US1757710A - Electromagnetic circuits and apparatus - Google Patents

Description

May 6, 1930. w. FONDILLER ELECTROMAGNETIC CIRCUITS AND APPARATUS Filed Dec. 17, 1926 kw W mm Wmfl WV. W W

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WILLIAM FONDIL LER, OF YO'NKERS, NEW YORK, -.ASSIGI\TOB TO WESTERN ELECTBIC COMPANY, INCORPORATED, OF NEJV YORK, N. 2., ii. CORPORATIOTZK OF NERV YORK ELECTROMAGNETIC cmcura's Ann APPARATUS;

' Application filed December 17, 1926. Serial no. 155,513.

This invention relates to electromagnetic tion with the accompanying drawing in circuits and apparatus, particularly to their which: application in signaling systems. Fig. 1 is a diagrammatic illustration of a An object of the invention is to secure concarrier wave telephone system containing 5 stancy of operating characteristics in elecmagnetic elements in accordance with the intromagnetic circuits and apparatus employvention; and 1 ing low field strengths. Fig. 2 is a magnetiaation curve of a par- A related object of the invention is to re-. ticular cobalt steel alloy which may be cinduce distortion due to energy dissipation'and ployed as the core material in the e1eDtr0- 19 intermodulation in signaling systems. magnetic circuits of Fig. 1.

It is well known that when iron and most Fig. 1 shows the west terminal of a carmagnetic compositions ofiron are subjected rier wave telephone system connected to the to magnetic fields setup by signaling curmultiplex transmission line ML. The usual rents, the permeability and hysteresis losses east terminal, which is similar to the west 5 vary appreciably with changes in the field terminal, is omitted for the sake of simplistrength or in the resultant flux density. fying the showing. A system of this general Such variations in magnetic characteristics type is illustrated in Fig. 42 of an article enproduce distortion in the signaling currents, titled Carrier current telephony and telegwhich is variously characterized as modularaphy by- Messrs. Colpitts and Blackwell,

tion, flutter efi'ect, etc., depending upon the published in the Transactions of the Americonditions under which it is produced. can Institute of Electrical Engineers, vol.

The present invention relates particularly 40, 19?1. to magnetic circuits containing cobalt steel The terminal apparatus includes a plural-' alloys which exhibit relative constancy of ity of transmitting and receiving channels of 25 magnetic characteristics over a range of which the transmitting channel TC and the magnetizing forces includingthe forces ordireceiving channel RC are typical. The channarily employed in signaling. These componel TO includes a modulator M, an oscillator sitions have heretofore been used extensively and .a' band filter F, and the channel RC for permanent magnets because of their high includes a demodulator amplifier DA and a 30 coercivity at large magnetizing forces, but band filter F. These channels are connected so according to the present invention are used to a low frequency telephone line L by means in circuits employing low magnetizing forces, of a special balanced transformer H and bal-- in which region these alloys have been found 'ancing network N. The band filters F and to exhibit low Coercivity with accompanying F are ofthe well known type disclosed in 5 constant permeability and low hysteresis U. S. Patent No. 1,227,113 to G. A. Campbell,

loss. issued May 22, 1917, and comprise a plural- The characteristics of substantially conity of inductance coils and condensers arstant permeability and low hysteresis los's exranged to pass with negligible attenuation hibited by these alloys in the range of magwaves comprised within predetermined bands as netizing forces below five gauss render them of frequencies, and substantially to suppress especially serviceable as the core material for Waves of all other frequencies. The multitransformers, loading coils, filter inductance plex transmission line ML is loaded at suitcoils, sensitive electrical measuring instruable intervalsby means of loading coils C, ments, etc., where uniformity of character-. only one of which is shown in the drawing.

45 istics over the operating range is demanded. Carrier waves are qtilized for transmission The advantage of obtaining a constant inover the line ML, a separate band of frequenductance with resulting low energy dissipacies being allotted to each channel. Voice tion and wave distortion is obvious'to those frequency waves originating in the low freskilled in the art. quency line L pass through the balanced 50 The invention will be described in connec transformer H into the modulator M where the oscillator 0. Of the components of modulation appearing in the output circuit of the modulator, the band filter Fmay suppress all but one sideband and the carrier, which it passes tothe multiplex line ML. In receiv-' ing 'signals,'the incoming carrier and sideband waves assigned to the channel BC are selectively passed by the band filter F and demodulated and amplified'in the demodulator-amplifier DA. The voice frequency com ponents of demodulation appearing in the outputcircuit of the demodulator-amplifier DA are transmitted through balanced trans.

former coil H to the low frequency line L.

The apparatus which may employ the magnetic cobalt steel alloys as the core material, according to the invention, are the balanced transfomer H, the inductance coils of the filters F and F and the loading coil C. Heretofore, it has been necessary in some cases to construct such apparatus with air coresbecause of thehysteresis loss and the variations in permeability attendant upon the use ofiron and other commonly used magnetic materials. Variations in these magnetic characteristics due to slight change in magnetizing force produce serious distortion in the signalingv waves which greatly impairs the transmission efliciency of the system. According to this invention, stability of magnetic characteristics is obtained by employing a hard'magnetic steel alloy containing carbon, iron, cobalt and other elements as the'core material in the electromagnetic field. Alloys suitable for this purpose have been upon the market un-- der the trade name of KS steel.

The magnetization curve of Fig. 2 illus trates the relation between the magnetizing force H and the induced flux indensityB in c. g. s. units, for an alloy containing 35% cobalt, 7% tungsten, 2% chromium, .7%.carlion and the remainder iron. This relation is linear over the range of magnetizing forces from zero to about 5 gauss, the permeability being approximately 10.9 over this range. Tests on another representative sample of this material were confined to the range of magnetizing forces from 0.025% gauss to 0.10 gauss, which includes the range of magnetizing forces ordinarily employed in signaling, this sample having a permeability of about 21 over this range. This latter sample was previously given a supplementary heat treatment which accounts for its higher permeability. The coercivity and hysteresis loss in each case are low. Other suitable cobalt-steel alloys are disclosed in U. S. Patents Nos. 1,338,132 and 1338,1133 to K. Honda, issued April 27, 1920. By employing these magnetic materials for they magnetic cores in the magnetic circuits of Flg. 1 the transmission eiiiciency of the system is greatly improved.

alloys exhibiting similar pron scribed but included within the scope of the appended claims. For example other steel es may be employed in place of cobalt steel, the term steell used in the claims referring to an alloy of iron in which carbon is an essential element.

The invention claimed is:

1. The cpmbinatien with a magnetic material comprising a steel alloy consisting chiefly of iron and cobalt having substantially constant permeability at low magnetizing forces, of a magnetic circuit containing said material, and means for impressing upon said 7 circuit a plurality of small magnetizing force components corresponding respectively to components of a composite signaling wave.

2 The combination with a magnetic material comprisinga cobaltsteel alloy containing from 5% to 60% cobalt and the balance chiefly iron, having substantially constant per meability at low magnetizing forces, of a magnetic circuit containing said material,

and means for impressing upon said circuit a plurality of small magnetlzing force components corresponding respectively to components of a composite signaling wave. 3. The combinatlon with a magnetic material comprising a steel alloy consistlng chiefly of iron and cobalt having substantially constant permeability over a range of low magnetizing'forces, of a magnetic circuit con taining said material. and means for impressing upon said circuit a plurality of small magnetizing force componentsnot exceeding the value at which the permeability of the magnetic material begins to vary substantially.

' 4. A signaling'system comprising an inductance the field of which contains a mag netic steel alloy consisting chiefly of iron and cobalt having substantially constant permeability over a range of low magnetizing forces, and a circuit for impressing upon said inductance a plurality of small magnetizing force components comprised within said range. i 5. vA signaling for transmitting waves of different frequencies, and a filter for selectively passing certain of said waves, said filter comprising an inductance the field of which contains a magnetic steel alloy consisting chiefly of iron and cobalt and having substantially constant persystem, comprising a circuit meability at magnetizing forces ofthe order impressed upon said circuit.

6. A signaling system comprising a circuit for transmitting Waves of different frequencies, and a filter for selectively passing certain of said waves, said filter comprising, an inductance the field of which includes a cobalt steel alloy containing from 5% to cobalt and the balance chiefly iron and having substantially constant permeability at magnetizing forces from zero to approximately five gauss.

In Witness whereof, I hereunto subscribe my name this 17th day of December, A. D.

WILLIAM FONDILLER.

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