US2461992A

US2461992A - Magnetic frequency reducer

Info

Publication number: US2461992A
Application number: US597460A
Authority: US
Inventors: Harold J Mccreary
Original assignee: Automatic Electric Laboratories Inc
Current assignee: Automatic Electric Laboratories Inc
Priority date: 1945-06-04
Filing date: 1945-06-04
Publication date: 1949-02-15
Anticipated expiration: 1966-02-15

Description

Feb. 15, 1949. H, J, MCCREMQY 2,461,992

MAGNETIC FREQUENCY REDUCER Filed June 4, 1945 INVENTOR. HAROLD J. M OREARY ATTORNEY Patented Feb. 15, 1949 2,461,992 MAGNETIC FREQUENCY REDUCED Harold J. McCreary, Lombard, lll., assignor to Automatic Electric Laboratories,

Inc., Chicago,

a corporation of Delaware Y Application June 4, 1945, Serial No. 597,460 16 Claims. (Cl. 172-281) My invention relates in general to frequency reducers which utilize saturation of a ferromagnetic core to produce alternating currents having a frequency less than that of an alternating current driving source; and in particular toimprovements in the construction of the magnetic cores and in the arrangement of the electrical circuits of such frequency reducers.

In my copending application, Serial No. 564, 879; filed November 23, 1944 now Patent 2,445,857, issued July 27, 1948; I described a novel core structure for use In this prior application my new core structure was employed in a frequency changer arranged to produce an output current having a frequency which is an even harmonic or subharmonic of the frequency of an alternating current driving source. In the present invention I provide circuit arrangements for using this same core structure to produce an output current which may have a frequency equal to an odd subharmonic of the frequency of the alternating current driving source, or which may have any other desired frequency less than that of the source. I accomplish this by inductively coupling a plurality of tuned circuits to the core, which is excited by a source of alternating current in such a manner as to cause oscillating currents of different frequencies to flow in the tuned circuits, the sum of the frequencies of the oscillating currents being equal to the frequency of the source.

The principal object of the present invention is to provide a subfrequency generator having a unitary magnetic structure.

Another object is to increase the efliciency of subfrequency generators through the use of an improved magnetic structure which permits one or more windings to each wholly link several magnetic circuits in such a manner as to result in decreased copper losses and shorter, more efficient, magnetic circuits than those previously used.

A further object of the invention is to provide a subfrequency generator of the character described above wherein the plurality of tuned circuits are inductively coupled to different magnetic' paths included in the core and wherein these circuits are electrically connected so as to control the wave-form of the oscillating current in the output circuit of the generator.

The invention has been illustrated in the form of schematic diagrams in the accompanying drawing, in which:

Fig. 1 shows one form of my improved subfrequency generator;

in magnetic frequency changers.

Fig. 2 shows a modified form of the subfrequency generator shown in Fig. 1;

Fig. 3 shows a further modified form of the subfrequency generator shown in Fig. 1;

Fig. 4 shows still another modification of the subfrequency generator; and

Figs. 1A through 4A show the waveforms of the output voltages obtained from the corresponding modifications of the generator.

My invention comprises a saturable magnetic core constructed in the form of a cross with its extremities connected and having windings thereon some of which are wound around the arms of the cross and others of which are wound through diagonally opposite corners of the cross. Two or more of these windings are serially connected to a source of alternating current, one or more windings are connected to a condenser and to an output circuit, and the remaining windings are connected to condensers and in some instances are interconnected with the first windings to produce variations in the waveform of the output voltage.

Referring now to Fig. 1, there is shown a magnetic core I, which is preferably constructed of laminations in the manner illustrated in the aforementioned copending application, upon which four windings are wound. One of these windings 2, is wound through one pair of diagonally opposite corners of the intersection of the crossed members of the core I. A second winding 3 is found through the remaining pair of diagonally opposite corners of the intersection. Two other windings 4 and 5 are each wound upon one of the arms of the cross formed in the center of the core i. windings 2 and 3 are serially connected across a pair of input terminals 6 and 1 which are in turn connected to a source of alternating current 8. Winding 3 is also connected to a pair of output terminals 9 and III which are in turn connected to a load H. Condensers I2 and I3 are connected across windings 2 and 3, respectively. Condenser I4 is connected across winding 4 and this parallel combination is connected in series with winding 5 and condenser IS. The core I has two magnetic paths included therein, one of these paths being directed through the vertical center leg, and the other path being directed through the horizontal center leg. Winding 2 links these two paths so as to exert magnetomotive forces therein which are directed upward in the vertical leg and to the left in the horizontal leg when. energized in one direction. Winding 3 also links these two paths but in an opposite sense with respect to winding 2 for winding 3 exerts magnetomotive forces therein which are directed downward in the vertical leg and to the left in the horizontal leg when energized in one direction. Thus it is apparent that the magnetomotive forces produced by currents flowing in coils 2 and 3 are always aiding in one of the paths and opposing in the other path. It has been found that alternating current having a frequencyequal to one third that of the source will be delivered to the load circuit with this arrangement when equal numbers of turns are used on each coil and the condensers l2, l4, l5, and I3 bear ratios of 1:4:l0z50, respectively. The waveform of the voltage developed across terminals 9 and I is shown in Fig. 1A.

Fig. 2 is identical to Fig. 1 excepting that in this case winding 3 is also connected in series with winding 5. condenser l5, and the parallel combination of winding 4 and condenser l4. change in connections brings about a considerable change in the waveform of the output voltage developed across

terminals

9 and 10, as shown in Fig. 2A. In this case the output'contains a large component of the input frequency, which component is negligible in the circuit of Fig. 1.

In Fig. 3 the connections have been further altered by connecting condenser l4 across the series combination of winding 5 and condenser in place of across winding 4. The waveform of the output voltage developed across terminals 9 and Ill with these connections is shown in Fig. 3A. .This is seen to be nearly a square wave which may advantageously be used as a source of impulses by rectification, or by inserting a source of direct current in series with the output, so as to provide a unidirectional pulsating output voltage. The steep wavefront and sharp corners in this wave indicate the presence of numerous high order harmonics, which are desirable in a subfrequency generator which is used as a source of ringing current in a telephone system. In such a system, the ringing current must contain high.

order harmonics in order to produce a satisfactory ring-back signal since the fundamental frequency of the ringing current is too low to be efficiently transmitted over the circuits involved and reproduced by the calling partys receiver.

The circuit arrangements described so far are particularly suited to the production of an alternating current having a frequency equal to onethird that of the source. The modification illustrated in Fig. 4 is readily adapted to produce an alternatin current having any desired frequency less than that of the source. In this arrangement two additional windings, f6 and I1, each wound on one arm of the cross formed in 'the center of the core I l, are connected in series with winding 2 across the input terminals 6 and I. The output current is obtained from windings 4 and 5, which are serially connected to output terminals 9 and iii across which condenser 18 is connected to tune the output branch to the output frequency. Winding 3 is in this case divided into two parts 3a and 3b. One of these parts 3a is tuned by condenser l3 to a frequency equa to that of the source 8 less the desired output frequency, and the other part 312 is connected to a source of direct current 19 in series with a choke coil 20 and an adjustable resistor 2|. The choke coil 20 is used to prevent alternating current from flowing through battery H! as a result of the alternating voltages induced in winding 31). Resistor 2! is used to control the magnitude of the direct current flowing through winding 3b so as to bias This the core H to a desired portion of its magnetization current to thereby facilitate the starting of oscillations in the tuned circuits. The wave-form of the output voltage developed across terminals 9 and Ill, when condensers l3 and I8 are chosen so as to make the output frequency equal to one third that of the source 8, is shown in Fig. 4A.

In all of the previously disclosed subfrequency .generators employing a plurality of tuned circuits coupled by a saturable magnetic core means it has been necessary to employ linear inductances andcondensers in each tuned circuit. I have found that the use of separate linear inductances in each tuned circuit is unnecessary when the several tuned circuits include windings linking different magnetic paths in the saturable core as herein illustrated, since in this case each winding may act as a linear inductance during the intervals when the particular magnetic path to which it is coupled is not saturated.

I have therefore been able to produce a subfrequency generator with a unitary magnetic structure,

struction. By electrically coupling in various ways the several tuned circuits, each of which is .inductively coupled to a different magnetic flux path in a common core, I am able to control the waveform of the output voltage of my subfrequency generator.

Although I have described my invention with a certain degree of particularity, it should be understood that the present disclosure has been I made only by way of example and that numerous changes in the details of construction and the combination and arrangement of parts may be resorted to without departing from the spirit and scope of the invention as hereinafter claimed.

What is claimed is:

1. A subfrequency generator comprising a saturable magnetic core means, a source of alternating current, a primary circuit including a winding on said core means connected to said source, a secondary circuit including a winding on said core means connected to a load circuit, an auxiliary circuit including a winding on said core means, condensers connected in said secondary and auxiliary circuits tuning them to different frequencles such that the sum thereof is equal to the frequency of said source, said secondary and auxiliary circuits being devoid of inductance elements other than the ,windings on said core means, the excitation of said core means by said source causing oscillating currents to be produced in said secondary and auxiliary circuits of frequencies corresponding to the tuning thereof.

2. A subfrequency generator comprising a saturable magnetic core means, a source of alternating current, a primary circuit including a winding on said core means connected to said source, a secondary circuit including a winding on said core means connected to a load, an auxiliary circuit including a winding on said core means, condensers connected in said circuits tuning them to different frequencies such that the sum thereof is equal to the frequency of said source, the windings on said core means constituting the sole inductance elements in said circuits, the excitation of said core means by said source causing oscillating currents to be produced in said circuits of frequencies corresponding to the tuning thereof.

3. In a subfrequency generator, a saturable magnetic core having two magnetic flux paths, a first single section winding on said core linking said paths in one sense, a second single section winding on said core linking said paths in an opposite sense, a source of alternating current, a primary circuit including one of said windings connected to said source, a secondary circuit including the other of said windings connected to a load, an auxiliary circuit including windings on said core each linking only one of said paths, condensers connected in said circuits so as to form a plurality of oscillatory circuits, the excitation of said core by said source causing oscillating currents to flow in said oscillatory circuits of frequencies such that the sum thereof is equal to the frequency of said source.

4. In a subfrequency generator, a saturable magnetic core having two magnetic paths, a first single section winding on said core linking said paths in one sense, a second single section winding on said core linking said paths in an opposite sense, a source of alternating current, a primary circuit including one of said windings connected to said source, an auxiliary circuit including the other of said windings, a secondary circuit including windings on said core each linking only one of said paths, condensers connected in certain of said circuits so as to form a plurality of oscillatory circuits, the excitation of said core by said source causing oscillating currents to flow in said oscillatory circuits of frequencies such that the sum thereof is equal. to the frequency of said source.

5. A subfrequency generator comprising a saturable magnetic core constructed in the form of a cross with its extremities connected, a first coil wound through one pair of diagonally opposite corners of the cross, a second coil wound through the remaining pair of diagonally opposite corners of the cross, a third and a fourth coil each wound on one of the arms of the cross, a source of alternating current connected to one' of said windings, condensers connected to the other windings so as to form a plurality of oscillatory circuits, a load connected to one of said oscillatory circuits, the excitation of said core by said source causing oscillating currents to flow in said circuits of frequencies such that the sum thereof is equal to the frequency of said source.

6. A subfrequency generator comprising a saturable magnetic core constructed in the form of a cross with its extremities connected, a plurality of windings linking different flux paths of said core, a source of alternating current connected to one of said windings, condensers connected to said windings so as to form a plurality of oscillatory circuits, a load connected to one of said oscillatory circuits, the excitation of said core by said source causing oscillating currents to flow in said circuits of frequencies such that the sum thereof is equal to the frequency of said source.

'7. A subfrequency generator comprising a saturable magnetic core means, a source of alternating current, a primary circuit including a winding on said core means connected to said source, a secondary circuit including a winding on said core means connected to a load, an auxiliary circuit including a winding on said 6 condensers connected in said cirthem to different frequencies such that the sum thereof is equal to the frequency of said source, certain of said circuits being electrically connected to eflect an interchange of energy therebetween so as to control the waveform of the reduced frequency alternating current delivered to the load.

8. A subfrequency generator comprising a saturable magnetic core and a pair of single section windings thereon, said core having two flux paths which link the senses, a primary circuit including one of said windings and a source of alternating current, a

core means, cuits to tune secondary circuit including the other of saidwindings and a load, further windings on said core, and condensers associated with said further windings and with said secondary circuit to cause alternating current having a frequency less than that of said source to be delivered to the load.

9. A subfrequency generator comprising a saturable magnetic core and a pair of single section windings thereon, said core having two flux paths which link the pair of windings in opposite senses, a primary circuit including one of said windings and a source of alternating current, further windings on said core, a secondary circuit including said further windings and a load, and condensers associated with the other of said first windings and with said secondary circuit to cause alternating current having a frequency less than that of said source to be delivered to the load.

10. A subfrequency generator comprising a saturable magnetic core, a primary circuit including a source of alternating current and a first winding on said core, a secondary circuit including a load and a second winding on said core, an auxiliary circuit including a third winding on said core, said core having two flux paths which link the whole of two of said windings in opposite senses, and condensers associated with said auxiliary circuit and said secondary circuit to cause subfrequency alternating currents to be delivered to the load.

11. In a static frequency changer, a saturable magnetic core having four openings therein, a first coil wound through one diagonally opposite pair of said openings, a second coil wound through the other diagonally opposite pair of said openings, a third coil wound through an adjacent pair of said openings, a source of alternating current connected to one of said coils, a condenser and a load connected to another of said coils, and a further condenser connected to the remaining coil, whereby alternating current having a frequency less than that of said source is delivered to said load.

12. In a static frequency changer, a saturable magnetic core having at least four openings therein, a first coil wound through one diagonally opposite pair of said openings, a second coil wound through another diagonally opposite pair of said openings, a third coil wound through an adjacent pair of said openings, a source of alternating current connected to one of said coils, a condenser and a load connected to another of said coils, and a further condenser connected to the remaining coil, whereby alternating current having a frequency less is delivered to said load.

13. In a static frequency changer, a saturable magnetic core having four openings therein, a first coil wound through one diagonally opposite pair of said openings, a second coil wound pair of windings in oppositethan that of said source openings, one of said openings being common to said third and fourth coils.

15. In a static frequency changer, a saturable magnetic core having four openings therein, a first coil wound through one diagonally opposite pair of said openings, a second coil wound through the other diagonally opposite pair of said openings, and four further coils each wound through a difierent adjacent pair of said openings.

16. In a static frequency changer, a saturable magnetic core having a plurality of diagonally opposed openings therein, a plurality of coils each wound through a diagonally opposed pair of said openings, and a plurality of further coils each wound through an adjacent pair of said openings.

HAROLD J. McCREARY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,088,620 Stacker Aug. 3, 1937 2,179,386 Stocker Nov. '7, 1939 FOREIGN PATENTS Number Country Date 448,341 Great Britain June 5, 1936