JPH0622166B2 - AC magnetic field generator - Google Patents

Description

TECHNICAL FIELD The present invention relates to a device for generating an alternating magnetic field with high accuracy and high responsiveness.

[Prior Art] With advances in science and technology, for example, in nuclear fusion devices and the like, it is necessary to create a magnetic field with extremely high accuracy.
In addition, a highly accurate AC magnetic field is required in a human body image diagnostic apparatus that utilizes the nuclear magnetic resonance phenomenon.

FIG. 5 is a main circuit diagram showing a conventional example of creating an alternating magnetic field, in which thyristor rectifiers 2 and 3 are connected in anti-parallel with each other,
An AC power supply 1 is connected to the AC input sides of these thyristor rectifiers 2 and 3, and a coil 4 wound around an iron core is commonly connected to the DC output side thereof. With such a configuration,
When the thyristor rectifier 2 is operated and when the thyristor rectifier 3 is operated, the direction of the current flowing through the coil 4 is reversed, so that the polarity of the magnetic field generated by the coil 4 also changes. Therefore, an alternating magnetic field can be obtained by alternately operating these thyristor rectifiers 2 and 3.

That is, in the conventional circuit shown in FIG. 5, the AC power from the AC power supply 1 is converted into DC power by the thyristor rectifiers 2 and 3 connected in antiparallel, and the DC power is supplied to the coil 4. By controlling the phase of each thyristor that constitutes these thyristor rectifiers 2 and 3,
Since the switching period of the direction of the current flowing through the coil 4 and the magnitude of the flowing current can be arbitrarily controlled, the strength and frequency of the alternating magnetic field generated by the coil 4 can be set to desired values.

[Problems to be solved by the invention]

By the way, in the conventional circuit shown in FIG. 5 described above, when the inductance value of the coil 4 has a large value or when a pulsed current is passed through the coil 4, an extremely high speed AC magnetic field can be generated with high accuracy. Even if it is tried to generate it, it has a drawback that it is difficult to realize it.

Therefore, an object of the present invention is to generate a high-speed alternating magnetic field with high accuracy and stably.

[Means for solving problems]

In order to achieve the above-mentioned object, the AC magnetic field generator of the present invention comprises two sets of coils wound around the same iron core, a DC power supply for separately supplying a DC current to each coil, and a DC power supply from the DC power supply. Connecting and disconnecting means for connecting and disconnecting the DC current, the two sets of coils are respectively connected to the DC power supply so that the magnetic field generated by one coil and the magnetic field generated by the other coil have opposite polarities. It is connected, and the connecting / disconnecting means controls to supply a DC current intermittently and alternately to the coil.

[Action]

According to the present invention, two sets of coils are wound around a common iron core, and the polarity of the magnetic field generated by applying a direct current to one coil and the polarity of the magnetic field generated when a direct current is applied to the other coil. , The common iron cores are configured so that the polarities thereof are opposite to each other, and if the intermittent control of the direct current flowing through one coil and the intermittent control of the direct current flowing through the other coil are appropriately performed, Focusing on the point that an alternating magnetic field can be obtained by combining the two sets of coils with each other, the magnitude and the intermittent period of the direct current flowing through these coils separately, and the rise and rise of this direct current. By controlling the downward inclination, the desired AC magnetic field can be accurately generated,
And it is a stable one.

〔Example〕

FIG. 1 is a main circuit connection diagram showing an embodiment of the present invention. In FIG. 1, a first DC power supply 10 includes a transformer 11 that also serves as an insulation, a thyristor rectifier 12, and a DC filter 13 that is composed of a reactor and a capacitor and removes the ripple component of the DC output from the thyristor rectifier 12. , And a transistor switch 14 for intermittently controlling this DC power. The first coil 16 is configured by converting the AC power from the AC power source 8 into the intermittent DC power.
Supply to. The second DC power source 20 is also connected to the transformer 2 as well.
1, thyristor rectifier 22, DC filter 23 and transistor switch 24
The AC power from the converter is converted into intermittent DC power and supplied to the second coil 26.

The first coil 16 and the second coil 26 are wound on the common iron core 9 common to both, and in the case of FIG. 1, the winding direction of these first coils 16 and
If the winding direction of the second coil 26 is the same,
Since the current directions are opposite,
The magnetic fields generated by and have opposite polarities. Or first
The winding direction of the coil 16 is opposite to that of the second coil 26,
Of course, the polarity of the magnetic field generated by each coil 16 and 26 may be reversed by connecting a DC power source so that a DC current flows in the same direction in each coil 16 and 26. Is.

In the embodiment circuit shown in FIG. 1, the transistor switch 14 is turned on and the transistor switch 24 is turned on.
If it is operated so that the ON period and the ON period alternately appear, the common iron core 9, the first coil 16 and the second coil 2
An alternating magnetic field can be generated by an electromagnet composed of 6 and. Further, the frequency of the AC magnetic field can be changed by changing the cycle of turning on the transistor switches 14 and 24 alternately, and the strength of the AC magnetic field generated can be changed by phasing the thyristor rectifiers 12 and 22. In addition, the current is made to flow in a pulse or rectangular shape, and the strength of the magnetic field generated by the first coil 16 and the second coil 2
By changing the strength of the magnetic field generated by 6 and the strength of the magnetic field generated by the second coil 26, it is possible to obtain an asymmetric alternating magnetic field.

FIG. 2 is a circuit diagram showing another system of the DC power source used in the circuit of the embodiment shown in FIG. That is, the DC power supply 30 shown in FIG. 2 is composed of a transformer 31, a thyristor rectifier 32,
It is composed of a DC filter 33, a transistor switch 34, and a freewheel diode 35, and converts the AC power from the AC power supply 8 into DC power which is intermittent at a desired cycle.

FIG. 3 is a time chart showing the waveform of the magnetic field obtained by the embodiment circuit shown in FIG. 1. FIG. 3 (a) shows the magnetic field generated by the first coil 16, and FIG. Represents the magnetic field generated by the second coil 26, and FIG. 3 (c) represents the magnetic field synthesized by both coils.

FIG. 4 is a second time chart showing the waveform of the magnetic field obtained by the circuit of the embodiment shown in FIG.
Figure (a) shows the magnetic field generated by the first coil 16, Figure 4 (b) shows the magnetic field generated by the second coil 26, and Figure 4 (c) shows the magnetic field synthesized by these coils. What is shown is the same as in the case of the time chart shown in FIG. However, in the time chart shown in FIG. 4, the rising timing of the magnetic field generated by the first coil 16 and the falling timing of the magnetic field generated by the second coil 26 overlap, and similarly, the magnetic field generated by the first coil 16 is the same. Is controlled so that the trailing edge of the magnetic field and the trailing edge of the magnetic field generated by the second coil 26 overlap.

As a result, the rising and falling slopes of the magnetic field generated by the first coil 16 and the second coil 26 are both the third slope and the third slope.
Although it is the same as that shown in the time chart in the figure, the gradient of the changing portion of the alternating magnetic field obtained by combining by both coils can be made steeper than that shown in FIG. (See Figure 4 (c)).

〔The invention's effect〕

According to the present invention, two sets of coils wound on a common iron core are connected to a DC power source for passing separate DC currents, and a magnetic field having a polarity opposite to the magnetic field generated by one coil is applied to the other. Since a circuit that intermittently supplies a DC current to each coil is configured so that each coil generates, it is not necessary to reverse the direction of the current flowing through the coil unlike the conventional AC magnetic field generator. Since the current flowing through the coil can be controlled with high accuracy and at high speed, the alternating magnetic field can be stably generated with high accuracy and at high speed.

[Brief description of drawings]

FIG. 1 is a main circuit connection diagram showing an embodiment of the present invention, FIG. 2 is a circuit diagram showing another system of a DC power source used in the embodiment circuit shown in FIG. 1, and FIG. FIG. 4 is a time chart showing the waveform of the magnetic field obtained by the embodiment circuit shown in FIG. 4, and FIG. 4 is a second time chart showing the waveform of the magnetic field obtained by the embodiment circuit shown in FIG. FIG. 5 is a main circuit connection diagram showing a conventional example for creating an alternating magnetic field. 1,8 ... AC power supply, 2,3,12,13,32 ... thyristor rectifier, 4 ... coil, 9 ... common core, 10 ... first
DC power supply, 11, 21 ... Transformer, 13, 23, 33 ... DC filter, 14, 24, 34 ... Transistor switch, 16 ... First coil, 20 ... Second DC power supply, 26 ... Second 2 coils, 30
...... DC power supply, 35 …… Freewheel diode.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location G21B 1/00 E 9014-2G

Claims (1)

[Claims] 1. A pair of coils wound around the same iron core, a DC power source for separately supplying a DC current to each coil, and an interrupting means for interrupting a DC current from the DC power source, The two sets of coils are respectively connected to the DC power source so that the magnetic field generated by one coil and the magnetic field generated by the other coil have opposite polarities, and the disconnecting means is connected to the coil. An alternating-current magnetic field generator characterized by controlling to supply a direct current intermittently and alternately.