US2197771A - Switching means for transformers - Google Patents

Description

April 23., 1940. w. REiCHE ET'AL 2,197,771

SWITCHING MEANS FOR TRANSFORMERS Filed June 25, 1938 3 Sheets-Sheet 1 Egg. 1.

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SWITCHING MEANS FOR TRANSFORMERS Filed June 25, 1938' s Sheets-Shut 2 INVENTOR 4 WILL! RE/CHE B WALTER 7Esc ATTORNEYS April 23, 1940. w. REICHE r AL 197,77

swrrcnme Imus FOR rmusroaunns Filed June 25, 1938 3 Sheets-Shoat 3 INVE TOR W/LL/ EICHE Y WALTER Tissc m4 ATTORNEY Patented Apr. 23, 1940 SWITCHING MEANS FOR TRANSFORMERS Willi Reiche and Walter Teach, Dresden, Germany, assig'nors to Koch & Sterne! Aktiengesellschaft, Dresden-A Zd, Germany, a corporation oi Germany Application June 25, 1938, Serial No. 215,784 In Germany July 10, 1937 4 Claims.

This invention relates to switching means for transformers and refers more particularly to a device for regulating a step-transformer under load.

5 A step-transformer has a secondary winding which is tapped off at several points, so that it is possible by means of a switch to vary the voltage of the secondary circuit while the transformer is under load by varying that length of the secondary winding which is included in the secondary circuit.

Prior art constructions of this type have the drawback that the voltage drops twice in the course of the switching from one step or stage to an adjacent one, and may even fall below the normal voltage of the step to which the transformer is being changed. constructional changes which were carried out to eliminate this drawback resulted in an increase of the current flow- 20 ing through the switch, with the result that the contacting surfaces of the switch were quickly destroyed.

An object of the present invention is the pro- Other objects will be apparent in the course 30 of the following specification.

The objects of the present invention may be realized through 'the use of two change-over switches namely, a main switch and an auxiliary one, which are included in the secondary circuit of a step-transformer. Each switch has two operative final or end positions, and there is a. pair of main contacts and a pair of advance contacts for each such position. Each main contact is connected to a separate advance contact and the contacts of the auxiliary switch are connected without any substantial increase in resistance to the corresponding main contacts of the main switch. The main contacts serve for the transmission of the electrical current in the oper- 5 ative end positions of the switches, while advance contacts are included in the circuit only in the course of the switching from one stage to another. In accordance with the present invention the movable elements of the two change-over present invention, in the course of the switching,

the current-transmitting main contacts of'the two switches are first replaced in the circuit by the adjacent advance contacts, then the two pairs of advance contacts of the main switch are electrically connected with each other, and final- 8' ly the two interengaging advance contacts of the auxiliary switch are separated, while shortly thereafter the other two advance contacts of the auxiliary switch are brought in contact with each other.

The invention. will appear more clearly from the following detailed description when taken in. connection with. the accompanying drawings showing, by way of example, a preferred embodiment of the inventive idea.

In the drawings: I

Figure 1 shows a device constructed in accordance with the principles of the presentinvention.

Figure 2 is a wiring diagram of the device for regulating the one-phase step-transformer shown 'l2,' l3 comprises a non-adjustable portion I2 which is connected to the terminal 4! of a switch i8. Themovable lever M of the switch it may be brought into engagement with either the positive terminal 42 or the negative terminal 43, which are connected to the opposite ends of an adjustable winding l3 constituting a part of the secondary winding. I

The primary and the secondary windings of the transformer are preferably situated in the casing M, which is filled with oil. A secondary casing 15, which is in reality considerably smaller 40 than the casing I4, is situated upon the latter and is used as a. container for the regulating device.

Two sequence switches i6 and i! are provided with movable elements 65 and 45, respectively. The element 45 of the sequence switch it is move able over contacts designated by the even, numerals 2, 4, and 6, while the movable element 46 of the sequence switch I1 is movable over the odd contacts I, 3, 5 and 1. The contacts 1 to 50 1 are connected with wires 41 to 53, which are. connected to various parts of the winding l3, thereby subdividing this winding.

The terminal 54 of the sequence switch I6 is connected by a wire 55 with the terminal 56 of 55 the main switch I8. A wire 51 connects the terminal 58 with the terminal 58 of the auxiliary switch 28. A wire 58 connects the terminal 88 of the sequence switch I! with the terminal 8| of the main switch l8, while the latter terminal is connected with the terminal 82 of the switch 28 by means of the wire 88.

The two sequence switches l8 and 28 are used alternately for the purpose of changing the operative length of the winding |3 by shifting from an odd step to the next even step and vice-versa. Any suitable mechanical or manually operated device 84 connects the two switches l8 and I1 and is so arranged that first one of these switches may be moved to the extent of one contact and then the other switch is moved to that extent.

The device 68 is preferably connected with the switch l8, which is moved from one of the contacts 42 or 43 to the other one of these contacts after the sequence switches I5 and I1 have been moved over all the contacts. This movement of the switch |8 reverses the connection of the winding l3 with the winding l2. Due to this arrangement, the extent of the regulation is doubled, or in other words, it is possible to carry out a plus-minus regulation by means of the switch l8.

Of course, in certain constructions, the use of the switch l8 may be unnecessary and then one end of the winding l3 may be connected directly with one end of the winding |2 or the two The carriage 25 carries an abutment or nose 28 which may be brought into engagement with the lever 23 in the course of the movement of the carriage to the right from the position shown in Figure 2. The coiled spring 28 is brought under tension by this movement of the carriage 25. The purpose of the nose 28 is to move the leverage system consisting of the members 2|, 22 and 23 out of its dead-end positions, in which the link 22 is in alinement with one of the levers 2| or 23. Due to the action of the nose 26, the spring 24 is able to move the link 22 and rapidly bring the leverage system into the opposite end position. The lever 2| carries a conducting leaf spring 21 which supports an advance contact 58 and a main contact 18. The advance contact 88 is adapted to cooperate with the immovable advance contact 1| connected to one end of a resistance 28, the opposite end of which is connected to the terminal 58. The main contact 18 is adapted to cooperate with an immovable main contact 12, which is connected to the terminal 58.

The same arrangement is substantially repeated on the opposite side of the switch l8. The lever 23 carries a conducting spring 28, which is provided with an advance contact 13 and a main contact 14 adapted to cooperate with the immovable advance contact 15 and the immovable main contact 15, respectively. The immovable contacts 15 and I8 are connected to the two ends of a resistance 88, and the conducting springs 2'! and 28 are electrically connected with each other by means of the wire 88.

The auxiliary switch 28 is substantially similar in construction to the main switch l8 and comprises the levers I1 and I8 which are connected by the link 18 and which carry the spring 3| and 82, respectively. A coil spring 88 connects the link 18 with the carriage 8|. The spring 3| of the lever 11 carries an advance contact 82 and a main contact 88, which are adapted to be brought into engagement with the immovable adyance contact 84 and the main contact 85, respectively. The spring 82 carried by the lever I8 is provided with the advance contact 86 and the main contact 81, which are adapted to be brought into engagement with the immovable contacts 88 and 88, respectively.

A'wire 83 which constitutes a continuation of the secondary winding l2, I8 is electrically connected by-means oi the wire 88 with the conducting springs 21 and 28 and the movable contacts 88, 18, 13 and 14, which are carried by these springs. The wire 8| connects the wire 33 with the movable contacts 82, 88, 85, and 81 of the auxiliary switch 28.

Consequently, a pair of main contacts and a pair of advance contacts are provided for each operative position oi each change-over switch. The pairs of contacts 18 and l2; l4 and I8; 83 and and 81 and 88 are designated as main contacts, since the contacts of one of these pairs are in engagement with each other in any end position of each change-over switch. On the other hand, the pairs of contacts 68 and ll; 18 and 15; 82 and 88; and 88 and 88 are designated as advance contacts, since they come into engagement with each other only in the course of the movement of the change-over switches from one end position to another end position.

As already mentioned, the main contact I2 is connected with the advance contact H by means of the resistance 28, and is connected with the sequence switch It by means 01' the terminal 58 and the wire 55. Similarly, the main contact 18 is connected by means of the terminal 8| and the wire 58 with the sequence switch I! and is connected by means 01' the terminal SI and the wire 58 with the sequence switch I! and is connected by means of the resistance 88 with the advance contact I8.

It is apparent that the auxiliary changeover switch 28 is substantially similar in construction to the main changeover switch l8. However, an important distinction in the construction 0! the two switches is that the advance contact 84 of the auxiliary switch is connected with the main contact 85 of that switch not through any substantial resistance but by means of a wire 82 having a very small resistance, while the advance contact 88 is connected with the terminal 82 and the main contact 88 by means of a wire 88 which also has a small resistance. On the other hand, the main switch I8 is provided with two resistances 28 and 38.

Any suitable mechanical device 84 known in the art is used for coupling the movable elements of the two switches I8 and 28 with a certain amount of play. The two carriages 25 and ll of the switches l8 and 28 are driven together by the same mechanism which operates the sequence switches l8 and I1 and the reversing switch l8.

' The drive is carried out in such manner that the two changeover switches l8 and 28 are moved from one of their end positions to the other end position after one of the two sequence switches IE or II has been moved forward to the extent of one contact. Mechanical drives of this type are knownperse inthe art,

As already mentioned, the electrical connection of the change-over switches I9 and 28 is such that the main contact 85 of the auxiliary switch 28 is electrically connected by the wire 51 with the main contact 12 of the main switch I9 while the main contact 89 of the auxiliary switch 28 is directly connected by the wire 83 with the main contact 18 of the main switch I9. The wire 9| connects the movable leaf springs 3| and 32 of the auxiliary switch 28 with each other; the wires 9| and 33 and 98 connect the leaf springs 3| and 32 of the switch 28 with the leaf springs 21 and 28 of the switch I9. Thus the movable contacts 82, 83, 88 and 81 of the auxiliary switch 28 are connected with the movablecontacts 89, 18, 13 and 14 of the main switch I9.

The leaf springs 3| and 32 of the auxiliary change-over switch 28 are somewhat differently located than the leaf springs 21 and 28 of the main change-over switch I9, since, as will appear from the following description, the pairs of ad vance contacts 84 and 82, and 88 and 88 of the auxiliary switch are not closed simultaneously and, in general, the contacts of the auxiliary 28 switch 28 are closed somewhat later than the contacts of the main switch I9.

In the position illustrated in Figure2, the movable lever 45 of the sequence switch I8 is situated'upon the contact 4. In that position the current flowing through the secondary circuit of the transformer passes through the winding I2, the switch I8, the contact 42 and a portion of the winding I3 up to the point 4', flowing through the wire 58 tothe terminal 4 of the sequence switch I8. Thence, the current flows through the lever 45 of the switch IS, the terminal 54 and the wire 55 to the terminal 58.

As shown in Figure 2, the contacts 18 and 12 of the switch I9 are in engagement one with the other, so that a portion of the current flows through these contacts and through the wire 98 to the wire 33. Since ,the contacts 83 and 85 of the auxiliary switch 28 are also closed, a portion of the current will flow through the wire 51 and the contact 58, and through the contacts 83 and 85 and the wire 9|, which is connected to the wire 33.

Let it be assumed that it is desired to move the device one step forward from the step 4 to the step 5. This is carried out first by actuating the drive 84 and thereby moving the movable element 48 of the sequence switch I1, which at that time does not constitute a part of the electrical circuit, from the contact 3 to the contact 5. At the same time, the device 94 is actuatedand causes the movement of the carriages 25 and 8| of the switches I9 and 28 from left to right (looking in the direction of Figures 2 and 3). carriages pull at the springs 24 and 88, which are connected with them. The abutments of the carriages move the levers 23 and 18 out of alinement with the links 22 and 19, and ,then the springs 24 and 85 cause the leverage systems to spring rapidly into the opposite end positions shown in Figure 3, in which the other two pairs of main contacts 14 and 18,-and 81 and 89 are in engagement with each other.

The following changes in the electrical circuit take place in the course of this rapid shifting of the movable elements of the switches I8 and 28 from one end position to the other end position:

At flrst. when the pairs of main contacts 18 and 12 and 83 and 85 are still closed, the advance contacts 1| and 88 of the main switch I9 are brought into engagement one with the other.

The

Then the electrical current flowing through the contact 4 of the sequence switch I8 and the wire 55 will be again subdivided at the terminal 58, a portion of the current flowing through the resistance 29' and the contacts 1| and 89 to the spring 21. Thus, the resistance 29 is switched into the circuit. I

.Shortly thereafter the advance contacts 82 and 84 of the auxiliary switch 28 are brought into engagement one with the other. This causes a division of the current at the terminal 58 of the switch 28, a portion of the current flowing through the wire 92 and the contacts 82 and 84 v to the spring 3|.

Then, the main contacts 83 and 85 of the auxiliary switch 28 are separated one from the other. At the same time, or shortly thereafter, the main contacts 18 and 12 of themain switch I9 are separated one from the other. Then the electrical current flowing through the contact 4 of the sequence switch I8 will flow along the wire 55 to the terminal 58, and from there a portion of the current will flow through the resistance 29 and the two contacts 89 and 1|, the spring 21 and the wire 98 to the wire 33. Another portion of the current will flow from the terminal 58 through the wire 51, the terminal 58, the wire 92, the contacts 82 and 84, and the spring 3|, joining the main circuit by means of the wire 9|.

In the course of the further movement of the carriage 25, the advance contacts 13 and 15 of the main switch I9 are brought into engagement one with the other. At that time another electrical circuit, which includes the sequence switch I1, is brought into being. A portion of the electrical current will flow in the manner hereinbefore described, while another portion of .the current will flow along the wire I3- to the point which is the.connecting point between the wire I3 and the wire 5| leading to the contact 5, of the sequence switch I1. This latter current will flow through the contact 5, the movable lever 48 and the terminal 88 of the sequence switch I1 and will then flow through the wire 59 to the terminal 8| of the resistance 18, passing through the contacts 15 and 13 and the spring 29 which is connected to the wire 98.

Shortly thereafter, the further movement of the carriage 8| will cause a separation of the advance contacts 82 and 84, so that at that time no current will flow through the auxiliary switch 28. In that position, the wire 33 is connected over the resistances 29' and 38 with both the contacts 4 and 5 of the sequence switches I8 and I1, while up to the time the contacts 82 and 84 were separated, the wire 33 was connected directly only with the contact 4.

Then in the course of the further movement of the switches, the advance contacts 88 and 88 of the auxiliary switch 28 'will be brought into engagement one with the other, so that a portion of the electrical current will flow from the point 98, which is the connecting point between the wires 9| and 33, and through a' portion of the wire 9| to the spring 32, passing through the contacts 88 and 88 to the wire 93, which is connected at 82 to the wire 83. This portion of the electrical current will joint the main circuit at the terminal 6 I. Thus the wire 33 is directly connected withthe contact 5.

Shortly thereafter, the advance contacts 89 and 1| of the main switch I9 will be brought out of engagement one with the other. Then the switch I8 is excluded from the circuit, so that the electrical current flowing in the secondary circuit through the switch l8 will flow along the wire ii to the point 5' and will then flow through the wire 5!, the switch l1, and the wire 58 to the resistance 88.. Thence, the current will flow through the advance contacts 13 and 15 and the spring 28 to the wire 98. At the terminal 98, a portion of the current will flow through the spring 32 and the advance contacts 86 and 88 of the auxiliary switch 20.

Thereupon, the main contacts H and 16 ofthe main switch I9 and the main contacts 81 and 88 of the auxiliary switch 28 will be brought into engagement. A portion of the electrical current will flow through the contacts 14 and 18, the wire 88 and the contacts 89 and 81 to the wire 8|. Another portion of the electrical current will flow from the terminal 82 through the wire 83 and the advance contacts 88 and 86 to the spring 32.

Finally, the advance contact 88 is moved away from the contact 88 and the advance contact 13 is moved away from the contact 15. In this final position of the device, which isshown in Figure 3' of the drawings, the secondary electrical current flows through the wire'l2 and the switch II to the point 5 of the winding l8, thence through the wire 5| and the contact 5 oi the sequence switch I! and through the wire 58 to the terminal 8i. A portion of the electrical current flows through the main contacts 14 and I8 to the wire 33 while another portion of the electrical current flows from the terminal 8| through the wire 63 and through the main contacts 81 and 88 to the wire 8|, which is connected at 88 with the wire 33; It is apparent that in this end position two pairs of main con tacts are in engagement.

If it is now desired to move from the contact 5 to the contact 6, the procedure is substantially repeated. The sequence switch It, which is not included in the electrical circuit, is actuated to move its lever 85 from the contact 4 to the contact i, and thereupon the movable elements of the two switches I8 and 20 are shifted from right to left (looking in the direction of Figures 2 and 3).

It will be noted from the above description that an important advantage of the described construction is that the main contacts of the main switch I9 and the auxiliary switch 20, namely,

the pairs of contacts I8 and l2, l4 and I6, 83 and i 85, and 81 and 88 do not participate in the switching operation, which is carried out under load, but are open at that time, so that their contacting surfaces remain smooth and even. Only the auxiliary contacts of the two switches 19 and 20 take part in the switching operation, with the result that there is no danger that the main contacts will be burned or deteriorated by the electrical current.

As shown in Figure 1, the Switches [9 and 28 are preferably situated in one plane, one behind the other, and the auxiliary contacts of the two switches are situated above the main contacts adjacent the cover 38 of the casing I5 so that the auxiliary contacts are easily accessible whenever the cover 34 is raised, and so that these auxiliary If the device is used in connection with threephase step transformers, then the windings necessary for the three phases may be arranged in a manner similar to the arrangement of the windings l2 and I3, while the three primary windings which would correspond to the winding 1 I, may be interconnected in a star connection. Each phase must be provided with its own pair of sequence switches, a main change-over switch and an auxiliary change-over switch. However, the arrangement may be such that the conduits which correspond to the wire 38 and which are connected with the three main change-over switches and the three auxiliary change-over switches, are connected in the star connection. In fact, various connections which are know per se can be applied to the regulating device constructed in accordance with the present invention. In the case of three-phase step transformers, it is advisable to arrange the sequence switches and the reverse switches in the common container, which is situated upon the casing of the transformer.

It is apparent that the specific illustrations shown above have been given by way of illustra- .tion and not by way 01' limitation, and that the structures above described are subject to wide variation and modification without departing from the scope or intent oi the invention, all of which variations and modiflcationsare to be included within the scope of the present invention.

What'is claimed is:

1. A switching device for step-transformers under load, comprising two sequence switches for the even and odd steps and a main change-over switch movable from one on position to another on position and having for each on position separate main contacting means, separate advance contacting means and a separate resistance connecting said advance contacting means with said main contacting means, said device being characterized by the provision of an auxiliary changeover switch, in addition to said main change-over switch, said auxiliary change-over switch being movable from one on position to another on position and also having for each on position separate main contacting means and separate advance contacting means, each of the contacting means having an immovable contact and a movable contact, the immovable contacts of each of the main contacting means and advance contacting means of said auxiliary change-over switch being connected with each other and with the immovable contact of the corresponding main contacting means of said main change-over switch, the movable contacts of the two change-over switches being coupled with each other and operating in such manner that the main contacting means of the two change-over switches, which transmit an electrical current when thechange-over switches are in the on positions, are open during the switching under load.

2. A switching device in accordance with claim 1, characterized in that only after the interruption of the connection of the contacts of the main contacting means of the two change-over switches and the establishment of a connection of the contacts of the advance contacting means corresponding to the same on position of the changeover switches and after the main change-over switch has provided a connection between its two advance contacting means, the connection of the contacts of the corresponding advance contacting means of the auxiliary change-over switch is interrupted and shortly thereafter the connection of the contacts of the other advance contacting means is established.

3. In a switching device, in combination with a main change-over switch having two immovable main contacts, two immovable advance contacts, resistances conneetingeach advance contact to a separate main contact, two movable main contacts and two movable advance contacts, said immovable main contacts being adapted to be connected to a source of electrical energy; an-

auxiliary change-over switch having two immovable main contacts, two immovable advance contacts, two movable main contacts and two movable advance contacts, each of the immovable advance contacts of the auxiliary change-over switch being connected to a separate immovable main contact of that switch and to a separate immovable main contact of the main change-over switch;' each of the two switches having two operative end positions, a separate immovable main contact of each switch engaging a movable main contact 01' that switch in each of said end positions; and separate conducting means movable from any one of said end positions to the other end position in the course of a switching operation for interrupting the engagement between the main contacts of each switch in the course of said switching operation, each of said conducting means carrying the movable contacts of its switch.

4. In a switching device, in combination with a main change-over switch having two immovable main contacts, two immovable advance contacts,

resistances connecting each advance contact to a separate main contact, two movable main contacts and two movable advance contacts, said immovable main contacts being adapted to be connected to a source of electrical energy; an auxiliary change-over switch having two immovable main contacts, two immovable advance contacts, two movable main contacts and two movable advance contacts, each of the immovable advance contacts of the auxiliary change-over switch being connected to a separate immovable main contact ,of that switch and to a separate immovable main contact of the main change-over switch; each of the two switches having two 0perative end positions, a separate immovable main contact of each switch engaging a movable main contact of that switch in each of said end positions; and separate conducting means movable from any one of said end positions to the other end position in the course of a switching operation for interrupting the engagement between the main contacts of each switch, providing an engagement between adjacent advance contacts of each switch, then providing an engagement between other advance contacts of the main changeover switch, theninterrupting the engagement between the engaged advance contacts of the auxiliary change-over switch and shortly thereafter providing an engagement of the other advance contacts of the auxiliary change-over switch, each ofsaid conducting means carrying the movable contacts of its switch and carying out this movement in the course of said switching operation.

WILLI REICHE. WALTER TESCH.

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