US3852553A

US3852553A - Vacuum switch with toggle assembly operating mechanism

Info

Publication number: US3852553A
Application number: US00385197A
Authority: US
Inventors: R Lingenfelter; A Sabella
Original assignee: Westinghouse Electric Corp
Current assignee: ABB Inc USA
Priority date: 1973-08-02
Filing date: 1973-08-02
Publication date: 1974-12-03
Anticipated expiration: 1991-12-03

Abstract

A load tap changer having vacuum switches driven by a uniformly rotated drive shaft. The shaft is coupled to a reciprocating yoke which directly drives a spur gear and a drive plate. The drive plate drives a toggle assembly after a predetermined dwell angle. The toggle assembly quickly rotates a slotted cam after an additional dwell period. The vacuum switches are attached to the slotted cam and are opened and closed in the proper sequence as determined by the shape and position of the cam slots.

Description

United States Patent 1191 Lingenfelter etal. Dec. 3, i974 i5 1 VACUUM SWITCH WITH TOGGLE 3,213,214 10/1905 Hyuga 200 111 TIN ME HANISM 3,247,333 4/l966 Bruckhoff..... ASSEMBLY OPERA G C 3,553,395 1/1971 White ZOO/ll TC X [75] Inventors: Robert Lingenfcltcr; Andrew 3,764,89l 10/1973 Lingenfelter et a]. 200/11 TC x Sabella, both of Sharon, Pa. 3,783,206 1/l974 Lingenfelter 200/11 TC [73] Assignee: Westinghouse Electric Corporation,

Pittsburgh, Pa Przmary Exammer-James R. Scott Attorney, Agent, or Firm.l. R. Hanway [22] Filed: Aug. 2, 1973 21 Appl. No.: 385,197 [57] ABSTRACT v A load tap changer having vacuum switches driven by [52 5, 3 200 153 53 L, 200 53 5 a uniformly rotated drive shaft. The shaft is coupled to 51 Int. Cl. H0111 3/46 a reciprocating y which directly drives a p gcar 5 Field f Search ZOO/1] TC, 17 R, 13 53 G, and a drive plate. The drive plate drives a toggle as- 200 153 H, 153 L, 153 LA, 53 p 153 SC, sembly after a predetermined dwell angle. The toggle 153 U, 53 PA, 14 323 435 R, 435 assembly quickly rotates a slotted cam after an addi- 74/22 R tional dwell period. The vacuum switches are attached v to the slotted cam and are opened and closed in the Y [56] References Ci d proper sequence as determined by the shape and posi- UNITED STATES PATENTS of the Cam Slots 3,066,208 l1/l962 Fannon, Jr. et al. 200/ll TC 9 Claims, 5 Drawing Figures- PATENTEL BEE 31974 same 0r 3 I 2 m 5 n I. L a 3 c. m k m w M W E [/1 Ill 0 Q m m mm 2 6 ll B m R, W. m 5. 3. 2% 2 M. m wm m M N i I .M.

FIG.2

PATENTELBEB 3W 3.852.553

SHEET 30? 3 VACUUM SWITCH WITH TOGGLE ASSEMBLY OPERATING MECHANISM BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates, in general, to electrical tap changers and, more specifically, to load tap changers having vacuum switches.

2. Description of the Prior Art Tap changing equipment capable of changing taps while the tapped apparatus is conducting current generally includes one or more switches which divert the load current during the tap changing process. In highvoltage, high-current apparatus, vacuum switches are used because of their ability to interrupt and divert current without significant arcing- Most tap changers which use vacuum switch current interrupters follow a predetermined switching and tap selecting sequence when making a tap change. Normally, the vacuum switch contactsa're opened and closed by a mechanism which is driven and timed with other drive mechanisms, such as the selector switch drive mechanism; Since vacuum switches must be opened and closed in a manner different than other switches of the tap changer, a separate drive mechanism for the vacuum switch contacts is required. Therefore, it is desirable, and it is an object of this invention, to provide a vacuum switch drive mechanism which economically and reliably produces'the desired vacuum switch contact moving action.

Tap changing apparatus using vacuum switches is described in U.S. Pat. Nos. 3,764,8 9l and 3,783,206,

which are both'assigned'to the assignee'of this invention. In the apparatus described therein, and in similar apparatus, it is desirable for the vacuum switch drive mechamism to close the vacuum .switchcontacts quickly, to maintain sufficient force between the contacts, and to'open the contacts quickly with sufficient force to separate partially welded contacts. These desiredmotions must be obtained from a relatively constant speed drive member which is normally motor driven. Therefore, it is desirable, and it is another object of this invention, to provide avacuum switch drive mechanism which converts substantially constant motion into properly timed abrupt motion of sufficient strength to open and close the vacuum switch contacts properly. I

I SUMMARY OF THE INVENTION pletesingle tap change, the input shaft is ro'tated,360.

The yoke meshes with a gear which rotates a plate having two drive surfaces with a gap therebetween. The plate rotates 90 before engaging with a pin which moves a toggle assembly. After the toggle assembly reaches its togglepoint, the toggle assembly quickly rotates a cam to which the vacuum switches are attached by means of a dampenedcoupler. The contacts of the vacuum switches are opened or closed depending on the shape and position of slots in the cam.

Further advantages and uses of this invention will become more apparent when considered in view of the following detailed description and drawing, in which:

FIG.'1 is a schematic diagram of a load tap changer;

FIG. 2 is an elevational view of the portion of a load tap changer which contains the vacuum switch drive mechanism;

FIG. 3 is a partial sectional view taken generally v along the line IIIIII of FIG. 2;

FIG. 4 isa partial sectional view taken generally along the line IVIV of FIG. 2; and I FIG. 5 is a partial sectional view taken generally along the line V--V of FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENTS which may be moved tocontact different winding taps.

The transfer switch 32 connects the moveable contacts of the selector switch 26 to' the load 34. When changing the load current, from one of the

selector switch contacts

28 and 30 to the other contact, the transfer switch 32 interrupts. the load current by opening one or more vacuum switches. The'vacuum switch contacts FIG. 2 illustrates, in detail, :a portion of a load tap changer constructed with a vacuum switch drive mechanism suitable for moving the vacuum switch contacts in the proper sequence. Descriptions of complete tap changers are contained inU.S. Pat. Nos. 3,764,89l and 3,783,206, which are assigned to the assignee of the present invention. The sequence of operation of the vacuum switches is described I in U.S. 'Pat. No. 3,783,206 in connection with FIGS. 4 through 9 of said patent. 1 i I v In FIG.2, the apparatus enclosure 36 supports the insulator 38 and the gear box 40. Rotational movement applied to the shaft 42 is transferred through the gear box 40, the universal joint 44, and the insulator 46 to the input shaft 48. Shaft 42 is rotated when a tap change is being made. The selector switches andthe reversing switches must be controlled at the appropriate time with respect to the rotation of the input shaft 48. However, only'the movement of the vacuum switches is described in detail herein.

Vacuum switches

50 and 52 are two of the three vacuum switches which must be controlled. The third vacuum switch is not shown in FIG. 2 for clarity of the Figure.

The input shaft 48 extends through the base plate 54 within the bearing 56. The spur gear 58 is keyed to the shaft 48 and meshes with the spur gear 60 which is free to rotate around the shaft 62. The cam follower 64'is attached to, the gear 60 and engages with the slot 66 in the yoke 68. The yoke 68 provides a linear movement from the rotational movement of the gear 641.

FIG. 3 better illustrates the arrangement of the yoke 68. The position of the elements shown in FIG. 3 is representative of the position existing at the time a tap change is beginning. As the gear 61) rotates in direction 70, the cam follower 64 travels within the slot 66 of the yoke 68 and moves the yoke 68 in the direction 72. The rollers 74 guide the movement of the yoke 68. The yoke 68 would also move in the direction 72 when the gear 60 rotates from the position illustrated in a direction opposite to direction '70, as would occur when the top selector is moving in the other direction.

A portion of the yoke 68 contains a rack of teeth 76 which mesh with teeth on the spur gear 78. The spur gear 78 is keyed to the shaft 11 which extends upward to drive other portions of the tap changing apparatus. A drive plate 82 is connected to the gear 711 and contains

surfaces

84 and 86 which are engageable with a forcing means, that is, the pin 118.

As shown in FIG. 3, rotation of the gear 78 in direction 84 rotates the drive plate 92 in the same direction. However, since the pin 88 merely extends into the space 85 between the

surfaces

84 and 86 and is not attached thereto, movement of the pin 98 is not provided by movement of the plate 112 until the surface 64 comes into contact with the pin 88. This dwell period permits other components of the tap changer to move, as required, before the beginning of the vacuum switch opening and closing sequence.

As shown in FIG. 2, the pin tit; extends through and is rigidly connected to the spur gear 90. The bearing 91 permits free movement of the gear 90 around the shaft 80. The gear 91) meshes with the gear 92 which drives the crank arm 94. Thus, when the pin 98 is moved by the plate 82, the crank arm 94 is rotated.

FIG. 4 illustrates the relative position of certain elements of the tap changer prior to the beginning ofa tap changing operation. Rotation of the gear 90 rotates the gear 92 and the crank arm 94 as previously described. The crank arm 94 is pivotally connected to a dampening cylinder assembly 96 by the pin 98. The cylinder 96 is pivotally connected to the base plate 54, as shown in FIG. 2, by the pin 100. The pin 98 also pivotally connects a coil spring assembly 102 to the crank arm 94. These components form a toggle assembly which provides the quick action necessary to operate the vacuum switches.

As the gear 90 rotates in direction 1114, the crank arm 94 begins to move to the position shown in phantom in FIG. 4. While moving to the position shown in phantom the spring 106 is compressed and the guide rod 108 slips through the pivotable anchor block 110. Thus, the potential energy of the spring assembly 102 is increased. Further rotation of the crank arm 94 moves the toggle assembly into the toggle position when the crank arm 94 is displaced 180 from the starting position.

When the crank arm 94 is moved just slightly beyond the toggle point, the energy of the spring assembly 102 causes the arm 94 to rotate quickly, in the same direction, toward the initial starting position. Movement of the arm 94 by the spring assembly 1112 is not impeded by the speed of the input shaft 48 since the pin 88 may travel freely between the engaging surfaces of the plate 82.

A drive means comprises the plate 112 which is positioned around the shaft and is free to rotate with respect thereto. Therefore, the plate 112 remains stationary until the pin fitil moves from the surface 114, through the space 115 to the surface 116. This movement of the pin fit is accomplished while the toggle assembly is being shifted to the toggle point. Thus, by the time the toggle point has been reached, pin 88 is engaged with surface 1 16. The quick rotation provided by the toggle assembly then quickly forces the plate 112 in direction 118 until the projection 120 hits the shock absorbing stop 122.

FIG. 5 illustrates, in a partial view, the connection of cam 124 to the connecting

arms

126, 128, and which are attached to the moveable contacts of the vacuum switches. The cam 124 is not keyed to the shaft 80 and is rotated only when the plate 112, which is attached to the cam 124 as shown in FIG. 2, is rotated. Referring to FIGS. 4 and 5, a quick rotation of the plate 112 in direction 11% rotates the cam 124 quickly in direction 132. The connecting

arms

126, 128, and 130 are attached to the

cam followers

134, 136, and 138, respectively, which are positioned in the slots of the cam 124. Thus, when the cam 124 rotates, the connecting arms 126, 123, and 1311 either move toward or away from the shaft 811 to open or close their respective vacuum switches. The slots 140 are shaped to provide the desired switching sequence and contact travel.

Each of the connecting

arms

126, 128, and 130 are connected to the respective vacuum switches through a coupler, or connecting means, which appropriately opens and closes the contacts of the vacuum switches. As shown in FIG. 2, the coupler 141 connects the vacuum switch 50) to the cam follower 136. The connecting arm 128 includes a cylindrical piston 142 which slides within the cylinder 144.

The coupler 141 is illustrated, in FIG. 2, in the position during which the contacts of the vacuum switch 50 is open. During a closing operation, the cam follower 136 moves the poston 142 toward the vacuum switch 56. The drive rod 146 is allowed to move, due to the hydraulic pressure on the vacuum switch 50, toward the vacuum switch 50 to close the contacts. The spring 149 is compressed against the ring 150 to add to the closing force. The piston 142 travels farther than needed to close the contacts, thus the spring 148 provides an override feature which allows for contact erosion. Oil contained within the spring and piston area produces a dampening action to prevent bouncing of the contacts.

When the contacts are opened, the piston 142 moves toward the shaft 80. Because of the override feature, a gap exists between the head 152 of the drive rod 146, and the piston 142. Thus, the piston 142 strikes the head with an impact force which increases the ability to open partially welded contacts. The detent mechanism 149, as shown in FIG. 5, engages with the cam 124 to prevent movement of the cam 124 except when forced by the drive mechanism.

The vacuum switches transfer the load current between the

moveable tap contacts

28 and 30 which move to contact alternate tap terminals. Therefore, a change of more than one tap position requires the sequence of vacuum switch operation to be reversed. Since the yoke 68 reverses movement every one-half revolution of the gear 60, this requirement is satisfied without the necessity of changing the direction of rotation of the shaft 48.

During a tap changing operation involving several taps, the shaft 48 is rotated in a constant direction provided that the tap positions are all in the same direction, that is, either raising or lowering the tap voltage. During 360 of rotation of the shaft, the gear 60 rotates 180. This moves the yoke 68 to its maximum travel position in one direction. At the same time, the gear 78 rotates approximately 270.

After 90 of rotation of the gear 78, the gear 90 starts to rotate. When the gear 90 is rotated 90, the crank arm 94 has rotated 180 to the toggle position. Continued rotation of the shaft 48 moves the toggle assembly past the toggle position and the force from the spring 106 quickly rotates the arm 94 an additional 180. The gear 90 and the cam 124 also quickly rotate an additional 90 to complete the switching of the vacuum switches. If the cam fails to rotate due to the force from the toggle assembly, the pin 88 will provide a positive force to the plate 112 to rotate the cam.

Since numerous changes may be made in the above described apparatus, and since different embodiments of the invention may be made without departing from the spirit thereof, it is intended that all of the matter contained in the foregoing description, or shown in the accompanying drawing, shall be interpreted as illustrative rather than limiting- I We claim as our invention: 1. Tap changing apparatus comprising: a selector switch which is moveable to contact different tap terminals; 7

first, second, and third vacuum switches switchable in a predetermined sequence to transfer a load connected to the tap changing apparatus from one tap terminal to another tap terminal, each of said vacuum switches having a stationary and a moveable contact;

a moveable cam; connecting means for connecting the moveable contact of each vacuum switch to said cam;

,drive means coupled to said cam to receive the force which moves said cam; forcingmeans for applying the moving force to said drive means;

toggle means for quickly moving said forcing means when said toggle means has been shifted to a predetermined position;

input means for shifting said toggle means to the predetermined position; and

an input shaft which drives said input means, with said input means comprising a plurality of mechanical members coupled to-said input shaft and said toggle means, and with the rotation of said input shaft in one direction providing movement of said forcing means and said toggle means together until said toggle means has been shifted to the predetermined position, and then allowing the forcing means to be quickly moved by said toggle means without a change in the speed of rotation of said input shaft.

2. The tap'changing apparatus of claim 1 wherein the moveable cam comprises a rotatable disc containing first, second and thrid slots shaped to move the moveable contacts in the desired direction at the desired time, and the connecting means comprises first, second and third dampened couplers each connected to a nected to the cam follower which extends into the slotted cam, a fixed cylinder within which said piston is moveable, a drive rod solidly connected to the moveable contact of the vacuum switch, said drive rod projecting through an opening in said piston and resilient means forcing said drive rod toward the moveable contact from said piston, said drive rod containing an enlarged portion which limits the travel of the drive rod through the opening in said piston.

4. The tap changing apparatus of claim 1 wherein the drive means comprises a plate member attached to the moveable cam and rotatable around the same axis as v the moveable cam, said plate member including first and second surfaces which the forcing means may push against to rotate said plate member, said first and second surfaces having a space therebetween wherein the forcing means may move without rotating said plate member.

5. The tap changing apparatus of claim 1 wherein the toggle means comprises:

a rotatable gear;

- a crank arm coupled to said gear;

resilient means connected to and providing a force on said crank arm, said resilient means increasing said force when said crank arm is rotated in one direction'to a predetermined position, and said force causing the crank arm to quickly rotate in the same direction after the predetermined position has been exceeded.

6. The tap changing apparatus of claim 5 wherein the resilient means includes a coil spring attached at one end to the crank arm and at the other end to a member which is substantially fixed with respect tothe movement of the crank arm and which is located substantially within the plane in which the crank arm rotates.

7. The tap changing apparatus of claim '5 wherein the forcing means includes a pin solidly connected to the rotatable gear and extending into engagement with the drive means and with the input means.

8. The tap changing apparatus of claim 1 wherein the input means comprises:

a first spur gear rotatable by the input shaft;

a yoke having a slot therein and a rack of teeth thereon;

a cam follower connected to said first spur gear and projecting into the slot in said yoke;

a second spur gear'engaged with the rack of teeth-on said yoke; I

a member attached to said second spur gear, said member including first and second surfaces which engage with the forcing means, said first and second surfaces having a space therebetween which permits movement of said member without the movement-of said forcing means.

9. Tap changing apparatus comprising:

a selector switch which is moveable tocontact different tap terminals;

first, second and third vacuum switches-each having a fixed and a moveable contact;

a rotatable cam having slots therein;

dampening couplers which connect the moveable contacts of the vacuum switches to cam followers which extend into the slots in said moveable cam;

faces with a substantial space between said surfaces, said plate member being rotatable around the same axis as said rotatable cam, with the other end of said pin extending between the first and second contact surfaces of said plate member;

a second gear solidly connected to said plate member;

a yoke having a slot therein and a rack of teeth thereon which engage with teeth on said second gear;

a third gear;

a cam follower attached to said third gear and extending into the slot in said yoke; and

a fourth gear which is engaged with said third gear and which is attached to a drive shaft.

Claims

1. Tap changing apparatus comprising: a selector switch which is moveable to contact different tap terminals; first, second, and third vacuum switches switchable in a predetermined sequence to transfer a load connected to the tap changing apparatus from one tap terminal to another tap terminal, each of said vacuum switches having a stationary and a moveable contact; a moveable cam; connecting means for connecting the moveable contact of each vacuum switch to said cam; drive means coupled to said cam to receive the force which moves said cam; forcing means for applying the moving force to said drive means; toggle means for quickly moving said forcing means when said toggle means has been shifted to a predetermined position; input means for shifting said toggle means to the predetermined position; and an input shaft which drives said input means, with said input means comprising a plurality of mechanical members coupled to said input shaft and said toggle means, and with the rotation of said input shaft in one direction providing movement of said forcing means and said toggle means together until said toggle means has been shifted to the predetermined position, and then allowing the forcing means to be quickly moved by said toggle means without a change in the speed of rotation of said input shaft.

2. The tap changing apparatus of claim 1 wherein the moveable cam comprises a rotatable disc containing first, second and thrid slots shaped to move the moveable contacts in the desired direction at the desired time, and the connecting means comprises first, second and third dampened couplers each connected to a moveable contact of a vacuum switch and to a cam follower which extends into one of said slots in the moveable cam.

3. The tap changing apparatus of claim 2 wherein each of the dampened couplers include a piston connected to the cam follower which extends into the slotted cam, a fixed cylinder within which said piston is moveable, a drive rod solidly connected to the moveable contact of the vacuum switch, said drive rod projecting through an opening in said piston and resilient means forcing said drive rod toward the moveable contact from said piston, said drive rod containing an enlarged portion which limits the travel of the drive rod through the opening in said piston.

4. The tap changing apparatus of claim 1 wherein the drive means comprises a plate member attached to the moveable cam and rotatable around the same axis as the moveable cam, said plate member including first and second surfaces which the forcing means may push against to rotate said plate member, said first and second surfaces having a space therebetween wherein the forcing means may move without rotating said plate member.

5. The tap changing apparatus of claim 1 wherein the toggle means comprises: a rotatable gear; a crank arm coupled to said gear; resilient means connected to and providing a force on said crank arm, said resilient means increasing said force when said crank arm is rotated in one direction to a predetermined position, and said force causing the crank arm to quickly rotate in the same direction after the predetermined position has been exceeded.

6. The tap changing apparatus of claim 5 wherein the resilient means includes a coil spring attached at one end to the crank arm and at the other end to a member which is substantially fixed with respect to the movement of the crank arm and which is located substantially within the plane in which the crank arm rotates.

7. The tap changing apparatus of claim 5 wherein the forcing means includes a pin solidly connected to the rotatable gear and extending into engagement with the drive means and with the input means.

8. The tap changing apparatus of claim 1 wherein the input means comprises: a first spur gear rotatable by the input shaft; a yoke having a slot therein and a rack of teeth thereon; a cam foLlower connected to said first spur gear and projecting into the slot in said yoke; a second spur gear engaged with the rack of teeth on said yoke; a member attached to said second spur gear, said member including first and second surfaces which engage with the forcing means, said first and second surfaces having a space therebetween which permits movement of said member without the movement of said forcing means.

9. Tap changing apparatus comprising: a selector switch which is moveable to contact different tap terminals; first, second and third vacuum switches each having a fixed and a moveable contact; a rotatable cam having slots therein; dampening couplers which connect the moveable contacts of the vacuum switches to cam followers which extend into the slots in said moveable cam; drive means connected to said cam and having first and second contact surfaces with a substantial space between said surfaces; a first gear rotatable about the same axis as said rotatable cam; a pin solidly connected to said first gear with one end thereof projecting between the first and second contact surfaces of said drive means; toggle means coupled to said first gear which provides the force to quickly rotate said first gear after said first gear has rotated to a predetermined position; a plate member having first and second contact surfaces with a substantial space between said surfaces, said plate member being rotatable around the same axis as said rotatable cam, with the other end of said pin extending between the first and second contact surfaces of said plate member; a second gear solidly connected to said plate member; a yoke having a slot therein and a rack of teeth thereon which engage with teeth on said second gear; a third gear; a cam follower attached to said third gear and extending into the slot in said yoke; and a fourth gear which is engaged with said third gear and which is attached to a drive shaft.