US3445611A - Selector switch for load tap-changers of regulating transformers - Google Patents

Description

y 1959 A. BLEIBTREU ETAL 3,445,511

SELECTOR SWITCH FOR LOAD TAP-CHANGERS OF REGULATIN G;TRANSFORMERS Filed July 12, 1967 Sheet of 5 um k v, WWW k W W W y 20, 1969 A. BLEIBTREU ETAL 3,445,611 I SELECTOR SWITCH FOR LOAD TAP-CHANGERS F REGULATING TRANSFORMERS Sheet Filed July 12, 1967 r //VVE/V70/PS (wumm mm um M. mm

May 20; 1969 A. BLEIBTREU ETAL 3,445,611

SELECTOR SWITCH FOR LOAD TAP-CHANGERS OF REGULATING TRANSFORMERS Sheet Filed July 12, 1967 May 20, 1969 A. BLEIBTREU ETAL 3,445,611

SELECTOR SWITCH FOR LOAD TAP-CHANGERS OF REGULATING TRANSFORMERS Filed July 12, 196'? Sheet 4 of 5 (Wm/m WM UM A. XMM

M WWW WW May 20,1969 A. BLElBTREU ETAL-Q 3,445,611

' SELECTOR SWITCH FOR LOAD TAP-CHANGERS OF REGULATING TRANSFORMERS Filed July 12, 1967 Sheet 5 015 3 llil 1 7 r vI.

United States Patent O US. Cl. 200-11 Claims ABSTRACT OF THE DISCLOSURE Disclosed below is a selector switch for load tapchangers of regulating transformers of the type including a plurality of fixed contacts arranged in two coaxial circular patterns each situated in one of two different planes. One of the two aforementioned circular patterns of fixed contacts is intended to be conductively connected to the even numbered taps of a transformer winding and the other of the two aforementioned patterns of fixed contacts is intended to be conductively connected to the odd numbers taps of a transformer winding. In such an arrangement the circular pitch is the distance from the center of one contact to the center of the next consecutive contact measured on the circle along which the contacts are arranged, or which may be drawn through the centers thereof. The structure disclosed includes means for operating a pair of contact arms or contact bridges engaging the fixed contacts in steps equal to half the circular pitch of the contacts and additional slide contacts which establish a conductive connection between the aforementioned pair of contact arms or contact bridges when the same are in registry positions. As a result of these features all contacts pertaining to one phase of a transfer switch and operatively related to the selector switch are maintained at the same potential, except during tap-changing operations of the transfer switch.

BACKGROUND OF INVENTION This invention relates to selector switches of the kind disclosed in US. Patent 3,176,089 to A. Bleibtreu at al., Load Tap Changers for Transformers, Mar. 30, 1965; US. Patent 3,233,049 to A. Bleibtreu, Integral Selector Switch and Transfer Switch Unit for Tapped Regulating Transformers, Feb. 1, 1966; and US. Patent 3,250,864 to A. Bleibtreu et al., Regulating Transformers Having a Large Number of Taps, May 10, 1966.

Such selector switches are intended to be operatively related to both a tapped transformer winding and a transfer switch. The transfer switch is interposed between a tap of a tapped transformer winding which carries current and other, or pre-selected, tap. In transfer switches of regulating transformers which are operatively related to selector switches of the kind disclosed in the above patents there is a difference of potential between the open contacts and the closed contacts of the transfer switch. This difference of potential is equal to the difference of potential between contiguous taps of the tapped regulating winding of the transformer. Under certain conditions the voltage, or difference of potential, between the open contacts and the closed contacts of a transfer switch may be of much larger magnitude than the voltage, or difference of potential, between contiguous taps of a tapped transformer winding, and may reach dangerous surge voltage proportions. This fact compels to take certain precautions in the design of transfer switches to preclude breakdown of insulation therein. This, in turn, results in a substantial increase of the cost of manufacturing transfer switches as well as an increase of the bulk of such switches.

There are a number of Ways of avoiding these drawbacks and limitations, and the present invention is concerned with one particularly desirable way of achieving this end.

A transfer switch has two limit positions. In one of these limit positions some of the contacts of a transfer switch, i.e. the closed contacts thereof, are connected by the intermediary of the selector switch to one tap of a tapped transformer winding. In that limit position of the transfer switch some of the contacts of the transfer switch, i.e. the open contacts thereof, are connected by the intermediary of the selector switch to another tap of a tapped transformer winding. This other tap is the pre-selected tap situated immediately adjacent the first mentioned tap. It is possible to provide a disconnect switch for disconnecting the open contacts of the transfer switch from the tap of the tapped transformer winding which is preselected by the position of the selector switch, and conductively connecting these contacts with the closed contacts of the transfer switch, thus equalizing the potential of the open contacts of the transfer switch and of the closed contacts thereof. The use of such auxiliary changeover disconnect switches for the intended purpose is disclosed and claimed in the copending patent application of Ulrich G. E. Schweitzer, filed July 5, 1967, Ser. No. 651,284, for Tap-Changing Transformer Including a Selector Switch and a Transfer Switch assigned to the same assignee as the present invention.

In a special type of selector switches both movable contacts, or contact bridges, thereof rest on the same fixed contact when a tap-changing operation has been performed by the transfer switch and the desired tap is connected into the load circuit. Then both movable contacts are carrying current and this makes it possible to increase the current-carrying capacity of this special type of selector switches. In such selector switches there are two fixed contacts for each tap of the tapped transformer winding, i.e. there are two fixed contacts which are conductively connected with the same tap and are current-sharing, thus achieving the desired increase in current-carrying capacity. In load tap-changers including such special selector switches all the contacts of the transfer switches are at the same potential when the latter are in one of their limit positions or, in other words, in a stationary currentcarrying position. The above referred-to special selector switches are, however, subject to serious drawbacks. Since all their dual fixed contacts of each phase must be arranged in one common plane (rather than in two parallel spaced planes) the diameter of such special selector switches tends to be extremely large, or excessive. This is due to the fact that a certain minimum distance or circular contact pitch must be maintained between the contacts thereof to achieve the required dielectric strength. In selector switches wherein the fixed contacts pertaining to the same phase are arranged in two parallel spaced planes the circular contact pitch may be much smaller than in the above special selector switches, assuming that there are equal dielectric strength of contact spacing requirements in both instances.

SUMMARY OF THE INVENTION Selector switches embodying this invention include a first plurality of fixed odd numbered contacts arranged in a first circular pattern defining a first plane and a second plurality of fixed even numbered contacts arranged in a second circular pattern coaxial with said first circular pattern and defining a second plane spaced from and parallel to said first plane. Said first plurality of fixed contacts and said second plurality of fixed contacts have a predetermined circular pitch. Selector switches embodying this invention further include a pair of slip rings arranged in coaxial relation to said first plurality of fixed contacts and to said second plurality of fixed contacts. Said pair of fixed slip rings includes a first slip ring and a second slip ring. Selector switches embodying this invention further include a pair of contact bridges pivotable about the common axis of said first plurality of fixed contacts and said second plurality of fixed contacts. Said pair of contact bridges include a first contact bridge and a second contact bridge. Said first contact bridge has a radially outer end permanently engaging said first slip ring and a radially inner end selectively engaging any of said first plurality of fixed contacts. Said second contact bridge has a radially inner end permanently engaging said second slip ring and a radially outer end selectively engaging any of said second plurality of fixed contacts. Selector switches embodying this invention further include a pair of operating means for pivoting said first contact bridge and said second contact bridge about said common axis of said first plurality of fixed contact and said second plurality of fixed contacts in steps equal to half said circular pitch to cause said radially outer end of said first contact bridge to engage consecutive contacts of said first plurality of contacts and to cause said radially outer end of said second contact bridge to engage consecutive contacts of said second plurality of contacts upon having been pivoted two said steps in the same direction. Selector switches embodying this invention further include additional contact means establishing a conductive connection between said pair of contact bridges in registering positions of said pair of contact bridges.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagrammatic representation of a single phase selector switch embodying the present invention combined with a conventional transfer switch of the type known as Jansen transfer switch;

FIG. 2 is a partial top-plan view of the selector switch shown in FIG. 1;

FIG. 3 is an isometric view of the selector switch shown in FIGS. 1 and 2;

FIG. 4 is a vertical section of a special Geneva gear drive for operating the selector switch of FIGS. 13, this drive including super-imposed Geneva gears;

FIG. 5 is a top plan view of the drive shown in FIG. 4;

FIG. 6 is a diagram illustrating the sequence of operations of a selector switch embodying this invention and of a transfer switch which is operatively related to it;

FIG. 7 is a vertical section of another special Geneva gear drive for operating the selector switch of FIGS. 1-3. This drive including Geneva gears which are arranged in a common plane;

FIG. 8 is a top plan view of the drive of FIG. 7;

FIG. 9 is a diagram illustrating the sequence of operations of a selector switch embodying the present invention and of a transfer switch when using the drive of FIGS. 7 and 8;

FIG. 10 is a top plan view of a cog-wheel drive for a selector switch embodying the present invention;

FIG. 11 is a vertical section through a drive of the kind illustrated in FIG. 10 including cog-wheels which are arranged in a common plane; and

FIG. 12 is a diagram illustrating the sequence of operations of a selector switch embodying the present invention and of a transfer switch when using the drive of FIGS. 10 and 11.

DESCRIPTION OF PREFERRED EMBODIMENTS In FIG. 1 reference character L has been applied to generally designate a Jansen type transfer switch and reference character St has been applied to generally designate a selector switch. As explained in US. Patent 3,174,097 to A. Bleibtreu, Transfer Switch for Tap Changes for Regulating Transformers, Mar. 16, 1965 there are many different kinds of Jansen type transfer switches involving different circuitries and different sequences of tap-changing switching steps. Reference may be had to this patent for details in regard to the design and performance features of various kinds of Jansen type transfer switches. The transfer switch L of FIG. 1 is one of many transfer switches which may be used jointly with selector switches embodying the present invention. The transfer switch of FIG. 1 includes a cylindrical support 15 for fixed contacts 11, 12, 13, 14. Only a portion of support 15 has been shown in FIG. 1. Fixed contacts .11, 12 are outer contacts, or main contacts, and fixed contacts 13, 14 are inner contacts, or auxiliary contacts. Reference characters 21 and 22 have been applied to indicate a pair of movable main contacts, and reference characters 23 and 24 have been applied to indicate a pair of movable auxiliary contacts. Contacts 11 and 21 are adapted to be brought into engagement. and out of engagement by means of a link which supports contact 21. In a like fashion contacts 13, 23; 14, 24 and 12, 22 may be brought into and out of engagement by links which support movable contacts 23, 24, 22. Reference character A has been applied in FIG. 1 to indicate an outgoing line to which all of the movable contacts 21, 22, 23 and 24 are conductively connected. Fixed contacts 11 and 13 are interconnected by a resistor R. In a like fashion fixed contacts 12 and 14 are interconnected by a resistor R. The operation of contacts 21, 22, 23 and 24 in the required sequence may be performed by linkage operating means of the character described in considerable detail in US. Patent 3,218,400 to A. Bleibtreu, May 16, 1965 for Transfer Switches for Tap-Changing Regulating Transformers Having Squirrel-Cage-Shaped Support for the Fixed Contacts Thereof. It will be apparent from FIG. 1 that the fixed contacts and the movable contacts of the structure shown therein are arranged in sector-like fashion, or encompass a space which is a sector of a cylinder. In three-phase circuits the transfer switch includes three such sector-like contact arrangements, each for one phase of the three-phase circuit. Line A may then be connected to the neutral point of the transformer, assuming the latter to be star-connected.

The selector switch St includes a pair of stationary slip rings 31, 32 of which the former is conductively connected by lead 25 to fixed contact 11 of transfer switch L, and the latter is conductively connected by lead 26 to fixed contact 12 of transfer switch L. The selector switch St includes a relatively large number of fixed contacts 1, 2, 3 Only three such contacts are shown in FIG. 2, and additional fixed contacts including contacts 5, 6 are shown in FIG. 3. All odd numbered contacts are arranged in a circular pattern on a relatively high level and all even numbered contacts are arranged in a coaxial circular pattern on a relatively lower level, as clearly shown in FIG. 3. The contacts 1, 2, 3 of selector switch St are supported by a system of vertical rods 33 of insulating material which form a squirrel-cake-like structure, as clearly shown in FIG. 3. Slip ring 31 is arranged in a plane defined by odd numbered contacts 1, 3 and slip rings 32 is arranged in a plane defined by even numbered contacts 2, 4 Slip rings 31, 32 are fixedly mounted on a column of insulating material arranged along the axis of the cylindrical surface defined by rods 33. Reference character 40 has been applied to indicate the housing of a gear mechanism for operating the selector switch St. The selector switch St further includes an upper contact arm, or contact bridge 35, whose radially outer end engages the odd numbered contacts 1, 3 and whose radially inner end engages slip ring 32. The lower contact arm 36 of selector switch St engages with the radially outer end thereof the even numbered contacts 2, 4 and with the radially inner end thereof slip ring .32. Contact arms or contact bridges 35, 36 are adapted to be pivoted about the axis of column 34, as will be shown below more in detail. Contact arm, or contact bridge 36, is provided with a sliding contact or brush contact 37 which establishes a conductive connection between contact bridges 35, 36 when these contact bridges are in positions of registry.

The odd numbered contacts of the selector switch are conductively connected with the odd numbered contacts of a tapped transformer winding (not shown), and the even numbered contacts of the selector switch are conductively connected with the even numbered contacts of that winding. Thus the following current path is established: tap 1 on a tapped transformer winding (not shown), fixed contact 1 of selector switch St, contact bridge 35, slip ring 31, lead 25, main contacts 11, 21 of transfer switch L and lead A. The contact bridge 36 does not carry current at the time contact bridge 35 engages contact 1 and carries current along the above current path 35, 25, 11, 21, A; 'but it is arranged at that time in registry wth contact bridge 35 and conductively connected with contact bridge 35 by sliding contact or brush contact 37. As a result, the same potential is applied to fixed contact 12 of transfer switch L as to the fixed contact 11 thereof. Because of the presence of resistors R fixed contacts 13-, 14 are at the same potential as contacts 11 and 12 which, as mentioned above, is the same by virtue of the particular design of selector switch St. On the other hand, all movable contacts 21, 22, 23, 24 of transfer switch L are at the same potential since they are conductively interconnected by lead A. Thus all contacts of transfer switch St are at the same potential when the transfer switch is either in its limit position shown in FIG. 1, or in its opposite limit position. In the latter movable main contact 22 is in engagement with fixed main contact 12, and all other contacts are out of engagement. In either of the two aforementioned limit positions the current flow through transfer switch L is stationary, transient conditions being limited to the short intervals of time when transfer switch L is moved between its two limit positions. As long as transfer switch L is in either of its two limit positions, and stationary circuit conditions prevail, all the contacts of transfer switch L are at the same potential, i.e. the potential of the current-carrying contact of selector switch St.

In three-phase transfer switches of the kind indicated in FIG. 1 a pair of closed main contacts of one phase is situated immediately adjacent a pair of open main contacts of another phase. This makes it particularly desirable to equalize voltages between main contacts in the fashion which has been outlined above.

Each switching step of contact bridges 35, 36 corresponds to one half of the circular pitch of fixed contacts 1, 3 and fixed contacts 3, 5 respectively. This is a prerequisite of achieving the registry position of contact bridges 35, 36 illustrated in FIG. 1. FIG. 2 illustrates the very instant in which contact bridge 36 is moving out of its registry position with contact bridge 35 into engagement with fixed contact 2 of selector switch Sr, this being effected by a pivotal motion of contact bridge 36 in clockwise direction, as seen in FIG. 2. When contact bridge 36 has engaged fixed contact 2 of selector switch St, transfer switch L becomes operative, and when its transfer operation is completed its contacts 12 and 22 are in engagement, and all its other contacts out of engagement. At this point of time tap 2 of the transformer winding (not shown) is conductively connected with lead A by the intermediary of selector switch St and transfer switch -L. After contact bridge 36 has engaged fixed contact 2 of selector switch St, the contact bridge 35' of the latter is moved one half circular contact pitch in clockwise direction, as seen in FIG. 2, i.e. half the distance between fixed contacts 1 and 3 of selector switch St. As a result, contact bridges 35 and 36 are again in one of their registry positions and are again conductively interconnected by sliding contact or brush contacts 37. Hence all contacts of transfer switch L are again at the same potential, which is now that of tap 2 and fixed contact 2 of selector switch St. It is thus apparent that differences in potential between the contacts of transfer switch L pertaining to the same phase are limited to the short periods of time during which the selector switch and the transfer switch are being operated.

The Geneva gear drive illustrated in FIGS. 4 and 5 is one of the possible means for achieving the required timing of the operations of the systems shown in FIGS. 1 and 2. The gear drive is arranged in a housing 40 which is preferably arranged above the selector switch (see FIG. 3). Geneva gears 41 and 42 are mounted on a common shaft 49 and arranged one above the other. Both Geneva gears 41, 42 are operated by a cam gear 43 mounted on and driven by shaft 44. The upper surface of cam gear 43 is provided with a cam 45 for engaging Geneva gear 41, and the lower surface of cam gear 43 is provided with a cam 46 for engaging Geneva gear 42. Verictal rod 47 is integral with Geneva gear 41 and projects downwardly to operate, or pivot, contact bridge 35 cooperating with the odd numbered contacts of the selector switch St. In like fashion vertical rod 48 is integral with Geneva gear 42 and projects downwardly to operate, or pivot, contact bridge 36 cooperating with the even numbered contacts of the selector switch St. Shaft 49 on which Geneva gears 41 and 42 are mounted is, in turn, supported by gear box or housing 40.

When transfer switch L is in one of its limit positions and the contact bridges 35, 36 of selector switch St in their registering positions, i.e. when both switches L and St are in one of their permanent positions, as distinguished from their transient positions, Geneva gears 41 and 42 are angularly displaced in such a fashion that the center lines of the slots 411 of gear 41 are-in registry with the center lines of the wing portions 422 of Geneva gear 42. In that position of geneva gears 41, 42 the center lines of slots 421 of Geneva gear 42 are in registry with the center lines of the wing portions 412 of Geneva gear 42. This is clearly apparent from FIG. 5. When cam gear 43 is pivoted in counterclockwise direction about a predetermined angle 06 as indicated by an arrow in FIG. 5, cam 46 of gear 43 pivots Geneva gear 42 in clockwise direction, as seen in FIG. 5. As a result of this pivotal motion of Geneva gear 42 the center lines of slots 421 of gear 42 and the center lines of slots 411 of gear 41 are arranged in registry. As cam gear 43 continues its pivotal motion in counterlockwise direction about angle 6, the transfer switch is caused to operate as a result of which its contacts are moved from the limit position shown in FIG. 1 to the opposite limit position wherein its contacts 12 and 22 are in engagement, and all its other contacts are out of engagement. Thereupon cam 45 on cam wheel 43 engages slot 411 of Geneva gear 41 and pivots about the angle 'y. As a result, Geneva gear 41 is moved in such a fashion that the center lines of its slots 411 are in registry with the center lines of wings 422 of Geneva gear 42. Now a tap-changing operation, or a tapchanging duty cycle, has been completed and all parts of switches L and St are in rest position, another tap and another contact of switch L now carrying current than the tap and the contact of switch St carrying current at the beginning of the tap-changing operation. In this position of rest Geneva gear 42 is locked by means of locking device 452. In like fashion Geneva gear 41 had been locked in its initial position shown in FIG. 4 by locking device 461 on cam gear 43. Locking devices 452 and 461 are integral with cam gear 43 and engage in the locking positions thereof corresponding recesses provided in wings or wing portions 412 and 422 of Geneva gears 41 and 42, respectively. Each cam 45 and 46, respectively, of cam gear 43 for operating Geneva gears 41, 42 is provided with one of the aforementioned locking devices 452 and 461 for locking the other Geneva gears 42 and 41 in position.

As mentioned above, FIG. 6 is a diagrammatic representation of the sequence of steps involved in the operation of the structure of FIGS. 4 and 5. The distances a and correspond to half the circular pitch steps of the Geneva gears 41, 42 driving selector switch St of FIGS. 1 and 2. The distance or length 7 represents the angle of rotation of cam gear 43 during which transfer switch L is moved from one of its limit positions to the other limit position thereof. It is apparent from FIG. 6 that the first half circular pitch step of the Geneva gear drive by which one of contact bridges 35, 36 is operated is performed prior to the movement of transfer switch L from one of its limit positions to the other, while the second half circular pitch step of the Geneva gear drive by which the other of the two contact bridges 35, 36 is operated is performed subsequent to the movement of transfer switch L from one of its limiting positions to the other.

The selector-switch-operating gear mechanism of FIGS. 7 and 8 includes a pair of Geneva gears 51, 52 which are arranged in a common plane, and a cam gear 53 which is arranged between the two aforementioned Geneva gears. A driving shaft 54 operates a worm gear mechanism 54a and cam gear 53 is mounted on the shaft 54b of the worm gear of worm gear mechanism 54a. Cam gear 53 is provided with a cam 55 which is adapted to cooperatively engage both Geneva gears 51, 52. Cam gear 55 is further provided with a locking device 551 which is angularly displaced 180 degrees relative to its cam 55. Selector-switch-operating rod 57 is secured to Geneva gear 51 and operates the contact bridge 35 for selecting odd numbered fixed contacts 1, 3 of selector switch St, and Geneva gear 52 is integral with selector-switch-operating rod 58 which operates contact bridge 36 for the even numbered fixed contacts 2, 4 of selector switch St. Reference numeral 50 has been applied to indicate a gear box or housing for the selector-switchoperating gear.

As shown in FIG. 8 both Geneva gears 51, 52 are arranged in such a fashion that when its above gears are in the rest position thereof the center line of one of the slits 511 in gear 51 is juxtaposed to the center line of one of the wings 522 of gear 52. In this rest position of the Geneva gear drive both contact bridges 35, 36 of selector switch St are in their rest positions wherein they are registering and conductively interconnected by slide contact or brush contact 37 and transfer switch L is like wise in a position of rest, i.e. in one of the two limit positions thereof. Operation of the selector-switch-operating gear is initiated by a pivotal motion of cam gear 53 in the direction of the arrow of FIG. 8, or in counterclockwise direction, about the angle 0:. As a result, Geneva gear 52 moves contact bridge 36 by the intermediary of contact-bridge-operating shaft 58 say from fixed contact 1 toward fixed contact 2. As cam gear 53 continues its pivotal motion in counterclockwise direction about the angle fi, it is out of meshing engagement with Geneva gear 52. As cam gear 53 moves along the trajectory corresponding to angle 5, the transfer switch L is caused to operate and to move from one of its limit positions to the other, e.g. from the limit position shown in FIG. 1 wherein its main contacts 11, 21 are in engagement and conductively connected to the fixed contact 1 of selector switch St to the limit position in which its main contacts 12, 22 are in engagement and conductively connected to fixed contact 2 of selector switch St. As cam gear 53 continues its pivotal or rotational motion along the trajectory which corresponds to angle 7, its cam 55 is in meshing engagement with Geneva gear 51. This causes a pivotal motion of Geneva gear 51 and of selector-switch-operating shaft 57 as a result of which contact bridge 35 is being operated, e.g. moved to fixed contact 2 of selector switch St and to a position of registry with contact bridge 36. This completes a switch over duty cycle as, for instance, switching from tap 1 and fixed contact 1 to tap 2 and fixed contact 2.

FIG. 9 illustrating the sequential steps involved in the operation of the Geneva gear of FIGS. 7 and 8 is selfcxplanatory in view of the foregoing.

Referring now to FIGS 10 and 11, the selector-switchoperating gear mechanism shown therein includes a pair of cog wheels or pin wheels 61 and 62 which are arranged side by side in a common plane. Cam gear 63 is arranged between cog wheels or cog gears 61, 62. Shaft 64 operates a worm gear 64a including a shaft 64b on which cam gear 63 is mounted. Cam gear 63 includes a pair of cams 65 and 66 arranged to one side thereof and a locking device 651 arranged to the other side thereof. Cog wheel 61 is provided with equidistant cogs 611 and operates a shaft 67 for operating contact bridge 35 cooperating with the odd numbered fixed contacts of selector switch St. Cog wheel 62 is provided with equidistant cogs 622 and operates a shaft 68 for operating contact bridge 36 cooperating with the even numbered fixed contacts of selector switch St. The cog-wheel-drive for operating contact bridges 35, 36 is arranged in a gear box or gear housing 60.

If cam gear 63 is pivoted about is shaft 64b in clockwise direction as seen in FIG. 10, cam '66 engages the cog 611 situated between earns 65 and 66 and moves cog wheel 61 along the angle a. As a result, shaft 67 moves contact bridge 35 one step. This corresponds to a pivotal motion of cam wheel 63 about the angle 06. As cam wheel 63 is further moved about the angle ,8, both cog wheels 61, 62 stand still. In this interval of time the transfer switch L is caused to switch to the fixed contact of selector switch L which has been pre-selected by the operation of cog wheel 61. The motion of deg. of cam wheel 63 is completed by moving along the angle 7. During the last phase of the aforementioned pivoted motion of cam wheel 63 its cam 65 pivots cog wheel 62 about the angle 7 indicated in FIG. 10. As a result, shaft 68 of cog wheel 62 moves contact bridge 36 one step into registry with contact bridge 35, thus establishing a conductive connection between both contact bridges 35, 36.

FIG. 12 illustrates the above referred-to switching cycle and is self-explanatory.

The gear mechanism of FIGS. 4 and 5 is intended to operate directly contact bridges 35, 36, i.e. merely by the intermediary of rods 47, 48 which are integral with contact bridges 35, 36. The shafts 57, 58 of the Geneva gear of FIGS. 7 and 8 are intended to operate an intermediate gear (not shown) which, in turn, operates contact bridges 35, 36. In the same fashion the shafts 67, 68 of cog wheels 61, 62 of FIGS. 10 and 11 are intended to operate an intermediate gear (not shown) which, in turn, operates contact bridges 35, 36.

Jansen type tap-changing regulating transformers are generally provided with an operating head arranged above the transfer switch. The transferswitch is arranged above the selector switch and both the transfer switch and the selector switch are operated by the aforementioned operating head. This has been indicated in the copending patent application of Ulrich G. E. Schweitzer, filed July 5, 1967, Ser. No. 651,284 for Tap-Charging Transformer Including a Selector Switch and a Transfer Switch. It is also shown in greater detail in the printed publication titled Stufenschalter Typ D System Dr. Jansen published by Maschinenfabrik Reinhausen Gebriider Scheubeck KG., Regensburg, West Germany (see particularly FIG. 11 which is self-explanatory). The Geneva gear drive of FIGS. 4 and 5 is intended to be arranged immediately above the selector switch, i.e. between the transfer switch and the selector switch, shaft 44 of FIGS. 4 and 5 extending upward to the aforementioned operating head and being driven by the same. The Geneva gear drive of FIGS. 7 and 8 and the cog wheel drive of FIGS. 10 and 11 are integral parts of the aforementioned operating head. In other words, they are intended to be arranged at a higher level than the Geneva gear drive of FIGS. 4 and 5. The shafts 57 and 58 of FIGS. 7 and 8 and the shafts 67 and 68 of FIGS. 10 and 11 transmit the step motions of the gears shown in these figures to an intermediate gear (not shown) arranged between the transfer switch and the se1ector switch which intermediate ear operates the contact bridges 35, 36 of the selector switch St. This intermediate gear may be a normal spur gear including a pair of wheels arranged in coaxial relation to the selector switch St of which each is integral with one of the contact bridges 35, 36. This may be achieved by means of vertical tie rods similar to the rods 47, 48 of FIG. 4. The above referred to Maschinenfabrik Reinhausen publication shows the positioning of an intermediate gear and the way it is being operated from the operating head of the regulating transformer. The aforementioned US. Patent 3,250,864 refers to a regulating transformer including a Geneva gear drive which is arranged between the transfer switch and the selector switch and driven by a shaft 57 extending upwardly to the operating head of the regulating transformer. The Geneva gear drive of FIGS. 4 and 5 is intended to be positioned and operated in the same fashion as the Geneva gear drive of US. Patent 3,250,864.

While, in accordance with the patent statutes, we have disclosed the specific details of preferred embodiments of the invention, it is to be understood that these details are merely illustrative and that many variations thereof may be made without departing from the spirit and scope of the invention. It is, therefore, our desire that the language of the accompanying claims be interpreted as broadly as possible, and that it be limited only by the prior state of the art.

We claim as our invention:

1. In a selector switch for load tap-changers of regulating transformers the combination of:

(a) a first plurality of fixed odd numbered contacts arranged in a first circular pattern defining a first plane, said first plurality of fixed contacts having a predetermined circular contact pitch;

(b) a second plurality of fixed even numbered contacts arranged in a second circular pattern coaxial with said first circular pattern and defining a second plane spaced from and parallel to said first plane, said second plurality of fixed contacts having the same predetermined circular pitch as said first plurality of fixed contacts;

(0) a pair of fixed slip rings arranged in coaxial relation to said first plurality of fixed contacts and to said second plurality of fixed contacts, said pair of fixed slip rings including a first slip ring and a second slip (d) a pair of contact bridges pivotable about the common axis of said first plurality of fixed contacts and said second plurality of fixed contacts, said pair of contact bridges including a first contact bridge and a second contact bridge, said first contact bridge having a radially inner end permanently engaging said first slip ring and having a radially outer end selectively engaging any of said first plurality of fixed contacts, and said second contact bridge having a radially inner end permanently engaging said second slip ring and having a radially outer end selectively engaging any of said second plurality of fixed contacts;

(e) a pair of operating means for pivoting said first contact bridge and said second contact bridge about said common axis of said first plurality of fixed contacts and said second plurality of fixed contact? in steps equal to half said circular contact pitch to cause said radially outer end of said first contact bridge to engage consecutive contacts of said first plurality of fixed contacts and to cause said radially outer end of said second contact bridge to engage consecutive contacts of said second plurality of fixed contacts upon having been pivoted two said steps in the same direction; and

(f) additional contact means establishing a conductive connection between said pair of contact bridges in registering positions of said pair of contact bridges.

2. A selector switch as specified in claim 1 including a squirrel-cage-structure having supporting rods of insulating material for said first plurality of fixed contacts and for said second plurality of fixed contacts.

3. A selector switch as specified in claim 1 including a sliding contact fixedly supported by and conductively connected to one of said pair of contact bridges and slidingly engaging the other of said pair of contact bridges in registering positions of said pair of contact bridges.

4. A selector switch as specified in claim 1 including a common drive for said pair of operating means and means establishing a lost motion connection between said common drive and said pair of operating means, said common drive being adapted to sequentially engage each of said pair of operating means and to be disengaged from both of said pairs of operating means in intervals of time following disengagement from one of said pair of operating means and prior to engagement of the other of said pair of operating means to establish a pausebetween each step of one of said pair of operating means and a consecutive step of the other of said pair of operating means.

5. A selector switch as specified in claim 1 including a common-drive-operated rotatable cam means and a pair of gears each operable by said cam means, said cam means and said pair of gears being shaped and arranged to cause sequential engagement by said cam means during a rotary degrees motion thereof of each of said pair of gears, and said cam means and said pair of gears being shaped and arranged to allow a predetermined travel of said cam means out of engagement with both said pair of gears subsequent to disengagement of said cam means from one of said pair of gears and prior to engagement of said pair of cam means with the other of said pair of gears.

6. A selector switch as specified in claim 1 including a cam gear having a pair of cams angularly displaced 180 degrees and a pair of superimposed Geneva gears each for operating one of said pair of contact bridges and each operable by one of said pair of cams, said pair of Geneva gears being normally angularly displaced so that the centers of the slots of one of said pair of Geneva gears register with the centers of the wings of the other of said pair of Geneva gears.

7. A selector switch as specified in claim 1, including a cam gear having on opposite sides thereof a pair of cams angularly displaced 180 degrees, said selector switch further including a pair of superimposed Geneva gears each for operating one of said pair of contact bridges and each operable by one of said pair of cams, said pair of Geneva gears being normally angularly displaced so that the centers of the slots in one of said pair of Geneva gears register with the centers of the wings of the other of said pair of Geneva gears, and said cam gear having an opposite sides thereof a pair of locking devices angularly displaced 180 degrees each adapted to enter the slots in one of said pair of Geneva gears.

8. A selector switch as specified in claim 1 including a pair of Geneva gears each for operating one of said pair of contact bridges, said pair of Geneva gears being arranged substantially in a common plane and having spaced centers, a cam arm pivotable about a shaft arranged at right angles to said common plane between said centers of said pair of Geneva gears, said cam arm having a cam means arranged to sequentially engage said pair of Geneva gears and said pair of Geneva gears being normally angularly displaced in such a fashion that the centers of the slots in one of said pair of Geneva gears are juxtaposed to the centers of the wings in the other of said pair of Geneva gears.

'9. A selector switch as specified in claim 1 including a pair of Geneva gears each for operating one of said pair of contact bridges, said pair of Geneva gears being arranged substantially in a common plane and having spaced centers, a cam arm pivotable about a shaft arranged at right angles to said common plane between said centers of said pair of Geneva gears, said cam arm having a cam means arranged to engage sequentially said pair of Geneva gears when pivoted about an angle of 180 degrees, said pair of Geneva gears being normally angularly displaced in such a fashion that the centers of the slots in one of said pair of Geneva gears are juxtaposed to the centers of the wings of the other of said pair of Geneva gears, said cam arm further having a locking device angularly displaced 180 degrees relative to said cam means thereof, and said locking device being shaped to conform with and to engage the radially outer edges of the wings of said pair of Geneva gears.

10. A selector switch as specified in claim 1 including a pair of spaced cog wheels each for operating one of said pair of contact bridges and a cam gear arranged between said pair of cog wheels and having a pair of fork-shaped cam projections cooperatively engaging and alternatingly driving one of said pair of cog wheels, said cam gear having a curve-shaped locking device angularly displaced 180 References Cited UNITED STATES PATENTS 3/1965 Bleibtreu et al. 200-l8 1/1941 St. Palley 323-435 ROBERT K. SCHAEFER, Primary Examiner.

M. GINSBURG, Assistant Examiner.

US. Cl. X.R. 32343.5

Images