Description: TECHNICAL FIELD
[0001] The present disclosure relates to a motorized version of a three-position switch that can be used to operate a potential transformer on a busbar side for gas insulated switchgear.

BACKGROUND
[0002] Background description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.
[0003] Potential transformers (PTs) or voltage transformers are used in electrical power system for various advantages. PTs supply protective relays with current and voltages of magnitude proportional to those of the power circuits. These current and voltage magnitudes supplied by the PTs are appropriately reduced, such that the relays can be made relatively small and inexpensive. In switchgear, PTs are generally used to monitor the voltage in line side or busbar side. In order to perform maintenance on a busbar side, firstly, it is required to ensure that the busbar side is not live. If the busbar side is earthed in live condition, an earth fault may occur, potentially leading to damage of the whole equipment. Further, during maintenance at busbar side of switchgear, PTs should be in OFF condition. Further, during maintenance of PTs, the PTs should be earthed properly to remove the residual charges.
[0004] There is, therefore, a requirement for a means to switch the PT between ON, OFF and EARTH conditions.

OBJECTS OF THE INVENTION
[0005] An object of the present invention is to provide a switching mechanism for a potential transformer.
[0006] Another object of the present invention is to provide a switching mechanism in which three conditions – ON, OFF, and EARTH are achieved.
[0007] Another object of the present invention is to provide a switching mechanism that is compact and less complicated.
[0008] Another object of the present invention is to provide a switching mechanism in which contact loading force is provided when the switch is in ON and EARTH positions.
[0009] Another object of the present invention is to provide a switching mechanism that may be operated manually or through a motor.
[0010] Another object of the present invention is to provide a switching mechanism that has an interlock to prevent excessive rotation.

SUMMARY
[0011] In an aspect, the present disclosure provides a switching mechanism for a potential transformer (PT). The switching mechanism includes an input shaft. The switching mechanism further includes a cam coupled to the input shaft, such that rotation of the input shaft results in corresponding rotation of the cam. The switching mechanism further includes a ball fixed in cam slot using a compression spring. The cam slot corresponds to any one of ON, OFF, and EARTH conditions of the PT. Rotation of the input shaft causes rotation of the cam. Rotation of the cam causes downward motion of the ball, such that the ball is pushed to an adjacent cam slot. The adjacent cam slot corresponds to another of ON, OFF, and EARTH conditions of the PT.
[0012] In some embodiments, the switching mechanism further incudes a leaf A coupled to the cam. The switching mechanism further includes a leaf B coupled to the leaf A through a connecting link and further coupled to a PT shaft, such that rotation of the cam results in the rotation of the PT shaft.
[0013] In some embodiments, radii of the leaf A, the connecting link, and the leaf B are such that a pre-defined rotation of the cam results in a corresponding pre-defined rotation of the PT shaft.
[0014] In some embodiments, the switching mechanism includes interlocking studs in order to prevent rotation of the input shaft beyond a pre-defined operating range for the input shaft.
[0015] In some embodiments, the input shaft is rotated by a handle coupled with the input shaft.
[0016] In some embodiments, the input shaft is rotated by a motor coupled to the input shaft through the gear train.
[0017] In some embodiments, the switching mechanism includes a motor spur gear coupled to the motor. The switching mechanism further includes a second spur gear coupled to the motor spur gear. The switching mechanism further includes a worm wheel coupled to the second spur gear through a worm shaft, and further coupled to the input shaft. The motor is configured to rotate the motor spur gear. Rotation of the motor transfers rotary torque from the motor to the input shaft through the motor spur gear, the second spur gear and the worm wheel.
[0018] In some embodiments, the motor is a 10 Nm, 10 RPM motor.
[0019] In some embodiments, the motor is controlled through a printed circuit board (PCB).
[0020] In some embodiments, the switching mechanism comprises a three-way auxiliary switch configured select a direction of rotation of the motor.
[0021] Various objects, features, aspects, and advantages of the inventive subject matter will become more apparent from the following detailed description of preferred embodiments, along with the accompanying drawing figures in which like numerals represent like components.

BRIEF DESCRIPTION OF DRAWINGS
[0022] The accompanying drawings are included to provide a further understanding of the present disclosure and are incorporated in and constitute a part of this specification. The drawings illustrate exemplary embodiments of the present disclosure and, together with the description, serve to explain the principles of the present disclosure.
[0023] FIG. 1 illustrates a schematic perspective view of a switching mechanism for a potential transformer (PT), according to an embodiment of the present disclosure;
[0024] FIG. 2 illustrates a schematic side view of the switching mechanism for the PT, according to an embodiment of the present disclosure;
[0025] FIG. 3 illustrates a schematic view of a ball and cam arrangement of the switching mechanism, according to an embodiment of the present disclosure;
[0026] FIG. 4 illustrates a schematic view of a PT switch, according to an embodiment of the present disclosure; and
[0027] FIG. 5 illustrates a schematic view of an interlock arrangement of the switching mechanism for the PT, according to an embodiment of the present disclosure.

DETAILED DESCRIPTION
[0028] The following is a detailed description of embodiments of the disclosure depicted in the accompanying drawings. The embodiments are in such details as to clearly communicate the disclosure. However, the amount of detail offered is not intended to limit the anticipated variations of embodiments; on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present disclosure as defined by the appended claims.
[0029] The present disclosure relates to a motorized version of a three-position switch that can be used to operate a potential transformer on a busbar side for gas insulated switchgear. A potential transformer (PT) or a voltage transformer is an instrument transformer that is used in an electrical power system for stepping down voltage to a safe value, which can be easily measured with the help of commercially available relays. During maintenance of PTs, the PTs should be in earthed conditions to earth the residual charges.
[0030] The present disclosure provides a mechanism, which can position a PT switch in any of three conditions – ON, OFF, and EARTH. This switching mechanism can be operated manually as well as remotely through the motor. Cam and ball arrangement gives sufficient contact loading force when the PT switch is in ON condition to avoid the arcing phenomenon. Even a small arcing can lead to a bursting of PT so contact loading is crucial. Cam and ball arrangement also helps in getting snapping action while changing the position of the switch.
[0031] In an aspect, the present disclosure provides a switching mechanism for a potential transformer (PT). The switching mechanism includes an input shaft. The switching mechanism further includes a cam coupled to the input shaft, such that rotation of the input shaft results in corresponding rotation of the cam. The switching mechanism further includes a ball fixed in cam slot using a compression spring. The cam slot corresponds to any one of ON, OFF, and EARTH conditions of the PT. Rotation of the input shaft causes rotation of the cam. Rotation of the cam causes downward motion of the ball, such that the ball is pushed to an adjacent cam slot. The adjacent cam slot corresponds to another of ON, OFF, and EARTH conditions of the PT.
[0032] In some embodiments, the switching mechanism further incudes a leaf A coupled to the cam. The switching mechanism further includes a leaf B coupled to the leaf A through a connecting link and further coupled to a PT shaft, such that rotation of the cam results in the rotation of the PT shaft.
[0033] In some embodiments, radii of the leaf A, the connecting link, and the leaf B are such that a pre-defined rotation of the cam results in a corresponding pre-defined rotation of the PT shaft.
[0034] In some embodiments, the switching mechanism includes interlocking studs in order to prevent rotation of the input shaft beyond a pre-defined operating range for the input shaft.
[0035] In some embodiments, the input shaft is rotated by a handle coupled with the input shaft.
[0036] In some embodiments, the input shaft is rotated by a motor coupled to the input shaft.
[0037] In some embodiments, the switching mechanism includes a motor spur gear coupled to the motor. The switching mechanism further includes a second spur gear coupled to the motor spur gear. The switching mechanism further includes a worm wheel coupled to the second spur gear through a worm shaft, and further coupled to the input shaft. The motor is configured to rotate the motor spur gear. Rotation of the motor transfers rotary torque from the motor to the input shaft through the motor spur gear, the second spur gear and the worm wheel.
[0038] In some embodiments, the motor is a 10 Nm, 10 RPM motor.
[0039] In some embodiments, the motor is controlled through a printed circuit board (PCB).
[0040] In some embodiments, the switching mechanism comprises a three-way auxiliary switch configured select a direction of rotation of the motor.
[0041] FIG. 1 illustrates a schematic perspective view of a switching mechanism 100 for a potential transformer (PT) (not shown), according to an embodiment of the present disclosure.
[0042] FIG. 2 illustrates a schematic side view of the switching mechanism 100 for the PT, according to an embodiment of the present disclosure.
[0043] FIG. 3 illustrates a schematic view of a ball and cam arrangement of the switching mechanism 100, according to an embodiment of the present disclosure.
[0044] FIG. 4 illustrates a schematic view of a PT switch, according to an embodiment of the present disclosure.
[0045] FIG. 5 illustrates a schematic view of an interlock arrangement of the switching mechanism 100 for the PT, according to an embodiment of the present disclosure.
[0046] Referring now to FIGs. 1 to 5, the switching mechanism 100 includes a cam (7) fixed on an input shaft (1). A ball (8) is fixed between a cam slot using a compression spring (6). The spring force maintains the cam (7) in its position. The input shaft (1) is further attached to leaf A (9), connecting link (10), leaf B (11) and PT shaft (12) inside a housing of the switching mechanism 100. A motion of the input shaft (1) is transferred to the PT shaft (12) through the connecting link (10). In other words, as the input shaft (1) rotates, leaf A (9) rotates. Consequently, the leaf A (9) pulls or pushes the connecting link (10). The connecting link (10), in turn, drives leaf B (11), which is mounted on the PT shaft (12). In some embodiments, the radii of leaf A (9), leaf B (11) and the connecting link (10) is such that, a specific rotation of the cam (7) results in a similar rotation of the PT shaft (12). For example, a 60-degree rotation of the cam (7) may lead to a 60-degree rotation of the PT shaft (12).
[0047] To manually operate the switching mechanism 100, a handle is inserted in the input shaft (1), and the handle is rotated clockwise, or anti-clockwise. The rotation of the handle results in the corresponding rotation of the input shaft (1). As the input shaft (1) rotates, a corresponding rotational torque is transmitted to the cam (7) and the ball (8) is pushed downwards. As the torque increases due to further rotation of the handle, the spring (6) is further compressed. After a pre-defined rotation of the handle, and thereby the cam (7), the ball (8) is at a lowest position. For example, after a 30-degree rotation of the cam (7), the ball (8) is at the lowest position. At the lowest position, the slot on the cam (7) is about to end. A further movement of the input shaft (1) by the handle causes a snapping action and the ball (8) is pushed to an adjacent slot on the cam (7). The adjacent slot on the cam (8) represents a change in condition of the switching mechanism 100, i.e., the switching mechanism 100 moves from any one of initial condition – ON, OFF, EARTH to another condition. In some embodiments, interlocking studs (13) are provided inside the housing in order to limit the rotation of the input shaft (1) beyond an operating range.
[0048] In some embodiments, the switching mechanism 100 may be operated using a motor (3). Rotary torque from the motor (3) is transferred using a system of gears. In some embodiments, four numbers of gears may be used – a motor spur gear (2), a second spur gear (4), a worm shaft, and a worm wheel (14).
[0049] The motor spur gear (2) is mounted on a motor shaft, such that the motor (3) drives the motor spur gear (2). The second spur gear (4) is coupled to the motor spur gear (2) and is mounted on the worm shaft. Thus, the motor (3) drives the worm shaft through the motor spur gear (2). The worm shaft, in turn, drives the worm wheel (14), which is mounted on the input shaft (1). Hence, the motor (3) drives the input shaft (1) through the motor spur gear (2), the second spur gear (4), the worm shaft, and the worm wheel (14). The input shaft (1) now rotates the cam (7).
[0050] In some embodiments, the gears (2, 4, 14) are selected in such a way that a small motor may drive them. In an example, the motor (3) may be a 10 Nm, 10 RPM motor.
[0051] In some embodiments, a three-position auxiliary switch (5) may be used to change a direction of rotation of the motor (3). The motor (3) may be operated from a PCB card.
[0052] It should be apparent to those skilled in the art that many more modifications besides those already described are possible without departing from the inventive concepts herein. The inventive subject matter, therefore, is not to be restricted except in the spirit of the appended claims. Moreover, in interpreting both the specification and the claims, all terms should be interpreted in the broadest possible manner consistent with the context. In particular, the terms “comprises” and “comprising” should be interpreted as referring to elements, components, or steps in a non-exclusive manner, indicating that the referenced elements, components, or steps may be present, or utilized, or combined with other elements, components, or steps that are not expressly referenced. Where the specification claims refer to at least one of something selected from the group consisting of A, B, C ….and N, the text should be interpreted as requiring only one element from the group, not A plus N, or B plus N, etc. The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the appended claims.
[0053] While the foregoing describes various embodiments of the invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof. The scope of the invention is determined by the claims that follow. The invention is not limited to the described embodiments, versions, or examples, which are included to enable a person having ordinary skill in the art to make and use the invention when combined with information and knowledge available to the person having ordinary skill in the art.

LIST OF NUMERAL REFERENCES
100 Switching Mechanism
1 Input Shaft
2 Motor Spur Gear
3 Motor
4 Second Spur Gear
5 Auxiliary Switch
6 Spring
7 Cam
8 Ball
9 Leaf A
10 Connecting Link
11 Leaf B
12 PT Shaft
13 Interlock Studs
14 Worm Wheel

ADVANTAGES OF THE INVENTION
[0054] The present invention provides a switching mechanism for a potential transformer.
[0055] The present invention provides a switching mechanism in which three conditions – ON, OFF, and EARTH are achieved.
[0056] The present invention provides a switching mechanism that is compact and less complicated.
[0057] The present invention provides a switching mechanism in which contact loading force is provided when The switch is in ON and EARTH positions.
[0058] The present invention provides a switching mechanism that may be operated manually or through a motor.
[0059] The present invention provides a switching mechanism that has an interlock to prevent excessive rotation.

, Claims: 1. A switching mechanism (100) for a potential transformer (PT), the switching mechanism (100) comprising:
an input shaft (1);
a cam (7) coupled to the input shaft (1), such that rotation of the input shaft (1) results in corresponding rotation of the cam (7); and
a ball (8) fixed in cam slot using a compression spring (6), wherein the cam slot corresponds to any one of ON, OFF, and EARTH conditions of the PT,
wherein rotation of the input shaft (1) causes rotation of the cam (7),
wherein rotation of the cam (7) causes downward motion of the ball (8), such that the ball (8) is pushed to an adjacent cam slot, and
wherein the adjacent cam slot corresponds to another of ON, OFF, and EARTH conditions of the PT.
2. The switching mechanism (100) as claimed in claim 1, wherein the switching mechanism (100) further comprises:
a leaf A (9) coupled to the cam (7); and
a leaf B (11) coupled to the leaf A (9) through a connecting link (10) and further coupled to a PT shaft, such that rotation of the cam (7) results in the rotation of the PT shaft.
3. The switching mechanism (100) as claimed in claim 2, wherein radii of the leaf A (9), the connecting link (10) and the leaf B (11) are such that a pre-defined rotation of the cam (7) results in a corresponding pre-defined rotation of the PT shaft.
4. The switching mechanism (100) as claimed in claim 1, wherein the switching mechanism (100) comprises interlocking studs (13) in order to prevent rotation of the input shaft (1) beyond a pre-defined operating range for the input shaft (1).

5. The switching mechanism (100) as claimed in claim 1, wherein the input shaft (1) is rotated by a handle coupled with the input shaft (1).
6. The switching mechanism (100) as claimed in claim 1, wherein the input shaft (1) is rotated by a motor (3) coupled to the input shaft (1).
7. The switching mechanism (100) as claimed in claim 6, wherein the switching mechanism (100) comprises:
a motor spur gear (2) coupled to the motor (3);
a second spur gear (4) coupled to the motor spur gear (2); and
a worm wheel coupled to the second spur gear (4) through a worm shaft, and further coupled to the input shaft (1),
wherein the motor (3) is configured to rotate the motor spur gear (2), and
wherein rotation of the motor (3) transfers rotary torque from the motor (3) to the input shaft (1) through the motor spur gear (2), the second spur gear (4) and the worm wheel (14).
8. The switching mechanism (100) as claimed in claim 7, wherein the motor (3) is a 10 Nm, 10 RPM motor.
9. The switching mechanism (100) as claimed in claim 7, wherein the motor (3) is controlled through a printed circuit board (PCB).
10. The switching mechanism (100) as claimed in claim 7, wherein the switching mechanism (100) comprises a three-way auxiliary switch (5) configured select a direction of rotation of the motor (3).