DE1051963B - Controllable choke coil for low current purposes - Google Patents

Description

The invention relates to a controllable choke coil for low current purposes, consisting of a ferromagnetic core lying in series with a magnetic yoke, which has at least two windings is provided and has two parallel main branches, each divided into two parallel sub-branches are, with a changeable magnetic field generated in the magnet yoke causing a change in the coil inductance causes.

Such reactors are, for. B. Applicable in magnetic modulators, controllable oscillation circuits, trigger circuits, etc. The core is in these Cases provided with a closed yoke, and the changeable magnetic field is through a Generates current that flows through a coil coupled to the yoke. The coil of the magnetic core is with connected to an alternating current source, and causes the magnetic field generated by this alternating current magnetic fluxes in the core, which are influenced by the aforementioned magnetic field of the yoke.

Such choke coils are also used in magnetic sound devices and magnetometers. The core in these cases lies in a yoke provided with an air gap, and the influencing of the fluxes occurring in the core, which are created by a current flowing in the core coil by means of a magnetic field occurring above the air gap.

As is known, the dimensions of the core must be as small as possible, especially at high frequencies of the alternating current flowing in the core coil. This is mainly due to the fact that, before the core material can have a modulating effect, this material has to be driven to saturation, so that the hysteresis loop of the material has to be practically completely run through. Now the resulting losses, which come to the external pressure as heat development in the core material, are proportional to the product of the frequency with which the hysteresis loop is passed, the area of this hysteresis loop and the core volume. At a certain frequency, these losses therefore increase in proportion to the core volume, that is to say proportionally to the third power of a length dimension. The core surface, which can dissipate the heat developed, only increases with the square of the length dimension, so that with larger core dimensions this heat development quickly becomes unacceptably large. In addition, the useful power of the alternating current source naturally also increases to a considerable extent. The small core dimensions er-controllable choke coil desired at high frequencies (from e.g. 0.5 to 10 MHz) in connection with the foregoing
for low voltage purposes

Applicant:

NV Philips' Gloeilampenfabrieken,
Eindhoven (Netherlands)

Representative: Dipl.-Ing. K. Lengner, patent attorney,
Hamburg 1, Mönckebergstr. 7th

Claimed priority:
Netherlands 7 April 1955

Simon Duinker, Eindhoven (Netherlands),
has been named as the inventor

However, it is very difficult to manufacture the core and the winding.

If the area of the hysteresis loop under the action of the alternating current could be significantly reduced, it follows from the above that it is on the one hand possible to enlarge the core dimensions at constant frequency, on the other hand at constant dimensions to increase the frequency. Both options have clear advantages.

According to the invention, the hysteresis losses of the core are substantially suppressed in that the Windings are wound in phase opposition to each other on the main branches of the core and that means are provided are the DC magnetic fluxes of the same magnitude in the two sub-branches of each main branch, but in the opposite direction, which put each branch into almost magnetic saturation.

There are already inductors of the type mentioned above are known in which the inductance of the Partial branches of the magnetic core seated windings from a magnetic constant field generated in the yoke being affected. In the case of the choke coil after the

4-5 Invention sits through a changeable magnetic field On the other hand, the coil to be regulated is on the main branches of the core. The ones on the sub-branches Windings serve to change the effective hysteresis loop of the main branches and thus to

This reduces the hysteresis losses.

It is known that the hysteresis losses of a magnetic core due to direct current bias to reduce. In the present case, however, this is done in a special way in the manner of a double

809 768/236

3 4

Push-pull circuit, so that neither a nor an S in the yoke can drive out. This means, however, that direct current bias is still one of one in that - except when the controlling alternating magnetic field flowing in the yoke 4 of the windings of the choke coil is very large - can occur during any current-originating magnetization. Period of the alternating current mentioned is a large part. This is particularly important for playback heads of 5 of the hysteresis magnetic sound recorders that actually always occur. With the known loop arrangements and with smaller values of the controlling flux, the magnetic flux always goes over the magnetic field even almost the entire hysteresis blending yoke and is thus influenced by the loop being passed on these yokes,
possibly additionally arranged coils. According to the invention, however, the main branches are 2

The sum of the cross-sections each and 3 is preferably divided into two sub-branches, which are

of the partial branch pair smaller than the cross section of the current flows through, namely in the

corresponding main branch. Way that each sub-branch is saturation

According to a further development of the invention, permanent magnets are attached and at the same time this direct current area of the two sub-branches of the ferromagnetic fluxes in the non-branched parts of the main core, which equalize in the sub-branches 2 and 3. The branches through the coil 13 generate direct current magnetic fluxes, the flowing direct current provides z. B. compensate for the sub-branch 9 in the main branches and bring each sub-branch of the main branch 2 formed core part to the almost saturation. Point Q of the hysteresis loop (see Fig. Z). Of the

The invention is based on the direct current flowing through the coil 14 in the drawing represents the

illustrated drawings explained in more detail. 20 formed by the sub-branch 10 of the main branch 2

1, 4, 5, 6 and 7 show embodiments of the core part at point P of the hysteresis loop

a controllable choke coil according to the invention (see also Fig. 2). The direct current flows in the

and sub-branches 9 and 10 thus have opposite directions

Fig. 2 and 3 characteristic curves to clarify the direction. Since the two rivers are also the same

Principle of the invention, 25 are chosen large, there is no DC flow com-

1 shows an exemplary embodiment of a control component in the non-branched part of the main branch 2.

baren choke coil according to the invention shown, the effective hysteresis loop of the main branch 2,

e.g. as an individual part of a magnetic amplifier such as that used for the one in windings 5 and 6

can be used. With 1 is the ferromagnetic flowing alternating current and generated in the yoke 4

The core, which occurs from a preferably electrical magnetic field, is represented by the

Trisch poorly conductive material consists; 2 and 3 shown characteristic curve.

are the main branches of the kernel, which when influenced- The occurrence of such a characteristic becomes clear-

solution by the aforementioned magnetic field is effective if one considers that for the aforementioned

are sam. The coil is driven by the series of magnetic fields in branch 9 that correspond to point Q

Windings 5, 6, 7 and 8 are formed. 35 speaking field strength H _q the new zero point of the

On the closed yoke 4, which also represents the H- axis for this branch and consists in part of ferromagnetic material, a branch 10, the field strength coil 17 corresponding to the point P is wound. A H ₁ flowing through this coil , the new zero point of the JT axis for this partial current, generates a magnetic field which represents the magnetic branch. The magnetic induction B affects the fluxes that occur in the core 1 under the influence of 40 whole main branch 2 simply by summing the terminals DE of the windings 5, 6, 7 and 8 of the alternating current supplied to the branches 9 and 10. The main ones are inductions, whereby the transfer to branches 2 and 3 is taken into account in two sub-branches 9, 10 or new iT axes.
11, 12 split. By means of a similar way to the terminals A , the effective hysteresis and F of two pairs of coils 13, 14 45 lying in series have a reset loop for the main branch 3, the direct current supplied in FIG .

sen sub-branches generated direct current flows, in which also in Fig. 3 by a dashed line the way that the direct current flow in sub-branch 9 of the relationship between B and H is indicated, again the same size, but from the opposite direction, the hysteresis losses are disregarded, to the direct current flow in branch 10, and the 50. In this case, the non-linearity of the normal direct current flow in branch 11 of the same magnitude, can be expressed when the magnetic current flow generated by means of the current flowing through the coil from the opposite direction to the direct current in part 12 is. The size of this constant field the main branches 2 and 3 over one of the points Ii current flows is such that each sub-branch modulates into the Sät- or K out,
care is brought. 55 It should be noted at this point that, depending on the

In Fig. 2, the hysteresis loop of the material of points P and Q of Fig. 2 is at a shorter distance from

Core 1 shown. It is assumed that the points R and JT are selected (by the

Main branches 2 and 3 of the core 1 are not divided. Direct current through the windings 13, 14 or 15, 16

The controllability of a choke coil is based on being selected to be smaller), including points M and K

Non-linearity between the magnetic inductor 60 come closer to each other, so that the field

tion B and the magnetic field strength H. In Fig. 2 strengths that are required to put the core in its

is to bring the connection nonlinear part by a dashed line, also be smaller

shown between B and H for core 1 if can.

the hysteresis losses left out of consideration. It is immediately evident from FIG. 3 that

will. From this connection it follows that 65 the hysteresis losses in the controllable throttle

the mentioned non-linearity but considerably reduced in the presupposed coil according to the invention

Traps are only then expressed in a useful way; for for most of the period

comes when that by means of the winding of the alternating current through the windings 5, 6, 7 and

The magnetic field generated by the flowing current is the core 8, the sub-branches 9, 10, 11 and 12 are located in the

material down to saturation, i.e. above the points Ji 70 saturation, where these losses are particularly low and

Claims (1)

are theoretically even zero. Only at particularly high values of the controlling magnetic field, at which the main branches 2 and 3 are controlled far outside one of the points M or K, do the losses increase again significantly. The fact that only small controlling magnetic fields are generally available renders this disadvantage insignificant. The magnetic resistance of the non-branched parts of the main branches 2 and 3 is preferably selected to be small compared to that of the sub-branches 9, 10 and 11, 12, so that significant losses still occur in these non-branched parts. According to a further characteristic of the invention, the sum of the cross-sections of each partial branch pair is therefore smaller than the cross-section of the corresponding non-branched main branch. In Fig. 4 an embodiment of a controllable choke coil according to the invention is shown, which z. B. can be used to read a fixed on a suitable carrier made of ferromagnetic material information. With 1 the magnetic core is again referred to, which is preferably made of electrically poorly conductive material, 2 and 3 are the main branches of the core 1, which are effectively effective when the inductance is influenced by the magnetic field mentioned. Here, too, the coil is again formed by the series of windings 5, 6, 7 and 8. The yoke 21 is provided with an air gap 22. The principle of such a magnetic sound reading head designed as a controllable choke coil is known per se. The alternating current flowing in the windings 5, 6, 7 and 8 generates magnetic fluxes in the main branches 2 and 3, which are modulated by the magnetic fields occurring at the air gap 22. These modulated magnetic fluxes or their components are converted into an alternating voltage by means of a winding 23 attached to the yoke 21, which after rectification supplies a current or a voltage which is proportional to the scanned magnetic field. Such a device offers the advantage over a normal magnetic sound device scanning head that the current or voltage, which is a measure of the scanned magnetic fields, is practically independent of frequency and that, in connection therewith, very low frequencies and constant fields can be scanned and reproduced without hesitation can. In addition, an amplifier stage can be saved in most cases. Not only do the small core dimensions desired at high frequencies make the production of the core and the winding very difficult, but the very small dimensions have the additional disadvantage that the magnetic resistance of the main branches 2 and 3 is so great that a large part of the over the air gap 22 occurring magnetic fields occurs as a dissipation field over this gap, so that only a small part has a modulating effect. Here, too, the invention creates the possibility of increasing the core dimensions at a constant frequency of the alternating current flowing through the windings 5, 6, 7 and 8 or, with constant core dimensions, to increase the frequency of the alternating current mentioned, without an inadmissible increase in the development of heat in the core connected is. The main branches 2 and 3 are again divided into two sub-branches 9, 10 and 11, 12 for this purpose. Direct current flows are again generated in these branches by windings 13, 14 and 15, 16, in such a way that the direct current flow in sub-branch 9 is of the same size, but in the opposite direction to the direct current flow in sub-branch 10, and so is the direct current flow in sub-branch 11 is of the same size, but in the opposite direction to the direct current flow in the branch 12. The magnitude of these direct current flows is such that each branch is brought into saturation. In this way it is achieved that the effective hysteresis loop both of the main branch 2 and of the main branch 3, as is the case for those flowing through the in the windings 5, 6, 7 and 8. Alternating current and magnetic fields generated in the yoke 21 occurs, which has the characteristic shown in FIG. 3; from this it follows that the hysteresis losses are again reduced to a very considerable extent. Finally, it should be noted that the arrangement as shown in FIGS. 1 and 4 is of course not essential to the invention. So z. B. the windings 5, 6 or 7, 8 can be combined into a single winding which completely surrounds the coils 13, 14 or 15, 16. Another possibility is that the coil of the inductance is formed by a simple line, which is led through the opening between the main branches 2 and 3, and that the coils for generating the direct current flows in the sub-branches 9, 10 and 11, respectively , 12 are formed by simple lines. This embodiment is shown in FIG. The corresponding parts of FIGS. 4 and 5 are labeled identically. The coil of the inductance is referred to here with 24. In connection with the symmetry desired in such devices, the coil 24 has two parallel branches 25 and 26 at one end, the terminals E1 and E2 of which can be connected to the same terminal of the alternating current source. The coils for generating the direct current flows are formed by the lines 27 and 28, which are connected to one another in series by means of the circular conductor 29 encompassing the line 24. But it is also possible to generate the mentioned direct current flows by small permanent magnets that z. B. are built into the sub-branches 9, 10, 11 and 12, naturally with a suitable strength and correct sign. These permanent magnets do not need to be attached in the sub-branches themselves, but can also be arranged in the non-branched parts or even in the openings between the sub-branches, as shown in FIGS. 6 and 7; here only the ferromagnetic core 1 is shown with the main branches 2 and 3, which are divided into the sub-branches 9, 10 and 11, 12, respectively. The permanent magnets are designated by 30. Patent claims: 1. Controllable choke coil for low current purposes, consisting of one with a magnetic yoke ferromagnetic core lying in series, which is provided with at least two windings and has two parallel main branches which are each divided into two parallel sub-branches, wherein a changeable magnetic field generated in the magnet yoke a change in the coil inductance causes, characterized in that the windings (5, 6 and 7, 8) are in phase opposition to one another the main branches (2, 3) of the core (1) are wound and that means (13 to 16 or 30) are provided are in the two sub-branches (9, 10 or 11, 12) of each main branch (2, 3) direct current