US1868484A - Transformer - Google Patents

Description

A. O. AUSTIN TRANSFORMER July 26, 1932.

Filed June 27, 1951 3 Sheets-Sheet l INVENTOR Arffiz/I 0.4052772 BY Q CZ MVQ. wfl

ATTORNEY July 26, 1932- A. o. AUSTIN 1,863,484

TRANSFORMER Filed June 27, 1951 5 Sheets-Sheet 2 Fly 0' INVENTOR Arf/lur 0 fluff/)7.

A. O. AUSTIN TRANSFORMER July 26, 1932.

Filed June 27, 1931 5 Sheets-Sheet 5 m w J U n AV R0 W mw@ R N O E T T m W Patented July 23, 1932 UNITED STATES PATENT OFFICE ARTHUR O.-AUSTIN, OF NEAR BARBER/TON, OHIO, ASSIGN OR, BY MESNE ASSIGNMENTS, TO THE BRASS COMPANY, OF MANSFIELD, OHIO, A CORPORATION OF NEW JERSEY TRANSFORMER Application filed June 27,

This invention relates to equipment for bushing insulators by means of which energy may be diverted from a high-potential conductor passing through the insulator.

One object of the invention is to provide a bushing insulator equipped with a plurality of current transformers which will supplement one another.

A further object is to provide a bushing insulator having means connected therewith for furnishing current of different characteristics for different purposes.

A further object is to provide a bushing insulator equipped with a ring type transformer in which objectionable features heretofore experienced are eliminated.

Other objects and advantages will appear from the following description.

The invention is exemplified by the combination and arrangement of parts shown in the accompanying drawings and described in the following specification, and it is more particularly pointed out in the appended claims.

In the drawings:

Fig. 1 is an elevation with parts in section of a bushing insulator equipped with one form of the present invention.

Fig. 2 is a fragmentary sectional View showing a slightly modified form of the invention.

Fig. 3 is a diagrammatic vertical section of a modified form of the invention.

Fig. 4 is a diagrammatic sectional elevation showing a modified secondary winding.

Fig. 5 is a view similar to Fig. 3 showing another modification.

Fig. 6 is a view similar to Fig. 4 showing another modification.

Fig. 7 is a top plan of Fig. 4.

Fig. 8 is a top plan of Fig. 6.

Figs. 9, 10, 11 and 12 are views similar to Figs. 4; and 5 but showing modified arrangements of the invention.

In the operation of high voltage transmission lines, it is frequently desirable to obtain current from the line for metering or other purposes requiring current transformers to obtain this current. The high insulation between the conductor and ground makes 1931. Serial N0. 547,257.

the construction of a current transformer for this purpose expensive. Where the insulation of a bushing, installed on the line for another purpose, can be used for the insulation between the primary and the secondary of the current transformer, it may be possible at relatively small extra cost to provide a current transformer for metering, current indication, relaying, operating trip coils or other purposes. W here the currents in the conductor are large, it is comparatively easy to design a current transformer of the single turn type. Where the currents are small, however, which is frequently the case at very high voltages, the ampere turns affecting the iron core of the ordinary single turn type of transformer may be so low that the characteristics or output of the current transformer are poor. In the ordinary ring type of current transformer, a magnetic core having a large diameter and long magnetic path is used to provide increased separation between the primary and secondary, so as to avoid the necessity for expensive insulation. This tends to increase the reluctance of the magnetic circuit and results in a poor transformer.

In my prior Patent #1,699,342 there 1s shown an arrangement of a ring type transformer inside of a bushing insulator, and some of the advantages of this arrangement are explained. In my present improved arrangement it is possible to equip the bushing with one or more ring type current transformers and, at the same time, provide the bushing with a current transformer having its primary wound about a magnetic core. The arrangement is such that the rmg type current transformer does not produce a shortcircuit turn about the core of the primary,

thereby making it possible to use the magnetic circuit produced by the wound primary. This current transformer may be used separately or in conjunction with one or more secondaries .of the ring type. It is POSSlble to use the voltage induced by either transformer in series or multi le with the other to change the characteristlcs so as to provlde increased output, or to correct phase angle or ratio. In addition to'the current transformers, the bushing may be equipped with an insulated control. The transformer having its primary wound about a core with the main path of flux in an axial direction makes it possible to obtain a bushing having the necessary'in'sulation and, at the same time,

. one which will give the desired output from the secondary, even though the amount of current in the primary is small.

In the embodiment shown in Fig. 1 the conductor 10 carrying the main current is wound around a magnetic core 11, as disclosed in my prior 'Patent #1,723,000. This primary winding may consist of any number of coils which may be used in series or multiple as desired. The current in passing from an incoming terminal 12 to an outgoing terminal or lead 13 may be used as a slngle turn primary to energize the secondary of a current transformer in the same way as if the conductor lead extended straight through the bushing; for the current passes through the bushing regardless of the number of turns it makes about the core 11.

This single turn primary will energize the magnetic cores 14 and 15 of ring type ourrent transformers; the cores of which are arranged just inside of the bushing shells as shown. The cores 14 and 15 are provided with windings 16 and 17 in the usual manner.

These windings may be provided with the.

necessary taps or made up into coils which may be connected in series or multiple. A secondary winding 18 has its turns coaxial with the multiturn primary 10 and magnetic core 11, and is energized by the field set up in core 11 by winding 10. The magnetic cores 14 and 15 of the ring type transformers may be used to direct the return flux from the core 11 affecting the secondary 18 of the transformer with multiturn primary. Leads 19 are connected with the secondary 18. The current passing through the bushing will set up a flux in the cores 14 and 15 in a circumferentialdirection. The field set up by the multiturn primary 10 will tend to set up a flux in a vertical direction in the core 11 and in the cores 14 and 15. The cores 14 and 15 provide a path for at least a portion of the flux which energizes the secondary 18, as described in my prior Patent #1,7 23,000.

I This flux being in a vertical direction affects the winding 16 and 17 little if any, as the flux energizing these windings is due to the single turn and is in a circumferential direction in the cores 14 and 15. The cores of thetransformers 14 and 15 can be used'to direct the flux affecting the primary 18 so as to make this flux more effective. This effect may be materially improved by tipping the outer edges of the ring cores inwardly at an angle so as-to reduce the reactance in the secondary 18 and reduce the" reluctance of the air path toward the ends of the magnetic circuit of the winding 10. An arrangement of this kind is shown in Fig. 2.

Other arrangements may be used so that the return path of the flux for the wound primary 10 may pass through not only the cores of the ring type current transformers but through a supplemental magnetic path tending to complete the circuit. It frequently happens that this magnetic circuit may be partially completed by bushing flanges or metal around the outlets of the bushings. The return path which is sufliciently far-outside of the secondary 18 may constitute a short-circuit turn without materially affecting the operation of the secondary 18. However, by using my improved core construction, shown in my application Serial Number 506,380, filed January 3, 1931, it is pos-,

fecting the cost of the installation or the performance of the current transformer. The large diameter in the bushing shells tends to reduce the electrostatic stress. This is particularly important for circuit breaker work where the insulator parts working in a strong electrostatic field may become coated with conducting material due to electrostatic precipitation, thereby reducing the efficiency of the surfaces. The current transformer with the wound primary may be used'where the current in the primary lead is small. For heavycurrents, this winding may be bypassed or shunted and the secondaries of the ring type current transformers used.- This transfer may be provided automatically, as shown in Fig. 3, by means of a relay QO. or, if desired, the secondaries of the various transformers may be used for entirely independent operations. Practically any number of ring type transformers may be used, as well as a transformer having the wound primary, thereby providing the bushing with current transformers which can be used to cover a wide'range of requirements.

Bywinding the cores 14 and 15 with the turns at an oblique angle to the core axis, as

shown in Fig.4, it is possible to make a por- I tion' of the flux produced by the wound primary thread the turns of the secondaries 16 by winding the secondary at an angle, as shown in Fig. 4, .or by arranging the magnetic core so that the flux produced by the wound primary and core 11 will thread some of the turns of the secondary of the ring type current transformers as shown in Fig. 2.

As shown in Fig. 5, it is possible to place a few tu rns 21 in a plane normal to the axis of the bushing on the inside of the cores 14 and 15 and in series with the windings 16 and 17 so as to utilize the flux set up by the wound primary in the core 11 in conjunction with the cores 15. While these turns 21 will affect the current in the secondary 18, this effect .will be small if theturns 21 are at a considerable distance from the turns 18 so as not to affect the return flux path of the secondary 18. These turns 21 may be used in series with the secondaries 16 and 17 or, as shown in Fig. 6, they may be made to energize the cores 14' and 15 by connecting them to turns 22 which will change the magnetic flux in a circumferential direction in the cores 14 and 15.

It is seen that an arrangement of this kind makes it possible to increase or decrease the magnetic flux in the cores 14 and 15 over that produced by the single turn primary. This arrangement may be used either with a single transformer or with the two different types of current transformers, depending upon the results desired. The arrangement may be used to increase output, to change the general characteristics of output or correct phase an gle. If the effect upon 18 is neglected, the characteristics of the ring type transformer may be changed materially by this auxiliary or compensating winding. By regulating the flux in the core 11 either by the size and nature of the magnetic material or the number of. ampere turns, the flux set up in the cores 14 and 15 may be made to vary greatly from that set up by the flux in the-ring type core, depending on the single turn provided by the main conductor.

tential in the auxiliary winding which can be used tobuck or boost the potential generated by the ordinary ring type. This mav be used to correct ratio or change the general characteristics of the output of the secondary.

Where the core 11 and winding 10 are such that saturation occurs very early, the flux set up in the auxiliary winding may be made to oppose the voltage in the secondary of the ring type winding so that the ratio will be increased for low currents. If the voltage induced by the auxiliary winding is made to increase the voltage of the ring type secondary, a drooping characteristic of the output may be obtained which may be an advantage in providing a large output at lower currents for the operation of relays or tripping circuits, but which will prevent damage to the The flux roduced by the wound primary may be made to set up a po-.

insulated from ground. The secondaries of the transformers may be covered with an electrostatic shield as previously explained in my prior Patent #1,699,342. The cores of the ring type transformer may be made in two portions which will abut together or in which the laminations will overlap, thus permitting'them to be assembled in a groove,- as in Fig. 2; the winding being placed on the two portions. As explained in my prior application Serial Number 506,380, the flux in the tangential path or core may be materially changed by magnetic shunts, tending to regulate the path'of flux between different layers and between different turns in the magnetic circuit. By using the shunts, the reluctance of the magnetic path may be made much lower for one portion of the core than for other portions of the core to change the characteristics for the output of the current transformer.

Where the current range is large, several methods may be used intransferring the burden from one type of transformer to the other. As shown in Figs. 9 and 11 the secondary of either the transformer of the ring type or of the one having the wound primary may be provided with a relay which will shift the burden from One transformer to the other when the load exceeds certain limits. In Fig. 9 the relay 25 is energized by a few turns of the secondary 26 and when energized connects the secondary 26 to the burden through leads 27. Wher'i' the current in the primary 10 reaches a predetermined value, the relay shunts the winding 10, de-energizing the winding 10 and its secondary 26, so that the relay 25 is de-energized and the burden is shifted to the ring type secondary 28. The transformer having the wound primary is thus used for the burden while the current in the primary is small but when theprimary current exceeds a given value, the current induced in the relay placed in the secondary will shift the load from the secondary of the transformer having the wound primary to the secondary of the ring type transformer. This arrangement makes it possible to provide "a transformer having a high degree of accuracy even for the very small currents inthe primary and, at the same time, will permit offlthaconstruction of a transformer which will have good characteristics for very heavy currents. When the current is high. the wound primary may not have sufficient current carrying capacity but when the cur- W rent exceeds a given value, the relay QO is rent. The relay for transfer from one secondary to the other may be energized from either secondary, providing the arrangement is such that the shunting of the current in the primary winding is taken into account.

The relay in the secondary circuit may be of either the magnetic type or a thermal type, or a combination of the two where the load tends to fluctuate rapidly. Since the secondaries of the two types of transformers may be made to have the same, general chartermined value.

In the construction shown in Fig. 10, the relay 33 is in series with the burden during light loads but as the load increases, the relay is energized to connect the resistance 34 in series with the secondary 26 and the relay 33 and disconnect the burden from this circuit. The resistance 34: is connected into the circuit before the burden is disconnected so that there is no discontinuation of current in the relay 33. At the same time that the burden is disconnected from the secondary 26, the secondary 28 is connected to the burden by'a supplemental contact 35 actuated by the relay 33.

In some arrangements, as shown in Fig. 12, it may be advisable to use the secondariesof the two types of transformers either in series or multiple to supply the burden. The relay may then be used to correct ratio or phase angle by changing the impedance inthe circuit or the relative number of turns on the secondaries. c a

In the arrangement shown, the secondaries 26 and 36 are connected in series to the burden and the relays 37 and 38 are energized by a supplemental secondary 39 and-control the ratio and phaseangle by adjusting the impedances 40.

Where both windings are used together, a wound primary 10 can be used to furnish the energy for low current values. As the current increases and the core of the primary winding 10 becomes saturated, the ring type transformer with lower saturation will compensate for the saturated core.

I claim 1. A current transformer comprising a primary conductor having a plurality of series turns disposed in planes transverse to the general direction of the conductor, a ring type magnetic core encircling said primary,

a secondary winding on said core, and an additional secondary winding encirclin said primary and disposed within the cylin er defined by said core.

2. The combination with a bushing insulator, of a current transformer having; a primary conductor extending through said insulator, said conductor having a plurality of series turns disposed within said insulator and transverse to the axis thereof, a ring type magnetic core disposed within said bushing insulator and encircling said primary and a secondary winding on said core.

3. A current transformer comprising a primary conductor having a plurality of series turns disposed in planes transverse to the general direction of the conductor, a ring type magnetic core encircling said primary, a secondary Winding on said core and an additional secondary winding encircling said primary and disposed within the cylinder defined by said core, said secondary windings being connected to modify the output of one by the other.

4. A bushing insulator comprising a primary conductor having series turns disposed in planes transverse to the general direction of said conductor, a secondary winding encircling said primary conductor and energized by lines of force setup by said series turns, a magnetic ring encircling said primary conductor-and disposed outside of said secondary winding for directing said lines of force, and an additional secondary winding on said magnetic ring.

5. The combination with a bushing insulator, of a primary conductor extending through said insulator andhavingseries turns disposed in planes transverse to the axis of said insulator, a secondary Winding encircling said primary turns and energized by the lines of force set up by said turns, a magnetic ring disposed outside of said secondary winding and encircling said primary conductor, and an additional secondary winding on said magnetic ring energized by the lines of force set up by said primary conductor in a circumferential direction about said conductor.

6. The combination with a bushing insulator, of a magnetic core disposed within said insulator and having its axis extending in the direction of the axis of said insulator, a primary conductor extending through said insulator and having a plurality of turns wound about said core, a secondary winding encircling said primary turns and energized by the lines of force set up in said core by said turns, a magnetic ring disposed within said insulator and outside of said secondary winding and-encircling said conductor, and a secondary winding on said magnetic ring and energized by the lines of force set up by I said primary winding of a circumferential direction in said ring.

7. The combination with a bushing insulasecondary turns encircling said core and energized by the lines of force set up in said core by the primary turns surrounding said COI'B.

8. A current transformer comprising a conductor having a plurality of series turns disposed in planes transverse to the general direction of said conductor, a magnetic ring encircling said primary winding, a secondary winding on said ring having the turns thereof disposed in planes transverse to the circumference of said ring, said secondary winding being energized by circumferential lines of force set up in said ring by said primary conductor, and means for correcting the output of said secondary winding comprising supplemental secondary turns disposed Within the cylinder defined by said ring and arranged in planes transverse to the axis of said primary turns, said supplemental winding being energized by the lines of force set up by said primary turns.

9. The combination with a bushing insu lator, of a magnetic core disposed within said insulator and extending in the direction of the axis of said insulator, a conductor extending through said bushing insulator and having series turns wound about said magnetic core, a secondary winding encircling said primary turns and disposed in planes transverse to the axis of said turns, a magnetic ring surrounding said primary conductor and disposed within said bushing insulator outside of said secondary winding, and an additional secondary winding having the turns thereof wound on said magnetic ring and disposed in planes transverse to the circumference of said ring.

10. The combination with a bushing insulator, of a primary conductor extending through said insulator having a plurality of series turns disposed in planes transverse to the axis of said insulator, a secondary winding encircling said primary winding and disposed in planes transverse to the axis of said insulator, a plurality of magnetic rings encircling said primary conductor and disposed outside of said secondary winding and within said bushing insulator, and secondary windings on said ma netic rings having the turns thereof dispose in plane's transverse to the circumferences of said rings.

11. The combination with a bushing insulator, of a magnetic core disposed within said insulator and extending in the direction of the axis of said insulator, a conductor extending through said insulator and having a plurality of series turns wound upon said core, a capacitance member Within said insulator and insulated from said conductor and forming therewith a capacitance coupling, a secondary winding encircling said series turns and energized by the magnetic lines of force set up in said core by said series turns, a magnetic ring encircling said primaryconductor and disposed within said insulator outside of said secondary winding, an additional secondary winding upon said magnetic ring and having the turns thereof arranged transverse to the circumference .of said ring and energized by the circumferential lines of force set up in said ring by said primary conductor, and conductor leads connected with said secondary windings and With said capacitance member respectively.

12. A current transformer comprising a conductor having series turns disposed transverse to the general direction of said conductor, a magnetic ring encircling said conductor and a secondary winding, on said ring, the turns of said secondary winding being disposed obliquely to the axis of said primary turns so that said secondary turns will be threaded by lines of force extending circumferentially in said ring about said conductor, and also by lines of force extending parallel to the axis of said primary turns.

13. A current transformer comprising a primary conductor, a magnetic ring encircling said conductor and having the sides thereof disposed at an oblique angle to the axis of said conductor, and a secondary winding on said ring.

14..A current transformer comprising a conductor having series turns disposed transverse to the general direction of said conductor, a pair of frustro-conical shaped magnetic rings encircling said conductor and having their largest portions adj acent-each other, secondary windings on said rings, and an additional secondary winding having the turns thereof disposed in planes transverse to the axis of said primary turns and disposed Within said magnetic rings.

15. The combination with a bushing insulator, of a primary conductor extending through said insulator and having a plurality of series turns disposed in planes transverse to the axis of said insulator, a secondary winding encircling said primary winding, frustro-conical shaped rings disposed outside of said secondary winding for directing the magnetic lines of force set up by said primary turns outside of said secondary winding and additional secondary windings on said lator, of a magnetic core extending along the axis of said insulator, a primary conductor extending through said insulator and comprising a primary winding on sa1d core, a secondary winding insulated from sa1d mag- 6 netic core and energized by the flux from said core, and a separate magnetic core insulated from said first named core and from the primary winding thereon and energized by the current in the primary conductor.

10 17. A current transformer comprising a core and a primary circuit including a'windong on said core, said transformer havlng two secondaries, one energized by the flux from said core and the other being of the ring 1 typeand having a magnetic core energized by the current of said primary circuit, said circuit forming asingle turn for said ring type core.

18. In combination a bushing insulator and a current transformer associated with said insulator, said transformer comprising a magnetic core and a primary circuit ineluding a winding on said core, said transformer having a secondary normal to the axis of the bushing and energizing by magnetic flux set up in said magnetic core,and another secondary of the ring type energized by the current passing through the bushing, the core of the ring type transformer being so 3 disposed as not to interfere with the excitation of the secondary with turns normal to the axis of the bushing.

19. A current transformer comprising a magnetic core and a primary circuit constitutinga single turn primary and a winding for sald core, said transformer having two secondaries, one of said secondaries being energized by said single turn primary and the other being energized by the flux from said 4 magnetic core.

20. A current transformer comprising two secondaries, one of which is energized by a closed magnetic circuit and the other energized by an open magnetic circuit.

4 21. A current transformer comprising two secondaries, one of which is energized by aclosed magnetic circuit and the other energized by an open magnetic circuit, the whole being so arranged that the secondaries do not interfere with each other.

22. A current transformer having a wound primary with a corresponding secondary, a ring type secondary, means of connecting a load to the secondary of the wound type for low current values in the primary, and means for transferring the load to the ring type for hi h current values.

n testimony whereof I have signed my name to this specification this 26th day of June A. D. 1931.

ARTHUR O. AUSTIN.

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