JPH0785105B2 - Magnetic material tester - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a tester for measuring characteristics of a magnetic material, and more particularly to a tester for measuring characteristics of a magnetic material as a saturable magnetic core for a magnetic amplifier used in a switching power supply. It is about.

[Conventional technology]

Before explaining the magnetic material tester according to the prior art, in order to make it easy to understand, a saturable magnetic core is taken as an example of the magnetic material, and the saturable reactor for a magnetic amplifier of a switching power supply shown in FIG. The operation when used for is explained. As the magnetic amplifier control type switching power supply using such a saturable reactor, the one shown in Technical Report PE84-37 of the Institute of Electronics and Communication Engineers is currently the most common one.

First, the saturable reactor 18 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 BH curve with a square characteristic 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 magnetic field strength. In the following texts and figures, the same symbols are used and the description thereof is omitted. The broken line B-H curve (P → t ₂ → S → t ₃ → Q → R → P) is the case where a sinusoidal AC voltage is applied to this ideal saturable reactor. -H curve (P'-t ₂ → S →
t ₃ → Q′−P ′) is when this saturable reactor is used as a switching power supply. In the solid BH curve used for the switching power supply, the saturable reactor 18
It is 'since high impedance between points t ₂ from, between the point t ₂ of the point S impedance becomes zero, the point P' state of the magnetic core point P blocking state from at point t _2, the point t ₂ From the point S to act as a switching element which becomes conductive.

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

In FIG. 7, it is assumed that the saturable reactor 18 uses a magnetic material having the above-mentioned ideal characteristics as a magnetic core. By driving the transistor 16 with the pulse generating circuit 15, a voltage Vi shown in FIG. 8A is generated between the secondary winding terminals of the transformer 17. In the figure, the vertical axis is the transformer.
The voltage Vi between the secondary winding terminals of 17 and the horizontal axis represent time t. T _ON represents the conduction period of the transistor 16 and T represents the cycle of the pulse generated by the pulse generation circuit 15.
Next, considering the state of the magnetic core, the time of saturable reactor 18
When the magnetic core of state at t ₁ and lies in t ₁ shown in FIG. 9, is at time t ₂ to t ₂ the point representing the state of the magnetic core saturable reactor 18 is the voltage at the subsequent stage from a state of high impedance Is not output. However, when the point t ₂ is reached, the magnetic core is saturated, the impedance of the saturable reactor 18 becomes substantially zero, and the current starts to be supplied to the load, and the load current is supplied at the point S. Next, at time t ₃ when the state of the magnetic core is represented by the point t ₃ , when the transistor 16 of FIG. 7 enters the blocking state, the saturable reactor 18 is passed from the control circuit 20 through the diode 19 to the saturable reactor 18 according to the output voltage of the switching power supply. A reverse voltage is applied and the core is reset to the state represented by point Q'in FIG. As a result, the voltage across the saturable reactor 18 becomes as shown in FIG. 8 (b). In the figure, the vertical axis represents the voltage V _L between the terminals of the saturable reactor 18, and the horizontal axis represents the time t. t _off represents a high impedance period (off period) of the saturable reactor 18, and t _on represents a low impedance period (on period). Further, when the output voltage of the switching-source and V _o, V is expressed by _o the following equation.

However, t _on : ON period of saturable reactor 18 t _off : OFF period of saturable reactor 18 T _ON : Conduction period of transistor 16 T: Period of pulse generated by pulse generation circuit 15 V _i : Secondary winding of transformer 17 The output voltage V _o of the switching power supply can be controlled by controlling the off period t _off of the saturable reactor 18 as can be seen from the equation (1) according to the voltage between the line terminals. That is, the off period o _off of the saturable reactor 18 is determined by the reset amount of the magnetic core by the control circuit 20 in the blocking period of the transistor 16, and when the output voltage V _o is desired to be decreased, the reset amount is increased and the output voltage V _o is decreased. When it is desired to raise the value, it can be controlled by reducing the reset amount.

However, the characteristics of the actual magnetic core of the saturable reactor 18 in FIG. 7 are the ideal B− as shown in FIG.
Instead of the H curve, it becomes a BH curve having a shape as shown in FIG. As shown in the figure, BH of the magnetic core operating as the switching power supply shown by the solid line
The curve and the BH curve of the magnetic core measured by applying a sinusoidal AC voltage represented by a broken line are also very different from those in FIG.
Further, the impedance of the saturable reactor 18 does not become zero when the state of the magnetic core is between the point t ₂ and the point S. The inclination between the points t ₂ and S has a great influence on the control characteristics of the switching power supply.

Normally, the saturable reactor 18 during the blocking period of the transistor 16
The magnetic core of is reset. However, as shown in Fig. 10, the actual magnetic core is when the load current becomes zero, that is,
When directed from the point S to the state of point t ₃ in FIG. 10, but the transistor 16 is in the conduction period T _ON, the magnetic flux density B is slightly reset, the voltage commensurate with the incremental ΔBd of the magnetic flux density B shown in FIG. Occurs at both ends of the saturable reactor 18. The reset at this time is not caused by the control voltage from the control circuit 20, but is caused by the property peculiar to the magnetic core. The increment of the magnetic flux density B represented by ΔBd is the difference between the saturation magnetic flux density and the residual magnetic flux density. Further, the increment occurs in the state where the saturable reactor 18 has a high impedance, and thus the increment period corresponds to the off period t _off of the saturable reactor 18 in which the load is not supplied with current. As is clear from the equation (1), since the output voltage V _o is controlled by changing the off period t _off , the existence of ΔBd which does not depend on the reset from the control circuit 20 is reset. Adversely affects the controlled variable,
This means that the control range of the power supply is narrowed.

As can be seen from the above description, it is extremely important that the magnetic core material used for the saturable reactor has a small increment ΔBd of the magnetic flux density, which is the difference between the saturated magnetic flux density and the residual magnetic flux density. It is necessary to accurately measure the increment ΔBd of this magnetic flux density. Also, B-H
The area of the hysteresis leap of the curve is proportional to the loss of the magnetic core. Therefore, in order to accurately grasp the loss of the saturable reactor, it is necessary to measure the BH curve of the magnetic core under the condition that it is close to the operating state.

Conventionally, the BH characteristic tester as shown in FIG. 3 has been used as the one used for evaluating this kind of magnetic material.
Alternatively, there is a measuring circuit of CMC shown in Fig. 5 as shown in Technical Report PE85-26 of IEICE.

In the magnetic material tester of FIG. 3, a coil 2 having a magnetic material 3 to be tested as a magnetic core is formed, an AC voltage is applied to this coil 2 by an oscillator 1, and a voltage between terminals of the coil 2 is measured by a voltage measuring circuit 4. , The current flowing through the coil 2 is measured by the current measuring circuit 5
Measure each with. From the obtained current value i, the strength H of the magnetic field is calculated from the equation (2) shown below, and from the obtained voltage value v, the magnetic flux density B is calculated from the equation (3) shown below. Is performed by the signal processing unit 6. However, N: number of turns of coil 2 i: current value flowing in coil 2 le: 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 area of coil 2 The BH curve measured by the tester shown in FIG. 3 is as shown in FIG. become. As can be seen from FIG. 4, the characteristic of the BH curve of the magnetic material 3 under test by this measurement is as follows.
This is very different from the characteristic of the BH curve of the magnetic core of the saturable reactor 18 of the actual switching power supply shown by the solid line in FIG. 10, and therefore the above-mentioned ΔBd and loss of the magnetic core cannot be correctly evaluated.

On the other hand, in the magnetic material tester of FIG. 5, a half-wave voltage is applied from the oscillator 1 to the coil 2 having the magnetic material under test 3 as the magnetic core by using the diode 11 and the resistor 12, and the control winding is used.
A DC magnetic field generated by applying a DC current to 13 is applied to this coil 2. The coil 14 is inserted in the control winding 13 so as not to pass an alternating current. The magnetic core 3 is reset to the point c in FIG. 6 due to the DC magnetic field H by the control winding 13 calculated by the following equation (4).

However, Nc: the number of turns of the control winding 13 Ic: control current le: average magnetic path length of the coil When a half-wave voltage is applied to the coil 2 in this state, the magnetic core 3 is moved to one side as shown in FIG. It exhibits a saturated BH curve and shows characteristics close to those of the actual switching power supply operating as shown by the solid line in FIG.

[Problems to be solved by the invention]

However, in an actual switching power supply, a DC magnetic field by a DC current is not applied to the magnetic core 3 for control as in the circuit of FIG. 5, but a magnetic material under test is applied between the terminals of the coil 2 having the magnetic core. Since it is controlled by changing the reset voltage, accurate evaluation is not achieved unlike the actual operation. Also, the coil on the side of the control winding 13
14 needs to have a sufficiently large impedance in order to make the AC current small enough to be ignored, and therefore has a drawback that the shape becomes large.

[Means for solving problems]

In order to solve the above problems, the magnetic material tester according to the present invention provides an oscillator for supplying a voltage and a current to a coil having a magnetic material under test as a magnetic core according to a reset amount of magnetization of the magnetic material under test. A voltage application circuit for applying a different voltage to the coil is provided between the oscillator and the coil.

[Action]

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

〔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 measuring circuit 4 for measuring a voltage across terminals of a coil 2 having a magnetic material under test 3 as a magnetic core, and a current measuring circuit 5 for measuring a current flowing through the coil 2. A signal processing unit 6 for converting a voltage value and a current value obtained from those circuits into a magnetic flux density B and a magnetic field strength H;
An oscillator 1 for supplying voltage and current to the coil 2,
It is composed of a voltage application circuit connected in series to the oscillator 1. This voltage application circuit is also connected to a series circuit of a first diode 7 and a resistor 8 which conducts in the positive half cycle of the oscillator 1 and an output voltage which is connected to a polarity in which the voltage generated in the negative half cycle of the oscillator 1 decreases. Is connected in parallel with a variable DC voltage source 10 and a series circuit of a second diode 9 that conducts in the negative half cycle of the oscillator 1.

The operation will be described below. In the positive half cycle of the voltage of the oscillator 1, the first diode 7 conducts and the second diode 9 enters the blocking state.
A voltage is applied through the diode 7 and the resistance 8 of the magnetic core 3, and the magnetic core 3 as the magnetic material under test is gradually magnetized and finally saturated. In the negative half cycle, the first diode 7 is in the blocking state and the second diode 9 is in the 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 is variable DC voltage source 10
It becomes variable by changing the output voltage of. The magnetic flux density B and the magnetic field strength H of the magnetic core 3 are obtained by measuring the voltage and current of the coil 2 by the voltage measuring circuit 4 and the current measuring circuit 5, respectively, and converting them by the signal processing unit 6.

The BH curve of the magnetic core 3 thus obtained is shown in FIG. As shown by the solid BH curve in FIG. 2, in the positive half cycle of the oscillator 1, the magnetic core 3 is magnetized and saturated from the point t ₁ to the point S, and in the negative half cycle, the magnetic core 3 is saturated. It is reset from a certain point S to a point t ₁ . When the output voltage of the variable DC voltage source 10 is increased, the voltage applied to the coil 2 in the negative half cycle is the difference between the output voltage of the oscillator 1 and the output voltage of the variable DC voltage source 10. Therefore, it naturally becomes smaller. Therefore, reset the core 3 becomes to a point t ₁ ', B-H curve at that time is as shown in dashed line in Figure 2.

In this way, the reset of the magnetic core 3 which is the magnetic material under test is
This is performed by the voltage applied to the coil 2 having this as a magnetic core, and the reset amount depends on the magnitude of this voltage, so that the BH curve obtained by this is very close to the actual use situation.

〔The invention's effect〕

As described above, the magnetic material tester according to the present invention is configured such that the conventional tester is provided with a voltage applying circuit for applying a voltage according to the reset amount of magnetization to the coil having the magnetic material under test as a magnetic core. The reset of the test magnetic material can be carried out by voltage as in the actual use method, so that the BH curve easily obtained by this tester becomes very close to the actual use. Further, since it is not necessary to increase the size of the coil 14 for eliminating the AC component shown in the conventional example of FIG. 5, there is also an effect that the shape is not increased as compared with the conventional case.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of a magnetic material tester according to the present invention, and FIG. 2 is a magnetic material under test measured using the circuit of an embodiment of the magnetic material tester shown in FIG. B-
H curve, FIGS. 3 and 5 are circuit diagrams showing a conventional magnetic material tester, and FIGS. 4 and 6 are B of magnetic materials to be tested by the magnetic material testers of FIGS. 3 and 5, respectively.
-H curve, FIG. 7 is a circuit diagram of a magnetic amplifier control type switching power supply for explaining a magnetic material under test applied to a magnetic material tester according to the present invention, and FIG. 8 (a) is a circuit diagram of FIG. Voltage waveform of the voltage between the secondary winding terminals of the transformer 17,
(B) is also the voltage waveform of the voltage across the saturable reactor 18, Fig. 9 is a BH curve of a magnetic material with ideal characteristics for use in a switching power supply, and Fig. 10 is an actual switching power supply. 3 is a B-H curve of a magnetic material used for. 1 ... Oscillator, 2 ... Coil having magnetic material under test 3 as magnetic core, 3 ... Magnetic material under test, 4 ... Voltage measuring circuit, 5
...... Current measurement circuit, 6 …… Signal processing unit, 7,9 …… Diode, 8 …… Resistance, 10 …… Variable DC voltage source.

Claims (1)

[Claims] 1. A magnetic material under test in which a first winding wire and a second winding wire are wound, a first series body composed of a series body of a first diode and a resistor, and the first diode. The first winding via a parallel body in which a second diode having a reverse polarity and a second series body formed of a series body of voltage variable power sources having a polarity opposite to the polarity of the second diode are arranged in parallel. And a current measuring circuit for detecting a current flowing through the first winding, and a voltage detecting circuit for detecting a voltage generated in the second winding. And magnetic material tester.