US2437021A

US2437021A - Transformer with regulatable leakage reactance

Info

Publication number: US2437021A
Application number: US620731A
Authority: US
Inventors: Fries Eduard
Original assignee: Individual
Current assignee: Individual
Priority date: 1945-10-06
Filing date: 1945-10-06
Publication date: 1948-03-02
Anticipated expiration: 1965-03-02

Description

Mai'ch 2, 1948. E. FRIES 2,437,021

TRANSFORMER WITH REGULATABLE LEAKAGE REACTANCE Filed Oct. 6, 1945 2 Sheets-Sheet l March 2, 1948. E. FRIES 2,437,021

TRANSFORMER WITH REGULATABLE LEAKAGE REACTANCE Filed Oct. 6, 1945 2 Sheets-Sheet 2 Patented Mar. 2, 1948 TRANSFORMER WITH REGULATABLE LEAKAGE REACTANCE Eduard Fries, Zurich-Oerlikon, Switzerland Application October 6, 1945, Serial No. 620,731 Claims. (Cl. 171-777) The invention relates to transformers with variable reactance and while not limited thereto is particularly applicable to welding transformers I whose secondary reactance must be varied within wide limits.

My copending application, Serial Number 490,- 787, filed June 14, 1943, Patent No. 2,411,370 granted November 19, 1946 discloses a transformer having a closed primary magnetic core provided with primary windings and secondary windings telescoped over the former with a transverse space between each primary and the respective secondary coils through which passes a secondary core with an adjustable air gap. The construction is such, that the secondary core is inductively interlinked with the secondary coil or coils only. The present application is a continuation in part of the aforementioned application and affords a structure in which a portion of the primary core completes the magnetic path of the secondary magnetic flux and vice versa. This results in substantial savings in material and in a compactstructure of relatively small size and high efliciency.

The present invention has forits object to pro- /vide a transformer of the aforementioned type which is simple in construction, requires a minimum of'active material and is highly eflicient in operation.

Another object is to provide in a transformer having primary and secondary windings magnetic cores affording paths for the primary and for the secondary fluxes, so disposed that the reluctance of the primary magnetic circuit is substantially unaffected by the adjustment of the reluctance of the secondary magnetic circuit.

Another object is to provide a unitary structure of a transformer having a variable secondary reactance, including a secondary magnetic circuit which is inductively coupled with the secondary winding only, and the reluctance of which is adjustable without affecting the reluctance of the primary magnetic circuit.

Another object is to provide a high reactance transformer having primary and secondary windings, a primary core inductively interlinked with the primary and the secondary winding and a secondary core having a variable reluctance and interlinked with the secondary winding only.

Another object is to provide a unitary transformer and variable reactor with a primary winding inductively mounted on the main magnetic frame of said transformer and a secondary winding inductively interlinked with said main frame and also with a secondary magnetic frame provided with a variable air gap, each of said frames having a part which completes the magnetic path for the magnetic fiux induced in the other frame.

Other objects and advantages will hereinafter appear.

- The accompanying drawings are illustrative of several embodiments of the invention. In the drawings,

Fig. 1 is a vertical section of a single phase transformer embodying the invention.

Fig. 2 is a top view and partially a cross-section along the lines 2-2 of Fig. 1.

Fig. 3 is a side view of a modification of the magnetic frame shown in Figs. 1 and 2.

Fig. 4 is a vertical section of a modified detail of Fig. 3.

Fig. 5 is a section along the lines 5-5 of Fig. 4 and Fig. 6 is a section along the lines 6-6 of Fig. 4

Referring to the drawing, Figs. 1 and 2, the same illustrates a core type transformer having a pair of primary windings l0 and H and a coordinated pair of secondary windings l2 and i3, telescoped over the coils Ill and II, respectively. The transverse cross section of the coils I D to [3, inclusive, is substantially rectangular and the transverse space between the coils I0 and I2 and the coils II and I3, respectively, is increased on one side to provide for the passage of a secondary magnetic core or frame therethrough, as will appear hereinafter. The coils Ill and II are mounted on the vertical legs l4 and I5 respectively, of a primary or main magnetic core or frame I6, the lower end of these legs being connected by a yoke IT. The legs I4 and I 5 and the yoke I'I form a substantially U- shaped magnetic core or frame. The upper ends of the two legs [4 and 65 are provided with inturned polar extensions I8 and I9, respectively. The secondary magnetic circuit comprises an inverted substantially U-shaped magnetic core or frame 20 having the legs 2i and 22, respectively, and a yoke 23. The transverse distance between the coils l0 and I2 and II and I3 is such that the legs 2| and 22 of the secondary core can freely slide therebetween. The distance between the polar extensions l8 and I9 is bridged by the yoke 23 of the secondary core. Thus the primary magnetic circuit includingthe core I! .is substantially closed, except for the

narrow gaps

24 and 25 between the polar extensions I8 and I9 and the yoke 23, which gaps are just sufficient re permit a free sliding longitudinal movement of the secondary core within the primary core.

The secondary magnetic circuit is completed aeeaoar 3 through

variable air gaps

26 and 21 between the yoke l1 and the legs 2| and 22, respectively. By moving the secondary core up and down within the secondary coils, the length of these air gaps is varied, thus varying the reactance of the secondary magnetic circuit.

It will be noted that the primary windings iii and it which closely embrace the legs it and [15, respectively, are only interlinked with the pri= mary magnetic circuit, while the secondary coils i2 and it which embrace corresponding legs of both the primary and secondary core are interlinked with both magnetic circuits. Thus by varying the air gaps 26 and 2'5, the reactance oi the secondary circuit may be varied without varying the reactance of the primary circuit. Fastened to the yoke 51 and aligned with the

legs

28 and 22, respectively, are fiat magnetic or nonmagnetic guide bars 28, which are straddled by the two halves of the secondary core legs, so that one half of the laminations of said core legs is arranged on each side of said guide bars 28 to slide longitudinally thereon.

The guide bars 28 are provided with lateral extensions 29 adjacent to the polar extensions i8 and I9, which extensions are inserted between thelaminations of the polar extension and riveted thereto. The secondary core legs are provided with insulating bolts 30, the ends of which are threaded and provided with nuts 3i and washers 32, interposed between the nut or the bolt heads and the laminations to hold the latter together and to press them against the guide bars to permit movement of the secondary core relative to the primary core, to thereby vary the

air gaps

26 and 21 between the respective parts of the secondary magnetic circuit.

To provide for adjustment of the air gap the secondary core yoke 23 has afilxed thereto a tapped boss 34 and a similar tapped boss 35 is .afflxed to the yoke ll of the primary core. A threaded shaft 36 provided with a hand wheel 31 engages the threads in the bosses 34 and 35. The threads in the bosses 34 and 35 and on the corresponding parts of the shaft 36 are cut in I opposite directions, so that upon turning of the coils l2 and IS in the usual manner, the open circuit secondary voltage. It now the secondary coils are connected to an external circuit,

' as for instance a pair of welding electrodes, at

current flows in the secondary winding. This current generates a leakage magnetic flux which passes through the leakage legs 2| and 22. This leakage magnetic flux is in opposition to the primary magnetic flux in thelegs l4 and I5, thus reducing the voltage induced in the secondary coils. The current flowing in the secondary coils l2 and i3 as well the leakage magnetic flux in the legs 2| and 22 will increase to such an extent until the sumof the magnetic fluxes in the legs l4 and 2| respectively I and 22 induces a reduced voltage which corresponds to the welding arc-voltage. The longer the air current which iiows in the secondary coils i2 and it in order to get the required value of leakage magnetic flux in the legs 2| and 22. On the other hand the open circuit secondary voltage of the transformer is not substantially affected by the length oi. the

air gaps

25 and 21. By adjustment of the air gaps it is thus possible to adjust the welding current within very wide limits.

Fig. 3 illustrates a modification of the ma netic frame shown in Figs, 1 and 2. The primary magnetic core 66 is similar to the core it of Fig. 1, except that the legs ii and d2 are not provided with intumed polar extensions. A secondary magnetic frame 413, corresponding to the frame 2% of Fig. 2 has core legs as and Q5. which extend only partly through the interspaces between the primary and secondary coils. The yoke d5 of the primary core is provided with polar extensions d? and 48 which are in alignment with the legs db and d5, respectively, to form with the latter variable air gaps 69 and 56, respectively, in the. secondary magnetic circuit. The yoke 5| of the secondary magnetic frame 43 is provided with

lateral extensions

52 and 53 at its ends, to bridge the magnetic gap between the ends of the core legs it and t2, the latter being of such length that the reluctance of the air gaps 5d and 55 between the

extensions

52 and 53 and the core legs 4| and 42 is not affected by the movement of the secondary frame 43. The

air gaps

54 and 55 are only sufficient to afford sliding movement between the respective parts and do not affect materially the reluctance of the primary magnetic circuit.

In the modifications Figs. 4, 5 and 6, a number of the laminations in the center of the core legs 4| and 42, are shortened to provide a slot 56. A corresponding number of laminations of the yoke 5| are extended to form a tongue 51 which fits in the slot 56. The legs ti and 42 are each further provided with an elongated hole 58 to afford free movement of a threaded bolt 55 which passes also through an elongated hole in the tonguev 51 of yoke 5| to afiord free movement of the latter. The bolt is provided with nuts 6! at its ends and spring washers 62 are interposed between the nuts and the leg, to provide for resilient engagement therebetween so as to compress the laminations and prevent vibration, while permitting relative movement between the primary and secondary core.

Other modifications within the scope of the present invention and appended claims will be obvious to those skilled in the art.

What I claim as new and desire to by Letters Patent is:

l. A transformer providing for substantial variation of its secondary reactance in response to variations of its secondary current, comprising, a first pair of legs and a first yoke to form therewith a unitary substantially U-shaped primary magnetic core, a second pair of legs and a second yoke to form therewith a unitary substantially U-shaped secondary magnetic core, coplanar with an inverted relative to said primary core, said second yoke being-located and arranged to provide a magnetic bridge between the open ends of said primary core, said first yoke providing a magnetic bridge including a pair of air gaps between the open ends of said secondary core, a pair of primary windings each S ecure

gaps

26 and 21 are adjusted, the greater is the encircling one each of said first pair of legs and a pair of secondary windings, each secondary winding encircling one each of said first pair of legs and the corresponding one of said second pair of legs and having its inner circumferential wall spaced from the outer circumferential wall of the respective primary winding to afiord pas sage therethrough of the respective leg or said secondary pair of legs.

2. A transformer providing for substantial variation of its secondary reactance in response to variations of its secondary current, comprising, a first pair of legs and a first yoke to form therewith a unitary substantially U-shaped primary magnetic core, a second pair of legs and a second yoke to form therewith a unitary substantially U-shaped secondary magnetic core coplanar with and inverted relative to said primary core, an intermediate portion of said secondary core being located and arranged to provide a magnetic bridge between the open ends of said primary core, an intermediate portion of said primary core providing a magnetic bridge including a pair of air gaps between the open ends of said secondary core, a pair of primary windings each encircling one each of said first pair of legs and a pair of secondary windings, each secondary winding encircling one each of said first pair of legs and the corresponding one of said second pair of legs and having its inner circumferential wall spaced from the outer cir cumferential wall of the respective primary winding to afford passage therethrough of the respective leg of said secondary pair of legs.

3. A transformer providing for substantial variation of its secondary reactance in response to a variation of its secondary current, comprising, a first pair of legs and a first yoke to form therewith a unitary substantially U-shaped primary magnetic core, a second pair of core legs and a second yoke to form therewith a unitary substantially U-shaped secondary magnetic core inverted relative to and coplanar with and reciprocable within said primary core, said second yoke being located and arranged between the open ends of said primary core to provide with the latter a magnetic circuit of substantially constant reluctance for all relative positions of said cores, the intermediate portion of said first yoke providing a magnetic bridge including a pair of variable air gaps between the open ends of said secondary core, a pair of primary windings each encircling one of said first pair of legs, and a pair of secondary windings, each secondary winding encircling one of said first pair and the corresponding leg of said second pair of legs and having its inner circumferential wall spaced from the outer circumferential wall of the respective primary winding to afiord passage therethrough of the respective leg of said secondary pair of legs.

4. A transformer providing for substantial variation of its secondary reactance in response to a variation of its secondary current, comprising, a first pair of legs and a first yoke to form therewith a unitary substantially U-shaped primary magnetic core, a second pair of core legs and a second yoke to form therewith a unitary substantially U-shaped secondary magnetic core inverted relative to and coplanar with and reciprocable within said primary core, said second yoke being located and arranged between the open ends of said primary core to provide with the latter a magnetic circuit of substantially constant reluctance for all relative positions of said cores, the intermediate portion of said first yoke providing a magnetic bridge including a pair of variable air gaps between the open ends or said secondary core, a pair of primary windings each encircling one each of said first pair or legs, and a pair of secondary windings, each secondary winding encircling one each of said first pair of legs and the corresponding one of said second pair of legs and having its inner circumferential wall spaced from the outer circumferential wall of the respective primary winding to afiord passage therethrough of the respective leg of said secondary pair of legs.

5. A transformer providing for adjustment of its secondary reactance, comprising, a substantially U-shaped primary magnetic core having its poles provided with inturned extensions, 9. coplanar substantially U-shaped secondary core reclprocable inside of and inverted relative to said primary core to provide a magnetic bridge of substantially constant reluctance between the polar extensions of said primary core for all relative positions of said core and a. variable air gap between the end of each of the poles of said secondary core and the opposed intermediate portion of said primary core, a pair of primary windings each encircling one of the legs of said primary core, and a pair of secondary windings, each secondary winding encircling one each of the legs of said primary and the corresponding leg oi! said secondary core and having its inner circumferential wall spaced from the outer circumferential wall or the respective primary winding to afford passage therethrough of the corresponding leg of said secondary magnetic core.

6. A transformer providing for substantial variation of its secondary reactance in response to a variation of its secondary current, comprising, a first pair of legs, each having at one end thereof a lateral polar extension and a first yoke connecting the other ends of said legs to form therewith a unitary substantially U-shaped primary magnetic core with said polar extensions extending towards the center of said U, a second pair of core legs and a second yoke to form therewith a unitary substantially U-shaped secondary magnetic core inverted relative to and coplanar with and reciprocable relative to said primary core, said second yoke being located and arranged to substantially close the magnetic gap between said polar extensions, said first yoke providing a. magnetic bridge including a pair of variable air gaps between the open ends of said secondary core, a pair of primary windings each encircling one each of said first pair or legs, a pair or secondary windings, each secondary winding encircling one each of said first pair of legs and the corresponding one of said second pair of legs and having its inner circumferential wall spaced from the outer circumferential wall of the respective primary winding to afiord passage therethrough of the respective leg of said secondary pair of legs and means to reciprocate said cores relative to each other.

7. A transformer providing for substantial variation of its secondary reactance in response to a variation of its secondary current, comprising, a primary laminated substantially U-shaped magnetic core having a first pair 01. legs and a. first yoke, a. secondary laminated substantially U-shaped magnetic core coplanar with and inverted and reciprocable relative to said pri-.

mar core and having a. second pair or core legs and a. second yoke, said second yoke being located and arranged between the open ends of said primary core to provide with the latter a magnetic circuit of substantially constant reluctance for all relative positions or said cores,

the intermediate portion of said first yoke providing a magnetic bridge including a pair of variable air gaps between the open ends of said secondary core, a pair of primary windings each encircling one of said first pair of legs and a pair of secondary windings, each secondary winding encircling one of said first pair and the corresponding leg of said second pair of legs and having its inner circumferential wall spaced from the outer circumferential wall of the respective primary winding to afiord passage therethrough of the respective leg of said secondary pair of legs, said windings being mounted in fixed relation to said primary core, and means to reciprocate said cores relative to each other. 7

8. A transformer providing for substantial variation of its secondary reactance in response to a variation of its secondary current, comprising, a stationary primary laminated and sub-' stantially U-shaped laminated magnetic core having a first pair of legs and a first yoke, a secondary laminated substantially U- shaped magnetic core coplanar with and inverted and reciprocable relative to said primary core and having a second pair of core legs and a second,

yoke, said second yoke being located and arranged to provide a magnetic bridge between the open ends of said primary core, said first yoke providing a magnetic bridge including a pair of variable air gaps between the open ends of said secondary core, a pair of stationary primary windings each encircling one of said first pair of legs and a pair of stationary secondary windings, each secondary winding encircling one of said first pair and the corresponding leg of said second pair of legs and having its inner circumferential wall spaced from the outer circumferential wall of the respective primary winding to afford passage therethrough of the respective leg of said secondary pair of legs and means to reciprocate said secondary core.

9. A transformer providing for substantial variations of its secondary reactance in response to a variation of its secondary current, comprising, a first pair of legs, an individual polar extension adjacent to one end of each of said legs and a first yoke connecting the other ends of said legs to form therewith a unitary substantially U-shaped primary magnetic core, a second pair of core legs and a second yoke to form therewith a unitary substantially U-shaped secondary magnetic core inverted relative to and coplanar with and reciprocable relative to said primary core, said second yoke being and said polar extensions being aligned to substantially close the magnetic circuit of said primary magnetic core, an inter- 5 mediate portion of said primary core providing a magnetic bridge including a pair of variable air gaps between the open ends of said secondary core, a pair of primary windings each encircling one each of said first pair of legs, a pair of secondary windings, each secondary winding encircling one each of said first pair of legs and the corre sponding one of said second pair of legs and having its inner circumferential wall spaced from the outer circumferential walls of the respective primary winding to afford passage therethrough of the respective leg of said secondary pair of legs and means to reciprocate said cores relative to each other.

10. A transformer providing for substantial variations of its secondary reactance in response to a variation of its secondary current, comprising, a first pair of legs, an individual polar extension adjacent to one end of said legs and a first yoke connecting the other ends of said legs to form therewith a unitary substantially U-shaped primary magnetic core, a second pair of core legs and a second yoke to form therewith a unitary substantially U-shaped secondary magnetic core inverted relative to and coplanar with and reciprocablerelative to said primary core, said second yoke being provided at each end with a polar extension to substantially close the magnetic circuit between the respective free end of each of said primary cores and said second yoke, a polar extension for each of said second pair of legs attached to said first yoke and aligned with the respective leg to provide with said first yoke a magnetic bridge including a pair of variable air gaps between the free ends of said secondary core, a pair of primary windings each encircling one each of said first pair of legs, a pair of secondary windings, each secondary winding encircling one each of said first pair of legs and the corresponding one of said second pair of legs and having its inner circumferential wall spaced from the outer circumferential walls' of the respective primary winding to afford passage therethrough of the respective leg of said secondary pair of legs and means'to reciprocate said cores relative to each other.

EDUARD FRIES.

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

UNITED STATES PATENTS Number Name Date 851,743 gGehrkens Apr. 30, 1907 2,032,705 Klinkhamer Mar. 3, 1936 2,411,370 Fries Nov. 19, 1946