US1373910A - System of distribution - Google Patents

Description

W. A. PRESSEY.

SYSTEM OF DISTRIBUTION.

APPLICATION FILED APR.23, 1920.

'1,373,9 1 O. Patented Apr. 5, 1921.

. Fig.2. ea 29 2a 29 2a 27 v FL I I u ,2, [I 2 5 7 [1/ 3' T LII I 28 28 28 Inventor:

Wilbur A.'Pr-'esse WWW His Attorney.

WILBUR A. PRESSEY, OE BOSTON, MASSACHUSETTS, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A. CORPORATION OF NEW YORK.

SYSTEM OF DISTRIBUTION.

Specification of Letters Patent.

Patented Apr. 5, 1921.

Application filed April 23, 1920. Serial No. 375,973.

tribution and more particularly to an alternating current polyphase system wherein the load is of such a character that it 1s necessary to transform the voltage of the source.

In such polyphase alternating current systems of distribution it is frequently necessary to Vary slightly the ratio of transformation from the source to the load, in order to take care of variations in line drop, or

other conditions necessitating the same remedy. Especially is this true of systems in which the source has a comparatively high E. M. F. transformed to a comparatively low E. M. F. for supplying the load. In systems of this character, the load, being a variable uantity, and being connected t9 the secon ary or low voltage side of the transforming apparatus may at times increase to such an extent that there is supplied a relatively heavy current over the conductors carrying the load; and thus there is caused an appreciable impedance drop at the point where the load is supplied. To maintain the voltage constant at this point it is necessary to increase the voltage at the source as the load increases, and on the other hand to decrease the voltage at thesource when the load decreases. In systems heretofore used it has been necessary to disconnect the load entirely and thus interrupt the service while the voltage adjustments were being made at the transformer. It is one of the objects of my invention to make it possible to vary the voltage supplied to the load circuit without interrupting the service. Another object of my invention is to insure the proper sequence of operation so that no serious unbalancing of the polyphase system may result. Another obje'ctof myinvention is to provide simple and inexpensive means for performing the various steps. Other objects and advantages of my invention will be apparent as the description proceeds.

The construction and mode of operation of my invention may be understood by reference to the accompanying drawings, in Whlch F lgure 1 shows the complete wiring (Ila-gram of the entire system, and particularly how the transforming apparatus is connected both to the source and to the load; and Fig. 2 is a view showing more in detail the apparatus for insuring proper sequence of operation for varying the voltage, and for the prevention of appreciable unbalancing.

Referring now more in detail to the drawin s, in which like reference characters refer to like parts throughout, I show a source of polyphase alternating current, in this case the three- phase mains 11, 12 and 13. This source of alternating current, after its voltage is appropriately transformed, supplies the load designated by the numeral 26. The transforming apparatus in this case consists of a plurality of primary and secondary coils, each primary coil being inductively associated with its corresponding secondary coil and so related to the other coils that all of them form a polyphase trans forming system. These coils may be arranged to form independent single-phase transformers, or else arranged on a single core to form one polyphase transformer. The primary coils 14, 15 and 16 are connected in any appropriate fashion to the mains 11, 12, and 13; these coils are shown in the present instance as delta connected. Each secondary coil is made up in this case of two parts, although a single part may be used as well. These secondary coils are thus made up of the coil sections 17, 18, 19, 20, 21 and 22 connectedtogether in as shown. Appropriate means are provided for varying the effective turns of the secondary coils of the transformers. In this case the means for accomplishing this result are conveniently inserted between the pairs of coil sections and comprise plugs and receptacles for varying the number of turns in the secondary coils by connecting any one of a plurality of taps on one coil section to any of the taps on the other coil section. The secondary coils are connected in delta by means of appropriate switching devices.

23, 24 and 25, which switching devices are so arranged that by opening any one of them, one of the secondary coils 1s disconnected entirely from the closed delta conof the secondary coils by small increments rendered inactive.

comprise a plurality of receptacles and a plug adapted to make electrical contact therein for controlling the tap change of the coils. While in this case the plugs and receptacles are adapted to make direct contact with the taps, it is evident that appropriate relay means may be used to accomplish the same result, if such be necessary. Receptacles 1, 2, 3, land 5 are arranged to cooperate with a plug to control the number of turns of the secondary coil comprisin the two sections 17 and 18; the receptac es 1, 2', 3', 4c-'and 5 cooperate in the same way with the secondary 'coil comprising the sections 19 and 20; and receptacles 1", 2", 3", 4" and 5" likewise cooperate in the same way with the secondary coil comprising the sections 21 and 22. In this instance, three taps are taken .from each left-hand coil section and two from each right hand coil section. The two coil sections are connected in series by means of these taps through one or other of the receptacles and the cooperating plug. The taps are located in such a way that by inserting the plug successively in receptacles l to 5 a decrease of voltage is accomplishedof say about 2%% of normal voltage for each plug change. sorted in receptacles 1,'all of the turns in section 17-18 are active, as may be readily verified by tracing the wiring. However, when the plug is' withdrawn from receptacle 1 and inserted in receptacle 2, some of the turns of the left hand coil 17 are rendered inactive, the number of turns being in this case equivalent to about 2 of the whole number in both of the coils 17 and 18.

When the plug is withdrawn from receptacle- 2 and inserted in receptacle'B, all of the turns in the left hand coil are rendered active, but in the right hand coil 18 a number.

of turns approximating double the number of turns between ta changes on coil 17 are en the plug is withdrawn from receptacle 3 and inserted in receptacle 4, some turns are again rendered inactive on the left hand coil 17 inaddition to the turns that are already inactive on the right hand coil 18. When the plug is with: drawn from receptacle 4 and inserted in receptacle 5,. the minimum E. M. F. is ob- Thus when the plug is in-* tained, since another small section of turns is rendered inactive on the secondary coil 17. As regards the secondary coil comprising sections 19 and 20 and their associated receptacles 1 to 5, it is seen that precisely the same effect is obtained in this case as in the case just considered, as the plug is grad.- ually moved from receptacle 1 to receptacle 5, and likewise precisely the same efiect is obtained for the third secondary coil comprising sections 21 and 22 when a plug is moved by single steps from receptacle 1" to receptacle 5". To vary the ratio of transformation, therefore, it is merely necessary to open any one of the switches 23, 24 and 25, and while any one of these switches is open, to adjust the plug in the receptacles associated with the secondary coil controlled by the open switch, then to close the switch 1 and to do this successively with both of the other switches. It will be noted that while this operation is being carried on the service is uninterrupted.

It is a necessary outcome of the uninterrupted supply to the load that the system of E. M. F.s obtained from the secondary coils of the transforming apparatus becomes slightly unbalanced while the voltage is being adjusted. This is due to the fact that but one secondary coil can be adjusted at a time. To prevent excessive or appreciable I unbalancing, which mightresult in objeccomprising the two sections 17 and 18, we .can withdraw the plug from receptacle 1 .and insert it into receptacle 2, but before .we can remove the plug from receptacle 2 and insert it into receptacle 3, it is necessary that both of the other plugs for the remaining secondary coils must be in receptacles 2' and 2". After all of the plugs are in the proper receptacles so that a balanced.

voltage is obtained, a further shift of the plugs may be accomplished. In this way ut one step at a time may be taken throughout all of the secondary coils and no greater unbalancing can take place in the voltage than that represented by the movement of the plug from one receptacle to an adj acent one. i

The means that I employ to accomplish this desirable result is an interlocking bar 27,

-. which is clearly shown in Fig. 2. This interlocking bar 27 is adapted to be moved 'we start in, say, with the secondary coil lengthwise and is guided in-its movementby appropriate metal clips 28. The interlocking bar is provided with a plurality of apertures 29 just large enough to uncover two adjacent receptacles such as receptacles 1 and 2, receptacles 1 and 2 and receptacles 1 and 2", as shown in Fig. 2. The number and arrangement of these apertures 29 depend upon the location of the receptacles and also upon whether the system is three-phase, four-phase, five-phase, etc. When the bar 27 is in its extreme left hand position, the receptacles 1 and 2 are uncovered as well as the receptacles 1' and 2 and 1" and 2". Suppose now that the three plugs are in receptacles 1, 1' and 1". 'In order to decrease the secondary Voltage by a small increment, we may start in for example with the plug in receptacle 1 and move it into receptacle 2. We cannot now remove the plug from receptacle 2 and insert it into receptacle 3 because the bar covers up this receptacle and it cannot be moved to uncover this receptacle while there are plugs in receptacles 1' and 1", said plugs blocking the movement of bar 27. Therefore, the next step after removing the plug from receptacle 1 to receptacle 2 is to remove the plug from receptacle 1' or 1" and insert it into receptacle 2 or 2", and repeating this process with the remaining plug. The bar 27 may now be moved to the right a distance corresponding to the distance between two adjacent receptacles and the process repeated. In this way appreciable unbalancing of the polyphase system is prevented, since there can be no greater unbalancing at any onetime, than is represented by the movement of the plug from one receptacle to its adjacent one. My interlocking bar therefore comprises a relatively simple means for insuring the proper sequence of operation of the tap changing scheme.

For a clear understanding of the mode of operation of my invention, it is perhaps appropriate at this point to review briefly the method of operation of the entire system, to vary the voltage supplied to the load 26. We will say that the switch 24 is opened first. The load is now being operated on open delta supplied by the secondary coils comprising sections 1718 and sections 2122. The secondary coil comprising sections 1920 is entirely disconnected from the system. The plug is moved from any of the receptacles 1' to 5 to an adjacent receptacle. The switch 24 is now closed. At this stage of the operation there is a slight unbalancing of the voltage system. The next step is to open either one of the two remaining switches 23 and 25. Suppose the switch 23 be opened. If this be done, the load is again operated on open delta supplied by the secondary coils made up of sections 19, 20 and. 21, 22. The secondary coils comprising sections 17-18 is entirely disconnected from the system. The plug is moved from one of the receptacles l to 5 to an adjacent one in the same direction as the plug first referred to. The switch 23 is now closed, and switch 25 opened and the plug shifted in the same direction as in the two previous instances to an adjacent receptacle. The switch may now be closed. Should a further variation in load be necessary, the interlockin bar 27 is shifted either to the right or to t e left so as to uncover the next receptacle of each set into which the plugs are to be inserted. Then the entire sequence-of operation as set out above is again performed. This is carried on until the E. M. F. of the secondary side of the system is varied to the required amount.

While I have shown in the accompanying drawing the preferred embodiment of my invention, I do not desire to be limited thereto, but aim to cover in the appended claims all modifications falling fairly within the scope of my invention.

What 'I claim as new and desire to secure by Letters Patent of the United States, is:

1. In a system of distribution comprising a source of polyphase alternating current, a plurallty of primary and secondary coils for transformingthe voltage of said source, the

secondary coils being connected in closed delta for supplying a load, the method of varying the ratio of transformation without disconnecting the load, which consists in opening the delta by disconnecting one of said coils therefrom, varying the number of turns on said coil, reconnecting said coil into the delta, and repeating this operation in succession with eachsecondary coil.

2. In a system of'distribution comprising a source of polyphase alternating current and a plurality of primary and secondary coils for transforming the voltage of said source, the secondary coils being connected in closed delta for supplying a load, the method of varying the secondary voltage without disconnecting the load, which con method of varying the ratio of transforma tion in a plurality of steps, which consists in opening the delta by disconnecting one of said secondary coils therefrom, varying the number of turns on said coil by a relatively small amount, reconnecting said coil into the delta, performing this operation in succes- 'sion with each secondary coil, and repeating this process until the required change in voltage is obtained.

4. In a system of distribution, in combination, a source of polyphase alternating current, a plurality of primary and secondary coils for transforming the 'voltageof said source, the secondary coils being connected in closed delta for supplying a load, means for varying the ratlo of transformat on without disconnecting the load, comprising means for disconnecting each of said secondary coils from the delta, means for varying the number of turns on said coils, and means for preventing an a preciable unbalancing of the system while t e who of transformation is being adjusted.

5. In a system of distribution, in combination, a source of polyphase alternating current, a plurality of primary and secondary coils for transforming the voltage of said source, the secondary coils being connected in closed delta for supplying a load, means for varying the secondary voltage in a plurality of steps without isconnecting the load, comprising means for disconnecting each of said secondary coils therefrom in regular sequence, means for varying the number of turns on said coils and means for araeao insuring that all of the coils have their turns varied b an e ual small increment before a for varying the ratio of transformation without disconnecting the load','comprising switches for disconnecting each of said secondary coils from the delta, a plurality of taps for each secondary coil for varying the number of active turns thereof, plugs and receptacles for controlling the tap connections, and an interlocking bar cooperating with said plugs and receptacles to insure that all of the coils have their turns varied by an equal, small increment before a further variation can be efl'ected, whereby appreciable unbalancing of the secondary voltages is obviated. I

- In witness whereof, I have hereunto set my hand this twentieth day of April 1990.

WILBUR A. ranssnv.

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