I pdc The inductance L can then be calculated. The nth pseudo-DC current I pdc This can be calculated using equation (7).

number

[0031] In other words, time τ n from τ n+1 The nth T up to sw Pseudo DC current I in the section pdc is time τ n from τ n+1 This is the average value of I0(t) in [location]. τ1 is arbitrarily determined. n (n=2,3,···,N,N+1) is defined by equation (8).

number

[0032] N is a positive integer. N can be arbitrarily determined.

[0033] The oscilloscope 44 captures at least the voltage V L (t) and the current I L (t) measured during at least one output period T0(=1 / f0), and the arithmetic unit 5 calculates V0(t), I0(t), V sw (t) and I sw (t) by means of FFT.

[0034] In the above-described embodiment, the length of the T sw interval is the same as the carrier period T sw , but may be sufficiently shorter than the output period T0. The extraction of the T sw interval may be appropriately determined by the measurer according to the relationship between I L (t) and I0(t), or the relationship between I L (t) and I sw (t). For example, as shown in FIG. 4, the time between adjacent intersections of I L (t) and I0(t) when I L (t) increases may be used as the T sw interval. Also, the time between adjacent intersections of I L (t) and I0(t) when I L (t) decreases may be used as the T sw interval. Further, as shown in FIG. 6, the time between adjacent points where I L (t) or I sw (t) changes from increasing to decreasing may be used as the T sw interval. Also, the time between adjacent points where I L (t) or I sw (t) changes from increasing to decreasing may be used as the T sw interval.

[0035] Also, when calculating the inductance L, FFT is performed on I n (t) and V n+1 in the n-th T sw interval from time τ sw to τ sw to obtain the components I sw and V sw0 (t) only at the carrier frequency f sw0Calculate (t). Furthermore, I sw0 (t) RMS value I sw0e , V sw0 (t) RMS value V sw0e and I sw0 (t) and V sw0 Calculate the phase difference θ with (t). Inductance L is I sw0e , V sw0e And it can be calculated using equation (9) based on θ.

number

[0036] Equation (9) shows that the impedance |Z| of sample 3 is V sw0e / I sw0e This is derived from the fact that the imaginary part of |Z| is the inductive reactance of sample 3. Thus, the nth T sw In the section, a pseudo-DC current I pdc The inductance L is then calculated.

[0037] time τ n τ1 in order τ N Change it to different T sw In the section, a pseudo DC current I is generated by the above method. pdc By calculating the inductance L, the pseudo DC current I pdc A combination of T and inductance L can be obtained. sw In the section, a pseudo-DC current I pdc By calculating the inductance L, we can obtain N pseudo-DC currents I pdc A combination of and inductance L can be obtained, and the DC superposition characteristics of sample 3 can be obtained. The T at which the current |I0(t)| is minimized is obtained. sw The interval and the maximum T sw A pseudo-DC current I is generated over a range of approximately 1 / 4 of the output period T0 (=1 / f0) that includes the interval. pdc If we can calculate the inductance L, then N is approximately f sw / 4f0 would be sufficient.

[0038] Figure 7 is a flowchart showing the procedure for measuring the DC superposition characteristics of sample 3 in this embodiment. A voltage is applied to sample 3 by the single-phase PWM inverter 1 (step S11). The voltage applied here is an AC voltage whose pulse width changes with time. When an AC voltage whose pulse width changes with time is applied to sample 3, sample 3 has a carrier frequency f sw A current flows in which a sawtooth wave current is superimposed with a sinusoidal current with output frequency f0. The measuring device 4 measures the voltage V between the two endpoints of the sample 3. L and the current I flowing through sample 3 L The arithmetic unit 5 measures the voltage V L and current I L By performing an FFT on this, the high-frequency component V sw (t) and I sw (t) is calculated, and the low-frequency components V0(t) and I0(t) are calculated (step S13).

[0039] The arithmetic unit 5 determines time τ1 and N (step S14). The arithmetic unit 5 also sets the variable n to 1 (step S15). The arithmetic unit 5 determines time τ n from τ n+1 The nth T up to sw Pseudo DC current I based on I0(t) in the interval pdc The calculation is performed (step S16). The calculation unit 5 calculates the time τ n from τ n+1 The nth T up to sw V in the interval sw (t) and I sw An FFT is performed on (t) (step S17). The arithmetic unit 5 calculates the carrier frequency f of the result of the FFT. sw Only ingredient I sw0 (t) and V sw0 (t) is calculated, I sw0 (t) RMS value I sw0e , V sw0 (t) RMS value V sw0e and I sw0 (t) and V sw0 Calculate the phase difference θ with (t) (Step S18).

[0040] The arithmetic unit 5 is I sw0e , V sw0e The inductance L is calculated based on θ (step S19). This calculates the time τ n from τ n+1 The nth T up to sw In the section, a pseudo-DC current I pdc The inductance L is then calculated. When the variable n is set to 1, the calculation unit 5 calculates the first T from time τ1 to τ2. sw Pseudo DC current I based on I0(t) in the interval pdc Calculate the first T from time τ1 to τ2 sw V in the interval sw (t) and I sw Perform an FFT on (t), and the carrier frequency f of the result of the FFT is obtained. sw Only ingredient I sw0 (t) and V sw0 (t) is calculated, I sw0 (t) RMS value I sw0e , V sw0 (t) RMS value V sw0e and I sw0 (t) and V sw0 Calculate the phase difference θ with (t), I sw0e , V sw0e And by calculating the inductance L based on θ, the first T from time τ1 to τ2 sw Pseudo DC current I in the section pdc Then calculate the inductance L.

[0041] Nth T sw Pseudo DC current I in the section pdc If the inductance L has not been calculated (step S20: NO), the calculation unit 5 increments the variable n by 1 (step S21) and performs the operation from step S16 with a different T sw I0(t) and I in the interval sw (t) and V sw Based on (t), pseudo-DC current I pdc Then calculate the inductance L for the Nth T. sw Pseudo DC current I in the section pdcIf the inductance L has been calculated (step S20: YES), the calculation unit 5 outputs the DC superposition characteristics which are the calculation results (step S22). In other words, the calculation unit 5 outputs the first T from time τ1 to τ2. sw Pseudo DC current I in the section pdc After calculating the inductance L, the second T from time τ2 to τ3 sw Pseudo DC current I in the section pdc The inductance L is calculated and this is used at time τ N from τ N+1 The Nth T up to sw Pseudo DC current I in the section pdc By repeating this process until the inductance L is calculated, N pseudo-DC currents I pdc The combination of the inductance L is calculated, and this combination is output as a DC superposition characteristic.

[0042] In the flowchart described above, the arithmetic unit 5 controls the pseudo DC current I pdc and the inductance L is the first T sw The Nth T from the interval sw The calculations were performed in ascending order up to the interval, but they could also be performed in descending order or any order. Furthermore, in the flowchart described above, the calculation unit 5 calculates the pseudo DC current I pdc After calculating in step S16, the inductance L is calculated in steps S17 to S19, but after calculating the inductance L, the pseudo DC current I pdc You may calculate this.

[0043] The above describes the method for calculating the DC superposition characteristics by the calculation unit 5. When the measuring device 4 measures in the DC superposition characteristics measurement system 100, the voltage V output from the single-phase PWM inverter 1 is... oThere is no need to change the parameters. As a result, the DC superposition characteristic measurement system 100 can measure the DC gravimetric characteristics of sample 3 in a shorter time. By measuring the DC superposition characteristics of sample 3 in a short time, the temperature rise due to iron loss in the core of the inductor (sample 3) and copper loss in the windings can be reduced, and the influence of fluctuations in inductance due to the temperature characteristics of the core's magnetic permeability can be reduced, enabling stable measurements.

[0044] Furthermore, in the DC superposition characteristic measurement system 100, the AC current flowing through the sample 3 is consumed by the load resistor 7. Therefore, a choke coil to prevent the AC current from flowing into the DC power supply 2 is unnecessary. Conventional DC superposition characteristic measurement methods require choke coils that have better frequency characteristics of DC superposition characteristics and permeability than the sample being measured, and that have sufficiently large inductance, thus requiring the preparation of very expensive choke coils. In the DC superposition characteristic measurement system 100 of this embodiment, a choke coil is unnecessary, so it can be implemented at a lower cost than conventional systems.

[0045] (First experiment) The first experiment performed is described below. In the first experiment, the core material of sample 3 was an Fe-based amorphous powder core manufactured by Toho Zinc, the number of turns N1 of the primary winding was 51, and the typical value of the inductance L was 500 μH. In the first experiment, the number of turns N2 of the secondary winding 41 was 51.

[0046] In the first experiment, the resistance R of the load resistor 7 was 15Ω, the capacitance C of the filter capacitor 6 was 20μF, and the DC voltage V dc The voltage is 380V, the modulation index α is 0.8, the output voltage V0 is 304V, the output frequency f0 is 50Hz, and the carrier frequency f sw The frequency was 25 kHz. At this time, the carrier frequency f sw This is 500 times the output frequency f0, and as mentioned above, T sw In this section, the low-frequency component I0(t) of the current can be considered as a DC current. Figure 8 shows the current I measured or calculated in the first experiment. L (t), I0(t) and Isw This is a figure of (t).

[0047] When the reference time τ1 is set to 0, the 118th T sw From the section, the 243rd T sw I0(t) and I in the 126 intervals up to the interval sw (t) and V sw Based on (t), 126 pseudo-DC currents I pdc The combination of and inductance L was calculated.

[0048] Figure 9 shows the DC superposition characteristics of sample 3 calculated in the first experiment. For comparison, Figure 9 also shows the DC superposition characteristics listed in the manufacturer's catalog for sample 3. In the first experiment, we were able to calculate DC superposition characteristics that were in close agreement with those listed in the manufacturer's catalog.

[0049] (Second experiment) The second experiment conducted is described below. In the second experiment, the core material of sample 3 was an FeNi-based powder core manufactured by Magnetics, the number of turns N1 of the primary winding was 29, and the typical value of the inductance L was 110 μH. In the second experiment, the number of turns N2 of the secondary winding 41 was 29.

[0050] In the second experiment, the resistance value R of the load resistor 7 was 15Ω, the capacitance C of the filter capacitor 6 was 20μF, and the DC voltage V dc The voltage is 320V, the modulation index α is 0.8, the output voltage V0 is 256V, the output frequency f0 is 50Hz, and the carrier frequency f sw The frequency was 50 kHz. At this time, the carrier frequency f sw This is 1000 times the output frequency f0, and as mentioned above, T sw In this section, the low-frequency component I0(t) of the current can be considered as a DC current. Figure 10 shows the current I measured or calculated in the second experiment. L (t), I0(t) and I sw This is a figure of (t).

[0051] When the reference time τ1 is set to 0, the 237th T sw From the section, the 488th T sw I0(t) and I in the 252 intervals up to the interval sw (t) and V sw Based on (t), 252 pseudo-DC currents I pdc The combination of and inductance L was calculated.

[0052] Figure 11 shows the DC superposition characteristics of sample 3 calculated in the second experiment. For comparison, Figure 11 also shows the DC superposition characteristics listed in the manufacturer's catalog for sample 3. In the second experiment, we were able to calculate DC superposition characteristics that were in close agreement with those listed in the manufacturer's catalog.

[0053] <Other Embodiments> Although one embodiment of this invention has been described in detail above with reference to the drawings, the specific configuration is not limited to that described above, and various design changes can be made without departing from the spirit of this invention.

[0054] The arithmetic unit 5 in the above-described embodiment may be implemented in whole or in part by a computer. In that case, the program for implementing this function may be recorded on a computer-readable recording medium, and the program recorded on this recording medium may be loaded into the computer system and executed. The term "computer system" here includes the OS and peripheral hardware. The term "computer-readable recording medium" refers to portable media such as flexible disks, magneto-optical disks, ROMs, CD-ROMs, and recording devices such as hard disks built into the computer system. Furthermore, the term "computer-readable recording medium" may include those that dynamically hold programs for a short period of time, such as communication lines used when transmitting programs via networks such as the Internet or communication lines such as telephone lines, and those that hold programs for a certain period of time, such as volatile memory inside the computer system that acts as a server or client in that case. The program may be for implementing a part of the functions described above, or it may be a program that can implement the functions described above in combination with a program already recorded in the computer system, or it may be implemented using a programmable logic device such as an FPGA (Field Programmable Gate Array). [Explanation of symbols]

[0055] 100 DC superposition characteristic measurement system, 1 single-phase PWM inverter, 2 DC power supply, 3 sample, 4 measuring device, 41 secondary winding, 42 differential voltage meter, 43 current meter, 5 calculation unit, 6 filter capacitor, 7 load resistor, 901 DC bias power supply, 902 inductor, 903 choke coil, 904 LCR meter, 905 AC power supply, 906 coupling capacitor, 907 current measuring device, 908 current measuring device, 909 voltage measuring device

Claims

1. A measurement step for measuring the inductor voltage, which is the voltage between the two endpoints of an inductor, and the inductor current, which is the current flowing through the inductor, when a voltage is applied to the inductor from a single-phase PWM inverter, wherein the inductor current is a superimposed current in which a second current, which is a sine wave with a second frequency, is superimposed on a first current, which is a sawtooth wave with a first frequency, A calculation step of calculating the DC superposition characteristics of the inductor based on the inductor voltage and the inductor current, It has, The aforementioned calculation step is, A pseudo-DC current calculation substep that calculates a pseudo-DC current based on the component of the inductor current at the second frequency in a section whose length is sufficiently shorter than the reciprocal of the second frequency, An inductance calculation substep for calculating the inductance corresponding to the pseudo-DC current based on the components of the inductor current and the inductor voltage at the first frequency in the aforementioned section, A DC superposition characteristic calculation substep for calculating the DC superposition characteristic based on the pseudo-DC current and the inductance, Having, A method for measuring the DC superposition characteristics of an inductor.

2. In the inductance calculation substep, The components of the inductor current and the inductor voltage at the first frequency in the aforementioned section are Fourier transformed, and the inductance corresponding to the pseudo-DC current is calculated based on the current and voltage components at the first frequency of the Fourier transform result. A method for measuring the DC superposition characteristics of an inductor according to claim 1.

3. The interval is equal to the reciprocal of the first frequency. A method for measuring the DC superposition characteristics of an inductor according to claim 1 or 2.

4. The interval is the time between adjacent intersections of the inductor current and the second frequency component of the inductor current when the inductor current increases, or the time between adjacent intersections of the inductor current and the second frequency component of the inductor current when the inductor current decreases. A method for measuring the DC superposition characteristics of an inductor according to claim 1 or 2.

5. The first frequency is 200 times or more the second frequency. A method for measuring the DC superposition characteristics of an inductor according to claim 3.

6. In the calculation step, the start time of the interval is changed and the pseudo-DC current calculation substep and the inductance calculation substep are executed, and the DC superposition characteristics are calculated based on the pseudo-DC current and the inductance calculated for each interval with different start times. A method for measuring the DC superposition characteristics of an inductor according to claim 1 or 2.

7. In the pseudo-DC current calculation substep, the pseudo-DC current is calculated as the average value of the component of the inductor current at the second frequency in the given section. A method for measuring the DC superposition characteristics of an inductor according to claim 1 or 2.

8. In the inductance calculation substep, the inductance is calculated based on the effective values ​​and phase difference of the current and voltage at the first frequency of the Fourier transform result. A method for measuring the DC superposition characteristics of an inductor according to claim 2.

9. A measuring device for measuring the inductor voltage, which is the voltage between the two endpoints of an inductor, and the inductor current, which is the current flowing through the inductor, when a voltage is applied to the inductor from a single-phase PWM inverter, wherein the inductor current is a superimposed current in which a second current, which is a sine wave with a second frequency, is superimposed on a first current, which is a sawtooth wave with a first frequency, and the measuring device, A calculation device for calculating the DC superposition characteristics of the inductor based on the inductor voltage and the inductor current, Equipped with, The calculation device calculates a pseudo-DC current based on the component of the inductor current at the second frequency in a section that is sufficiently shorter than the reciprocal of the second frequency. Based on the components of the inductor current and the inductor voltage at the first frequency in the aforementioned section, the inductance corresponding to the pseudo-DC current is calculated. Based on the pseudo-DC current and the inductance, the DC superposition characteristics are calculated. A system for measuring the DC superposition characteristics of an inductor.

10. A program that causes a computer to calculate the DC superposition characteristics of an inductor based on the measurement results of the inductor voltage, which is the voltage between the two endpoints of the inductor, and the inductor current, which is the current flowing through the inductor, when a voltage is applied to the inductor from a single-phase PWM inverter, The inductor current is a superimposed current in which a second current, which is a sine wave with a second frequency, is superimposed on a first current, which is a sawtooth wave with a first frequency. Based on the component of the inductor current at the second frequency in a section whose length is sufficiently shorter than the reciprocal of the second frequency, a pseudo-DC current is calculated. Based on the components of the inductor current and the inductor voltage at the first frequency in the aforementioned section, the inductance corresponding to the pseudo-DC current is calculated. The DC superposition characteristics of the inductor are calculated by calculating the DC superposition characteristics based on the pseudo-DC current and the inductance. program.

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