US2723318A

US2723318A - Load selector for tapped transformers with insulating cylinders unrolling within each other

Info

Publication number: US2723318A
Application number: US214282A
Authority: US
Inventors: Jansen Bernhard
Original assignee: Individual
Current assignee: Individual
Priority date: 1951-03-07
Filing date: 1951-03-07
Publication date: 1955-11-08
Anticipated expiration: 1972-11-08

Description

Nov. 8, 1955 2,723,318

B. JANSEN' LOAD SELECTOR FOR TAPPED TRANSFORMERS WITH INSULATING CYLINDERS UNROLLING WITHIN EACH OTHER Filed March 7 1951 IN VENTOR 5512mm JANSEN 43:. AT'roRNEYs,

LOAD SELECTOR FOR TAPPED TRANSFORMERS WITH INSULATING CYLINDERS UNROLLING WITHIN EACH OTHER Bernhard Jansen, Regensburg, Germany Application March 7, 1951, Serial No. 214,282

8 Claims. (Cl. 200--6) This invention relates to load tap selectors for tapped transformers and particularly for transformers having hollow insulating cylinders with parallel axes and rollable one within the other.

In tapped transformers of small and medium output load tap selectors, i. e. tap selectors switching under load, usually the stationary load switching contacts connected to the transformer tappings are fixed on a stationary outer insulating hollow cylinder, and the counteracting load switching contacts are movably mounted on an inner hollow insulating cylinder rollable on the inner surface of the outer cylinder. Such load tap selectors may be built single-phase or polyphase, the p'olyphase tap selectors being built only for application onthe neutral point of the transformer. In order to guide the movement of the inner rollable cylinder, the polyphase tap selectors have been built only for application on the neutral point of the transformer and this has been accomplished by providing an elongated metal axle extending throughout the length of the inner rollable cylinder and by means of eccentric drives on the upper and lower ends of said cylinder. Such an elongated metal axle is objectionable as it causes a disturbing influence, especially if in the polyphase load tap selector each phase is assigned its own load changeover switch part having phase potential, since the stationary and movable contacts must be completely insulated from the contacts of the neighboring phase. An elongated insulating axle is also objectionable as it would take up too much space unless the diameter of the load tap selector were increased to uneconomical dimensions.

It is therefore an object of the present invention to provide means for guiding and controlling the movement of the innerrollable cylinder without the necessity of using an elongated axle either of metal or of insulating material.

It is another object of the invention to maintain the axes of the outer and inner cylinders in parallelism without the necessity of using an elongated axle either of metal or of insulating material.

It is another object of the invention to insulate the load tap selector parts of the individual phases completely from each other, without the necessity of increasing the dimension of the cross-section of the load tap selector.

It is another object of the invention to provide a load tap selector wherein the body of the inner rollable cylinder is used to transmit the torque necessary for its rolling movement from one end of the body to the other.

It is another object to provide improved means for urging the gear teeth of the inner rollable cylinder'into continuous meshwith the gear teeth of the outer fixed cylinder.

Other objects and advantages of the invention will be apparent from the description thereof to follow taken in connection with the accompanying drawings in which Fig.1 is a vertical sectional view of a load tap selector for a three-phase transformer embodying my invention,

ice

the view being taken on the plane of the line I-I of Fig. 2.

Fig. 2 is a horizontal sectional view taken on the plane of the line II of Fig. l. I

Fig. 3 is a horizontal sectional view taken on the plane of the line IIII of Fig. 1.

Fig. 4 is a horizontal sectioinal view taken on the plane of the line IHIII of Fig. 1.

With particular reference to the drawing, Fig. 1 shows a three-part load switch for a polyphase current transformer which is to efiect the regulation at the three-phase ends of the transformer whichconduct the entire operat ing voltage. This is, in general, necesary both for power transformers connected in delta and for booster transformers operating in open series connection. The load selector head is fastened to the transformer cover by screws passing through packing material between the head and cover. The selector head supports the load switch oil container consisting of an outer hollow insulating cylinder Za having a bottom end closure plate to which is connected the container for the contaminated oil.

Supported on the cylinder Za adjacent its upper end is a group or series of spaced stationary contacts U1, U2, U3, U4 arranged in a circle as shown in Fig. 3. A similar group or series of stationary contacts V1, V2, V3, V4 is supported below and spaced and insulated from the U-group of contacts; and a similar group or series of stationary contacts W1, W2, W3, W4 is supported below and spaced and insulated from the V-group' of contacts. These contacts are connected to the transformer taps of the three-phase current windings. These groups of contacts are at all times in normal operation. One of the contacts U1, U2, U3, U4 is connected by the shunt contact Au to the conductor or bus bar Sr: of the cylinder Za. One of the contacts V1, V2, V3, V4 is connected by the shunt contact Av to the conductor or bus bar Sv. One of the contacts W1, W2, W3, W4, is connected by the shunt contact Aw to the conductor or bus bar Sw. These connections are effected in any manner well known in the art.

Referring to Fig. l, the load switches corresponding to the three-phases U, V, W are designated Lu, Lv, Lw,

respectively. Such a load switch forms no part of the present invention, but one form of such switch is shownl in Fig. 3 wherein a main contact H is shown in contact with the tap U2 of the transformer so that current is taken therefrom and fed through the shunt contact Au to the current shunt Su. The auxiliary switch contacts ha and hb are connected in the customary manner to the main contact H by switch-over resistances, and serve for the load switching during uninterrupted operation.

In the same manner, the current of the transformer phase V is'taken from tap V2 and conducted through shunt contact Av to the current shunt Sv. Similarly, the current of the transformer phase W is taken from tap W2 and conducted through shunt Aw to the end of the load switch from where it passes over the current shunt Sw.

The current shunts or conductors Su, Sv and Sw can be switched by the load selector to the other taps U1 to U4, V1 to V4 and W1 to W4.

In order to effect the switching of the main contact H (Fig. 3), for instance, from tap U2 to tap U3, the main contacts H of the three transformer phases, together with the auxiliary contacts ha and hb, together with the switchover resistances (not shown in the drawings), are supported and insulated from each other on an inner hollow insulating cylinder Zi, the axis m of which is arranged uninterrupted operation. The inner cylinder Zi is mounted to roll in the outer insulating cylinder Za by means of the structural parts. described hereinafter. Such parts are arranged in the load selector head and in the opposite end of the selector in such a manner that the main contacts H (Fig. 3) first of all rises in the path of a cycloidal curve, in the well known manner, from contact U2 and then swings around in an arc to contact U3, upon which it seats, in a radial direction. For this purpose, the central axis In of the inner cylinder Zi is offset a distance equal to the space indicated by the arr w r (Fig. l) to bring it into parallelism with and eccentric to the axis M of the outer cylinder Za. This is effected by means positioned in the load selector head including a crank cam E and by means positioned in the opposite end of the load selector including pins Z1 and Z2 which engage each other as shown in Fig. 1.

Inasmuch as in each contact group Lu, Lv, Lw which correspond to the three phases U, V, W, respectively, considerable contact forces are produced, due to the spring action of the load switch contacts and the shunt contacts coming into contact with each other, there is a tendency on the part of the inner insulating eylinde. Zz' to move out laterally to avoid these spring forces. This movement is prevented in the present invention by the rigid connection between the cylinders provided by the meshing of the teeth R1 formed on the outer periphery of the top end plate of the inner cylinder Zi with teeth R2 of a ring mounted on the inner surface of the outer cylinder Za at its upper end, and by the meshing of the teeth R3 formed on the outer periphery of the closure plate on the bottom end of inner cylinder Zi with the teeth R4 of a ring mounted on the inner surface of the outer cylinder Za at its lower end. These teeth however can only prevent such lateral movement when and if they are in mesh or in engagement with each other. Such meshing is only certain when the inner cylinder Z1 is in proper position relative to the outer cylinder Zn, that is, when the axis m of the inner cylinder Z! is offset from the central axis M of the outer cylinder Za a distance equal to the distance r for the entire length of said inner cylinder. To accomplish this in the present invention, a pin Z1 is mounted on and depends from the plate closing the lower end of the inner cylinder directly in line with its axis In. A similar pin Z2 is mounted on and extends upwardly from the plate closing the adjacent lower end of the outer cylinder Za. Pin Z2 is directly in line with the axis M of the outer cylinder. The upper pin Z1 rests on and contacts the lower pin Z2, the lower pin thus serving as a bearing for the upper pin. In order to avoid frictional wear of the two pins, one of them is preferably rigidly fastened to its cylinder while the other is rotatably mounted on double-cone hearings or the like on its cylinder. In order to facilitate the insertion of the inner insulating cylinder, the pins are preferably formed with slight tapers running in opposite directions. Fig. 1 shows such pins Z1 and 22 only at the lower or load selector end. At the upper head end of the selector, the crank cam E is rotatably mounted with its upper pin journalled in the head and arranged in line with the central axis M of the outer insulating cylinder Zn, and with its lower pin journalled in the top closure plate of the inner cylinder Zi in line with the axis In of the inner cylinder. The crank cam E thus serves to maintain the gear teeth of the cylinders in mesh. In order to prevent motion of the eccentric crank cam E in either a clockwise or counterclockwise direction, under the pressure forces of the three main contacts H and the shunt contacts Au and Av and Aw, the crank cam E is locked in its various operating positions by spring-pressed pawls K1 and K2 which are pivctally mounted in the selector head with the gear portion R1 of the upper closure plate of the inner cylinder Zi.

'Iihe forcenecessary for the cycloid-like switching movement of the main contact H from the transformer tap U2 to tap U3, for example, is provided as follows: housed in the load selector head is a coiled or torsion spring device or accumulator indicated generally at F. A protruding portion of this spring acts upon a part of the crank cam E. The spring is wound to the extent of the angle necessary for the switching operation by a bevel gear operatively connected thereto and which is operatively connected to a source of power. When the winding operation is finished, the pawl lock is released in any well known manner to permit movement of the cam. If the pawl K2, for example, is disengaged, the spring acting upon the crank cam E is free to turn the cam in the direction of the arrow in Fig. 2. In this way, the crank cam E can rotate in a clockwise direction under the action of the spring device F from the radial position corresponding to U2 to the radial position corresponding to U3 and is therefore moved a distance equal to 5 of the total circumference. The crank cam E simultaneously rolls the upper part of the inner cylinder Zi with its upper gear teeth R1 rolling eccentrically in the spaces between the teeth R2 of the outer cylinder Za, which rolling movement is transmitted to the cylinder Zi, the axis in thereof rotating around the main axis M of the outer cylinder. The rolling motion of the inner cylinder Zi stops when the crank cam E is again caught by the two pawls K1 and K2 and held fast in the radial direction looking toward tap contact U3. This movement from the radial position U2 to the radial position U3 results because the gears R1 and R3 on the upper and lower closure plates, respectively, of the inner cylinder Zi, each has only eleven teeth for rolling in the spaces provided by the twelve teeth on each of the gears R2 and R4, respectively, on the outer cylinder Za. Due to the difference in total lengths between the spaces provided by the eleven teeth and the spaces provided by the twelve teeth, there results, upon an 5 rotation of the crank cam E, a difference in distance of movement of a size of one tooth. This corresponds to the distance of the step or movement from U2 to U3. During this movement, the connections between main contact H and U2, ha and U2, hb and U3, and H and U3 become disengaged. As the main contact H is directly connected to the shunt contact Au and to the auxiliary contacts ha and hb in any well known manner, such as by ohmic resistances, no interruption of the circuit takes place by the aforesaid mutual disengagements of the contacts. A load switching under load is therefore effected by insertion of switchover resistances.

It is important that the inner insulating cylinder Zi remains, in all phases of its motion, in axial parallelism with the central axis of the outer insulating cylinder Za so that the corresponding stationary and movable contacts will always properly contact or engage each other. This axial parallelism is assured in accordance with the present invention by the relative arrangements of the inner and outer teeth in the load selector head and in the opposite load selector end as well as by the fixture of the eccentricity of the axes M and m, which are offset from each other a distance equal to the radius r, by means of the cam E and the lower tapered pins Z1 and Z2.

I claim:

1. A load tap selector for tapped transformers including an outer hollow insulating cylinder, an inner hollow insulating cylinder rollable on the inner surface of said outer cylinder, said cylinders being positioned with their axes in parallelism, means for rolling said inner cylinder, stationary contacts mounted on the inner surface of said outer cylinder, movable contacts carried by said inner cylinder and mounted on the outer surface thereof, said rolling means for said inner cylinder including a top end plate of the inner cylinder, teethformed upon the outer periphery of said plate, aring mounted onthe inner surface of the outer cylinder at the upper end thereof, teeth formed on said ring, said respective teeth intermeshing, and also including a closure plate on the bottom end of the inner cylinder, teeth formed on the outer periphery of said closure plate and a toothed ring mounted on the lower end of the inner surface of the outer cylinder, said last two sets of teeth respectively intermeshing.

2. A load tap selector for tapped transformers including an outer hollow insulating cylinder, an inner hollow insulating cylinder rollable on the inner surface of said outer cylinder, said cylinders being positioned with their axes in parallelism, means for rolling said inner cylinder, stationary contacts mounted on the inner surface of said outer cylinder, movable contacts carried by said inner cylinder and mounted on the outer surface thereof, and means for maintaining the parallelism of the axes of said cylinders, the means for rolling said inner cylinder including a spring-pressed device operatively connected to one end of said inner cylinder, said rolling means for said inner cylinder including a top end plate of the inner cylinder, teeth formed upon the outer periphery of said plate, a ring mounted on the inner surface of the outer cylinder at the upper end thereof, teeth formed on said ring, said respective teeth intermeshing, and also including a closure plate on the bottom end of the inner cylinder, teeth formed on the outer periphery of said closure plate and a toothed ring mounted on the lower end of the inner surface of the outer cylinder, said last two sets of teeth respectively intermeshing.

3. A tap selector switch of the class described, comprising: a hollow outer cylinder; a plurality of relatively stationary contact means electrically insulated from each other, said stationary contact means being carried by said outer cylinder and disposed in spaced relationship about the internal peripheral portion thereof; an inner cylinder disposed within said outer cylinder and having its longitudinal axis parallel to and spaced from the longitudinal axis of said outer cylinder; movable contact means carried by said inner cylinder and selectively engageable with said stationary contact means; internally toothed ring gear means fixed to said outer cylinder; externally toothed gear means fixed to said inner cylinder and meshing with said ring gear means; means for producing rolling motion of said externally toothed gear means relative to said ring gear means; and interengaging axially extending means comprising one portion carried by said outer cylinder and another portion carried by said inner cylinder, said axially extending means maintaining said longitudinal axes in fixed spaced parallel relationship during said rolling motion.

4. A switch according to claim 3, in which said axially projecting means comprises a pin of circular crosssection carried by said outer cylinder and a pin of circular cross-section carried by said inner cylinder, the external circular surfaces of said pins interengaging each other during said rolling motion.

5. A switch according to claim 4, in which said pins are axially tapered in opposite directions.

6. A tap selector switch of the class described, comprising: a hollow outer cylinder; a plurality of relatively stationary contact means electrically insulated from each other, said stationary contact means being carried by said outer cylinder and disposed in spaced relationship about the internal peripheral portion thereof; an inner cylinder disposed within said outer cylinder and having its longitudinal axis parallel to and spaced from the longitudinal axis of said outer cylinder; movable contact means carried by said inner cylinder and selectively engageable with said stationary contact means; internally toothed ring gear means fixed to said outer cylinder; externally toothed gear means fixed to said inner cylinder and meshing with said ring gear means; and crank means comprising one portion pivotally and axially connected to said outer cylinder and another portion pivotally and axially connected to said inner cylinder, rotary movement of said crank means causing rolling motion of said externally toothed gear means relative to said ring gear means, said crank means maintaining said longitudinal axes in fixed spaced parallel relationship during said rolling motion.

7. A switch according to claim 6, in which said stationary contact means are uniformly spaced and wherein said two gear means are provided with teeth arranged to cause displacement of said movable contact means from one stationary contact means to an adjacent stationary contact means in response to rotation of said crank means through one complete revolution. I 8. A switch according to claim 7, further comprising controllable spring actuated means connected to said crank means, said spring actuated means driving said crank means through one complete revolution upon each actuation thereof.

References Cited in the file of this patent UNITED STATES PATENTS 2,231,627 Jansen Feb. 11, 1941 FOREIGN PATENTS 705,659 Germany May 6, 1941 886,836 France July 19, 1943