JPS5847692Y2 - eccentric magnetic core - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an eccentric magnetic core suitable for use in preventing magnetic saturation in a transformer or a choke coil through which an asymmetrical current flows.

In a transformer or choke coil in which an asymmetrical current flows, a magnetic field corresponding to the asymmetrical component current generated in the magnetic core is maintained by inserting a biased magnet magnetized in one direction in the direction of the magnetic flux passing through the magnetic core into the air gap of the magnetic core. Alternatively, a method is already known in which magnetic saturation is prevented by bridging the gap in the magnetic core with a biased magnet magnetized in the longitudinal direction.

However, they have the following drawbacks.

In other words, in the case where a biased magnet is inserted into the air gap (referred to as the first conventional example), when a current is passed through a coil wound around the magnetic core, most of the magnetic flux generated in the magnetic core by the current flows through the air gap of the magnetic core. It passes through the gap in the magnetic core because its magnetic resistance is small.

That is, it passes through a biased magnet inserted into the gap of the magnetic core.

This biased magnet is magnetized by a current flowing through a coil wound around the magnetic core so that magnetic flux is generated in the opposite direction to the direction of magnetic flux generated in the magnetic core, and is inserted into the gap of the magnetic core. It was designed to prevent magnetic saturation of the magnetic core by canceling out the magnetic flux within the magnetic core generated by the current flowing through the coil.

However, most of the magnetic flux generated by the current flowing through the coil wound around the magnetic core acts in the opposite direction to the magnetization direction of the biased magnet, causing the magnet to demagnetize or become magnetized in the opposite direction. There were some inconveniences, such as the fact that it could no longer function as an office.

In addition, in the case of a biased magnetic core (referred to as the second conventional example) in which a biased magnet that is magnetized in the longitudinal direction and has two magnetic poles is bridged to the side surface of the air gap, it is possible to obtain more advantages than the biased magnet. The magnetic flux generated is
It is the value obtained by subtracting the leakage flux from the product (Am-Bd) of the cross-sectional area Am of the biased magnet in the magnetization direction and the magnetic flux density Bd at the operating point of the biased magnet.

In this second conventional example, when trying to obtain a large amount of biased magnetic flux, the cross-sectional area of the biased magnet increases, resulting in a disadvantage that the overall size becomes large.

In order to eliminate this drawback, it has been proposed to bridge the gap in the magnetic core using a biased magnet as shown in FIG. 1 (referred to as the third conventional example).

In FIG. 1, 1 is a coil, 2 is a magnetic core, 3 is a gap provided in the same magnetic core, and 4 is a biased magnet provided to bridge the gap.

The biased magnet 4 has a magnetic pole N formed on a surface that is in contact with one side of the air gap end of the magnetic core, and a magnetic pole S formed on the surface opposite to the contact surface.
′, and a magnetic pole N′ is formed on the same surface as the S′ magnetic pole surface that is not in contact with the magnetic core, and a magnetic pole S is formed by contacting the other side of the air gap end of the magnetic core. It is magnetized by.

That is, the biased magnet 4 has a first magnet portion having magnetic poles N and S', and a magnetic pole S.

N'.

The eccentric magnet 4 is coupled to the magnetic core so that the surface on which the magnetic pole S of the first magnet part and the magnetic pole N of the second magnet part are formed bridges the air gap 3.

The magnetic poles S and N are located on opposite sides of the air gap 3.

In this way, the biased magnet 4 is attached to the magnetic core 2 so that the magnetization directions of the first magnet portion and the second magnet portion are opposite, but the magnetization directions thereof are perpendicular to the side surface of the magnetic core 2. Therefore, the path of the magnetic flux caused by the two magnet parts of the bias magnet 4 is as shown by the broken line in FIG. 1, and the magnetic core 2 can be biased.

On the other hand, most of the magnetic flux generated through the current in the coil 1 passes through the magnetic core 2 and its air gap 3, and only a small amount of leakage flux passes through the bias magnet 4.

This is because the magnetic permeability of the magnet is about 1.1 times, and the biased magnet 4 is placed on the side of the air gap 3 of the magnetic core 2.

Therefore, the reverse magnetic field acting on the biased magnet 4 is extremely small.

Therefore, in the third conventional example shown in FIG. 1, unlike the first conventional example in which a biased magnet is inserted into the air gap of the magnetic core, the biased magnet 4 is used to suppress the magnetic field generated by the coil. It does not become demagnetized or magnetized in the opposite direction due to the action.

In addition, a second magnet in which the side surfaces at both ends of the air gap of the magnetic core are bridged by a biased magnet magnetized in the longitudinal direction instead of magnetized in the width direction as in the third conventional example shown in FIG. In the conventional example, in order to increase the biased magnetic flux, it is necessary to increase the cross-sectional area Am of the biased magnet as described above, and therefore, the widthwise length (i.e., the thickness) of the biased magnet must be increased. In contrast, in the third conventional example, the first
In order to increase the cross-sectional area of the second magnet part, the length of the biased magnet 4 in the longitudinal direction can be increased, and the length and thickness of the biased magnet 4 can be left as they are, so the biased magnet is bulky. There is no.

In this way, the third conventional example (Fig. 1)
It has fewer drawbacks than the conventional example.

However, if the thickness of the biased magnet 4 is made thinner in order to reduce the size of the biased magnetic core, the magnetic pole distances N-8' and N' of the biased magnet 4 will be reduced.
Since the magnetic path length of -5 becomes shorter, the magnetic resistance inside the biased magnet 4 increases from the biased magnet through the air from the magnetic poles N' to S' of the biased magnet 4. Compared to the external magnetic resistance seen, the magnetic permeability μr of the magnet (ferrite magnet) is 1
．． Since the magnetic permeability μa of the first rank is approximately equal to the magnetic permeability μa of air, the magnetic resistance inside the magnet is so small that it cannot be ignored.

Therefore, the third conventional example has the following drawbacks.

1. The value obtained by dividing the magnetic resistance between the magnetic poles inside the magnet by the magnetic resistance between the magnetic poles outside the magnet is the permeance coefficient p of the magnet, and the magnetic flux density Bd at the operating point at that time is l3d = 8r p p + μr (However, Br is the residual magnetic flux density of the magnet.) Therefore, if the thickness of the biased magnet is made thinner in order to reduce the size of the biased magnetic core, the magnetic resistance inside the magnet will decrease and the permeance coefficient of the magnet will decrease. The magnetic flux density Bd at the operating point of the magnet is determined by the fact that the magnetic flux emitted from the magnet passes through the interior of the magnet, which has low magnetic resistance, and acts in the opposite direction to the magnetization direction of the magnet itself (demagnetizing field), causing a decrease in the operating point. .

2. Most of the magnetic flux Φ passing through the magnetic core 2 passes through the air outside the biasing magnet 4, and since the magnetic resistance of the air is large, the overall magnetic resistance of the magnetic core 2 and the biasing magnet 4 is large. I can't help but become.

3. Even though the biased magnetic flux acting on the magnetic core 2 is reduced, it may not be possible to obtain a sufficient biased magnetic flux.

4. Therefore, in order to obtain a sufficient biasing effect, the biasing magnet 4 must be made large.

5. The magnetic flux leaking to the outside acts on surrounding electrical components such as Lou coils, transformers, CRTs, etc., causing malfunctions and deterioration of accuracy of these components.

These drawbacks have narrowed the practical limits of the biased magnetic core.

Conventionally, as a means of improving the permeance coefficient of a biased magnetic core, there is a method in which a high permeability material is brought into contact with the surface of a biased magnet opposite to the surface that is in contact with the biased magnetic core. The magnet is a bar-shaped magnet whose lengthwise ends are simply magnetized with opposite polarities, or magnetized simply in the thickness direction (direction from the contact surface of the magnetic core and the magnet to the opposite surface). Therefore, in the former case, two magnetic circuits are formed by the magnetic flux emitted from the magnet, one of which is a first magnetic circuit that circulates between the high magnetic permeability material and the magnet,
The other is a second magnetic circuit that circulates between the magnet and the magnetic core, and since the first magnetic circuit is useless for the magnet to impart biased magnetic flux to the magnetic core, the magnetic flux of the first magnetic circuit is This has the disadvantage that the magnet must be made larger by a corresponding amount, and in the latter case, it is unavoidable that some of the magnetic flux passes through the air, so the effect of sufficiently increasing the permeance coefficient cannot be produced. Ta.

The present invention eliminates the drawbacks of the prior art and widens the practical range of biased magnetic cores.Hereinafter, one embodiment of the invention will be explained in detail with reference to FIG. The same reference numerals are given to parts having the same functions as in the figures, and detailed explanation thereof will be omitted.

As is clear from FIG. 2, in the present invention, the magnetic poles N' and S' of the polarized magnet 4 facing the air are made of a magnetic material with low magnetic resistance, such as a high magnetic permeability material such as a ferrite iron plate (low magnetic It is characterized in that it is short-circuited through the resistive material (resistance material) 5.

Now, the permeance of the magnetic path passing through the inside of the magnet in a direction that demagnetizes the magnet is Pm: The permeance of a magnetic path passing through the air in a direction that does not demagnetize the magnet is Pa; Magnetic poles N', S of the magnet ' is short-circuited with a high magnetic permeability material, and the external permeance seen from the magnet when this high magnetic permeability material is added is PC; Then, the permeance Pc is short-circuited in a magnetic path with low magnetic resistance, so the magnetic When compared with the permeance Pa when no body is added, Pa(PC) is obtained, and the permeance coefficient of these magnetic circuits is as follows.

On the other hand, since the magnetic flux density at the operating point is proportional to the permeance coefficient, the magnetic pole N' of the biased magnet 4 is
, S' are short-circuited with a high permeability material 5 to increase the permeance coefficient. 1. The operating point of the bias magnet increases, so a large bias magnetic flux can be obtained, and sufficient bias magnetization can be applied. be able to.

2. In some cases, a small biased magnet can serve the purpose, and therefore it can be made smaller than a conventional one using a high magnetic permeability material.

3. Since the magnetic poles are short-circuited, the magnetic flux leaking to the outside is reduced, reducing the negative impact on other electrical components.

4. Since the magnetic circuit through which the magnetic flux flowing through the biasing magnet 4 and the magnetic flux flowing through the high permeability material 5 passes is in series, both magnetic fluxes are useful for biasing, and therefore, compared to conventional magnets, the biasing magnet is Even if the cross-sectional area is small, sufficient polarizing magnetic flux can be obtained.

It has the following effects.

It goes without saying that the biased magnet 4 may be of a composite type, in which a plurality of magnetized magnets are connected, similar to the one in the embodiment of the present invention.

FIG. 3 is a diagram showing another embodiment of the present invention, in which a is a front view, b is a side view, and C is a bottom view. Reference numbers are given and detailed explanations thereof are omitted.

According to this embodiment, the magnetic flux leaking to the outside has almost no adverse effect on surrounding electrical components, and
When used on a magnetic floor, there is an advantage that the effect can be further increased.

As is clear from the above explanation, according to the present invention, a large biased magnetization can be obtained with a simple configuration, and the adverse effect on surrounding electrical components can also be reduced, making it efficient and practical. A wide range of eccentric magnetic cores can be provided.

[Brief explanation of drawings]

FIG. 1 is a front view of a conventional biased magnetic core, FIG. 2 is a front view for explaining one embodiment of the present invention, and FIG. 3 is a diagram for explaining another embodiment of the present invention. Here, a is a front view, b is a side view, and C is a bottom view. 1... Coil, 2... Magnetic core, 3...
...Air gap, 4...Polarized magnet, 5...
・High magnetic permeability material.

Claims (1)

[Claims for Utility Model Registration] A magnetic core 2 around which a coil 1 is wound and has an air gap 3; a first magnet portion magnetized in a first direction and having magnetic poles N and S';
The magnetic pole S is magnetized in a second direction opposite to the first direction.
, N', one of the magnetic poles N, S of each of the first and second magnetic portions faces the magnetic core 2, and the magnetic poles N and S thereof A biased magnet 4 is attached to the magnetic core 2 so that S' is located on the opposite side across the air gap 3, and the other magnetic pole S' of each of the first and second magnet parts is
, N' is provided with a high magnetic permeability material 5 attached to a biasing magnet 4 to bridge between N'.