US3004171A - Transverse magnetic devices providing controllable variable inductance and mutual inductance - Google Patents

Description

Oct. 10, 1961 D M. LIPKIN 3 0 TRANSVERSE MAGNETIC DEVICES PROVIDING CONTROLLABLE VARIABLE INDUCTANC'E AND MUTUAL INDUCTANCE Filed March 17, 1955 Max. Loss Region Of lncreaslngly Effective Clamping Action Between B And H Vectors FIG. I.

E G mmtm Applied Field Oersteds l fl hp Asymptotic FIG. 2.

lad lml 1 R)? Choke S ecandary Primary D. C. Bias 0 C. 36 las l-l Longitudinal INVENTOR. DANIEL M. LIPKIN l I I 394 4 Modulated R F.

Output 8 Longitudinal Linear Induction FIG. 3.

l Auxiliar C 2 Bios A Larger Value of Bias One Particular Value of Bias Signal Input B: H H

A GENT United States Patent Ofifice 3,004,171 Patented Oct. 10, 1961 3,004,171 TRANSVERSE MAGNETIC DEVICES PROVIDING CONTROLLABLE VARIABLE INDUCTANCE AND MUTUAL INDUCTANCE I Daniel M. Lipkin, Philadelphia, Pa., assignor to Sperry Rand Corporation, a corporation of Delaware Filed Mar. 17, 1955, Ser. No. 494,946

7 Claims. (Cl. 307-88) The present invention concerns radio-frequency transformers employing transverse magnetization and having vanishingly small core losses.

It is an object of the invention to provide a substantially loss-less controllablevariable reaotance or modulator.

It is an object of the invention to provide a controllable variable reactance or modulator having a core of magnetic material which is to be operated in a magnetic field of higher value than that required to saturate the magnetic material comprising the core. a

It is an object of the invention to provide a radio-ire quency transformer having a core of magnetic material With a substantially rectangular characteristic loop to be operated in a magnetic field greater than that required for saturation.

It is a particular purpose of the present invention to provide loss-less transverse magnetic circuit components which exhibit variable self inductance and variable mutual inductance. In these devices a bias current is varied to produce controllable variation, and it has been found that the mutual inductance depends inversely upon the magnitude of the bias current, whereby the device can be used as a variable self-inductor, variable mutual inductor, or modulator. Loss-less operation can be a particularly desirable factor in designs employing these components.

Among the magneticmatcrials that may be used in this invention are those having a substantially rectangular hysteresis characteristic. Copending application Serial No. 494,903 for Transverse Magnetic Amplifier, of even date herewith, is referred to for background discussion of the present invention which supplements the present disclosure. 7

The basic considerations concerning transverse devices comprising the present invention may be formulated as follows:

(1) Transverse fields are in general applied to a core of ferromagnetic material simultaneously. It may be noted that the BH relationships are quantitatively unknown except under the conditions to be described below.

(2) It is possible by means of the invention to obtain quantitatively predictable B-,-H relationships in trans verse core structures, consisting in the resultant B vector being a simple mathematical function of the resultant H vector.

(3) The above is accomplished by observing strictly the condition that the scalar magnitude of the vector resultant magnetizing force be kept above a predeterminable level characteristic of the magnetic material.

(A) When the above condition is met, the vector flux density B is substantially given by the vector equation: (1) B I? where Bs is the saturation flux density magnitude for the material; H is the resultant magnetizing force vector in g the material; and h is the scalar magnitude of H. The

(E) When Equation l is satisfied, the core itself does P where hp is the predeterminable level referred to in 3 above 1 (5) In a practical embodiment, a transverse magnetic structure, constructed in accordance with the foregoing considerations, would comprise a body of magnetic material having magnetizing means associated therewith and adapted to impress mutually orthogonal fields on the said body. An output etfect may be produced from such a transverse structure by varying the magnitude of at least one of the transverse fields and, so long as the condition represented by Equation 2 is satisfied, the operation of the device will be substantially loss-less.

(6) The predeterminable level hp referred to above, may be taken to be that value of magnetizing field larger than the value at which the specific rotational hysteresis loss for the material peaks (see FIGURE 1) and for which the specific rotational hysteresis loss is appreciably less than said maximum rotational hysteresis loss.

In the drawings, like numerals refer to like parts throughout.

'FIGURE 1 is a loss diagram for a ferromagnetic core.

FIGURE 2 is a schematic diagram of a controllable variable reactance according to the invention having unregion of vanishing rotational hysteresis loss is reached and any changes of magnetization of the core will take place without storage'or irreversible loss of energy in the core or shell. Just Where the region of substantially diminishing rotational loss occurs will vary greatly as the characteristic hysteresis loop departs from a rectangle which gives the steepest slope for the curve of FIGURE 1. This curve is not necessarily symmetrical, but starts nearthe origin, passes through a more or less critical maximum and is asymptotic to the X axis as field H increases. The region weare here concerned with lies to the right of this maximum. 5

In the region beyond the maximum rotational loss, an increase in applied field tends to bring the magnetic field closer to saturation. Under'a condition of saturation, the field and flux vectors have substantially the same direction, and as the field vector rotates, the flux vector tends to rotate with it continuing in the same direction as the field vector. At lesser values of the field, the field and flux vectors have different directions and the angle between them may vary. This characteristic of the saturated fiux vector having the same direction as the field vector is termed clamping action between the flux and field vectors B and H in FIG. 1' and elsewhere in this specification andin certain claims.

In FIGURE 2, a core of magnetic material 20 is made in the form of a long slender cylinder having a central channel .21 therethrough. Threading the channel 21 is a winding 22 having two radio- frequency chokes 23 and 24 as part of its circuit. Winding 22 is provided with terminals 25 for connection to a bias current supply. Around the cylinder 22 is wound a radio-frequency input winding 26 provided with input signal terminals 27. A second winding 28, spaced from winding 26, is also wound around core 20 and provided with terminals 29. Winding 28 is a radio-frequency output winding and may be regarded as a secondary, while winding 26 may be regarded as a primary winding.

The material of tube 29 is preferably ferro-magnetic and coils 23 and 2 are quite large so as to inhibit severely A.C. current flow in the circuit of winding 22. Although winding 22 is shown as a single turn, it may, of course, be any number of turns that the design of the device may indicate as desirable.

The structure of FIGURE 2 can be used as a controllable mutual inductor or as a modulator by varying the applied currents. If current were applied to coil 22 only, the produced magnetic flux would be circumferential and would not induce a potential in the secondary 28. The concurrent application of a signal to the primary 26, however, causes the resultant magnetic flux vector to deviate from a strictly circumferential direction and to attain a longitudinal component. It is this deflection or rotation of the resultant flux vector which effects induction of a voltage in the secondary. Without this deflection toward the longitudinal axis of core 20, there could not be any mutual inductance between windings 26 and 28. Since the degree of deflection depends on the relative values of the currents in coils Z2 and 26, a variation of the current flowing through coil 22 will vary the inductive coupling between the primary and the secondary, modulating any electrical waveform which may be transferred from the primary to the secondary and, thus, affecting the latters output at terminals 2 9. The BH relationship for coil 26 (assuming coil 28 to be open), if it were measured without knowledge of the transverse bias current in coil 22, would be the following:

Jfi Bius where Bs is the saturation induction for the core material, HBias is the transverse magnetizing field due to the bias current in coil 22; and in the usual sense: H is the longitudinal magnetizing field due to current in coil 26 and B is the component of induction linking coils 26 and 28 (i.e. longitudinal component of induction in FIG. 2).

The following facts should be noted:

(1) The BH relationship is expressible analytically, provided that H Ehp at all times.

(2) The BH relationship is free of hysteresis.

(3) The BH relationship is such that coil 26 acts as a hysteresis-free saturable reactor, with saturation induction Bs.

(4) FIGURE 4 shows in its center a dotted square representing a region of substantially linear induction where H is smaller than HBias on account of relatively small currents in coil 26. In this region coil 26 acts as a linear inductor. It is, thus, apparent that the linear inductance of coil 26 depends inversely on the value of H The way in which H influences the BH relationship for coil 26 is indicated by the two curves in FIGURE 4. The solid curve shows the effect of a relatively smaller H while the dotted curve illustrates the efiect of a comparatively larger H This provides the basis for a hysteresis-free controllable mutual inductor and a modulator the operation of which is controlled through selection of values of the HBi (5) Assuming now that coil 28 is energized. If and when the combined magnetic field of both coils 26 and 28, due to the currents in these coils, is less in magnitude than H then each coil acts as a linear self-inductor, and both coils possess a linear mutual inductive coupling. Furthermore, all three inductance values, the two selfinductances and the mutual inductance, are influenced inversely by the value of the HBias while bearing constant proportions to one another.

- In FIGURE 3 a magnetic modulator or amplifier utilizing transverse magnetization comprises a long slender ferromagnetic tube 30* having a central channel 31 through which are threaded a signal input winding 32 supplied with terminals 31, and a bias current winding 33 having large radio-frequency choke coils 34 and 35 in its circuit. Windings 33 are supplied with terminals 36 for connection to a bias supply. Around the circumference of tube 38 is wound an auxiliary radio-frequency winding 37 having terminals 38 for connection to an auxiliary radio-frequency current source. A second Winding 39, also around core 35} but spaced from winding 37, is provided with terminals 4% from which may be taken a modulated radio-frequency output signal. This device employs the principle of design discussed above in connection with FIGURE 2, but has a signal current augmenting the action of the bias current. The sheet of this combination is to change the mutual inductance between the auxiliary and output windings 37 and 39 and therefore the magnitude of the output voltage at terminals 40. The output may then be detected by suitable rectification.

The circuit of FIGURE 3 has the advantage that the induced high frequency voltage appearing across the signal winding 32 has at least twice the frequency of current flowing in the auxiliary radio-frequency winding 37. With this difference in frequency, it is relatively easy to eliminate such induced voltages in the signal winding 32. by including tuned traps or the like in its circuit.

The structure of FIGURE 3 may be used as a modulator. Modulation is effected by virtue of a signal input applied to terminals 31 adding to or detracting from the bias current in winding 33 and, thereby, varying the magnitude of the net bias field.

While there have been described above what are presently believed to be preferred forms of the invention, the appended claims are intended to include all variations thereof which fall within the true spirit of the invention.

I claim:

1. A magnetic device comprising a saturable magnetic element, a plurality of winding means linked to said element and respectively associated with transverse directions of magnetization, means for energizing at least a part of each of said winding means simultaneously and at least one of said parts in a varying amount with the net magnetizing force produced by said winding means when energized being sufficient to maintain said element in substantial saturation, and means for deriving output signals from a part of one of said winding means.

2. A magnetic device comprising a saturable magnetic element, a plurality of windings linked to said element and arranged to apply magnetizing forces thereto in a plurality of transverse directions, means for energizing said windings and at least one thereof in a varying amount with the net magnetizing force produced by said windings during operation being sufficient to maintain said element in substantial saturation, and an output winding linked to said element.

3.'A magnetic device as recited in claim 2 wherein said output Winding is linked transversely to said one winding that is to be energized in a varying amount.

4. In combination, a device comprising a ferro-magnetic core, a first Winding on said core comprising means to supply a first current to said first winding, a second winding on said core comprising means to supply a variable current thereto simultaneously with said first means, a third winding on said core comprising signal input means whereby a supplied signal can be modulated and a fourth winding on said core comprising modulated signal output means whereby a modulated signal output may be obtained.

' 5. The combination set forth in claim 4, means for controlling the value of at least one of said first and second means to supply current.

6. The combination set forth in claim 5, said first current being direct current and said first winding having choke means connected thereto.

7. The combination set forth in claim 4, said first winding and said signal input winding being so positioned on said core that their fields combine to vary the net bias 1,794,717 Lindenblad Mar. 3, 1931 field prolcluced thereby? h fi f th- OTHER REFERENCES eferences cued m l e 1e 0 18 Patent Abstract of application S.N. 212,266, published June UNITED STATES PATENTS 5 30 1953 (L do f) 1,208,982 Hartley Dec. 17, 1918

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