JPS63223583A - Magnetic material tester - Google Patents

Abstract

PURPOSE:To simply obtain a very near B-H curve at the time of practical use by providing a voltage applying circuit for applying a voltage corresponding to the reset quantity of magnetization, to a coil in which a magnetic material to be tested is a magnetic core. CONSTITUTION:When a voltage of an oscillator 1 is in a positive half period, a diode 7 conducts, and a diode 9 becomes an obstructed state, therefore, to a coil 2, a voltage is applied through the diode 7 and a resistance 8, and a magnetic core 3 being a material to be tested is magnetized gradually, and saturated in the end. When said voltage becomes a negative half period, the diode 7, and the diode 9 become an obstructed state, and a conducting state, respectively, and to the coil 2, a voltage is applied through a variable DC voltage source 10 and the diode 9. This applied voltage becomes variable by changing an output voltage of the voltage source 10 in accordance with the reset quantity of magnetization of the coil. Also, the magnetic flux density B of the magnetic core 3 and the intensity H of the magnetic field are obtained by measuring a voltage and a current of the coil 2 by a voltage measuring circuit 4, and a current measuring circuit 5, respectively, and converting them by a signal processing part 6.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a tester for measuring the characteristics of magnetic materials, and particularly to a tester for measuring the characteristics of magnetic materials as a saturable magnetic core for a magnetic amplifier used in a switching power supply. It is related to.

[Conventional technology]

Before explaining the magnetic material tester according to the prior art, in order to make it easier to understand, we will take a saturable magnetic core as an example of a magnetic material and use it as a saturable magnetic core for a magnetic amplifier of a switching power supply as shown in Fig. 7. The operation when used in the reactor 18 will be explained.

As a magnetic amplifier-controlled switching power supply using such a saturable reactor, the one shown in IEICE technical research report PE84-37 is currently common.

First, the saturable reactor 1B used as a control element in this switching power supply will be described.

Ideally, the saturable reactor is one in which the magnetic material forming the magnetic core has a B-H curve with square characteristics as shown in FIG. In FIG. 9, B on the vertical axis represents the magnetic flux density, and H on the horizontal axis represents the strength of the magnetic field. Hereinafter, the same symbols mean the same in the text and figures, and the explanation thereof will be omitted. In addition, the broken line B-H curve (P-4t2→S→t3
→Q→R→P) is the result when a sinusoidal AC voltage is applied to this ideal saturable reactor, and the solid line B-H
The curve (p'→t2→S→t3→Q'-P') is a curve when this saturable reactor is used as a switching power supply. In the solid line B-H curve used for the switching power supply, the state of the magnetic core of the saturable reactor 18 is at point P.
Since the impedance is high between ' and point t2 and zero between point t2 and point S, it acts as a switching element that is blocked from point P' to point t2 and conductive from point t2 to point S. ing.

Next, the overall operation of the switching power supply circuit shown in FIG. 7 will be described below using FIGS. 8, 9, and 10.

In FIG. 7, it is assumed that the saturable reactor 18 has a magnetic core made of a magnetic material having the above-mentioned ideal characteristics.

A transistor 16 is connected between the secondary winding terminals of the transformer 17.
By driving the pulse generation circuit 15, the result shown in FIG. 8 (
A voltage Vi shown in a) is generated. In the figure, the vertical axis represents the voltage vi between the secondary winding terminals of the transformer 17, the horizontal axis represents the time t, TON is the conduction period of the transistor 16, and T is the voltage generated by the pulse generating circuit 15. It represents the period of the pulse. Next, considering the state of the magnetic core, the state of the magnetic core at time tl of the saturable reactor 1B is the 9th state.
Assuming that it is at point tl shown in the figure, the saturable reactor 1B up to point t2 representing the state of the magnetic core at time t2
is in a high impedance state, so no voltage is output to the subsequent stage. However, when the point t2 is reached, the magnetic core is saturated, the impedance of the saturable reactor 18 becomes almost zero, and current begins to be supplied to the load, and at point S, the load current is supplied. Next, when the transistor 16 in FIG. 7 enters the blocking state at time t3 when the state of the magnetic core is represented by point t3, the control circuit 20 passes the diode 19 to the saturable reactor 1.
8, a voltage in the opposite direction corresponding to the output voltage of the switching power supply is applied, and the magnetic core is reset to the state represented by point Q' in FIG. ~ From these facts, the voltage between the terminals of the saturable reactor 18 becomes as shown in FIG. In the figure, the vertical axis represents the voltage Vt between the terminals of the saturable reactor 18, and the horizontal axis represents the time t. toff represents a high impedance period (off period) of the saturable reactor 18, and ton represents a low impedance period (on period) t. Also, switching
When the output voltage of one source is vo, vo is expressed by the following equation.

However, ton = ON period L6ff of the saturable reactor 18: OFF period T□N of the saturable reactor 18:) Conduction period T of the transistor 16: period of the pulse generated by the pulse generating circuit 15 vis Secondary winding terminal of the transformer 1T Therefore, as can be seen from equation (1), the off period t of the saturable reactor 1B. The output voltage V of the switching power supply by controlling ff. can be controlled. In other words, the off period t of the saturable reactor 18. ff is determined by the amount of reset of the magnetic core by the control circuit 20 during the blocking period of the transistor 16, and is controlled by increasing the reset amount if you want to lower the output voltage v0, and by decreasing the reset amount if you want to increase the output voltage vo. be able to.

However, the actual magnetic core characteristics of the saturable reactor 18 in FIG. 7 do not have the ideal B-H curve as shown in FIG. 9, but have a B-H curve as shown in FIG. It becomes an H curve. As shown in the figure, B of the magnetic core in operation as a switching power supply is represented by a solid line.
The -H curve and the B-H curve of the magnetic core measured by applying a sinusoidal alternating voltage represented by a broken line are significantly different from those in FIG. Further, when the state of the magnetic core is between point t2 and point S, the impedance of the saturable reactor 18 does not become zero. This slope between point t2 and point S has a particularly large influence on the control characteristics of the switching power supply.

Normally, the magnetic core of the saturable reactor 18 is reset during the blocking period of the transistor 16. However, as shown in FIG. 10, in the actual magnetic core, when the load current becomes zero, that is, when moving from point S to point t3 in FIG. 10, the transistor 16 is in the conduction period TOH, but the magnetic flux density B is slightly reset, and a voltage corresponding to the increment ΔBd of the magnetic flux density B shown in the figure is applied to the saturable reactor 1.
Occurs at both ends of 8. At this time, the control circuit 20
This is not caused by the control voltage from the magnetic core, but is caused by the unique properties of the magnetic core. The increase in magnetic flux density B expressed by ΔBd is the difference between the saturation magnetic flux density and the residual magnetic flux density. Moreover, since the increment occurs when the saturable reactor 18 is in a high impedance state, the increment time is
This corresponds to the off period toff of the saturable reactor 18 during which no current is supplied to the load. This means (1)
As is clear from the equation, since the output voltage vo is controlled by changing the off period toff, the existence of ΔBd that is not caused by the reset from the control circuit 20 has a negative effect on the reset control amount. This means that the control range of the power supply is narrowed.

As can be seen from the above explanation, it is extremely important to use a magnetic core material used in a saturable reactor that has a small increment ΔBd of magnetic flux density, which is the difference between the saturation magnetic flux density and the residual magnetic flux density. For this purpose, it is necessary to accurately measure this increment ΔBd in magnetic flux density. Also, B
The area of the hysteresis loop in the -H curve is proportional to the loss in the magnetic core. Therefore, in order to accurately understand the loss of the saturable reactor, it is necessary to measure the B-H curve of the magnetic core under conditions that approximate the operating state.

Conventionally, the equipment used to evaluate this type of magnetic material is a -H characteristic tester as shown in Figure 3;
Alternatively, there is a CMC measurement circuit shown in FIG. 5 as shown in the Technical Research Report PE85-26 of the Institute of Electronics and Communication Engineers.

In the magnetic material tester shown in FIG. 3, a coil 2 is formed with the magnetic material 3 to be tested as a magnetic core, an oscillator 1 applies an alternating current voltage to the coil 2, and a voltage measurement circuit 4 measures the voltage between the terminals of the coil 2. , the current flowing through the coil 2 is measured by the current measuring circuit 5
Measure each.

From the obtained current value i, the magnetic field strength H can be calculated using the following formula (2
), and from the obtained voltage value V, the magnetic flux density B is calculated according to the following equation (3), and these calculations are performed in the signal processing section 6.

i H: □ ...(2) 1゜Where, N: Number of turns of coil 2 i: Current value flowing through coil 2 te: Average magnetic path length of coil 2 However, N: Number of turns of coil 2 V : Voltage value between terminals of coil 2 Ae: Effective cross-sectional area of coil 2 The B-H curve measured by the tester shown in FIG. 3 becomes K as shown in FIG. 4. As can be seen from FIG. 4, the characteristics of the B-H curve of the magnetic material under test 3 obtained by this measurement are as follows:
The characteristics of the B-H curve of the magnetic core of the saturable reactor 18 of an actual switching power supply shown by the solid line in FIG.

On the other hand, in the magnetic material tester shown in FIG. A DC magnetic field generated by passing a current is applied to this coil 2. The coil 14 is inserted to prevent alternating current from flowing through the control winding 13.

The magnetic core 3 is reset at a point at in FIG. 6 due to the DC magnetic field H generated by the control winding 13, which is calculated by the following equation (4).

NcIc, e#@II
(4) 1° However, Nc: Number of turns of the control winding 13 ■c: Control current te: Average magnetic path length of the coil If a half-wave voltage is applied to the coil 2 in this state, the magnetic core 3 will become as shown in Fig. 6. It exhibits a B-H curve that saturates on one side as shown, and exhibits characteristics close to those during operation of an actual switching power supply as shown by the solid line in FIG.

[Problem that the invention seeks to solve]

However, in an actual switching power supply, the DC magnetic field generated by DC current is not applied to the magnetic core 3 to control it as in the circuit shown in Figure 5, but is applied between the terminals of the coil 2 whose core is the magnetic material under test. Since it is controlled by changing the reset voltage, it is not an accurate evaluation, unlike actual operation. Further, the coil 14 on the control winding 13 side needs to have a sufficiently large impedance in order to reduce the alternating current to a negligible level, and therefore has the disadvantage of being large in size.

[Means for solving problems]

In order to solve the above-mentioned problems, the magnetic material tester according to the present invention has an oscillator that supplies voltage and current to a coil whose core is the magnetic material to be tested. A voltage application circuit is provided between the oscillator and the coil to apply a voltage corresponding to the voltage to the coil.

[Effect]

The magnetic material to be tested is magnetized and saturated by the coil during the positive half cycle of the oscillator, and is reset during the negative half cycle by applying a voltage to the coil according to the amount of magnetization reset.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a circuit diagram showing an embodiment of a magnetic material tester according to the present invention.

The magnetic material tester shown in the figure includes a voltage measurement circuit 4 that measures the voltage between the terminals of a coil 2 having the magnetic material 3 to be tested as a magnetic core, a current measurement circuit 5 that measures the current flowing through the coil 2, a signal processing unit 6 that converts voltage values and current values obtained from those circuits into magnetic flux density B and magnetic field strength H;
an oscillator 1 that supplies voltage and current to the coil 2;
It consists of a voltage application circuit connected in series to this oscillator 1. This voltage application circuit also includes a series circuit of a first diode 7 and a resistor 8 that conduct during the positive half cycle of the oscillator 1, and an output voltage connected to the polarity such that the voltage generated during the negative half cycle of the oscillator 1 decreases. It is constituted by a parallel connection of a DC voltage source 10 whose voltage is variable and a series circuit of a second diode 9 that conducts during the negative half period of the oscillator 1.

The operation will be explained below. During the positive half cycle of the voltage of the oscillator 1, the first diode T is conductive and the second diode 9 is in the blocking state, so that the coil 2 has the first
A voltage is applied through the diode 7 and the resistor 8, and the magnetic core 3, which is the magnetic material to be tested, is gradually magnetized and finally saturated. In the negative half cycle, the first diode 7 is in a blocking state, the second diode 9 is in a conducting state, and a voltage is applied to the coil 2 through the variable DC voltage source 10 and the second diode 9. . This applied voltage can be made variable by changing the output voltage of the variable DC voltage source 10.

The magnetic flux density B of the magnetic core 3 and the strength H of the magnetic field are determined by measuring the voltage and current of the coil 2 by a voltage measuring circuit 4 and a current measuring circuit 5, respectively.
It is obtained by measuring the signal and converting it in the signal processing section 6.

The B-H curve of the magnetic core 3 thus obtained is shown in FIG. As shown by the solid line B-H curve in Figure 2, during the positive half cycle of the oscillator 1, the magnetic core 3 is magnetized and saturated from point t1 to point S, and during the negative half cycle, the magnetic core 3 is saturated. From a certain point S to a point T! will be reset to. When the output voltage of the variable DC voltage source 10 is increased, the voltage applied to the coil 2 during the negative half cycle is equal to the difference between the output voltage of the oscillator 1 and the output voltage of the variable DC voltage source 10. Therefore, it is naturally smaller. Therefore, the magnetic core 3 is reset at point t, 1
At that time, the B-H curve becomes as shown by the broken line in FIG.

In this way, resetting the magnetic core 3, which is the magnetic material under test, is as follows:
This is done by the voltage applied to the coil 2 with the magnetic core, and the amount of reset depends on the magnitude of this voltage, so the B-H curve obtained by this is very close to the actual usage situation. .

〔Effect of the invention〕

As explained above, the magnetic material tester according to the present invention can be applied to a conventional tester by providing a voltage application circuit that applies a voltage corresponding to the amount of magnetization reset to a coil whose core is the magnetic material to be tested. The test magnetic material can be reset by voltage in the same manner as in actual use, so that the B-H curve easily obtained by this tester is very close to that in actual use. Furthermore, since there is no need to increase the size of the coil 14 in order to eliminate the AC valve shown in the conventional example shown in FIG. 5, there is also the effect that the coil 14 does not become larger in size than the conventional example.

[Brief explanation of drawings]

Figure 1 is a circuit diagram showing an embodiment of the magnetic material tester according to the present invention, and Figure 2 is a magnetic material to be tested measured using the circuit of the embodiment of the magnetic material tester shown in Figure 1. B-
H curve, Figures 3 and 5 are circuit diagrams representing conventional magnetic material testers, and Figures 4 and 6 are B curves of magnetic materials to be tested by the magnetic material testers of Figures 3 and 5, respectively.
-H curve, FIG. 7 is a circuit diagram of a magnetic amplifier controlled switching power supply for explaining the magnetic material to be tested applied to the magnetic material tester according to the present invention, and FIG. The voltage waveform of the voltage between the terminals of the secondary winding of the transformer 17, (b) also the voltage waveform of the voltage between the terminals of the saturable reactor 18, and Figure 9 shows the magnetic material with ideal characteristics for use in switching power supplies. Figure 10 shows the B-H curve of a magnetic material actually used in switching power supplies. DESCRIPTION OF SYMBOLS 1.... Oscillator, 2... Coil whose magnetic core is the magnetic material to be tested 3, 3... Magnetic material to be tested, 4...
・Voltage measurement circuit, 5...Current measurement circuit, 6...
Signal processing unit, 7.9...Diode, 8...Resistor, 10...Fist/variable DC voltage source. Figure 1 Figure 2 Date Figure 3 Figure 4F Figure 5 Figure 6 Figure 7 Q Figure 8 t+tz t3

Claims (2)

[Claims] (1) A voltage measurement circuit that measures the voltage between the terminals of a coil whose magnetic core is the magnetic material under test, a current measurement circuit that measures the current flowing through the coil, and the voltage and current values obtained from these circuits. In a magnetic material tester consisting of a signal processing unit that converts density and magnetic field strength, and an oscillator that supplies voltage and current to the coil, a voltage is applied to the coil according to the amount of resetting the magnetization of the magnetic material under test. A magnetic material tester characterized in that a voltage application circuit for applying voltage is provided between the oscillator and the coil. (2) The voltage application circuit is constituted by a parallel connection of a series circuit of a first diode and a resistor, and a series circuit of a DC voltage source with variable output voltage and a second diode. The magnetic material tester described.