US2471817A - Variable impedance device - Google Patents

Description

May 31, 1949. A, HERZ vAnIABLE IMPEDANcE DEVICE Driginal -Filed Aug. 19, 1942 s sheets-sheet 1 fg, AUM

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May 31', 1949. A. HERZ 2,471,817

I VARIABLE IMPEDANCE DEVICE Original Filed Aug. 19, 1942 3 Sheets-Sheet 2 @e 58k Y @5' @$959 J6 Wi@ I I I I I I I I I I l l l I I I I I I l I I I I I I I I I I I I I I May 31, 1949,

A. HERZ VARIABLE' IMPEDANCE DEVI-GE Original .Filed Aug. 19, 1942 3 Sheets-Sheet 3 .di J4 INVENTOR.

13k/MMM Patented May 31, 1949 UNITED STATES PATENT OFFICE VARIABLE IMPEDANCE DEVICE Alfred Herz, Chicago, Ill.

Original application August 19, 1942, Serial No.

455,283. Divided and this application December 16, 1943, Serial No. 514,505

. vide a relatively high impedance in a winding by virtue of its linking a closed magnetic circuit and for reducing the impedance of said winding by energizing another winding which completely surrounds the magnetic circuit and has a relatively low impedance so that when the other winding is energized both windings together offer a relatively low impedance to the flow of current therethrough and at the same time are capable of permitting the ow of a relatively large amount of current therethrough.

Another object of the invention is to provide an improved core structure for the above type of impedance device, including novel I adjusting means for adjusting air gaps in said core structure.

Another object of the invention is to provide an improved arrangement of reactance winding and exciting winding on said core structure, and particularly to provide an arrangement wherein the core structure forms a substantially closed magnetic circuit for the reactance winding but only forms a non-continuous or partial magnetic circuit for the exciting winding.

Other objects, features, and advantages of my invention will be apparent from the following detailed description of one preferred embodiment thereof.

In the accompanying drawings illustrating such embodiment:

Figure 1 is a diagrammatic view for the purpose of illustrating a typical use of my improved variable impedance device in an electric control system;

Figure 2 is a view, in end elevation, of the variable impedance device constituting the present invention;

Figure 3 is a view, in side elevation, of the variable impedance device shown in Figure 2;

Figure 4 is a top plan view of the variable impedance device shown in Figures 2 and 3;

Figure 5 is a detail sectional View taken along the line 5-5 of Figure 3;

.Figure 6 is a perspective view of the magnetic core structure employed in the variable impedance device;

Figure 7 is a detail sectional view taken along the line 'l-I of Figure 3; and

13 Claims. (Cl. 323-89) Figure 8 is a detail sectional view of one of the legs of the magnetic core structure shown in Figure 6.

The circuit diagram of Figure 1 serves to illustrate a particular field of utility of my improved variable impedance device in an electric control system, wherein the variable impedance device performs a regulating function on a supply circuit. Figure 1 also constitutes a schematic wiring diagram of the variable impedance device. In this gure it will be observed that the reference character I0 designates the source of alternating current, such as a cycle source. The source I0 is arranged to be connected by switches I I and I2 to load circuit conductors I3 and I4 to permit energization of the same. The load circuit conductors I3 and I4 are arranged to energize a load device, indicated generally at I5. In this particular instance the load device I5 is one which is particularly characterized by requiring the intermittent ow of relatively large amounts of current. A particular illustration of such a device is a spot welder which requires the flow of relatively large amounts of current during brief intervals.

The load device may `comprise a transformer, shown generally at I6, having a primary winding I1 arranged to be connected for energization to the load circuit conductors I3 and I4. The transformer I 6 includes a secondary winding I8 which, as shown, is connected to energize the spot welding electrodes I9.

The current ow to the primary winding Il of the transformer I6 and consequently the current flow 5between the welding electrodes I9 can be controlled in any suitable manner, now well known to those skilled in the art. For illustrative purposes a conventional timer controller is shown at 2D. The timer 2D may comprise suitable control apparatus for permitting the flow of current to the primary winding I'l in any desired manner. For example, the timer controller Z- may be arranged to permit the ow of a predetermined number of .cycles or half cycles of the alternating current as conditions may warrant. The timer controller 20 may be of the electronic type or of the contactor type as will be readily understood.

Now when provision is made for energizing a. load device, such as a load device I5, which requires that relatively large amounts of current flow periodically, the voltage across the load circuit conductors I3 and I4, as well as across the conductors connecting the source I0 to the switches I I and I2, varies more or less depending upon the stability of the system and its regulation. It often happens that other loads connected across the load circuit conductors. even when connected between the source Iii and the switches II and I2, are adversely aected by the application of the intermittent load applied by the Vdevice I5. This is particularly noticeable when a lighting load is connected across the load circuit conductors. When the load device i5 is energized,

. there is the tendency for the voltage across the load circuit conductors to dip or decrease and consequently the lights tend to icker in a corresponding amount.

As fully disclosed in the above parent application Serial No. 455,283, filed August 19, 1942, now Patent No. 2,401,156, I propose to rectify this undesirable situation by automatically connecting across the load circuit conductors I3 and I4 an auxiliary load of such character that the regulation of the system is substantially unaffected by the energization or deenergization of the load device I5. In this manner the eiective load supplied by the source is more or less constant in so far as the load device I is concerned, depending upon the degree of correction that is desired. It has been found that it is unnecessary to apply an auxiliary load which has exactly the same characteristics as the load device I5. The degree of correction that can be provided is determined by the economics of the situation and the amount of voltage dip which can be tolerated without being particularly objectionable. The auxiliary load device is arranged to be automatically connected across the load conductors l 3 and I4 so that the same is fully energized when the current flow to the load device I5 is reduced or ceases. As soon as the load device I5 is again energized, energize.- tion of the auxiliary load is reduced to a very low value.

The improved variable impedance device of the present invention can be employed very advantageously as the above mentioned auxiliary load device. This variable impedance device is indicated generally at 22. It comprises a magnetic core structure formed by side legs 23 and 2li and end legs 25 and 2t. The end legs 25 and 26 are arranged, as shown, to abut the adjacent sides of the legs 23 and 24. As will hereinafter appear the core structure is formed of laminated magnetic material. Around the leg 23 there is provided a winding 21 which is connected by conductors 23 and 33 for energizationto load circuit conductors I3 and I4. When the switches II and I2 are closed the Winding 21 is energized. However, since the winding 21 links a closed magnetic circuit formed by the legs 23, 24, 25, and 2S, its impedance is relatively high and a relatively small amount of current ows therethrough..

An exciting winding 3| is provided around both legs 23 and 24 of the magnetic circuit and is connected by conductors 33 and 34 for energization to the load circuit conductors I3 and I4. As will hereinafter appear, the winding 21 is formed in two sections and is distributed uniformly along the leg 23. Also, as will be set forth hereinafter the exciting winding 3| extends along substantially the full length of both legs 23 and 24 and around the winding 21. However, for illustrative purposes the windings 21 and 3| have been illustrated as shown in Figure 1 to clarify the disclosure. These windings 21 and 3| are so connected and arranged that when the exciting winding 3| is energized the alternating current control flux impedance winding 21 both have the same instantaneous direction of flow in the left hand leg 23 of the core structure.

Normally the exciting winding 3l is not energized. For the purpose of energizing it, switch means, shown generally at 35. are provided. As will hereinafter appear the switch means 35 are arranged to be closed when current ceases to flow to the load device I5.

When the switch means 35 are operated so as to energize the exciting winding 3|, a substantial amount of current flows therethrough in view of the fact that it does not link a closed magnetic circuit. Accordingly, the impedance of the exciting winding 3| is relatively low. The arrangement of the exciting winding 3i is such that on flow of current therethrough sufficient ux is generated by it to produce a high degree of saturation in the leg 23 of the core structure while the ilux in the leg 24 is reduced. As a result, the impedance of the winding 21 is materially reduced and the current iioW therethrough is correspondingly increased. The design of the variable impedance device 22 is such that the combined ilow of the currents through the windings 21 and 3| produces an effect which simulates that of the load device I5 whenit is energized. However, the power factor of the current fiowing to the variable impedance device 22 may be, and preferably is, substantially lower than the power factor of the current supplied to the load device I5. For example, the variable impedance device 22 may have a power factor at full load of the 4order of 5%. Because of this, the amount of actual power taken by the variable impedance device 22 is kept at a minimum. The net result of the auxiliary load or impedance device 22 is such as to aiect the regulation of the power system or feeder circuit so that voltage dips caused by power drafts taken by the welding or like load are within tolerable limits.

Any suitable formiof switch means 35 can be employed provided that it is capable of satisfactorily handling the current ow to the exciting winding 3I and can be controlled so as to substantially instantaneously follow the changes in the iiow of current to the load device I5.

For example, the switch means 35 may comprise a pair of ignition rectifiers 36 and 31 having control electrodes 38 and 39. As is well known the ignitrons 36 and 31 are of the mercury vapor type and each is arranged to conduct half cycles of one polarity. By connecting two of the rectifiers 35 and 31 in the conductor 34 in reverse, or backto-back, relation successive half cycles of the alternating current can be conducted. By controlling the excitation of the control electrodes 38 and 39, the conductivity of the rectiers 3S and 31 is correspondingly controlled. For this purpose rectiers 4U and 4| are provided for the rectifier 36 and the rectifiers 42 and 43 are provided for the rectifier 31. The circuit between the rectifiers 4| and 42 is controlled by means of separable contact members shown generally at 44 which are normally held in the closed position by a coil spring 45. An armature 46 is provided for cooperating with a core 41 and winding 48 for opening the contact members 44. The winding 48 is arranged to be energized from the secondary winding 49 of a transformer, the primary winding of which is a single turn and comprises the load circuit conductor I4. If desired, other means, such as electronic or electric valve control means, can be used in lieu of the contact members 44 and the associated operating means.

In operation, as long as current is being supplied to the load device il there is a predetermined current ilow through the secondary winding 43 of the current transformer and the armature II is attracted to the core l1. Contact members M are held in the. open position 'and the rectiers 36 and 31 are rendered non-conducting. No current then flows throughthe exciting winding 3|, and only exciting current'iiows through the winding 21.

As soon as the current ilow to the load device I5 ceases or isreduced'to a predetermined value, the amature 46 is' released and contact members Il are closed. The circuit between the rectiflers 4| and-.42 is then closed and the rectiers -38 and 31 are then rendered conducting during succesvsive half cycles 'as long as the contact members M remain in the closed position;l The rectiiiers 36 and 31 thenconduct successive halt cycles of the valternating current and the exciting winding 3| is energized. As previously described, the current flow through the exciting winding 3| is sumcient to increase the saturation oi the magnetic core structure and consequently the impedance of the winding 21 is materially reduced. The auxiliary load or variable impedance device 22 then has much the same effect on the power system as does the load device l5. Consequently, the `range in variation of the voltage across the load circuit conductors, caused by intermittent energization oi' the load device I5, is materially' reduced. The extent to which it is reduced will, of course, depend, as previously set forth, upon the economics of the situation and the degree of compensation that is required or the variation in voltage which can be tolerated. Il desired, the control of the auxiliary load device can be combined with the control of the welder, as i'or example with the timer controller 20, although I consider the separate control through relay M-l8 preferable.

The details oi construction that are desirable in the impedance device 22 are shown in Figures 2 through 8 of thev drawings, to which reference will now be had. Y l

As shown more clearly in Figure 6 of the drawings, the magnetic core structure is formed by the elongated legs 23 and 24 of laminated magnetic materialand members or legs 25 and 26 of the same material. The butt joints between the juxtaposed surfaces of the legs 23, 24, 25, and 26 will be noted. This butt joint construction is provided so as to permit varying the effectiveness ofY the magnetic circuit by varying the air gaps bev tween the abutting members by means which will be described hereinafter.

It will be observed in Figures 4 and 5 that the winding 21 is formed in two sections which are .magnetic circuit. The winding 3| is coextensive with the windings 21a and 21h.

AGenerally L-shaped clamp members 56 and 61 are provided-at the top and bottom of the core structure, as illustrated in Figures 2, 3, and 4 of the drawings, for the purpose of'holding the various parts in rigid spaced relation. The upstanding flanges of the L-shaped members 56 are spaced apart by a wood spacer 58 through which clamp bolts 59 extend. The spacer 58 can be extended lengthwise beyond the ends of the clamp members 56 to provide a means for supporting or rigidly locating the entire assembly in a metallic tank, if desired.

The lower L-shaped clamp members 51 are spaced apart by a wood block 60 and clamped in place by bolts 6|. Feet 62 extend outwardly from the depending portions of the clamp members 51 to provide a footing for the device as it is mounted on the bottomof a tank. Longitudinally extending bolts 63 serve to interconnect the parallel ilat portions of the clamp members 5,6 and 51.

As previously indicated, the variable impedance device is intended to be mounted in a tank and to be covered with a suitable insulating and/or cooling liquidas is conventional in transformer practice. In order to facilitate circulation of the insulating liquid the flat portions of the clamp members 56 and 51 are provided with large openings 64, Figure 4, some of which register with the spaces between the various windings mounted on the core structure.

With a view to providing for adjusting the air Vgaps between the legs making up the main leg core structure, adjusting screws 61 yare provided in yokes 68 which extend between the upwardly and downwardly extending portionsV of the clamp members 56 and 51 respectively. By tightening or loosening the adjusting screws 61 it is possible to decrease or increase the air gaps between the juxtaposed surfaces of the legs making up the magnetic core structure. If desired, non-metallic spacer shims can ybe provided between these juxtaposed surfaces to increase the rigidity of the j magnetic core structure.

Since various changes can lbe made in the foregoing construction of variable impedance device without departing from the spirit and scope of the present invention, it is understood that the As shown m Figure e of the drawings, suitable clamp members 53 are provided along the leg 23, and clamp bolts 54serve to hold them, and thereby the laminations making up the leg 23, in4 place. 'Ihe laminations making up the legs 2l, 25, and 26 are held together by through bolts, the apertures forwhich are shown in Figure 6.

-subject matter set forth hereinbefore and shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

I claim as my invention:

1. In a variable reactance device, the combination o`f a closed magnetic core structure, a reactance winding confined solely to one leg of said core structure, said reactance winding being adapted to be connected in shunt across an alternating current load circuit, and an alternating current saturating winding entirely surrounding said core structure and adapted to be energized from said alternating current load circuit, said reactance winding and said saturating winding being so connected to said source of said alternating current load circuit that during the successive alternations of thealternating current the reactance flux generated by said reactance winding and the saturating flux generated by said saturating winding always have the same directions of flowV in said one leg of the core structure.

`2. In a variable reactance device of the class described, the combination of a generally rectangular magnetic core structure having two sideV legs and tcp and bottom connecting legs, a reactance winding mounted on one of said side legs, said reactance winding being adapted to be connected in shunt across an'alternating current load circuit, and an alternating current saturating winding wound entirely around both of said side legs and adapted to be energized from said alternating current load circuit, said reactance winding being conned solely to said one side leg of said core structure and said saturating Winding being so connected to said alternating current load circuit that for each alternation of said current the saturating flux generated by said saturating winding and the reactance flux generated by said reactance winding always have the same direction of ow in said one side leg'of the core structure, whereby the saturating flux from the saturating winding has a minimum tendency to generate a counter electromotive rforce in said reactance winding.

3. A variable impedance device comprising, in combination, a generally rectangular magnetic core structure, a reactance winding, the impedance of which is to be varied, confined solely to one leg of said core structure, and an alternating current exciting winding entirely surrounding said core structure for varying the degree of saturation of said core structure and thereby the impedance of said reactance Winding, said core structure, reactance winding and exciting winding being so constructed and arranged that the alternating current reactance flux produced by said reactance Winding and the alternating current control flux produced by said exciting winding always have the same instantaneous direction of ow in that leg of said core structure on which said reactance winding is mounted.

4. A variable impedance device comprising, in combination, a generally rectangular core structure formed by legs of laminated magnetic material and an air gap in series with said legs, an alternating current reactance winding, the impedance of which is to be varied, confined solely to one leg of said core structure, and an alternating current exciting winding surrounding opposite pairs of legs of said core structure and adapted to be energized from the same source of alternating current as said reactance winding for varying the degree of saturation of said core structure and thereby the impedance of said reactance winding, said core structure and said reactance and exciting windings being so conthe reactance winding to said one leg of the core structure minimizes any tendency of the alternating current control flux produced by said exciting winding to generate a counter electromotive force in said reactance winding.

6. A variable impedance device comprising, in combination, a generally rectangular core structure formed by legs of laminated magnetic material disposed in abutting relation with an air gap in series with said legs, a reactance winding,

the impedance of which is to be varied, Wound solely around one leg of said core structure, and an alternating current exciting winding surrounding opposite pairs of legs of said core structure and superposed over said reactance winding, said windings, being in inductive relation, said exciting winding adapted to be energized from a source of alternating current for varying the degree of saturation of said core structure and thereby the im-pedance of said reactance winding, said core structure affording a substantially continuous magnetic path for said reactance winding and a substantially non-continuous magnetic path for said exciting winding, the reactance ilux of said reactance winding and the control ux of said exciting winding both having the same instru'cted and arranged that when the exciting winding is energized the alternating current control ux produced by said exciting winding and the alternating current reactance flux Iproduced by said reactance winding both have the same instantaneous direction of ow in that leg of said core structure on which reactance winding is mounted, the current flow through said exciting winding making up a substantial part of the phantom load of said variable impedance device.

'5. A variable impedance device comprising, in

combination, a closed magnetic core structure, an.

alternating current reactance winding, the impedance of which it to be varied, confined solely to one leg of said core structure, and an alternating current exciting winding entirely surrounding said core structure and adapted to be energized from the same source of alternating current as said reactance winding for varying the degree of saturation of said core structure and thereby the impedance of said reactance Winding, said windings being in inductive relation, said core structure affording a substantially continuous magnetic path for said reactance Winding and a noncontinuous magnetic path for said exciting winding, said core structure and windings being so constructed and arranged that 4the confinement of stantaneous direction of flow in that leg of said core structure on which said reactance winding is mounted, and the confinement of the reactance winding to said one leg of the core structure minimizing or preventing the alternating current control ux produced by said exciting winding from generating a counter electromotive force in any portion of said reactance winding.

'7. A variable impedance device comprising, in combination, a generally rectangular core structure formed by legs of laminated magnetic material disposed in abutting relation, an alternating current reactance winding divided into two sections and both mounted concentrically on only one leg of said core structure, said two sections being spaced to permit a cooling circulation therebetween, and an alternating current exciting winding surrounding opposite legs of said core structure and superposed over said reactance winding, said exciting winding being adapted to be energized from the same source of alternating current as said reactance winding for varying the degree of saturation of said core structure and thereby the impedance of said reactance winding, said core structure and winding being so constructed and arranged that the alternating current control ux produced by the exciting winding and the alternating current reactance llux produced by the reactance winding both have the same instantaneous direction of flow in that leg of said core structure on which said reactive winding is mounted, the intermittent current flow through said exciting winding making up a substantial part ofthe phantom load of said variable impedance device.

8. In a variable impedance device for producing a phantom load, the combination of a generally rectangular core structure formed by legs of laminated magnetic material disposed in abutting relation, an alternating current reactance Winding, the impedance of which is to be varied, linking one leg of said core structure, and an alternating current exciting winding of D-shaped contour so located on said core structure that a portion of the core structure is located between said exciting winding and said reactance winding, said core structure and windings being so constructed and arranged that the alternating current control ux of said exciting winding and the alternating current reactance ux of said reactance winding both have the same instantaneous direction of flow in that leg of said core structure on which said reactance winding is mounted, said reactance winding and said exciting winding both being supplied from the same load line whereby the alternating current ilow through both the reactance winding and the exciting winding at the time of excitation together make up the phantom load of the variable impedance device.

9. In a variable impedance device comprising. in combination, a generally rectangular core structure formed by legs of laminated magnetic material, said legs being disposed in close proximity with air gaps between the juxtaposed surfaces of said legs, an alternating current reactance winding, the impedance of which is to be varied, conilned solely to one leg of said core structure and adapted to be connected to a load line, an alternating current exciting winding surrounding opposite legs o1' said core structure and adapted to be energized from the same load line as said reactance winding for varying the degree of saturation of said core structure and` thereby the impedance of said reactance winding, and adjusting means enabling said air gaps between the juxtaposed surfaces of said core structure legs to be increased or decreased, the alternating current vrlow through both the reactance winding and the exciting winding at the time of excitation of the latter together making up, the phantom loadA oi the variable impedance device.

10. In a variable impedance device for producing a phantom load on an alternating current circuit in alternating sequence with a line load thereon, the combination of a generally rectangular core structure formed by legs of laminated magnetic material, certain of said legs being disposed in close proximity to each other with small air spaces defined between the juxtaposed surfaces of said legs, a reactance winding, the impedance of which is to be varied, conilned solely to one leg of said core structure and connected to said alternating current circuit, an a1- ternating current exciting winding surrounding opposite legs of said core structure and also connected to said alternating current circuit, said exciting winding serving to vary the degree or saturation of said core structure and thereby the impedance of said reactance winding when said exciting winding is energized, the alternating current now through both `the reactance winding and the exciting winding at -the time of excitation together making up the phantom load of the variable impedance device, brackets secured to said core structure adjacent to said air gaps, and adjusting screws carried by said brackets and operative to increase or decrease the size of said air gaps.

11. In a variable impedance device for producing a phantom load on an alternating current circuit in alternating sequence with a line load thereon, the combination of a generally rectangular core structure formed by legs of laminated magnetic material disposed in abutting relation, an alternating current reactance winding divided into a plurality of sections mounted concentrically on only one leg of said core structure, said seclatter together making up the phantom load of l th-e variabler impedance device, the D-shaped contour of said exciting winding establishing a relatively large oil circulating passageway between said reactance and exciting windings along the other leg of said core structure.

12. In a variable impedance device for producing a phantom load on an alternating current circuit in alternating sequence with a line load thereon, the combination of a generally rectangular magnetic core structure, an alternating current reactance winding and an alternating current exciting winding both mounted on said core structure, said reactance winding being connected in shunt acrosssaid alternating current circuit and said exciting winding being adapted for connection in shunt across said alternating current circuit in alternating sequence with said line load, said core structure affording a substantially continuous magnetic path for saidreactance winding and a non-continuous magnetic path for said exciting winding, and said reactance winding being so disposed on said core structure that it is nonsymmetrical with respect to said exciting winding.

13. In a variable impedance device, the combination of a generally rectangular'magnetic core structure, an alternating current reactance winding on saidcore structure, an alternating current exciting winding on said core structure, said core structure affording a substantially continuous magnetic path for said reactance winding and a non-continuous magnetic path for said exciting winding. and said reactance winding being so disposed on said core structure that it is non-symmetrical with respect to said exciting winding.

ALFRED HERZ.

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

UNITED STATES PATENTS Number Name Date 1,563,354 Fortescue Dec. 1, 1925 1,724,968 Schelleng Aug. 20, 1929 1,870,093 Boyajian et al. Aug. -2, 1932. 2,127,237 Sola Aug. 16, 1938 2,333,015 Kramer et al. Oct. 26, A194:3

FOREIGN PATENTS Number Country Date 376,867 Great Britain July 2.1, 1932

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