JP3033272B2 - High frequency magnetic property measurement system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a system for determining a relationship between a magnetic field and a magnetic flux density at a high frequency of a core made of a ferromagnetic material used for a magnetic switch or the like of a pulse shaping circuit.

[0002]

2. Description of the Related Art A magnetic switch is formed by winding a winding around a ferromagnetic core. An electric current is applied to the winding to generate a magnetic flux in the core. When this current is increased, the magnetic flux in the core is suddenly saturated at a certain current value, and the impedance of the winding decreases to near zero. As described above, the current flowing through the winding can be turned on or off depending on whether or not the core magnetic flux is saturated. Therefore, such a core can be used as a magnetic switch. A magnetic switch is used in a pulse shaping circuit or the like for compressing the rising edge of a pulse and the pulse width (for example, see Japanese Patent Application No. 2-68992).
. In order to manufacture this magnetic switch, it is necessary to know the high-frequency magnetic characteristics of the ferromagnetic core used in this switch.

FIG. 6 is a block diagram showing a configuration example of a conventional high-frequency magnetic characteristic measuring system. This system is wound around a DUT 2 composed of a high-frequency AC power source 1 and a ferromagnetic toroidal core, and is wound around a DUT 1 that is excited by the AC power source 1 and a DUT 2. And the secondary winding 4. In addition, this system has a secondary winding 4
A voltage sensor 5 that detects and outputs a voltage generated at
A current sensor 6 for detecting and outputting a current flowing through the secondary winding 3
Receiving the output signal 5S of the voltage sensor 5 and converting it to the magnetic flux density B of the DUT 2 to output an output signal 7B, and receiving the output signal 6S of the current sensor 6 to generate the magnetic field H of the DUT 2. An arithmetic unit 7 that converts and outputs an output signal 7H;
A display unit 8 is provided for receiving the output signals 7B and 7H of the arithmetic unit 7 and displaying the relationship between the magnetic field H and the magnetic flux density B.
The magnetic path length of the DUT 2 is d, the cross-sectional area is s, the number of turns of the primary winding 3 and the secondary winding 4 are n ₁ and n ₂ ,
Let f be the frequency of f, and if a voltage v ₂ is generated in the secondary winding 4 when the current i ₁ flows in the primary winding 3, the magnetic field H and the magnetic flux density B of the DUT 2 are Become. H = n ₁ · i ₁ / d (1) B = v ₂ /(4.44 f · s · n ₂ ) (2) Therefore, the voltage v ₂ and the current i ₁ are respectively detected by the voltage sensor 5. And the output signal 5 detected by the current sensor 6
When S and 6S are calculated by the calculation unit 7 using the equations (1) and (2), the magnetic field H and the magnetic flux density B are obtained. Since the AC power supply 1 outputs a sine wave, the magnetic field H and the magnetic flux density B vary with time, but repeat the same value in each cycle. The display unit 8 prints the values of the magnetic field H and the magnetic flux density B at each time point or at each phase angle, or displays a so-called BH curve on the recording paper if the arithmetic unit 7 includes a digitizer.

[0004]

However, the conventional system as described above has a problem that the required capacity of the AC power supply is extremely increased as the object to be measured becomes larger. In FIG. 6, since the capacity P of the AC power supply 1 is the product of the current i ₁ flowing through the primary winding 3 and the voltage v _{1 of the} primary winding 3, P = i ₁ · v ₁ (3) . i ₁ it can be expressed as _{(1) i 1 = H ·} d / n 1 ··· (4) from equation because the self-inductance L ₀ of the object to be measured 2 is a toroidal shape, L ₀ = 2 × 10 ^{- _{7 μ r · n 1 2 ·}} D · log e (Φ 2 / Φ 1) can be expressed as (5). Here, μ _r is the relative magnetic permeability, D is the thickness, and Φ ₂ / Φ ₁ is the ratio of the outer diameter to the inner diameter. v ₁
Can be expressed as: v ₁ = 2πf · L ₀ · i ₁ (6), and substituting equations (4), (5), and (6) into equation (3), P = 4πf × ^{_{10 -7 μ r · H 2 ·}} d 2 · D · log e (Φ 2 / Φ 1) ··· (7) , and the volume P, along with increases in proportion to the frequency f, of the object to be measured 2 It increases in proportion to the square of the magnetic path length d and the thickness D. For example, assuming that the size of the DUT 2 with μ _r = 1000 is Φ ₂ = 200 mm, Φ ₁ = 150 mm, D = 25 mm, and a magnetic field of H = 1000 (A / m) is to be formed, 7)
The equation is: P = 2.7 f (8) To obtain the BH characteristic at f = 1 MHz, the AC power supply 1 having a capacity of P = 2.7 MW is required.
Due to thermal limitations, a high-frequency AC power supply 1 having a capacity of about several kW is practical even if it has a large capacity. Therefore, in the system of FIG. It was possible to measure only those smaller by about one digit (the outer diameter Φ ₂ was about several tens of mm).

Therefore, to design a large core so far, first, a toroidal core having an outer diameter of several tens of millimeters is manufactured from the same material as the core and its BH characteristics are determined, and the material characteristics of the small toroidal core are determined. Were designed to be the same as those of the larger core. However, as the size of the core increases, the material manufacturing method also differs slightly,
There was no guarantee that the magnetic properties would be identical to those of the smaller core.

An object of the present invention is to provide a system capable of measuring high-frequency magnetic characteristics of a large object to be measured by applying a pulse voltage.

[0007]

According to the present invention, there is provided a system for determining a relationship between a magnetic field and a magnetic flux density at a high frequency of a device to be measured comprising a ferromagnetic core. An excitation winding that winds the measurement body, a pulse generation circuit that applies a pulse voltage that rises to the excitation winding for a predetermined time, a voltage sensor that detects and outputs a voltage applied to the excitation winding, A current sensor that detects and outputs a current flowing through the exciting winding; and receives an output signal of the voltage sensor, converts the output signal into a magnetic flux density of the device under test, and outputs the converted signal. The high-frequency magnetic characteristic measuring system, comprising: a calculation unit that converts the output into a magnetic field of the body and outputs the signal; and a display unit that receives the output signal of the calculation unit and displays a relationship between the magnetic field and the magnetic flux density. The generator circuit is composed of a DC power supply, a switch connected in parallel to the output terminal of the DC power supply via a resistor or an inductor, and a series circuit of a reactor, a series capacitor, and a shunt capacitor connected in parallel to the switch. And the exciting winding is connected in parallel to the shunt capacitor. Further, in addition to the above-described configuration, another current sensor that detects and outputs a current flowing in the series capacitor is provided, and the calculation unit also receives an output signal of the other current sensor and flows from the output signal to the shunt capacitor. It is assumed that the current component is subtracted and converted into a magnetic field of the measured object and output. Further, in addition to the above configuration, a reset winding that winds the DUT, a DC reset power supply that excites the reset winding, and a reset current sensor that detects and outputs a current flowing through the reset winding. Prepared,
It is assumed that the arithmetic unit also receives the output signal of the reset current sensor, converts the signal into a magnetic field of the measured object and outputs the magnetic field, and includes a temperature control device capable of controlling the temperature of the measured object.

[0008]

According to the structure of the present invention, the excitation winding is wound around the object to be measured, and the pulse generating circuit for applying a pulse voltage rising at a predetermined time to the excitation winding is provided. By making the rise time of the pulse voltage correspond to 高周波 wavelength of the high frequency, a high frequency magnetic field can be formed in the ferromagnetic core. Moreover, by changing the rise time of the pulse voltage, a high-frequency magnetic field having an arbitrary frequency can be formed on the measured object. Therefore, a voltage sensor that detects and outputs a voltage applied to the excitation winding of the device under test, a current sensor that detects and outputs a current flowing through the excitation winding, and an output signal of the voltage sensor and the current sensor A calculation unit for receiving and converting the magnetic flux density and the magnetic field of the measured object into a magnetic field and a magnetic field, respectively, and a display unit for receiving the output signal of the calculation unit and displaying a relationship between the magnetic field and the magnetic flux density. The high frequency magnetic characteristics of the measured object at the frequency of can be obtained.

In the above configuration, the pulse generating circuit includes a DC power supply, a switch connected in parallel to the output terminal of the DC power supply via a resistor or an inductor, and a reactor, a series capacitor, and a shunt connected in parallel to the switch. It consists of a series circuit of capacitors. Further, the excitation winding of the device under test is connected in parallel to the shunt capacitor. When the switch is closed after charging the DC voltage to the series capacitor, a pulse voltage is generated in the excitation winding of the DUT. This pulse voltage has a waveform that oscillates at a frequency that resonates with the inductance and capacitance of the series circuit. By changing the resonance frequency, the rise time of the pulse voltage changes, so that a high-frequency magnetic field of an arbitrary frequency can be formed on the measured object.

In addition to the above configuration, another current sensor for detecting and outputting a current flowing through the series capacitor is provided. The arithmetic unit also receives the output signal of the other current sensor, subtracts the current flowing through the shunt capacitor from this output signal, converts the current into the magnetic field of the measured object, and outputs the result. The current flowing through the exciting winding differs by an order of magnitude between when the magnetic flux in the measured object is not saturated and when it is saturated. By arranging another current sensor, it is possible to measure the current of the exciting winding with higher accuracy by sharing the current measurement in both the unsaturated state and the saturated state.

Further, in addition to the above configuration, a reset winding is wound around the DUT, and a DC reset power supply for DC exciting this reset winding is connected, so that a reverse bias is applied to the magnetic flux density of the DUT in advance. Can be added.
A reset current sensor that detects and outputs the current flowing through the reset winding is provided.The arithmetic unit also receives the output signal of the reset current sensor and converts it to the magnetic field of the device under test. The high frequency magnetic characteristics of the measured object can be obtained.

Further, by providing a temperature control device capable of controlling the temperature of the measured object, it is possible to obtain a change in the high-frequency magnetic characteristics of the measured object with temperature.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on embodiments.
FIG. 1 is a block diagram showing a configuration of a high-frequency magnetic characteristic measuring system according to an embodiment of the present invention. The pulse generating circuit 31 includes a DC power supply 9, a switch 11 connected in parallel to the DC power supply 9 via a resistor 10,
And a series circuit 12 formed of a reactor 13 (self-inductance L), a series capacitor 14 (capacitance C ₁ ), and a shunt capacitor 15 (capacitance C ₂ ). The measured object 16 is formed of a ferromagnetic toroidal core, and is housed in a temperature control device 30 formed of a thermostat. An excitation winding 17 is wound around the measured object 16.
7 is connected in parallel with the shunt capacitor 15. Further, the current I ₁ flowing through the exciting winding 17 is detected and the output signal 2
A current sensor 20 that outputs 0S is attached to a connection line with the exciting winding 17 and a voltage sensor 21 that detects a voltage V applied to the exciting winding 17 and outputs an output signal 21S is Connected between terminals. Arithmetic unit 22 receives output signals 20S and 21S and converts them into magnetic field H and magnetic flux density B of device under test 16, respectively, and outputs output signals 22H and 22B, and display unit 23 receives output signals 22H and 22B and generates magnetic field H And the relationship between the magnetic flux density B and the magnetic flux density B are displayed. In FIG. 1, when the switch 11 is open, the DC power supply 9 charges the series capacitor 14 via the resistor 10 and the reactor 13, and when the switch 11 is closed in this state, the series circuit 12 pulsates at the resonance frequency f in the series circuit 12. Since a high-frequency oscillation waveform is generated between the terminals of the shunt capacitor 15, a pulse voltage that rises in a predetermined time is applied to the excitation winding 17 of the DUT 16 connected in parallel to the shunt capacitor 15. Assuming that the magnetic path length of the DUT 16 is d, the cross-sectional area is s, and the number of turns of the excitation winding 17 is N, the magnetic field H and the magnetic flux density B of the DUT 16 are as follows. _{H = N · I 1 / d} ··· (9) B = ΔB-B r ··· (10) where, .DELTA.B is

[0014]

(Equation 1)

## EQU1 ## _Br is the residual magnetic flux density of the DUT 16, and is the BH of the DUT 16 due to the DC voltage.
The characteristics are determined in advance. In FIG. 1, switch 1
Assuming that the time after the closing of 1 is t, ΔB is the change of the magnetic flux density B from t = 0. Since up to t = 0 the switch 11 is opened, the direct current for charging the series capacitor C ₁ flows through the excitation winding 17, the object to be measured 16 -
It is magnetized in B _r. t = 0 Thereafter, the magnetic flux density of the object to be measured 16 is a value ΔB is applied to -B _r. Therefore, the detected voltage V and current I ₁ to a voltage sensor 21 and current sensor 20, respectively, if as computed by the output signal 21S and 20S in the calculating portion 22 (9) to (11), a high frequency , The magnetic flux density B and the magnetic field H are obtained. In the integration in the equation (11), since the voltage V changes with time in a pulsed manner, ΔB or the magnetic flux density B can be obtained by sequentially calculating the integration from t = 0 to an arbitrary time t. For example, if the calculation unit 22 includes a digitizer, the display unit 23 may display the magnetic field H at each time point or each phase angle.
And the values of magnetic flux density B and ΔB are printed, or a so-called BH curve or ΔBH curve is displayed on the recording paper.

The temperature control device 30 shown in FIG.
The temperature dependency of the BH characteristic can be obtained. The resistor 10 in FIG. 1 suppresses the charging current of the DC power supply 9 and does not return the discharge current by the switch 11 of the series circuit 12 to the DC power supply 9 side. That's what we do. Therefore, an inductor may be used instead of the resistor 10. Also, in FIG.
2, the shunt capacitor 15 and the reactor 13
Both or one of them may not be interposed.
When neither the shunt capacitor 15 nor the reactor 13 is interposed, the series capacitor 14 and the exciting winding 17
By selecting the circuit constants so that the resonance condition is satisfied by the above, a pulse voltage that rises in a predetermined time can be generated. When the shunt capacitor 15 is not provided, the reactor 13 and the series capacitor 14
In the case where there is no 3, a pulse voltage that rises in a predetermined time can be generated by selecting circuit constants so that the resonance condition is satisfied by the exciting winding 17 and the series capacitor 14, respectively. Further, the interposed positions of the switch 11 and the series capacitor 14 in FIG. 1 may be interchanged. Even in this case, since the series capacitor 14 is DC-charged from the DC power supply 9, a pulse voltage is generated by closing the switch 11. However, in this case, the switch 11 needs to have a structure in which both poles are insulated from the ground.

FIG. 2 is a block diagram showing a configuration of a high-frequency magnetic characteristic measuring system according to another embodiment of the present invention. A current sensor 25 that detects a current I ₂ flowing through the reactor 13 and outputs an output signal 25 S is attached to a connection line with the reactor 13, and an arithmetic unit 32 receives the output signal 25 S and converts it into a magnetic field H of the DUT 16. Thus, the output signal 22H can also be output. The other configuration is the same as that of FIG. In FIG. 2, the current I ₂ is divided into a current I ₁ flowing through the exciting winding 17 and a current flowing through the shunt capacitor 15. Since the capacitance of the shunt capacitor 15 is _{C 2, I 2 = I 1} + C 2 · dV / dt ··· (12) becomes, substituting I ₁ of the (12) equation (9) into equation H = N (I ₂ −C ₂ · dV / dt) / d (13) The magnetic field H can be obtained if the calculation unit 32 performs the calculation according to the equation (13). The calculation of the magnetic flux density B is the same as that described in the embodiment of FIG.
The magnetic flux density B can be obtained by performing calculations using the expressions (0) and (11). The current flowing through the exciting winding 17 differs by an order of magnitude between when the magnetic flux in the measured object 16 is not saturated and when it is saturated. Therefore, by measuring the current at the time of saturation with the current sensor 20 and measuring the current at the time of non-saturation with the current sensor 25, the accuracy of the measurement under both current conditions can be improved.

FIG. 3 is a block diagram showing a configuration of a high-frequency magnetic characteristic measuring system according to still another embodiment of the present invention. A reset winding 18 is wound around the device 16 to be measured, and the reset winding 18 has a DC reset current I _R.
Is connected. Further, the reset winding 18 has a reset current sensor 2
4 is connected, and the calculating section 26
4 output signal 24S is also received. Other configurations are shown in FIG.
It is the same as that of The reset winding 18 is connected to the DUT 16
This is for adjusting the initial operating point of the magnetic characteristics.
The reset winding 18 can be DC-excited by the DC reset power supply 19 to apply a magnetic bias to the DUT 16 in advance. The calculation unit 26 in FIG.
Operation is performed according to the following equation instead of equation (9). H = (N · I ₁ −I _R ) / d (14) The magnetic flux density B is based on the equations (10) and (11).

An example in which the magnetic characteristics of a ferromagnetic toroidal core having an outer diameter of 200 mm are obtained by the circuit shown in FIG. Table 1 shows the shape of the measured object and the DC magnetic characteristics.

[0020]

[Table 1]

The circuit constants in FIG. 3 are as follows: C ₁ and C ₂ are 32.4 nF, L is 2.5 μH, and the series capacitor 14
The charge voltage 10 kV, the reset current I _R = 0 and I _R = -
80A. Figure 4 is a time chart of the detected V, I ₁ in the circuit of FIG. 3 for toroidal cores of Table 1. The horizontal axis represents time t (that is, switch 11 when t = 0).
Is closed), the vertical axis shows the voltage and current, and the solid characteristic curves 27A and 28A are I _R = 0 and the dotted characteristic curve 2
7B and 28B are the cases where I _R = −80 A.

FIG. 5 shows that the arithmetic unit 26 converts the waveform of FIG. 4 into a change ΔB of the magnetic field H and the magnetic flux density according to the equations (14) and (11) and displays it as a ΔB-H characteristic on the display unit 23. FIG. 6 is a characteristic diagram. The horizontal axis represents the magnetic field H, and the vertical axis represents the change Δ in the magnetic flux density.
Scale a B, solid characteristic curve 29A is I _R = 0, the dotted characteristic curve 29B is of the case of the I _R = -80A. At time t = 0, the characteristic curve 29A has the origin (H = 0, Δ
B = 0), and draws a curve in the direction of arrow A with time and returns to the origin. On the other hand, at time t = 0, the characteristic curve 29B is at H = −0.145 (kA / m) and ΔB = 0, and draws a curve in the direction of arrow B with time and returns to the original point. FIG.
, The starting position of the characteristic curve 29B is H = −0.145 (k
Was shifted to the A / m) is due to a pre DC excitation by the reset current I _R. Therefore, ΔB−H
The curve is also shifted to the left as a whole. The characteristic curve in FIG. 5 is a characteristic at a resonance frequency of 1 MHz as can be seen from FIG.
By changing the circuit constants in FIG. 3, higher frequency BH characteristics can be obtained. For example, C ₁
= C ₂ = 32 nF, when measuring the frequency f in the range of 50 kHz to 2.5 MHz, change L from 630 μH to 250 nH and resonate the circuit at that frequency. The reason why such high-frequency high-frequency magnetic characteristics of the DUT can be obtained is that a pulse-like means of discharging the electric charge charged in the capacitor in a short time is used. The problem of heat generation, which has been a problem, has been solved by the present invention.

[0023]

According to the present invention, as described above, a pulse voltage that rises for a predetermined time is applied to the excitation winding of the DUT,
The relationship between the magnetic field of the DUT and the magnetic flux density is determined from the current flowing through the exciting winding and the voltage applied to the exciting winding. As a result, it is possible to provide a system in which high-frequency magnetic characteristics can be obtained even with a large toroidal object having an outer diameter of several hundred mm and a thickness of several tens mm. Moreover,
Since a pulse-like means that power is supplied only for a short time is used, there is an advantage that the voltage of the equipment can be easily increased and no heat is generated.

Further, as a pulse generation circuit, a series circuit composed of a reactor and a capacitor is connected in parallel to a switch. This provides an advantage that the resonance frequency can be easily changed by selecting the inductance of the reactor or the capacitance of the capacitor. Further, since the measurement system has substantially the same circuit configuration as the pulse compression circuit formed by the capacitor and the magnetic switch, it is also effective for measuring the magnetic characteristics of the magnetic switch in a practical state.

Further, by using a system that detects the current flowing through the exciting winding and also detects the current flowing through the series capacitor to determine the magnetic field, it is possible to accurately determine the magnetic characteristics in both the saturated and unsaturated ranges. Can be.

Further, a reset winding is wound around the object to be measured, and the reset winding is DC-excited, whereby
A reverse bias can be applied in advance to the magnetic density of the device under test, and the magnetic characteristics of the device under test that is practically used in a biased state such as a pulse shaping circuit can be directly measured.

Further, by providing a temperature control device capable of controlling the temperature of the object to be measured, it is possible to obtain a change in the magnetic characteristics of the object to be measured with temperature.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a high-frequency magnetic characteristic measuring system according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a high-frequency magnetic characteristic measuring system according to another embodiment of the present invention.

FIG. 3 is a block diagram showing a configuration of a high-frequency magnetic characteristic measuring system according to still another embodiment of the present invention.

FIG. 4 is a time chart of V and I ₁ detected by the circuit of FIG.

FIG. 5 is a characteristic diagram showing the waveform of FIG. 4 as ΔB-H characteristics.

FIG. 6 is a block diagram showing a configuration example of a conventional high-frequency magnetic characteristic measurement system.

[Explanation of symbols]

 9 DC power supply 10 Resistance 11 Switch 12 Series circuit 13 Reactor 14 Series capacitor 15 Shunt capacitor 16 DUT 17 Excitation winding 18 Reset winding 19 DC reset power supply 20 Current sensor 25 Current sensor 21 Voltage sensor 22 Operation unit 26 Operation unit 32 Calculation part 23 Display part 30 Temperature control device 24 Reset current sensor 31 Pulse generation circuit

Claims (4)

(57) [Claims] 1. A system for obtaining a relationship between a magnetic field and a magnetic flux density at a high frequency of a device under test comprising a ferromagnetic core, comprising: an exciting winding for winding the device under test; A pulse generation circuit that applies a pulse voltage that rises with time, a voltage sensor that detects and outputs a voltage applied to the excitation winding, a current sensor that detects and outputs a current flowing through the excitation winding, An arithmetic unit that receives an output signal of the voltage sensor, converts the output signal into a magnetic flux density of the device under test, and receives the output signal of the current sensor and converts the signal into a magnetic field of the device under test; In a high-frequency magnetic characteristic measuring system including a display unit that receives a signal and displays a relationship between a magnetic field and a magnetic flux density, the pulse generation circuit includes a DC power supply, and a resistor or an input connected to an output terminal of the DC power supply. A switch connected in parallel via a rectifier, and a series circuit of a reactor, a series capacitor, and a shunt capacitor connected in parallel to the switch, wherein the exciting winding is connected in parallel to the shunt capacitor. A high frequency magnetic characteristic measurement system characterized by the following. 2. The device according to claim 1, further comprising another current sensor for detecting and outputting a current flowing through the series capacitor, wherein the arithmetic unit also receives an output signal of the other current sensor and outputs the current signal from the output signal. A high frequency magnetic characteristic measuring system, wherein a current component flowing through a shunt capacitor is subtracted and converted into a magnetic field of a measured object and output. 3. The reset winding according to claim 1, wherein a reset winding for winding the object to be measured, a DC reset power supply for exciting the reset winding, and a current flowing through the reset winding are detected. And a reset current sensor for outputting.
A high-frequency magnetic characteristic measurement system, wherein a calculation unit also receives the output signal of the reset current sensor, converts the output signal into a magnetic field of the measured object, and outputs the converted signal. 4. The method according to claim 1, 2, or 3,
A high-frequency magnetic characteristic measurement system comprising a temperature control device capable of controlling the temperature of a measured object.