US3250864A

US3250864A - Regulating transformers having a large number of taps

Info

Publication number: US3250864A
Application number: US288636A
Authority: US
Inventors: Bleibtreu Alexander; Baumgartner Ernst
Original assignee: Maschinenfabrik Reinhausen Gebrueder Scheubeck GmbH and Co KG
Current assignee: Maschinenfabrik Reinhausen Gebrueder Scheubeck GmbH and Co KG
Priority date: 1962-07-04
Filing date: 1963-06-18
Publication date: 1966-05-10
Anticipated expiration: 1983-05-10
Also published as: GB990146A; NL294842A; BE634502A; CH410172A; NL121328C; DE1220033B

Description

May 10, 1966 BLElBTREu I ET AL 3,250,864

REGULATING TRANSFORMERS HAVING A LARGE NUMBER OF TAPS 4 Sheets-Sheet 1 Filed June 18, 1963 May 10, 1966 A. BLEIBTREU ETAL 3,250,864

REGULATING TRANSFORMERS HAVING A LARGE NUMBER OF TAPS Filed June 18, 1963 4 Sheets-Sheet 2 o l O I m m H5 I 5 fi 65 (I h 62; 66 W-JI :r I I V i/ l u 55 w I l l I w 52 wk 6/ I I 55 Wyn/70,93;

MA- WMMM Mm WWW m May 10, 1966 BLEIBTREU ETAL REGULA'IING TRANSFORMERS HAVING A LARGE NUMBER OF TAPS Filed June 18, 196;

4 Sheets-Sheet 5 M 'WAM RAW y 1956 A. BLEIBTREU ET AL REGULATING TRANSFORMERS HAVING A LARGE NUMBER OF TAPS 4 Sheets-Sheet 4 Filed June 18, 1963 FIG. 3a

lNVENfOPS:

lam-om United States Patent 3,250,864 REGULATING TRANSFORMERS HAVING A LARGE NUMBER OF TAPS Alexander Bleibtreu and Ernst Baumgartner, Regensburg, Germany, assignors to Maschinenfabrik Reinhausen Gebriider Scheubeclr K.G., Regensburg, Germany Filed June 18, 1963, Ser. No. 288,636 Claims priority, application Germany, July 4, 1962, M 53,434; July 12, 1962, M 53,531 Claims. (Cl. 200-11) This invention relates to regulating transformers, particularly high voltage transformers, having one or more tapped windings which serve the purpose of regulating the voltage of the transformer.

The above requirements are generally conducive to bulky selector switches forming part of the regulating transformer, and prior art regulating transformers meeting the above requirements comprise bulky selector switches.

It is, therefore, another object of this invention to provide regulating transformers which, though meeting the above requirements, comprise selector switches whose bulk is minimal.

Another object of this invention is to provide regulating transformers meeting the above requirements and comprising selector switches which lend themselves to be built into the tank of the respective transformer.

Another object of this invention is to provide regulating transformers having a simple and compact Geneva gear drive for operating the selector switches thereof.

Another object of this invention is to provide regulating transformers having a Geneva gear drive for operating the selector switches thereof which drive includes alternately operating drive units, whereby the wear and tear to which the Geneva gear drive is subjected are minimized.

Another object of this invention is to provide regulating transformers including Geneva gear drives for the selector switches thereof which drives can be housed immediately adjacent to the selector switches, thus greatly simplifying the transmission means which must be arranged between the selector switches and their Geneva gear drives.

Another object of this invention is to provide regulating transformers comprising selector switches, Geneva gear drives for the latter and transfer switches, wherein the aforementioned switches are integrated to form self-sustained structural units.

The above objects and additional objects and advantages of the invention will become more apparent from the ensuing description of the invention, and of a specific embodiment thereof, when read in connection with the accompanying drawings.

Tap-changing regulating transformers include selector switches and transfer switches. The former serve the purpose of selecting any desired tap along a tapped trans- 1 to fixed tap contact 1, and reference character 32a has 3,250,864 Patented May 10, 1966 cuits. This task is assigned exclusively to the transfer switches. The latter perform all switching operations under load.

Referring now to the accompanying drawings:

FIG. 1 is a circuit diagram which shows a tapped transformer winding in one phase of a circuit and its associated selector switch means and transfer switch means operatively related to the selector switch means;

FIG. 2 is in part a front elevation of, and in part a vertical section through, a selector switch embodying the present invention having internal connections as shown in FIG. 1; V

FIG. 3 is a section along 33 of FIG. 4a and shows a cross-section through a Geneva gear drive unit for operating the selector switch illustrated in FIG. 2;

FIG. 3a is a section-along 3a--3a of FIG. 5a and shows a cross-section through another Geneva gear drive unit for operating the selector switch illustrated in FIG. 2;

FIGS. 4a and 4b show in top plan view two Geneva gears for operating the selector switch unit illustrated on the left side of FIG. 2,- and certain parts operatively related to said two Geneva gears; and

FIGS. 5a and 5b show in top plan view the two Geneva gears for operating the selector switch unit illustrated on the right side of FIG. 2 and certain parts operatively related to said two Geneva gears.

Referring now to the drawings, and more particularly to FIG. 1 thereof, reference character T has been applied to indicate a tapped winding of one phase U of a polyphase transformer. The other phases and their associated parts have been omitted in drawing FIG. 1 since each additional phase structure is identical to that shown in FIG. 1. Phase winding T, is provided with a large number of taps which have an unequal spacing depending upon the regulating requirements of the particular application for which the transformer is intended.

It is assumed that winding T is provided with 32 taps which will be referred-to hereinafter by numbers 1 to 32, inclusive. In FIG. 1 the first tap has been indicated by the reference number 1 and-the last tap has been indicated by the reference number 32. The transformer winding T, is associated with four selector switch sub units 1, II, III and IV having 32 fixed tap contacts of which each is conductively connected to one of the taps 1 to 32 of transformer winding T,. The fixed tap contacts of selector switch sub-units I, II, III, and IV will hereinafter be referred-to by the same reference number as the tap to which the particular fixed tap contact is conductively connected. Reference character 1a has been applied to indicate the lead conductively connecting tap been applied to indicate the lead conductively connecting tap 32 to fixed tap contact 32. The other leads conductively connecting corresponding taps and corresponding fixed tap contacts have only been indicated in part and no reference characters have been applied to these leads in order not to encumber FIG. 1. The fixed tap contacts of each selector switch sub-unit I, II, III, IV are arranged in a circle, or a circular pattern, around the center of each particular sub-unit.- Sub-units I and 111 include all the fixed tap contacts connected to odd numbered taps and sub-units II and IV include all the fixed tap contacts connected to even numbered taps. Sub-unit I includes fixed tap contacts 1 to 15 and subunit III includes fixed tap contacts 17 to 31. In like fashion sub-unit II includes fixed tap contacts 2 to 16 and sub-unit 1V includes fixed tap contacts 18 to 32. Sub-units I and III are arranged at the same level. In like fashion sub-units II and IV are arranged at the same level. However sub-unit I is stacked or superimposed upon sub-unit II and sub-unit III is stacked or superimposed upon sub-unit IV as will-be shown below contacts H H and in.

more in detail in connection with FIG. 2. Each subunit I, II, III, IV comprises a center contact Z Z Z and Z and a contact bridge or contact arm B B E and B pivotable about a fulcrum situated in the center of each sub-unit I, II, III, IV. Center contact Z is conductively connected to center contact Z by means of lead L In like fashion center contact Z is conductively connected to center contact Z by means of lead L Each sub-unit I, II, III and IV further comprises an auxiliary contact K K K and K Reference character L has been applied to generally indicate a transfer switch of the particular type known as Janson transfer switch. Transfer switch L comprises two fixed main contacts H and H and four fixed intermediate or switch-over contacts m. Contacts H and H and contacts m are arranged along a cylindrical surface in a circular pattern. Each switch-over contact In to the left of FIG. 1 is conductively connected to one of a pair of switch-over resistors R and each switch-over contact m to the right of FIG. 1 is conductively connected to one of a pair of switch-over resistors R Transfer switch L is further provided with six movable Contacts H and H are adapted to cooperatively engage contacts H and H and to be separated from the latter. Contacts m are adapted to cooperatively engage contacts m and to be separated from the latter. All movable contacts H m and H are conductively connected to a common point indicated by reference character Y. In a Y-connected system point Y is the neutral point of the system. Reference characters T T have been applied to indicate the terminals of transfer switch L Contact H and terminal T of transfer switch L are conductively connected to auxiliary contact K; of sub-unit I by lead L and to auxiliary contact K of sub-unit III by leads L and L Contact H and terminal T of transfer switch L are conductively connected to auxiliary contact K of sub-unit II by'leads L and to auxiliary contact K of sub-unit IV by leads L and L The ends of the pair of switch-over resistors R remote from fixed switch-over contacts m are conductively'connected to terminal T and lead L and'the ends of the pair of switch-over resistors R remote from fixed switch-over contacts m are conductively connected to terminal T and lead L 7 In the positions of parts which are shown in FIG. 1 the following current path is established: Tap 1 of transformer winding T lead 1a, fixed tap contact 1, contact arm or bridge B center contact Z lead L center contact Z contact arm or bridge B' auxiliary contact K leads L and L terminal T contacts H and H and point Y of the electric system. Hence, in the position of the parts which is shown in FIG. 1 tap 1 is included in the load circuit and all other taps 2-32 are ineffective.

The transfer switch L is provided with a mechanism (not shown) for operating its movable contacts H m and H Contact H the second contact m from the left and first contact m from the right are operable by a first lever system and the first contact m' from the left, the second contact m' from the right and contact H are operable bya second separate lever system. Movable contact I-I parts from its cooperating fixed contact H after the second movable contact m from the left has engaged its cooperating fixed contact m. After completion of the aforementioned sequential operations tap 1 and the pair of resistors R are connected into the load circuit of the transformer, switch-over resistors R being connected in parallel into the latter. Thereupon the movable contact m second from the right engages its cooperating fixed contact m and movable contact m. first from the left parts from its cooperating fixed contact m. The next operating steps of transfer switch L comprise engagement by the movable contact m first from the right of its cooperating fixed contact m and parting of movable contact m second from the left from its fixed cooperating contact m. Finally movable contact H engages its cooperating fixed contact H and movable contact m second from the right parts from its cooperating fixed contact m.

As a result of the above described operation of transfer switch L the transformer tap 1 is disconnected and the transformer tap 2 inserted into the circuit. The circuit including transformer tap 2 runs as follows: tap 2,

tap contact 2 of switch sub-unit II, bridge contact B center contact Z lead L center contact Z of switch sub-unit IV, bridge contact B auxiliary contact K leads L and L and terminal T The type of transfer switch shown in FIG. 1 is known as a Flag-Pennant transfer switch for reasons more fully set forth in the copending patent application of Alexander Bleibtreu, filed January 31, 1963, Ser. No. 255,291 for Transfer Switch for Tap Changers for Regulating Transformers, now US. Patent 3,174,097 issued March 16, 1965. Reference may be had to this patent for further particulars on so-called Flag-Pennant transfer switches, or F-P transfer switches, and on the vector diagram to which this type of transfer switch owes its name. The particular transfer switch shown in FIG. 1 has been selected to better illustrate the invention, but this type of transfer switch is known per se. Moreover the F-P transfer switch shown in FIG. 1 may be replaced by another type of transfer switch such as a Flag transfer switch or a Pennant transfer switch more fully described in the above referred-to patent application of Alexander Bleibtreu.

When selector switch sub-units I, II are operated, i.e. the contact bridges B B thereof pivoted about the respective fulcrum thereof, selector switch sub-units III, IV'are at rest. In the rest positions of sub-units III, IV the contact bridges E and E thereof conductively interconnect the center contacts Z and Z respectively, with the auxiliary contacts K and K respectively. Thus the center contact Z; of selector switch sub-unit I is conductively connected with the terminal T and the fixed main contact H, of transfer switch L by the intermediary of lead L contact 2 contact bridge B I auxiliary contact K and leads L L In like fashion center contact Z of selector switch sub-unit II is conductively connected to terminal T and fixed main contact H of transfer switch L by the intermediary of lead L center contact Z contact bridge B auxiliary contact K and leads L L The two selector switch sub-units I, II which are stacked operate in alternate steps and thus include consecutively taps 1 to 16, inclusive, of Winding T into the load circuit of the transformer. Upon completion of the operation of selector switch sub-units I, II contact bridge B establishes a conductive connection between contacts Z and K and contact bridge B establishes a conductive connection between contact Z and contact K If it is intended to insert any of the taps numbered 17-32 of Winding T into the load circuit of the transformer, selector switch units I, II are kept at rest in the above positions thereof in which contacts Z K and contacts Z K are conductively interconnected, and selector switch sub-units III and IV are operated in alternate steps. When selector switch sub-units III and IV are operated, i.e., bridge contacts B B pivoted about the fulcra at Z and Z any of taps 17-32 of transformer winding T may be conductively connected to the terminals T T and to fixed main contacts H H of transfer switch L This is achieved by the intermediary of contacts Z Z leads L L contacts 2;, Z contact bridges B B contacts K K and leads L L Thus the selector switch sub-units I, II operate as a pre-selector for selector switch sub-units III, IV, and vice-versa.

As indicated in FIG. 1 contact arms B and B may be pivotable about common shaft A and contact arms E and B -may be pivotable about common shaft A As has been shown above, in the position of the parts illustrated in FIG. 1 tap 1 of winding T is inserted into the load circuit of the transformer, and contacts H H of transfer switch L are in cooperative engagement. In that position of the constituent parts of the regulating transformer everything is prepared for insertion of tap 2 into the load circuit. As briefly outlined above, insertion of tap 2 into the load circuit is effected by operating transfer switch L resulting in disengagement of contacts H H thereof and in cooperative engagement of contacts H H thereof. This establishes the following current path: tap 2, fixed tap contact 2 of selector switch sub-unit II, contact bridge B central contact Z lead L central contact Z contact bridge B llead L lead L terminal T fixed main contact H movable contact H point Y. If it is now intended to include tap 3 of winding T into the load circuit, first selector switch sub-unit I is operated causing engagement between fixed tap contact 3 and contact bridge B and thereafter transfer switch I. is operated causing disengagement of its contacts H H and engagement of its contacts H H Bridge contact B does not carry any current at the time of its transfer from fixed tap contact 1 to fixed tap contact 3 of selector switch sub-unit I. The aforementioned operation of selector switch sub-units I, II and transfer switch L may be continued until bridge contact B engages fixed contact 15 of selector switch sub-unit I and contact bridge B engages fixed contact 16 of selector switch sub-unit II. The final operating steps of selector switch sub-units I and 11 consist in engagement of contact K by contact bridge B and engagement of contact K by contact bridge B During the two last operating steps of selector switch sub-units I, II the bridge contact B of selector switch sub-unit III is moved from auxiliary contact K to fixed contact 17 and the bridge contact B of selector switch sub-unit IV is moved from auxiliary contact K to fixed contact 18.

Thus taps 17-32 of winding T may now be sequentially connected to point Y by the intermediary of transfer switch L While taps 17-32 are being sequentially connected to point Y selector switch sub-units I, II remain at rest, the contact bridges B and B thereof remaining in engagement with fixed auxiliary contacts K and K respectively.

FIG. 2 shows a physical embodiment of the arrangement more diagrammatically illustrated in FIG. 1.

Referring now to FIG. 2, reference numeral 51 has been applied to indicate a housing for three transfer switches such as the one described in connection with FIG. 1 and indicated in FIG. 1 by reference character L Each transfer switch in housing 51 is intended for one phase of a three phase circuit and the transfer switches 'for the three phases may be integrated into a unitary transfer switch structure, as common in the art. In FIG. 2 reference character 52 has been applied to generally indicate three pairs of selector switch sub-units, each pair being similar to the pair of selector switch sub-units described in connection with FIG. 1 and indicated in FIG. 1 by the reference characters I and II. FIG. 2 further shows three pairs of'selector switch sub-units generally indicated by reference character 53, each pair being similar to the pair of selector switch sub-units described in connection with FIG. 1 and indicated in FIG; 1 by the reference characters III and IV. The two

structures

52, 53 are arranged side by side at the same level. Superimposed upon structure 52 is a housing 54 for a Geneva gear drive for operating the selector switch sub-units which are arranged underneath, and superimposed upon structure 53 is a housing 55 for a Geneva gear drive for operating the selector switch sub-units which are arranged underneath. Reference numeral 56 has been applied to indicate a gear housing topping transfer switch housing 51. Shaft 57 which includes a pair of universal joints operatively relates the gear in housing 56 with the Geneva gear drive in housing 54. In like fashion shaft 58 which includes a pair of universal joints operatively relates the gear in housing 56 with the Geneva gear drive in housing 55. The

shafts

57, 58 operate the

crankshafts

59, 60 by which the Geneva gears in

housing

54, 55 are operated. This will be shown below more in detail in connection with a description of FIGS. 4a, 4b and 5a, 5b.

In a three phase transformer two pairs of selector switch sub-units such as the selector switch sub-units I, II, III and IV shown in FIG. 1 must be provided for each phase. In FIG. 2 referencecharacters U, V, W have been applied to the left of structure 52 to generally indicate that structure 52 includes a first pair of selecltor sub-units for each of the three phases of a threephase transformer. Similarly the letters U, V, W have been applied to the right of structure 5-3 to generally indicate that structure 53 includes a second pair of selector switch sub-units for each of the three phases of a three-phase transformer. The symbol 1-15 has been applied in FIG. 2 to indicate the eight tap contacts conductively connected to the odd numbered taps 1 -15 of a transformer winding of phase U in the way shown in FIG. 1, and described in connection therewith. FIG. 2 actually shows but one of the eight fixed tap contacts numbered 1-15 arranged along a circle, or in a circular pattern, and forming part of one selector switch sub-unit corresponding to sub-unit I shown in FIG. 1. The symbol 2-16 has been applied in FIG. 2 to indicate one of the eight tap contacts conductively connected to the even numbered taps 2-16 of a transformer winding of phase U in the way shown in FIG. 1 and described in connection therewith. FIG. 2 actually shows but one of the eight fixed tap contacts numbered 2-16 arranged along a circle, or in a circular pattern, and forming part of a selector switch sub-unit corresponding to sub-unit II shown in FIG. 1. FIG. 2 further shows to the right thereof fixed contacts to which the symbols 17-31 and 18-32 have been applied. These contacts form part of two selector switch sub-units corresponding to the selector switch sub-units III and IV shown in FIG. 1, each comprising eight fixed tap contacts arranged along a circle or in a circular pattern, and numbered 17-31 and 18-32, respectively. The top selector switch sub-units to the left of FIG. 2 comprise two fixed auxiliary contacts K K and the top selector switch sub-units to the right of FIG. 2 comprise two fixed auxiliary contacts K K These contacts correspond to the contacts in FIG. 1 to which the same reference characters have been applied All fixed contacts which are arranged in registry are mounted on rod 61 of insulating material. Since there are eight fixed tap contacts numbered 1-15 on the highest level in addition to auxiliary contact K and since there are eight fixed tap contacts numbered 2-16 on the level next to the highest level in addition to auxiliary contact K the switch structure 52 comprises nine vertical contact-supporting insulating rods similar to insulating rod 61 shown in FIG. 2. The nine rods are arranged in a cylindrical surface and form a squirrel-cage-like structure. Reference numeral 68 has been applied to indicate a hollow insulating column arranged along the axis of the aforementioned squirrel-cage-like contact-supporting insulating structure. Insulating column 68 supports fixed center contacts 66 and 67 arranged at different levels. (These contacts correspond to contacts Z Z of FIG. 1.) The cylindrical space inside of column 68 is used as a duct for receiving leads terminating in center contacts 66 and 67 (which leads correspond to leads L L of FIG. 1). Reference numeral 62 has been applied to indicate a pivotable bridge contact having a radially inner end permanently engaging fixed center contact 66 and having a radially outer end adaptedto selectively engage odd numbered fixed contacts 1-15 and also fixed auxiliary contact K (This bridge contact corresponds to contact B of FIG. 1.) Reference numeral 63 has been applied to indicate a pivotable bridge contact having a radially inner end permanently engaging fixed center contact 67 and-having a radially outer end I 7 adapted to selectively engage even numbered fixed tap contacts 2-16 and also fixed auxiliary contact K .v (This bridge contact corresponds to contact B of FIG. 1.)

Contact bridge 62 is supported by an insulating rod 64 and contact bridge 63 is supported by an insulating rod 65. Both insulating

rods

64 and 65 extend parallel to hollow insulating column 68 and are adapted to revolve around this insulating column as will be described below more in detail. The pairs of selector switch subunits for phases V, W which are arranged below the pair of selector switch sub-units for phase U are identical to the two upper selector switch sub-units which control phase U. The pairs of selector switch sub-units forming part of structure 53 are substantially identical to the pairs of selector switch sub-units forming part of structure 52. The. odd numbered taps 17-31 of the transformer winding of phase U are conductively connected to the odd numbered fixed tap contacts 17-31 of the selector switch sub-unit on the highest level of structure 53, and the even numbered taps 18-32 of the transformer winding of phase U areconductively connected to even numbered fixed tap contacts 18-32 of the selector switch sub-unit on the level next to the highest level of structure 53 in the fashion shown in FIG. 1 and more fully described in connection therewith. The structure 53 further comprises pairs of selector switch subunits for phases V and W arranged below the pairs of selector switch sub-units for phase U and identical with the pair of selector switch sub-units provided for controlling phase U.

The Geneva gear drives in

housings

54, 55 each comprises a pair of coaxially arranged superimposed Geneva gears 69, 70 and 71, 72, respectively. (See FIGS. 3, 3a, 4a, 4b, 5a and 5b.) The Geneva gear 69 is positively connected to contact bridge-operating-and-supponting rod 64, and Geneva gear 70 is positively connected to contactbridge-operating-and-supporting rod 65; ('FIG. 3). Geneva gears 69 (FIG. 3) and 71 (FIG. 3a) are adapted to operate the movable rods 64 and contact bridge 62 which scan the odd numbered fixed tap contacts 1-15 and 17-31 and auxiliary contacts K K The lower Geneva gears 70 (FIG, 3) and 72 (FIG. 3a) are adaped to operate the movable contact bridges 63 which scan the even numbered fixed tap contacts 2-16 and 18-32 and auxiliary contacts K K Geneva gears 69 and 70, and Geneva gears 71 and 72, respectively are driven by

crankshafts

59 and 60, respectively. Crankshaft '59 is provided with an upper operating pin 73 adapted to cooperatively engage Geneva gear 69 and with a lower operating pin 74 adaptedto cooperatively engage Geneva gear 70.

Pins

73, 74 are angularly displaced 180 degrees as a result of which gears 69, 70 are alternately operated by shaft 59. In like fashion crankshaft 60 is provided with

operating pins

73, 74 for alternately operating Geneva gears 71, 72.

Pins

73, 74 are preferably mounted by means of roller bearings 01'" other anti-friction bearings (not shown) on their respective crankshafts. Reference numeral 75 has been applied to indicate the relatively narrow radial slots in Geneva gears 69, 70 and 71, 72 intended to be engaged by the aforementioned opera-ting pins of which the upper pins 73 engage the upper Geneva gears 69 and 71 and the lower pins 74 engage the lower Geneva gears 70 and 72.

Each

Geneva gear

69, 70, 71, 72 defines a gap 76 of increased width, i.e., wider than radial slots 75. Gaps 76 are situated between contiguous sectors of

gears

69, 70, 71, 72. These relatively wide gaps'are formed by omission of one gear sector situated between adjacent pin slots 75 of each Geneva gear. Furthermore each

Geneva gear

69, 70, 71, 72 supports a pivotable pawl 77. Reference numeral 78 has been applied to indicate the fulcra of pawls 77 situated on Geneva gears 69, 70, 71 and 72. Each pawl 77 has a pair of arms which enclose an angle of 90 degrees. One of each of these arms FIGS. 4a, 4b, 5a and 517.

:3 to which reference numeral 79 has been applied projects into one of the inter-sector gaps 76 of increased width. The other of each of these arms is provided with a roller 80. Each of the pawls 77 defines a slot 81 engaged by a pin 82 mounted integral with the Geneva gear by which the respective pawl 77 is pivotally supported. Slots 81 and pins 82 form a pair of cooperating abutments limiting the pivotal motions of pawls 77 and about fulcra 78. Each pawl 77 is biased by a helical spring 83 tending to movethe arms of pawls 77 into the wide inter-sector gaps 76.

Pawls 77 of Geneva gears 69, 70, 71, 72 are controlled by disc-shaped

cams

84, 85 engaging rollers and pivoting pawls 77 against the bias of springs 83. Cams 84, are driven by gears 86a-86d which, in turn, are driven by crankshafts'59 and 60, or

shafts

57 and 58, respectively. The transmission ratio between

crankshafts

59, 60 and

cams

84, 85, i.e., that of gears 86a-86d, is determined by the circular pitch between slots 75. The two

cams

84, 85 which are associated with each pair of Geneva gears 69, 7t); 71, 72 and with the switch structures in each of

housings

52, 53 are supported by a common shaft and hub member 87, and are thus jointly rotatable (see FIG. 3).

Each

Geneva gear

69, 70, 71, 72 is provided with a pin 88 spring-biased. in a direction longitudinally thereof.

Pins 88 are adapted to engage a recess in fixed abutments 89. Such an engagement occurs any time the

respective Geneva gear

69, 70, 71, 72 comes to a rest position there of and, as a result of such engagement, the respective Geneva gear is firmly held in its rest position until such time as its motion is resumed. Each of the Geneva gears 69, 70, 71, 72 comes to its rest position when its wide gap 76 is in

juxtapositions'to crankshafts

59 and 60, respectively, so that pins 73, 74 can freely move through gaps 76 without either engaging

gears

69, 70, 71, 72 proper or pawls 77 supported by these gears.

In FIGS. 4a, 4b, 5a and 5b the fixed contacts of the selector switch sub-units which are situated at a lower level below Geneva gears 69, 70, 71, 72 have been indicated by reference characters 1-32 and K K K and K arranged along circular dash-and-dot lines. Since Geneva gear 69 operates rod 64 and bridge contact 62 which engages fixed odd numbered tap contacts 1-15 and fixed auxiliary contact K these fixed contacts arranged in FIG. 4a around the center of Geneva gear 4a. In a similar way even numbered fixed tap contacts 2-16 and auxiliary contact K are arranged in FIG. 4b around the center of Geneva gear 70 and odd numbered fixed tap contacts 17- 31 and fixed auxiliary contact K are arranged in FIG. 5a around the center of Geneva gear 71 and even numbered fixed tap contacts 18-21 and fixed auxiliary contact K are arranged in FIG. 55 around the center of Geneva gear 72. In FIGS. 4a,. 4b, 5a and 5b the movable contact bridges 62, 63 have been indicated by dash-and-dot lines.

It is apparent from FIGS. 5a and 5b that contact

arms

62, 63 of the selector switch structure 53 are in engagement with fixed contacts numbered 17 and 18, respec tively. The switch structure is ready to switch to the next lower tap or fixed contact 16. Hence tap 17 is effective in the particular position of the parts illustrated in In that position Geneva gears 69 and 70 are at rest and maintained in their rest positions by cooperative engagement of pins 88 and recesses in abutments 89.

In the position of the parts shown in FIG. 4a arm '79 of pawl 77 is not yet fully overlapping wide inter-sector gap 76. Hence crankshaft 59 and pin 73 are still able to move freely through intersector gap 76 without engaging arm 79 of pawl 77 and without rotating Geneva gear 69.

In the position of the parts shown in FIG. 4b cam 85, by,virtue of its clockwise rotation (as seen in FIG. 4b), has allowed roller 80 to move from the cylindrical surface of cam 85 to the fiat surface thereof. This allowed a pivotal motion of pawl 77 under the bias of spring 83, as a result of which arm 79 of pawl 77 has fully entered 9 the intersector gap 76. Arm 79 of pawl 77 and the Geneva gear segment to the right of arm 79 (as seen in FIG. 4b) jointly define a slot 75 adapted to be engaged by pin 74 of crankshaft 59. When crankshaft 59 is rotated in counterclockwise direction (as seen in FIG. 4b) pin 74 enters slot 75 and operates Geneva gear 70.

In the position of the Geneva gear 71 shown in FIG. a pawl 77 projects with arm 79 into the wide intersector gap 76 and forms a pin-engaging slot 75' jointly with the gear sector situated to its left.

The same applies in regard to the position of Geneva gear 72 shown in FIG. 5b wherein arm 79 of pawl 77 forms slot 75' jointly with the gear sector situated to its left.

It may be assumed that contact bridge 62 is initially in cooperative engagement with fixed tap contact 17 con nected to tap 17 of transformer winding T that transfer switch L of FIG. 1 has changed the connection of point Y from fixed contact 18 to fixed contact 17, and that it is intended to change from tap 17 to tap 16 of winding T Counterclockwise rotation (as seen in FIGS. 5a and 5b) of crankshaft 60 causes engagement of slot 75 formed between Geneva gear 72 and pawl 77 by pin 74 on crankshaft 60 and consequent rotation of Geneva gear 72. As a result of that rotation bridge contact 63 is disengaged from fixed contact 18 and moved into engagement with fixed auxiliary contact K Crankshaft 59 is rotated counterclockwise (as seen in FIGS. 4a and 4b) simultaneously with crankshaft 60. As a result of that rotation of crankshaft 59, pin 74 on crankshaft 59 engages the slot 75' formed between Geneva gear 70 and arm 79 of pawl 77, causing rotation of that Geneva gear. This, in

' turn, causes contact bridge 63 driven by Geneva gear 70 to be moved from fixed auxiliary contact K to fixed tap contact 16 conductively connected to tap 16. During the aforementioned rotary motions of crankshafts 6t] and 59 the upper pin 73 of crankshaft 60 engages slot 75 formed between Geneva gear 71 and arm 79 of its pawl 77 and simultaneously the upper pin 73 of crankshaft 59 enters into the wide gap 76 of Geneva gear 69. Upon completion of these motions the transfer switch L of FIG. 1

which is enclosed in housing 51 of FIG. 2 switches point Y from contact 17 of selector switch means in housing 53 to contact 16 of selector switch means in housing 52. The counterclockwise sense of rotation of

crankshafts

59 and 60 has been indicated by arrows in FIGS. 4a, 4b, 5a and 5b. A continued counterclockwise rotation of 180 degrees of

crankshafts

59 and 60 causes Geneva gear 71 to move contact bridge 62 out of engagement with fixed contact 17 and into engagement with auxiliary contact K and causes Geneva gear 69 to move contact bridge 62 out of engagement with fixed auxiliary contact K and into engagement with fixed contact 15. The aforementioned operation of Geneva gear 69 is made possible by the formation of a pin-receiving slot 75 between Geneva gear 69 and arm 79 of its pawl 77 into which pin 73 on crankshaft 59 enters.

Upon completion of the aforementioned operating steps Geneva gears 71 and 72 for driving the selector switch means in housing 53 remains at rest. This is due to the fact that the pawls 77 of Geneva gears 71, 72 have been pivoted during the two preceding operating steps by cams 84, 85 (FIGS. 5a and 5b)- in such away that arms 79 have been moved out of Wide intersegment gaps 76. Consequently pins 73, 74 on crankshaft 60 are free to travel through gaps 76 of gears 71, 72 without driving these gears, or transmitting a torque to thesegears. If crankshaft 59 is driven continually Geneva gears 69 and 70 move their

contact bridges

62 and 63, respectively, in sequential alternating steps from fixed contact 16 to fixed contact 1. This is due to the fact that pawls 77 then are in such a position that pins 73 and 74 on crankshaft 59 during rotation of the latter always find a slot in one of the

gears

69, 70 in which to enter and to operate the respective gear. As mentioned above, alternate operation of Geneva gears 69 and 70 results from the fact that operating pins 73 and 74 on crankshaft 59 are angularly displaced 180 degrees.

If it is intended to change from tap 1 to tap 16, or to change from a tap having a relatively low order number to a tap having a relatively higher order number the direction of rotation of crankshaft 59 is reversed. If it is intended to connect to point Y taps having a higher order number than 16 the selector switch means in housing 52 are held in their rest position and the selector switch means in housing 53 are operated in consecutive alternate steps made by Geneva gears 71 and 72. The changeover from the selector switch means in housing 52 to those in housing 53 is the reverse of the change-over from the selector switch means in housing 53 to those in housing 52 which has been described above in detail.

FIG. 2 indicates but diagrammatically the way in which contact-bridge-operating

rods

64, 65 are connected to the Geneva gear drive inside of housing 54. This is shown in detail in FIG. 3. As shown in FIG. 3 a column 100 is arranged in the center of housing 54 which centers and supports Geneva gears 69 and 70. Gear 69 is provided with a support 69 for insulating rod 64 and gear 70 is provided with a support 70 for insulating rod 65.

The circular pitch between the sectors of Geneva gears 69, 70, 71, 72 is equal to the angle enclosed between any of the fixed contacts situated below. In other words, the

angle between contiguous slots 75 is equal to the angle between contiguous fixed contacts, e.g.,

tap contacts

1 and 3.

Any kind of gear transmission may be used for operating cams 84, by

shafts

59, 60. FIGS. 3 and 3a show the lower ends of

shafts

57, 58 which transmit the movement of the gear mechanism enclosed in housing 56 to the Geneva gear mechanisms enclosed in

housings

54, 55, or to the Geneva-gear-driving

crankshafts

59, 60, respectively. Gear 86a operates gear 86d coaxially arranged with

cams

84 and 85 by the intermediary of gears 86b and 86c which are in meshing engagement with each other. Gear 86a is in meshing engagement with gear 86b and gear 860 is in meshing engagement with gear 86d.

While, in accordance with the patent statutes, we have disclosed the specific details of a preferred embodiment 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. A regulating transformer comprising in combination:

(a) a transformer winding having a plurality of odd taps and having a plurality of even taps;

(b) a transfer switch having a pair of terminals;

(c) a selector switch for selectively connecting to said transfer switch taps of said winding, said selector switch including a pair of switch stacks arranged side by side at substantially the same level, each of said pair of stacks including two superimposed selector switch sub-units, each selector switch sub-unit having a center contact, a plurality of fixed tap contacts and an auxiliary fixed contact arranged in a circle around said center contact, and each selector switch unit further having a pivotable contact bridge for selectively connecting said center contact with each of said plurality of tap contacts and with said auxiliary contact;

- ((1) leads connecting a portion of said plurality of odd taps to a selector switch sub-unit forming part of one of said pair of stacks and leads connecting another portion of said plurality of odd taps to a selector switch sub-unit forming part of the other of said pair of stacks;

(e) leads connecting a portion of said plurality of even taps to a selector switch sub-unit forming part of one of said pair of stacks and leads connecting another portion of said plurality of even taps to a selector switch sub-unit forming part of the other of said pair of stacks;

(f) leads inter-connecting the center contacts of selector switch sub-units having tap contacts connected to said plurality of odd taps;

(g) leads inter-connecting the center contacts of selector switch sub-units having tap contacts connected to said plurality of even taps;

(h) leads connecting the auxiliary contacts of selector switch sub-units having tap contacts connected to said plurality of odd taps to one of said pair of terminals of said transfer switch; and

(i) leads connecting the auxiliary contacts of selector switch sub-units having tap contacts connected to said plurality of even taps to the other of said pair of terminals of said transfer switch.

2. A regulating transformer as specified in claim 1 comprising:

(a) a first Geneva gear drive including a pair of superimposed Geneva gears arranged'above one of said pair of stacks alternately operating the contact bridges of the selector switch sub-units included in said one of said pair of stacks;

(b) a second Geneva gear drive including a pair of superimposed Geneva gears arranged abovethe other of said pair of stacks alternately operating the contact bridges of the selector switch sub-units included in said other of said pair of stacks;

(c) mechanical control means for rendering said first Geneva gear drive ineffective when the contact bridges of the selector switch sub-units included in said other of said pair of stacks is in any of a plurality of a predetermined position thereof; and

(d) mechanical control means for rendering said second Geneva gear drive ineffective when the contact bridges of the selector switch sub-units included in said one of said pair of stacks is in any of a plurality of predetermined positions thereof.

3. A regulating transformer comprising in combinatron:

(b) a transfer switch having a pair of terminals;

(c) a selector switch for selectively connecting to said transfer switch taps of said winding, said selector switch including a pair of squirrel cage structures each formed of a plurality of vertical insulating rod-s arranged in a cylindrical surface, each of said squirrel cage structures supporting a plurality of fixed contacts forming part of a pair of superimposed selector switch sub-units, each of said pair of selector switch sub-units including a plurality of fixed tap contacts arranged in a circuit pattern and a fixed auxiliary contact arranged in the same circular pattern, each of said selector switch sub-units further including a center contact and a bridge contact pivotable around said center contact for selectively connecting said center contact with said plurality of tap contacts and with said auxiliary contact, and each of said selector switch sub-units further including an operating rod of insulating material operatively secured to said bridge contact and movable around said center contact;

(d) leads connecting a portion of said plurality of odd taps to a selector switch sub-unit having tap contacts supported by one of said pair of squirrel cage structures and leads connecting another portion of said plurality of odd taps to a selector switch subunit having tap cont-acts supported by another of said pair of squirrel cage structures;

(e) leads connecting a portion of said plurality of even taps to a selector switch sub-unit having tap contacts supported by one of said pair of squirrel cage structures and leads connecting another portion of said plurality of even taps to a selector switch subunit having tap contacts supported by another of said squirrel cage structures;

(f) leads interconnecting the center contacts of selector switch sub-units having tap contacts connected to said plurality of odd ta-ps;

(g) leads interconnecting the center contacts of selec tor switch sub-units having tap contacts connected to said plurality of even taps;

(-h) leads connecting the auxiliary contacts of selector switch sub-units having tap contacts connected to said plurality of odd tarps to one of said pair of terminals of said transfer switch; and

(i) leads connecting the auxiliary contacts of selector switch sub-units having tap contacts connected to said plurality of even ta-ps to the other of said pair of terminals of said transfer switch.

4. A regulating transformer comprising in combination:

(a) a transformer having a plurality of odd taps and having a plurality of even taps;

(-b) a transfer switch having a pair of terminals to be connected selectively to pairs of adjacent taps of said winding;

(c) a selector switch for selectively connecting pairs ofvadjacent taps of said winding to said transfer switch, said selector switch including a first selector switch unit for connecting a first portion of said plurality of said odd taps and a first portion of said plurality of said even taps to said transfer switch, and said selector switch further including, a secondselector switch unit for connecting a second portion of said plurality of odd taps and a second portion of said plurality of even taps to said transfer switch, said first selector switch unit and said second selector switch unit being arranged below said transfer switch side by side substantially at the same level;

(d) a common drive for said first selector switch unit and for said second selector switch unit arranged above said transfer switch;

(e) a first Geneva gear drive including a pair of superimposed alternately operating Geneva gears arranged above said first selector switch unit and driven by said common drive for operating said first selector switch unit;

(f) a second Geneva gear drive including a pair of superimposed alternately operating Geneva gears arranged above said second selector switch unit driven by said common drive for operating said second selector switch unit;

(g) mechanical control means for rendering said first Geneva gear drive ineffective when said second selector switch is in any of a plurality of predetermined positions thereof; and

(h) mechanical control means for rendering said second Geneva gear drive ineffective when said first selector switch unit is in any of a plurality of predetermined positions thereof. 7

5. A regulating transformer comprising in combination:

(b) a transfer switch having a pair of terminals to be selectively connected to pairs of adjacent taps of said winding;

(c) a selector switch for selectively connecting pairs of adjacent taps of said winding to said transfer switch, said selector switch including a first selector switch unit for connecting a first portion of said plurality of odd taps and for connecting a first portion of said plurality of even taps to said transfer switch, said first selector switch unit further including a squirrel cage insulating structure supporting radially outer fixed contacts, a hollow insulating column supporting fixed center contacts,- and contact bridges for selectively interconnecting said radially outer contacts and said center contacts, and said selector switch further including a second selector switch unit for connecting a second portion of said plurality of odd taps and for connecting a second portion of said plurality of even taps to said transfer switch, said second selector switch unit including -a squirrel cage insulating structure supporting radially outer fixed contacts, .a hollow insulating column supporting fixed center contacts and contact bridges for selectively interconnecting said radially outer contacts and said center contacts, said first selector switch unit and said second selector switch unit being arranged side by side substantially at the same level;

(d) a first Geneva gear drive including a pair of alternately operating Geneva gears for operating said first selector switch unit;

(e) a second Geneva gear drive including a pair of alternately operating Geneva gears for operating said second selector switch unit;

(f) mechanical control means for rendering said first Geneva gear drive ineffective when said second selector switch unit is in any of a plurality of predetermined positions thereof; and

(g) mechanical control means for rendering said second Geneva gear drive ineffective when said first selector switch unit is in any of a plurality of predetermined positions thereof.

6. A regulating transformer comprising in combination:

(a) transformer winding having a plurality of taps;

() a selector switch for selectively connecting pairs of adjacent taps of said winding to said transfer switch, said selector switch comprising a pair of selector switch units arranged side by side substantially at the same level;

(d) a pair of Geneva gear drives each for operating one of said pair of selector switch units;

(e) each of said pair of Geneva gear drives comprising a pair of superimposed alternately operating Geneva gears; and

(f) mechanical control means for rendering each of said pair of Geneva gear drives ineffective when the other of said pair of Geneva gear drives is in any of a plurality of predetermined positions thereof.

7. A regulating transformer as specified in claim 6 wherein each pair of Geneva gears of said pair of Geneva gear drives is operated by crankshaft means including Geneva-gear-engaging pins angularly displaced 180 degrees.

8. A regulating transformer as specified in claim 6 wherein said mechanical control means include:

(a) a relatively wide gap defined by each Geneva gear of each of said pair of Geneva gear drives in addition to a plurality of angularly displaced relatively narrow substantially radially extending slots;

(b) a plurality of spring biased pawls, each Geneva gear of each of said pair of Geneva gear drives pivotally supporting one of said plurality of pawls, and each of said plurality of pawls having a pair of arms;

(c) a plurality of rotatable cams each cooperatively engaging one of said pair of arms of one of said plurality of pawls to move the other of said pair of arms of said one of said plurality of pawls into and out of said relatively wide gap in each Geneva gear of each of said pair of Geneva gear drives; and

(d) rotatable crankshaft means operating said pair of Geneva gear drives and operating said plurality of.

cams, said crankshaft means including driving pin means cooperatively engaging said other of said pair of arms of said plurality of pawls when said other of said pair of arms has been moved into said wide gap defined by each Geneva gear of said pair of Geneva gear drives.

9. A regulating transformer comprising in combination:

(a) a transformer winding having a plurality of taps;

(c) a selector switch for selectively connecting pairs of adjacent taps of said winding to said transfer switch, said selector switch comprising a pair of selector switch units arranged side by side substantially at the same level;

(d) a pair of Geneva gear drives each for operating one of said selector switch units, each of said pair of Geneva gear drives including a pair of superimposed coaxially arranged Geneva gears, each of said pair of gears defining a relatively wide gap in addition to a plurality of angularly displaced relatively narrow slots;

(e) a pair of driving shafts each operatively related to one of said pair of Geneva gear drives and each including pin means alternately engaging the Geneva gears of said pair of Geneva gear drives;

(f) a plurality of spring biased pawls, each Geneva gear of said pair of Geneva gear drives pivotally supporting one of said plurality of pawls, and each of said plurality of pawls having a pair of arms;

(g) a plurality of rotatable cams each cooperatively engaging one of said pair of arms on one of said plurality of pawls to move the other of said pair of arms on said one of said plurality of pawls into and out of the path of movement of said pin means on said pair of shafts; and

V (h) means under the control of said pair of shafts for rotating said plurality of cams.

10. A regulating transformer comprising in combination:

(b) a transfer switch having a pair of terminals;

(c) a selector switch for selectively connecting to said transfer switch taps of said winding, said selector switch including a pair of switch stacks arranged side by side at substantially the same level, each of said pair of stacks including a pair of superimposed selector switch sub-units, each of saidpair of selector switch sub-units having a center contact, a plurality of fixed tap contacts and an auxiliary fixed contact arranged in a circular pattern around said center contact, and each of said pair of selector switch sub-units further having a pivotable contact bridge for selectively connecting said center contact with each of said plurality of tap contacts and with said auxiliary contact;

(d) leads connecting a portion of said plurality of add taps to a selector switch sub-unit forming part of one of said pair of stacks and leads connecting another portion of said plurality of odd taps to a selector switch sub-unit forming part of the other of said pair of stacks; .(e) leads connecting a portion of said plurality of even taps to a selector switch sub-unit forming part of one of said pair of stacks and leads connecting another portion of said plurality of even taps to a selector switch sub-unit forming part of another of said pair of stacks;

(f) leads interconnecting the center contacts of selector switch sub-units having tap contacts connected to said plurality of odd taps;

(g) leads interconnecting the center contacts of selector switch sub-units having tap contacts connected to said plurality of even taps;

(h) leads connecting the auxiliary contacts of selector switch sub-units having tap contacts connected to said plurality of odd taps to one of said pair of terminals of said transfer switch;

(i) leads connecting the auxiliary contacts of selector switch sub-units having tap contacts connected to said plurality of even taps to the other of said pair of terminals of said transfer switch;

(j) a pair of Geneva gear drives each for operating one of said switch stacks of said selector switch, each of said pair of Geneva gear drives including a pair of superimposed coaxially arranged Geneva gears and each of said Geneva gears defining a relatively wide gap in addition to a plurality of angularly displaced relatively narrow slots;

(k) a pair of driving shafts each operatively related to one of said pair of Geneva gear drives and each including pin means alternately engaging said Geneva gears of said pair of Geneva gear drives;

(l) a plurality of spring biased pawls, each Geneva gear of said pair of Geneva gear drives pivotally supporting one of said plurality of pawls; and

(m) means under the control o'f said pair of driving shafts for pivoting said plurality of pawls to move said plurality of pawls into and outof the path of movement of said pin means on said. path of driving shafts.

References Cited by the Examiner UNITED STATES PATENTS 2,253,183 8/1941 Le Count. 2,791,648 5/1957 Maloney. 3,176,089 3/1965 Bleibtreu et a1 200-11 X KATHLEEN H. CLAFFY, Primary Examiner.

J. R. SCOTT, Assistant Examiner.

Claims

1. A REGULATING TRANSFORMER COMPRISING IN COMBINATION: (A) A TRANSFORMER WINDING HAVING A PLURALITY OF ODD TAPS AND HAVING A PLURALITY OF EVEN TAPS; (B) A TRANSFER SWITCH HAVING A PAIR OF TERMINALS; (C) A SELECTOR SWITCH FOR SELECTIVELY CONNECTING TO SAID TRANSFER SWITCH TAPS OF SAID WINDING, SAID SELECTOR SWITCH INCLUDING A PAIR OF SWITCH STACKS ARRANGED SIDE BY SIDE AT SUBSTANTIALLY THE SAME LEVEL, EACH OF SAID PAIR OF STACKS INCLUDING TWO SUPERIMPOSED SELECTOR SWITCH SUB-UNITS, EACH SELECTOR SWITCH SUB-UNIT HAVING A CENTER CONTACT, A PLURALITY OF FIXED TAP CONTACTS AND AN AUXILIARY FIXED CONTACT ARRANGED IN A CIRCLE AROUND SAID CENTER CONTACT, AND EACH SELECTOR SWITCH UNIT FURTHER HAVING A PIVOTABLE CONTACT BRIDGE FOR SELECTIVELY CONNECTING SAID CENTER CONTACT WITH EACH OF SAID PLURALITY OF TAP CONTACTS AN D WITH SAID AUXILIARY CONTACT; (D) LEADS CONNECTING A PORTION OF SAID PLURALITY OF ODD TAPS TO SELECTOR SWITCH SUB-UNIT FORMING PART OF ONE OF SAID PAIR OF STACKS AND LEAD CONNECTING ANOTHER PORTION OF SAID PLURALITY OF ODD TAPS TO A SELECTOR SWITCH SUB-UNIT FORMING PART OF THE OTHER OF SAID PAIR OF STACKS; (E) LEADS CONNECTING A PORTION OF PLURALITY OF EVEN TAPS TO A SELECTOR SWITCH SUB-UNIT FORMING PART OF ONE OF SAID PAIR OF STACKS AND LEADS CONNECTING ANOTHER PORTION OF SAID PLURALITY OF EVEN TAPS TO A SELECTOR SWITCH SUB-UNIT FORMING PART OF THE OTHER OF SAID PAIR OF STACKS; (F) LEADS INTER-CONNECTING THE CENTER CONTACTS OF SELECTOR SWITCH SUB-UNITS HAVING TAP CONTACTS CONNECTED TO SAID PLURALITY OF ODD TAPS; (G) LEADS INTER-CONNECTING THE CENTER CONTACTS OF SELECTOR SWITCH SUB-UNITS HAVING TAP CONTACTS CONNECTED TO SAID PLURALITY OF EVEN TAPS; (H) LEADS CONNECTING THE AUXILIARY CONTACTS OF SELECTOR SWITCH SUB-UNITS HAVING TAP CONTACTS CONNECTED TO SAID PLURALITY OF ODD TAPS TO ONE OF SAID PAIR OF TERMINALS OF SAID TRANSFER SWITCH; AND (I) LEADS CONNECTING THE AUXILIARY CONTACTS OF SELECTOR SWITCH SUB-UNITS HAVING TAP CONTACTS CONNECTED TO SAID PLURALITY OF EVEN TAPS TO THE OTHER OF SAID PAIR OF TERMINALS OF SAID TRANSFER SWITCH.