US3213214A

US3213214A - Drive mechanism for on-load tap changers including lever and cam rollers activating spring tensioned drive levers

Info

Publication number: US3213214A
Application number: US300360A
Authority: US
Inventors: Hyuga Shigeyuki
Original assignee: Hitachi Ltd
Current assignee: Hitachi Ltd
Priority date: 1963-08-06
Filing date: 1963-08-06
Publication date: 1965-10-19
Anticipated expiration: 1982-10-19

Description

Oct. 19, 1965 SHIGEYUKI HYUGA 3,213,214

DRIVE MECHANISM FOR ON-LOAD TAP CHANGERS INCLUDING LEVER A D CAM ROLLERS ACTIVATING SPRING-TENSIONED DRIVE LEVERS Filed Aug. 6, 1963 2 Sheets-Sheet 1 INVENTOR Oct 1965 SHIGEYUKI HYUGA 3,213,214

DRIVE MECHANISM FOR ON-LOAD TAP CHANGERS INCLUDING LEVER AND CAM ROLLERS ACTIVATING SPRING-TENSIONED DRIVE LEVERS Filed Aug. 6, 1965 2 Sheets-Sheet 2 Fig. 4 EL INVENT R SHKSEYUKI Hfuen HTTORNE? United States Patent 3,213,214 DRIVE MECHANISM FGR ON-LOAD TAP CHANG- ERS INCLUDING LEVER AND CAM RULLIERS ACTIVATING SPRING TENSIONED DRIVE LEVERS Shigeyuki Hyuga, Hitachi-shit, Japan, assignor to Hitachi, Ltd., Tokyo, Japan, a corporation of Japan Filed Aug. 6, 1963, Ser. No. 300,360 2 Claims. (Cl. 20tl13) This invention relates to switch devices for on-load tap changers and has for its object to provide an improved switch device of the kind including a novel drive mech anism.

Tap-changer switches are generally classified into reactor and resistance types, according to whether the shortcircuit current flowing between adjacent taps during a tap-changing cycle is limited by a current-limiting reactor or by current-limiting resistors.

Most recently, there is a pronounced trend to employ resistance type switches because they can be made compact by use of current-limiting resistors of very short time ratings.

Tap-changer switches of the resistance type are further divided into two subtypes, one of which employs a fourlink mechanism and the other of which is a so-called rotary type, which includes a cylinder carrying on its inner peripheral surface a multitude of switch contacts and cooperating movable contactors mounted on a shaft arranged axially in said cylinder for rotation in opposite directions.

In the former, which employs a four-link mechanism, one or two current-limiting resistors are employed. On the other hand, the rotary type switch employs currentlimiting resistors in a larger number, say, of 4, 6 or 8 to minimize the rupturing capacity required of each of the contactors. It is apparent that the rotary type of tapchanger switch is more desirable from the standpoint of service life because of its limited rupturing duty.

The present invention is intended to provide an improved rotary type switch device for a tap-changing unit which has a novel drive mechanism designed to give a highly increased initial driving torque ensuring high-speed switching action of the device.

The foregoing and other objects, features and advantages of the present invention will become apparent from the following detailed description when taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a schematic diagram of a typical resistance type rotary switch and its connection with transformer taps;

FIG. 2 is a perspective view of the drive mechanism of the rotary switch;

FIG. 3 is a diagrammatic front view of a drive mechanism embodying the present invention;

FIG. 4 is a side view of same; and

FIGS. 5a to Sc schematically illustrate the sequential operation of the drive mechanism.

Referring first to FIGS. 1 and 2, which illustrate a typical rotary type switch, reference character Tw indicates a tap Winding to which the rotary switch is connected by way of tap selectors Tsl and Ts2 cooperable with two adjacent taps on the winding.

An insulated cylinder or drum A carries on its inner peripheral surface two groups of fixed contacts, S1, S2, S3, S4 and S4, S3, S2, S1 for each phase. A number of sector discs B are arranged in the drum A and each carry two groups of movable contacts S11, S12, S13, S14 and S14, S13, S12, S11 to cooperate with the respective fixed contacts on the drum. As illustrated, the fixed contacts in one group are connected with one of the tap 3,213,214 Patented Oct. 19, 1965 selectors Ts1 through respective resistors R1, R2 and R3 except one contact S1, which is connected directly to the tap selector Tsl. Similarly, the fixed contacts in the other group are connected to the other tap selector Ts2 through respective resistors R1, R2 and R3 except one contact S1, which is connected directly with the tap selector Ts2.

The sector discs B are pivotally supported by respective arms D on a drive shaft C so as to be driven in a direction indicated by the arrow. A drive mechanism is provided to operate the drive shaft in a quick-break fashion and includes a motor-driven shaft E, a lever G pivotally fixed at one end, a link F interconnecting the lever and an arm extending laterally from the shaft E, a lever arm I secured to the drive shaft C and a tension spring H arranged between the extremities of the lever G and arm I, as illustrated in FIG. 2.

It will be observed that, if the motor-drive shaft E is rotated in either direction, the lever G will be rotated counter-clockwise, as viewed in FIG. 2, under the pull of link F while at the same time energizing tension spring H, which is arranged between the lever G and the arm I of the drive shaft C. Just when the line joining the opposite ends of the tension spring H passes across the axis of the drive shaft C the spring H passes its dead center starting to rapidly rotate the arm I and drive shaft C clockwise as indicated by the arrow so that the sector discs B are each rocked clockwise while being translated in the direction indicated by the arrow in FIG. 1. During this time, it will be understood that the contacts S1, S2, S3, S4 and S4, S3, S2, S1 are successively shortcircuited in that order to complete one step-up cycle from tap T2 to tap T3.

This type of tap-changing switch, however, has involved a deficiency that the initial torque applied to the drive shaft C and hence its initial acceleration are very limited and an excessively heavy tension spring is thus required to obtain a satisfactorily large initial drive force. This difiiculty is inherent to the rotary switch, which is required to effect current interruption from the very start of operation as long as its employs a drive mechanism involving a snapping action over a dead center for quickbreak switching operation, as described hereinbefore.

In view of the above, the present invention proposes to employ a novel drive mechanism adapted to obtain a drive force which is satisfactorily large even at the very start of a switching movement.

Referring next to FIGS. 3 to 5, the illustrated embodiment of the present invention includes a drive shaft 1 for actuating switching discs as indicated at B in FIG. 1 and a stop earn 2 mounted on the drive shaft 1 and notched to define a pair of spaced stop shoulders 3 and 4 along the periphery of the cam. A main roller R is carried on a radial arm of the cam 2 formed on that side thereof which is remote from the pair of stop shoulders 3 and 4. Stop levers 5 and 6 carry at one end respective stop pins and rollers 7 and 8 for engagement with the stop shoulders 3 and 4 on the cam 2. Trip pins and rollers 9 and 10 are also carried by stop levers 5 and 6, respectively. The stop levers 5 and 6 are pivoted at the other end by respective pins 11 and 12 and are normally urged into contact with the periphery of the cam 2 by

respective compression springs

13 and 14.

Reference numeral 15 indicates a main, substantially cruciform, lever pivotally mounted at its cross point on a pin 16. The top extremity of the main lever 15 is connected with a motor-driven shaft 19 by way of a crank arm 18 and a connecting link 17. A pair of Z-shaped drive levers 22 and 23 are pivoted to the rightand lefthand ends of the cruciform lever 15 by way of

pins

20 and 21, respectively. A roller 24 for storing spring energy is carried by the main lever 15 at its bottom end. Said

drive levers

22 and 23 have their free extremity portions arranged opposite to each other with the main roller R on the stop cam 2 and roller 24 on the main lever 15 interposed therebetween. A stop-release or trip bar K is secured to the downwardly extending arm of the main lever adjacent to its bottom end for cooperation with the trip rollers 9 and 10. A pair of tension springs 25 are arranged between the opposite drive levers 22 and 23 to normally bias the levers toward each other so that their free extremity portions are normally held in pressure contact with both of the main and spring energy storing rollers R and 24.

FIG. 3 illustrates the drive mechanism in its one end position in which the stop roller 7 on one of the stop levers 5 is in engagement with one of the stop shoulders 3 on the cam 2 to hold the drive shaft 1 stationary keeping the movable contact S1 in contact with fixed contact S11, as shown in FIG. 1. In this position, the main lever 15 is inclined to the left with the main and spring energy storing rollers R and 24 held between the free extremity portions of the drive levers 22 and 23.

Under this situation, when it is desired to effect one step-up or step-down tap-changing cycle, a drive motor not shown is started to drive the shaft 19 with its crank arm 18 in a counterclockwise or clockwise direction to rock the main lever 15 through link 17 in a clockwise direction.

As the main lever 15 is rocked clockwise, spring energy storing roller 24 carried on the downwardly extending arm of the lever acts to pivotally push the left-hand drive lever 22 away from the right-hand drive lever 23, to store energy in the tension springs 25, which extend between the two drive levers. On this occasion, the right drive lever 23 cannot follow the roller 24 due to engagement with the main roller R carried on the stop cam 2, which is now held stationary with its shoulder 3 engaged by stop roller 7.

FIG. 5b schematically illustrates the drive mechanism in this intermediate operating position during the tapchanging cycle. FIG. 5a schematically illustrates the drive mechanism in one of its end positions shown in FIG. 3.

Just when the motor-driven shaft 19 has rotated through an angle of approximately 180, the main lever 15 reaches the position indicated by the chain lines in FIG. 3 so that the stop releasing bar K secured to the downwardly extending arm of the main lever 15 is brought into engagement with the trip roller 9 to release the stop roller 7 from the cam shoulder 3. Thus, the stop cam 2 is allowed to rotate rapidly in a clockwise direction under the restoring action of the tension springs 25, which act on the stop cam 2 by way of the right drive lever 23 and main roller 24. In this manner, the drive shaft 1 is rapidly rotated in the same direction to operate the contact-carrying sector discs B to complete the tap-changing cycle. FIG. 50 schematically illustrates the state of the drive mechanism at the end of the cycle.

In this state, it will readily be noted that the stop roller 8 on the other stop lever 6 is in engagement with the stop shoulder 4 on the cam 2. If another step of tap-changing is required, the above cycle of operation is repeated this time in the opposite direction after the next higher or lower tap is selected, as will be readily understood.

As apparent from the foregoing, the present switching device employs a drive mechanism adapted to impart a substantial drive torque to the switch shaft from the very start of its operation by releasing a stop device immediately after a substantial energy has been stored in spring means for actuating the switch shaft. Accordingly, it will readily be appreciated that the resent switch device can rapidly and positively interrupt the current flowing through the switch contacts, and thus may employ current-limiting resistors of limited ratings. Further advantages of the present device include its compactness and improved reliability.

What is claimed is:

1. A rotary switch device for an on-load tap-changer including a drive mechanism adapted to quickly start the rotation of the switch drive shaft, said drive mechanism comprising a notched cam mounted on the drive shaft of the switch, a stop device engageable with the notch in said cam, a main roller carried on said cam, a main, substantially cruciform lever pivoted at its cross point and operatively connected at the top end with a motor-drive shaft, a spring energy storing roller carried by said cruciform lever at its bottom end, a pair of drive levers pivoted at one end to the right and left extremities of said cruciform lever, and tension spring means arranged to normally bias said drive levers into engagement with said main and spring energy storing rollers, the arrangement being such that upon rotation of said motor-driven shaft said main lever is rocked to push one of said drive levers away from the other drive lever by way of said spring energy storing roller thereby to store energy in said tension spring means, said drive mechanism further comprising stop releasing means on said main lever for releasing said stop device when a predetermined amount of spring energy has been stored to allow said tension spring means to release the energy stored therein to drive said cam by way of said main roller thereon.

2. A rotary switch device for an on-load tap-changer including a drive mechanism adapted to quickly start the rotation of the switch drive shaft, said drive mechanism comprising a notched cam mounted on the switch drive shaft, stop levers pivoted at one end and alternately engageable with the notch in said cam, a main roller carried on an extension from said cam, a main, substantially cruciform, lever pivoted at its cross point and operatively connected at the top end with a motor-driven shaft, a spring energy storing roller mounted on the bottom end of said main lever, a pair of drive levers pivoted at one end to the right and left ends of said main lever, tension spring means arranged to normally bias said drive levers into engagement with said main and spring energy storing rollers, and a stop releasing bar secured to the downwardly extending arm of said main lever for engagement with either of said stop levers, the arrangement being such that upon rotation of said motor-driven shaft said main lever is rocked to push one of said drive levers away from the other drive lever by way of said spring energy storing roller thereby to store energy in said tension spring means until said stop releasing bar releases one of said stop levers previously held in engagement with the notch in said cam when a predetermined amount of spring energy has been stored to allow said tension spring means to release the energy stored therein to drive said cam by way of said main roller thereon.

References Cited by the Examiner UNITED STATES PATENTS 2,680,164 6/54 Lennox 20017 2,680,790 6/54 Jansen ZOO-17 2,833,873 5/58 Jansen 20017 2,878,333 3/59 McCarty et al. 20062 3,066,208 11/62 Fannon et al. 200153 3,164,689 1/65 Pensis 200l1 BERNARD A. GILHEANY, Primary Examiner.

Claims

1. A ROTARY SWITCH DEVICE FOR AN OLD-LOAD TAP-CHANGER INCLUDING A DRIVE MECHANISM ADAPTED TO QUICKLY START THE ROTATION OF THE SWITCH DRIVE SHAFT, SAID DRIVE MECHANISM COMPRISING A NOTCHED CAM MOUNTED ON THE DRIVE SHAFT OF THE SWITCH, A STOP DEVICE ENGAGEABLE WITH THE NOTCH IN SAID CAM, A MAIN ROLLER CARRIED ON SAID CAM, A MAIN, SUBSTANTIALLY CRUCIFORM LEVER PIVOTED AT ITS CROSS POINT AND OPERATIVELY CONNECTED AT THE TOP END WITH A MOTOR-DRIVE SHAFT, A SPRING ENERGY STORING ROLLER CARRIED BY SAID CRUCIFORM LEVER AT ITS BOTTOM END, A PAIR OF DRIVE LEVERS PIVOTED AT ONE END TO THE RIGHT AND LEFT EXTREMITIES OF SAID CRUCIFORM LEVER, AND TENSION SPRING MEANS ARRANGED TO NORMALLY BIAS SAID DRIVE LEVERS INTO ENGAGEMENT WITH SAID MAIN AND SPRING ENERGY STORING ROLLERS, THE ARRANGEMENT BEING SUCH THAT UPON ROTATION OF SAID MOTOR-DRIVE SHAFT SAID MAIN LEVER IS ROCKED TO PUSH ONE OF SAID DRIVE LEVERS AWAY FROM THE OTHER DRIVE LEVER BY WAY OF SAID SPRING ENERGY STORING ROLLER THEREBY TO STORE ENERGY IN SAID TENSION SPRING MEANS, SAID DRIVE MECHANISM FURTHER COMPRISING STOP RELEASING MEANS ON SAID MAIN LEVER FOR RELEASING SAID STOP DEVICE WHEN A PREDETERMINED AMOUNT OF SPRING ENERGY HAS BEEN STORED TO ALLOW SAID TENSION SPRING MEANS TO RELEASE THE ENERGY STORED THEREIN TO DRIVE SAID CAM BY WAY OF SAID MAIN ROLLER THEREON.