US2753513A - Transformers - Google Patents

Description

July 3, 1956 .1. e. SOLA 2,753,513

TRANSFORMERS Filed Nov. 6,1953 2 Sheets-Sheet 1 IN V EN TOR.

July 3, 1956 Filed Nov. 6, 1953 J. G. SOLA 2,753,513

TRANSFORMERS 2 Sheets-Sheet 2 United States Patent TRANSFORMERS Joseph G. Sola, River Forest, Ill. Application November 6, 1953, Serial No. 390,559 19 Claims. (Cl. 32348) This invention relates to alternating current apparatus for connection between a load and a source of voltage which is subject to fluctuations, whereby the load may be supplied with constant voltage irrespective of the supply voltage fluctuations. The invention is an improvement upon the subject matter disclosed and claimed in the Patent No. 2,143,745, to Joseph G. Sola, dated January 10, 1939, and entitled Constant Potential Transformer. More particularly, it relates to apparatus including a novel high-reactance transformer whereby a voltage transformation, as well as constant voltage after transformation, may be obtained, and it is an object of the invention to provide improved apparatus of this character.

It is a further object of the invention to provide improved constant voltage apparatus of the character indicated which makes use of the phenomenon of resonance as it occurs in circuits including iron, or other suitable magnetic core materials.

It is a further object of the invention to provide an improved high-reactance, limited-current transformer and especially one having particular usefulness in constant voltage apparatus.

It is a further object of the invention to provide apparatus of the character indicated which has an improved wave shape of output voltage, has an improved ratio of weight and size to power output, has an improved power factor over a wide range of load, and is substantially free of surrounding stray fields.

It is a further and especially important object of the invention to provide improved apparatus of the character indicated which is particularly economical to manufacture.

Further objects and advantages of the invention will appear as the description proceeds.

The invention may be better understood by reference to the accompanying drawings, in which:

Figure 1 is a top plan view of one form of transformer which may be utilized in carrying out the invention;

Fig. 2 is a sectional view taken substantially along the line 2-2 of Fig. 1;

Fig. 3 is a schematic top plan view of the transformer of the preceding figures;

Fig. 4 is a schematic elevational view of the transformer shown in Fig. 3;

Fig. 5 is a top plan view of a modified form of transformer which may be utilized in carrying out the invention;

Fig. 6 is a sectional view taken substantially along the line 66 of Fig. 5;

Fig. 7' is a fragmentary view taken substantially in the direction of arrows 7-7 of Fig. 5; and

Fig. 8 is a circuit diagram showing electrical connections of the apparatus shown in the preceding figures according to the invention.

Referring to Figs. 1 to 4, inclusive, a transformer 10 is shown including a primary winding 11, a secondary 2,753,513 Patented July 3, 1956 winding 12 and a compensating winding 13. The secondary winding 12 surrounds a central core member 14, two auxiliary core members 15 and 16 are disposed one on each side of the core member 14 and winding 12, and the primary winding 11 surrounds the combination of the core members 15 and 16, the secondary winding 12 and the core member 14. Surrounding the complete combination is the compensating winding 13.

The core members 14, 15 and 16 are advantageously formed of thin strips of appropriate magnetic material having the necessary width which are spirally wound to produce cores of the desired thickness.

The two auxiliary core members preferably are of equal cross-sectional area and in one satisfactory form of device the sum of the cross sectional areas of the auxiliary core members was equal to the cross-sectional area of the central core member.

The transformer may be made by first winding the turns of winding 12 around core member 14, by thereafter placing the cores 15 and 16 alongside the already wound core 14 and winding 12, and finally by winding the turns of winding 11 around the resulting combination. A separate winding 13 may then be disposed around the winding 12, or, when the winding 11 is Wound a sufiicient additional number of turns may be added which become the separate winding 13 upon severance of the wire at the appropriate point. Known winding techniques may be utilized for disposing the various windings on the cores. in the form shown in Figs. 1 and 2, the resulting appearance of the finished transformer is toroidal.

The invention may be better understood by a reference to Figs. 3 and 4 in which the reference characters are the same as those used to designate corresponding parts in Figs. 1 and 2. In these figures the core members 14, 15 and 15 are shown disposed side by side. The secondary winding 12 is shown in dotted lines disposed around the central core 14, the primary winding 11 is shown in solid lines disposed around the core members 15 and 16, the central core 14 and secondary winding 12, and the compensating winding 13 is shown in dot-- dash lines disposed around the whole combination.

A further form of transformer, according to the invention, which may be the preferred form inasmuch as it is simpler to construct than the form described in the preceding paragraphs, is shown in Figs. 5, 6 and 7. In this form of the transformer, as shown, only two coremembers 17 and 18, of equal cross-sectional areas, are used. These core members may be conveniently formed by spirally Winding strips of material of desired width into ringdike structures of desired thickness. Thereafter, each core member is severed at two points to form U- shaped members, for example, the U-shaped members 1711 and 17b of the auxiliary core member 17, as may be seen best in Figs. 5 and 7. In Fig. 7 the abutting ends of the U-shaped portions 18a and 18b of the main core member 18 may be seen.

In this form of construction, the windings may be form-wound, as is Well understood, into coils of the desired numbers of turns and layers. Thus, a secondary winding 19 may be form-wound into two coils, one each of which is disposed over each leg of the U-shaped core member 18a. Thereafter, the core member is disposed in overlying relationship to the secondary winding 19 as may be seen best in Fig. 6, and two coils constituting a primary winding 21, respectively surrounded by two coils constituting a compensating winding 22, are disposed with the legs of the core members 17a and 18a extending into their openings, as may be seen best in Fig. 6. After this assembly has been made, the corresponding core members 17b and 1817 are placed with their legs extending into the coil openings from the other side so that the respective ends of the core members are brought into end-to-end relationship, as may be seen best in Figs. and 7. The core members as thus assembled are then clamped together by any well known means, not shown.

In the particular form of transformer illustrated, the ends of the legs of the core members 18a and 18b, which may be termed the main core inasmuch as both the primary and the secondary windings surround it, are brought into abutting relationship so as to make as good a magnetic circuit as may be obtained. The ends of the legs of the core members 17a and 1712, which may be termed the auxiliary core or shunt core, are brought close together, but with non-magnetic gaps, for example air gaps 23, therebetween as may be seen best in Fig. 7. Certain magnetic characteristics may be obtained in this manner but, if desired in particular constructions, the gaps 23 in core member 17 may be omitted. Also non-magnetic gaps may be provided in both cores 17 and 18. Instead of a single auxiliary core 17, a pair of cores, similar to those shown in Figs. 1 and 2, may be used.

While a circular core construction has been shown in Figs. l4 and a generally rectangular core has been shown in Figs. 5-7, it will be apparent that other shapes may be used.

The auxiliary cores of the preceding figures carry flux generated by the primary winding which does not link with the secondary winding. High reactance is thereby provided by the auxiliary core and the transformers described are of the high-reactance, limited-current type. That is, on short circuit and with low impedance loads, only a limited current will flow.

For a further description of the invention and an understanding of the operation thereof, reference may be had to Fig. 8 which is a circuit diagram showing the connections for the various components. In this figure, the reference characters are the same as those used in Figs. 1 and 2 to designate corresponding parts, but the application of this description to the structure of Figs. 5-7 is believed to be obvious. In Fig. 8, the primary winding 11 is shown coupled to the secondary winding 12 by means of the main core 14, and the primary winding is shown linking with the cores and 16, as, of course, is also the compensating winding 13, but the secondary winding 12 does not link with the core members 15 and 16.

A condenser 24 is connected in circuit with the secondary winding 12 and in the particular disclosure is connected across it at its terminals and 26. The secondary winding is tapped at a desired point 27 so that the voltage between the terminal 25 and tap 27 combined with the voltage of the compensating winding 13 is the voltage which is intended to be applied to a load 28 through a circuit as shown.

The condenser 24 is selected to produce a resonant effect of a character determined by the fact that the iron or other magnetic alloy, of which the core is made, is nonlinear in its electromagnetic characteristics. Consider for the moment that the windings 11 and 12 are disposed on the core members 14, 15 and 16 as described, that the condenser 24 is disconnected from terminals 25 and 26 and that there is no load at 28, that is to say, the windings 11 and 12 together with their associated cores, are being considered alone. In this condition, with a voltage of predetermined frequency and magnitude applied to the terminals 29 and 31 of the primary winding, an open circuit voltage of a magnitude less than the turns ratio value will appear across the terminals 25 and 26, since a certain amount of the flux caused by the primary winding exists in the cores 15 and 16 and, consequently, does not link with the secondary winding which is disposed on the core 14. If new the primary voltage is increased from a low value to a high value, the voltage across the terminals 25 and 26 will increase substantially in direct proportion to the increase in voltage across the primary winding. This will continue until saturation occurs in the cores, after which a falling off of the secondary voltage from turns ratio value will occur. v

Consider now that the condenser 24, having a capacity value greater than a certain minimum value, is connected across the terminals 25 and 26, and a variable voltage is applied to terminals 29 and 31 of the primary winding, a very difierent effect will be observed over that when the condenser 24 is absent. For example, as the primary voltage is increased from a low value to a somewhat higher value, the voltage which appears across terminals 25 and 25 will be substantially the same as that obtained when condenser 24 is absent. However, at a certain critical point of primary voltage, a very slight increase therein results in a very large increase in voltage across the terminals 25 and 26, the current in the local circuit of Winding 12 and condenser 24 increases to a very large value and the primary current also increases very much, with a change in phase. Thereafter, as the primary voltage is increased, the voltage across terminals 25 and 26 does not increase proportionally, but increases only a relatively slight amount. That is to say, substantially constant voltage appears across terminals 25 and 26 as compared with the voltage change across the primary winding.

It has been found that the central core 14, after this point of criticality has occurred, will be in a condition of high saturation, that is, high flux density, whereas the auxiliary cores 15 and 16 are in a condition of relatively low saturation, that is, low flux density when no load or only a light load is connected at 28. In one form of device constructed, the flux density in central core 14- under these conditions was of the order of 112,000 to 120,- 000 lines per square inch, whereas the flux density in the core members 15 and 16 was of the order of 50,000 to 60,000 lines per square inch. The phenomenon resulting in the conditions described, and as a result of which a constant voltage effect is obtained, is seen to be in the nature of series resonance arising out of the fact that a properly related condenser and iron core inductance components are associated in the transformer circuit. Since the core member 14 saturates so highly, it appears that primarily the inductive reactance of the secondary winding relative to the capacitive reactance of the condenser, both at the frequency of the applied voltage, gives rise to the resonance effect. The effective inductive reactance is that viewed from the terminals 25 and 26 to which the condenser is connected.

Diiierent voltages will appear across terminals 25 and 26, depending upon the capacity value of the condenser, the particular value of capacity being selected to maintain the constant voltage desired over the necessary load range Without unduly overloading the transformer windings. In any case, however, the condenser must be of a capacity such as to produce the point of criticality, already indicated, substantially below the desired operating range of primary voltage. The resultant voltage across terminals 25 and 26, after the resonance effect has occurred, is ordinarily too high for use in practical applications, it frequently being of the order of 600 volts. The desired load voltage is obtained by placing the tap 27 at the point which will give the desired voltage.

Such minor fluctuations as occur in the voltage across terminal 25 and tap 27 as a result of primary voltage fluctuations within the operating range may be compensated for by disposing the winding 13 in close coupling to the primary winding 11 so that the voltage of winding 13 bucks the slight increase in secondary voltage resulting from an increase in the primary voltage. Correspondingly, when the primary voltage decreases, the bucking effect is reduced and the load voltage tends to remain constant.

By way of example, a suitable transformer and condenser combination according to the invention, designed to be operated from a 115-volt, 400-cycle supply circuit and to give an output of 115 volts and 1,000 watts at rated full load, and in which the primary winding 11 has turns, the secondary winding 12 has approximately 470 turns, of which approximately 104 turns are included between the terminal 25 and the tap 27, and the compensating winding 13 has approximately 22 turns, the con denser 24 may have a capacity of approximately 3.5 microfarads and a rating of approximately 660 volts. The cores may be suitably formed of strips of low-loss ironsilicon alloy of approximately .007 inch gauge, wound to give a cross-sectional area of approximately .625 square inch in the case of the central core and approximately .547 square inch in the case of the auxiliary core or two auxiliary cores in the aggregate.

It has been found that when a load is applied at 28, the flux densities in the central core member 14 and in the auxiliary core members 15 and 16 change. As the load is increased, the flux density in central core member 14 decreases and the flux density in the core members 15 and 16 increases until at the full rated load the flux densities in all members tend to be about equal. The fluxes in the central core member 14 and the core members 15 and 16 are not in phase, but when similar exploring coils are placed around these respective core members, and the voltages induced into the exploring coils are added in series, it is found that the voltage sum tends to stay relatively constant with varying loads, indicating that the effective flux density as generated by the primary winding tends to stay about the same.

While Wound cores for power transformers are known and have desirable properties, for example, low iron losses at power and higher frequencies, economy of manufacture, small material wastage and uniform orientation of the magnetic particles, such cores have not been employed heretofore in high-reactance transformers for applications to which the present invention is adapted, because of the seeming impossibility or great difficulty of providing magnetic shunts to produce the desired high reactance. The present invention overcomes this difiiculty and in a simple manner provides effective magnetic shunts in a wound-core, high-reactance transformer while at the same time retaining the known advantages of wound cores in power transformers. The combination of these advantages in mechanically simple, high-reactance and constant voltage transformer structures, as disclosed herein, results in devices of execellent performance characteristics which are much more economical to manufacture than was hitherto believed possible.

Devices of the present character have a high power factor from no-load to full-load, it being above ninety per cent throughout the whole range, and also have output voltages of very good wave shape at all loads.

Since the central core member 14 is under a condition of high flux density under operating conditions, there is a tendency for large stray fields to exist outside of this core member. However, since the core members 15 and 16 are disposed alongside the central core member 14 and the windings placed therearound effectively increase the distance of the central core member 14 to the exterior, the stray field surrounding the transformer is very much reduced.

It will be understood that, while in Fig. 8 a two-winding transformer is shown, the invention is adaptable to autotransformer connections.

While particular embodiments of the invention have been shown, it will be understood, of course, that the invention is not limited thereto since many modifications may be made, and it is, therefore, contemplated by the appended claims to cover any such modifications as fall within the true spirit and scope of the invention.

The invention having thus been described, what is claimed and desired to be secured by Letters Patent is:

1. A high-reactance, limited-current transformer comprising a first magnetic core member, an auxiliary magnetic core member separate from said first core member, a non-magnetic gap in said auxiliary core, a primary winding linking both said first and auxiliary core mem- 6 bers, and a secondary winding for supplying a load linking only said first core member, said auxiliary core member providing a leakage path for flux linking only said primary winding when said secondary winding is carrying current, thereby eifectuating high reactance and consequent current limiting.

2. A high-reactance, limited-current transformer comprising a first magnetic core member having a predetermined cross-sectional area, an auxiliary magnetic core member separate from said first core member and having a predetermined cross-sectional area approximately equal to that of said first core member, a non-magnetic gap in said auxiliary core, a primary winding linking both said first and auxiliary core members, and a secondary winding for supplying a load linking only said first core member, said auxiliary core member providing a leakage path for flux liking only said primary winding when said secondary winding is carrying current, thereby effectuating high reactance and consequent current limiting.

3. A high-reactance, limited-current transformer comprising a first magnetic core member having a predetermined cross-sectional area, an auxiliary magnetic core member separate from said first core member and disposed on one side thereof, a further auxiliary magnetic core member separate from said first core member and disposed on the other side thereof, said auxiliary and further auxiliary core members having substantially equal crosssectional areas and having an aggregate cross-sectional area approximately equal to that of said first core member, a non-magnetic gap in each of said auxiliary and said further auxiliary core members, a primary winding linking said first, auxiliary and further auxiliary core members and a secondary winding for supplying a load linking only said first core member, said auxiliary core member providing a leakage path for flux linking only said primary winding when said secondary winding is carrying current, thereby etfectuating high reactance and consequent current limiting.

4. A high-reactance, limited-current transformer comprising a first wound magnetic core member, an auxiliary wound magnetic core member separate from said first core member, a non-magnetic gap in said auxiliary core, a primary winding linking both said first and auxiliary core members, and a secondary winding for supplying a load linking only said first core member, said auxiliary core member providing a leakage path for fiux linking only said primary winding when said secondary winding is carrying current, thereby effectuating high reactance and consequent current limiting.

5. A high-reactance, limited-current transformer comprising a first wound magnetic core member having a predetermined cross-sectional area, an auxiliary wound magnetic core member separate from said first core member and having a predetermined cross-sectional area approximately equal to that of said first core member, a non-magnetic gap in said auxiliary core, a primary winding linking both said first and auxiliary core members, and a secondary winding for supplying a load linking only said first core member, said auxiliary core member providing a leakage path for flux linking only said primary winding when said secondary winding is carrying current, thereby effectuating high reactance and consequent current limiting.

6. A high-reactance, limited-current transformer comprising a first wound magnetic core member having a predetermined cross-sectional area, an auxiliary wound magnetic core member separate from said first core member and disposed on one side thereof, a further auxiliary wound magnetic core member separate from said first core member and disposed on the other side thereof, said auxiliary and further auxiliary core members having approximately equal cross-sectional areas and having an aggregate cross-sectional area substantially equal to that of said first core member, a non-magnetic gap in each of said auxiliary and said further auxiliary core members,

a primary winding linking said first, auxiliary and further auxiliary core members and a secondary winding for supplying a load linking only said first core member, said auxiliary core member providing a leakage path for flux linking only said primary winding when said secondary winding is carrying current, thereby efiectuating high reactance and consequent current limiting.

7. Constant voltage apparatus comprising a first magnetic core member, a second magnetic core member separate form said first core member, a primary winding arranged for connection to a source of alternating current of predetermined voltage and frequency linking both said first and said second core members, a secondary winding linking only said first core member, at least a predetermined portion of said secondary winding being arranged for connection to a load, and a condenser connected in circuit with said secondary winding, said condenser having such value of capacitive reactance at the frequency of said source relative to the value of the inductive reactance of said secondary winding at said frequency throughout a predetermined range of primary voltage above a certain minimum value thereof as to establish a condition in the nature of series resonance in the circuit of said condenser and said secondary Winding.

8. Constant voltage apparatus comprising a first magnetic core member, a second magnetic core member separate from said first core member and having a nonmagnetic gap therein, a primary winding arranged for connection to a source of alternating current of predetermined voltage and frequency linking both said first and said second core members, a secondary winding linking only said first core member, at least a predetermined portion of said secondary winding being arranged for connection to a load, and a condenser connected in circuit with said secondary winding, said condenser having such value of capacitive reactance at the frequency of said source relative to the value of the inductive reactance of said secondary winding at said frequency throughout a predetermined range of primary voltage above a certain minimum value thereof as to establish a condition in the nature of series resonance in the circuit of said condenser and said secondary winding.

9. Constant voltage apparatus comprising a first magnetic core member, a second magnetic core member separate from said first core member, said core members having approximately equal cross-sectional areas, a primary winding arranged for connection to a source of alternating current of predetermined voltage and frequency linking both said first and said second core members, a secondary winding linking only said first core member, a predetermined portion of said secondary winding being arranged for connection to a load, and a condenser connected in circuit with said secondary winding, said condenser having such value of capacitive reactance at the frequency of said source relative to the value of the inductive reactance of said secondary winding at said frequency throughout a predetermined range of primary voltage above a certain minimum value thereof as to establish a condition in the nature of series resonance in the circuit of said condenser and said secondary winding.

10. Constant voltage apparatus comprising a first magnetic core member, a second magnetic core member separate from said first core member, a primary winding arranged for connection to a source of alternating current of predetermined voltage and frequency linking both said first and said second core members, a secondary winding linking only said first core member, a predetermined portion of said secondary winding being arranged for connection to a load, a condenser connected in circuit with said secondary winding, said condenser having a value of capacitive reactance at the frequency of said source relative to the value of the inductive reactance of said secondary winding at said frequency throughout a predetermined range of primary voltage above a certain minimum value thereof as to establish a condition in the nature of series resonance in the circuit of said condenser and said secondary winding, and a compensating winding linking said first and second core members and connected in circuit with that portion of said secondary winding arranged for connection to a load.

11. Constant voltage apparatus comprising a first magnetic core member, a second magnetic core member separate from said first core member but disposed alongside thereof, a primary winding arranged for connection to a source of alternating current of predetermined voltage and frequency linking both said first and said second core members, a secondary winding linking only said first core member and disposed substantially inside of said primary winding, a predetermined portion of said sec ondary winding being arranged for connection to a load, and a condenser connected in circuit with said secondary winding, said condenser having a value of capacitive reactance at the frequency of said source relative to the value of the inductive reactance of said secondary winding throughout a predetermined range of and above a certain minimum primary voltage and at the frequency of said source whereby a condition in the nature of series resonance exists in the circuit of said condenser and said secondary winding.

12. Constant voltage apparatus comprising a first wound magnetic core member, a second wound magnetic core member separate from said first core member, a primary Winding arranged for connection to a source of alternating current of predetermined voltage and frequency linking both said first and said second core members, a secondary winding linking only said first core, a predetermined portion of said secondary winding being arranged for connection to a load, and a condenser connected in circuit with said secondary winding, said condenser having a value of capacitive reactance at the frequency of said source relative to the value of the inductive reactance of said secondary winding at said frequency throughout a predetermined range of primary voltage above a certain minimum value thereof as to establish a condition in the nature of series resonance in the circuit of said condenser and said secondary wind- 13. Constant voltage apparatus comprising a first magnetic core member, a second magnetic core member separate from said first core member and disposed on one side thereof, a third magnetic core member separate from said first and second core members and disposed on the other side of said first core member, a primary winding arranged for connection to a source of alternating current of predetermined voltage and frequency linking all three core members, a secondary winding linking only said first core member, a predetermined portion of said secondary winding being arranged for connection to a load, and a condenser connected in circuit with said secondary winding, said condenser having a value of capacitive reactance at the frequency of said source relative to the value of the inductive reactance of said secondary winding at said frequency throughout a predetermined range of primary voltage above a certain minimum value thereof as to establish a condition in the nature of series resonance in the circuit of said condenser and said secondary winding.

14. Constant voltage apparatus comprising a first wound magnetic core member, a second wound magnetic core member separate from said first core member and disposed on one side thereof, a third wound magnetic core member separate from said first and second core members and, disposed on the other side of said first core member, a primary winding arranged for connection to a source of alternating current of predetermined voltage and frequency and linking all three core members, a secondary winding linking only said first core member and disposed substantially inside of said primary winding, a predetermined portion of said secondary winding being arranged for connection to a load, and a condenser connected in circuit with said secondary Winding, said condenser having such value of capacitive reactance at the frequency of said source relative to the value of the inductive reactancc of the said secondary winding at said frequency throughout a predetermined range of primary voltage above a certain minimum value thereof as to establish a condition in the nature of series resonance in the circuit of said condenser and said secondary winding.

15. Constant voltage apparatus comprising a first wound magnetic core member, a second wound magnetic core member separate from said first core member and disposed on one side thereof, a third wound magnetic core member separate from said first and second core members and disposed on the other side of said first core member, the cross-sectional area of said second and third core members being equal to each other and the sum thereof approximately equal to the crosssectional area of said first core member, a primary winding arranged for connection to a source of alternating current of predetermined voltage and frequency and linking all three core members, a secondary winding linking only said first core member and disposed substantially inside of said primary Winding, a predeten mined po ion of said secondary winding being arranged for connection to a load, and a condenser connected in circuit with said secondary Winding, said condenser haviug such value of capacitive reactance at the frequency or" said source relative to the value of the inductive reactance of the said secondary winding at said frequency throughout a predetermined range of primary voltage above a certain minimum value thereof as to establish a condition in the nature of series resonance in the circuit of said condenser and said secondary winding.

l5. Constant voltage apparatus comprising a first magnetic core member, a second magnetic core member separate rem said first core member, a primary winding arranged for connection to a source of alternating current of predeterinied voltage and frequency linking both said first and s d second core members, a secondary winding linking only said first core member, at least a predetermined portion of said secondary Winding being arranged for connection to a load, and a condenser connected in circuit with said secondary Winding, said condenser having such value oi capacitive reactance at the frequency of said source relative to the value of the inductive reactanee of said secondary winding at said frequency as to produce currents in said secondary windlug accompanied by flux densities of high values in both said core members when said secondary winding is supplying a lead of substantially rated value.

17. Constant voltage apparatus comprising a first magnetic core member, a second magnetic core member separate from said first core member, a primary Winding arranged for connection to a source of alternating current of predetermined voltage and frequency linking both said first and said second core members, a secondary winding linking only said first core member, at least a predetermined portion of said secondary Winding being arranged for connection to a load, and a condenser connected in circuit with said secondary Winding, said condenser having such value of capacitive reactance at the frequency of said source relative to the value or" the inductive reactance of said secondary winding at said frequency as to produce currents in said secondary winding accompanied by substantially saturated flux conditions in both said core members when said secondary Winding is supplying a load of substantially rated value.

18. Constant voltage apparatus comprising a first magnetic core member, a second magnetic core member separate from said first core member, a primary winding arranged for connection to a source of alternating current of predetermined voltage and frequency linking both said first and said second core members, a secondary winding linking only said first core member, at least a predetermined portion of said secondary winding being arranged for connection to a load, and a condenser connected in circuit with said secondary winding, said condenser having such value of capacitive reactance at the frequency of said source relative to the value of the inductive reactance of said secondary winding at said freq eney as to produce currents in said secondary winding accompanied by a flux density of high value in said first core member and of low value in said second core member when said secondary winding is supplying a. load of low value and flux densities of high values in both c. d core members when said secondary winding is supplying a load of substantially rated value.

19. Constant voltage apparatus comprising a first magnetic core member, a second magnetic core member separate from said first core member, a primary Winding arranged for connection to a source of alternating current of predetermined voltage and frequency linking both said first and said second core members, a secondary winding linking only said first core member, at least a predetermined portion of said secondary Winding being arranged for connection to a load, and a condenser connected in circuit with said secondary winding, said condenser having such value of capacitive reactance at the frequency of said source relative to the value of the inductive reactance of said secondary Winding at said frequency as to produce currents in said secondary winding accompanied by a substantially saturated flux condition in said first core member and a nonsaturatcd flux condition in said second core member when said secondary winding is supplying a load of low value and substantially saturated flux conditions in both said core members when said secondary Winding is supplying a loader substantially rated value.

Dowling Dec. 8, 1931 Sola Jan. 10, 1939

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