Patent Description:
Vacuum interrupters are widely used in utility power transmission systems, power generation units and powerdistribution systems for railways, for example. Therein, the vacuum interrupter realizes a switch of a medium-voltage circuit-breaker, generator circuit-breaker, or high-voltage circuit-breaker which uses electrical contacts in a vacuum to reliably separate the electrical contacts resulting in a metal vapour arc, which is quickly extinguished.

Document <CIT> discloses an on-load tap changer that includes a plurality of modules disposed in an interior space of a tank and arranged in a side-by-side manner. Each module has a bypass switch assembly and a vacuum interrupter assembly mounted to a first side of a board. The bypass switch assembly is actuated by rotation of a bypass cam and the vacuum interrupter assembly is actuated by rotation of an interrupter cam. A transmission system rotates the bypass cam and the interrupter cam. The transmission system is mounted on a second side of the board.

Document <CIT> discloses a damping mechanism in the field of switches of medium and high voltage switch devices. The voltage switch device comprises a base frame and a switch unit for fixing the base frame. The switch unit comprises a vacuum bubble, an insulating cylinder, an electromagnetic driver and a debouncing device which are axially connected.

In this respect, it is a challenge to provide stable and reliable mechanisms to transmit the motion from a driving cam to a contact rod of the vacuum interrupter and with respect to interacting components to keep wear low.

The present disclosure relate to a vacuum interrupter assembly for a power diverter switch according to claim <NUM> that enables secure and reliable switching of electrical contacts of the vacuum interrupter and contributes to an enhanced life of the vacuum interrupter. Further embodiments of the present disclosure relate to a corresponding power diverter switch for a transformer load tap changer and a transformer load tap changer including such a vacuum interrupter assembly.

The vacuum interrupter assembly for a power diverter switch comprises a vacuum interrupter which is configured to open and close associated electrical contacts in a vacuum and a driving mechanism which is coupled with the vacuum interrupter and which is configured to drive opening and closing of the electrical contacts of the vacuum interrupter. The driving mechanism includes a driving rod and a guiding tube enclosing the driving rod such that the driving rod is axially movable along a longitudinal axis of the vacuum interrupter assembly arranged inside the guiding tube. The vacuum interrupter assembly further comprises a damping unit which is coupled with the driving mechanism and includes a first chamber, a second chamber and a piston arranged there between with respect to the longitudinal axis. The chambers are coupled with each other hydraulically and limited by the guiding tube and the piston. The piston is coupled with the driving rod axially movable along the longitudinal axis such that in interaction with a fluid the damping unit provides hydraulic damping both when opening and when closing the electrical contacts of the vacuum interrupter due to movement of the driving rod and the piston. A first disc and a second disc are fixedly arranged to the guiding tube at opposite sides of the piston with respect to the longitudinal axis limiting the first and the second chamber respectively. Thus, the cambers and their hydraulic volume are defined by the fixed discs, a wall of the guiding tube and the movable piston. The first disc, the second disc and the piston all are arranged axially with respect to the longitudinal axis inside the guiding tube enclosing the driving rod. The first disc and the second disc are connected to the guiding tube whereas the piston is connected to the driving rod. Thus, the discs and the piston all are arranged radially between the guiding tube and the driving rod. Substantially, the guiding tube, the driving rod, the discs and the piston are formed rotationally symmetrical, for example.

Due to the described configuration a vacuum interrupter assembly is feasible that enables secure and reliable switching of electrical contacts of the vacuum interrupter and contributes to reduced wear of interacting components and an enhanced life of the vacuum interrupter and a corresponding power diverter switch. The damping unit realizes a cost-efficient design of a damping mechanism for precise vacuum interrupter control.

It is a recognition of the present disclosure that conventional designs for power diverter switches and control of a vacuum interrupter often has a relatively complex mechanism with many moving parts and modules. These modules are interdependent and follow specific sequence, which lead to their complex design and further difficulties during manufacturing and maintenances.

By use of the vacuum interrupter assembly of the present disclosure it is possible to counteract the aforementioned adverse effects at least. Due to the simple and compact design of the damping unit precise control of the movement of the driving rod in two directions is possible and the vacuum interrupter assembly contributes to reduce bouncing through closing of the vacuum interrupter and its electrical contacts resulting in reduced wear and enhanced assembly life.

According to a further embodiment of the vacuum interrupter assembly the first disc and the second disc comprise at least one orifice each defining a respective fluid passage out and into the first chamber and the second chamber. Thus, due to movement of the driving rod and the piston thereon towards the first disc the volume of the first chamber is reduced and fluid is pressed out through the orifice of the first disc. Accordingly, due to movement of the driving rod and the piston thereon in the opposite direction towards the second disc the volume of the second chamber is reduced and fluid is pressed out through the orifice of the second disc. In this way, hydraulic damping force can be used to influence an opening and closing speed of the vacuum interrupter and to reduce unwanted bouncing effects during closing of the vacuum interrupter, in particular.

Both the at least one orifice of the first and the one of the second disc can comprise a circular shape or are limited circularly by the corresponding disc, wherein a diameter of the orifice of the first disc can be smaller than a diameter of the orifice of the second disc. For example, the respective diameter of the orifice of the first disc is <NUM> and the respective diameter of the orifice of the second disc is <NUM>. Thus, a higher damping force can be provided in the direction of the first disc comprising the smaller orifice. According to the aforementioned embodiment, the first disc would be configured to provide hydraulic damping when closing the electrical contacts of the vacuum interrupter and the second disc when opening the electrical contacts.

According to a further embedment of the vacuum interrupter assembly the guiding tube can also comprise two recesses. Such recesses can be configured to penetrate a wall of the guiding tube defining a first channel and a second channel associated to the first chamber and the second chamber respectively such that a fluid passage is defined by the orifice of the first disc, the first channel, the second channel and the orifice of the second disc. Thus, in view of an arrangement of the discs inside the guiding tube, a fluid could flow through the orifice of the first disc into the guiding tube and then through the first channel out of the guiding tube again. Accordingly, fluid from outside can flow through the second channel into the guiding tube and from inside through the orifice of the second disc to the outside again. To beneficially control the fluid flow and the hydraulic damping force, the piston is connected to the driving rod such that it closes the first channel when closing the electrical contacts of the vacuum interrupter and such that it closes the second channel when opening the electrical contacts of the vacuum interrupter due to movement of the driving rod. Thus, a distance of the first and the second channel is configured in coordination with a thickness of the piston with respect to the longitudinal axis.

Furthermore, a size of the piston and/or a size and/or a location of the first and the second channel in the wall of the guiding tube can be configured in coordination with each other to provide a predetermined hydraulic damping force in interaction with a fluid that is intended to wash around the vacuum interrupter assembly and to flow inside and outside the guiding tube with respect to an operational state of the vacuum interrupter assembly.

According to a further embodiment of the vacuum interrupter assembly at least one of the orifice of the first disc, the orifice of the second disc, the first channel and the second channel comprises a respective size configured in coordination with a viscosity of a fluid that is intended to flow inside and outside the guiding tube to provide a predetermined hydraulic damping force in interaction with the fluid with respect to an operational state of the vacuum interrupter assembly. The vacuum interrupter assembly is configured to be immersed in a predetermined fluid, for example a mineral transformer oil, inside a tank of a transformer load tap changer and thus, the size of the one or more intentionally implemented fluid openings can influence the hydraulic damping force depending on the viscosity of the fluid or the temperature of the fluid as well.

According to an embodiment, a power diverter switch for a transformer load tap changer comprises an insulation plate, a control cam and an embodiment of the described vacuum interrupter assembly, which is coupled to both the insulation plate and the control cam. The control cam is configured to drive the driving mechanism of the vacuum interrupter assembly in order to open or close the electrical contacts of the vacuum interrupter.

According to an embodiment, a transformer load tap changer for setting a gear ratio comprises a tank that encloses a fluid and at least one embodiment of the aforementioned power diverter switch which is arranged inside the tank immersed in the fluid.

Such a configuration of a power diverter switch and a transformer load tap changer using an embodiment of the described vacuum interrupter assembly with an improved damper enables secure and reliable switching or separation of electrical contacts of the vacuum interrupter. As a result of that the power diverter switch and the transformer load tap changer comprise an embodiment of the vacuum interrupter, described features and characteristics of the vacuum interrupter are also disclosed with respect to the power diverter switch and the transformer load tap changer and vice versa. Thus, the present disclosure comprises several aspects, wherein every feature described with respect to one of the aspects is also disclosed herein with respect to the other aspect, even if the respective feature is not explicitly mentioned in the context of the specific aspect.

With respect to an operational state assembled in the transformer the described configuration of the vacuum interrupter assembly and its specific hydraulic damper are immersed in a dielectric fluid and allows for beneficial control of opening and closing the electrical contacts of the vacuum interrupter. The damping unit enables precise and reliable operating mode of the vacuum interrupter and the transformer load the tap changer, respectively. The described configuration allows for a cost-effective assembly with an improved damping implemented in the driving mechanism and in addition one or more of the following advantageous effects:.

Exemplary embodiments are explained in the following with the aid of schematic drawings and reference numbers. The figures show:.

The accompanying figures are included to provide a further understanding. It is to be understood that the embodiments shown in the figures are illustrative representations and are not necessarily drawn to scale. Identical reference numbers designate elements or components with identical functions. In so far as elements or components correspond to one another in terms of their function in different figures, the description thereof is not repeated for each of the following figures. For the sake of clarity elements might not appear with corresponding reference symbols in all figures possibly.

<FIG> illustrates a cross section side view of an embodiment of a transformer load tap changer <NUM> for setting a gear ratio comprising a tank <NUM> that encloses a fluid, and three power diverter switches arranged inside the tank <NUM> and immersed in the fluid. The transformer load tap changer <NUM> comprises drive motor drive shaft <NUM> and insulation shafts <NUM> to control the power diverter switches and their vacuum interrupter modules <NUM>. A movement to operate the transformer load tap changer <NUM> is received through the motor drive shaft <NUM>. That motor drive shaft <NUM> is connected to a motor drive unit, which is mounted to the tank <NUM>. The motor drive shaft <NUM> is then connected to a bevel gear structure, which by the means of the insulation shafts <NUM> is distributing the movement to the three phases of the corresponding vacuum interrupter modules <NUM>.

<FIG> illustrates one power diverter switch assembly or vacuum interrupter module <NUM> of the transformer load tap changer <NUM> in a perspective view. The vacuum interrupter module <NUM> comprises an insulation plate <NUM> and current transformer <NUM> attached to the insulation plate <NUM>. The insulation plate forms a support structure for the vacuum interrupter module <NUM> and may be composed of a rigid dielectric material, such as fiber-reinforced dielectric plastic. On a front side of the insulation plate <NUM> a bypass switch assembly and a vacuum interrupter assembly <NUM> is mounted. A back-side of the insulation plate <NUM> can be used for carrying copper bars used for schematic connection. Incoming motion from a selector is transferred to a cam end of a control cam <NUM> through the means of the insulation shafts <NUM>. The control cam <NUM> is configured to actuate the bypass contacts <NUM> through corresponding bypass levers <NUM>. At the same time the control cam <NUM> is configured to load and discharge a spring accumulator inside a driving mechanism <NUM>.

The vacuum interrupter module <NUM> comprises the vacuum interrupter assembly <NUM> including a vacuum interrupter <NUM> and the driving mechanism <NUM> that is coupled with the vacuum interrupter <NUM> and that is configured to drive opening and closing of electrical contacts of the vacuum interrupter <NUM>. The transformer load tap changer <NUM> and the respective vacuum modules <NUM> may further include for each phase winding, a selector switch assembly and a bypass switch module. The selector switch assembly can be configured to make connections between taps, while the bypass switch module may be configured to connect the tap to a main power source. During tap changes, the vacuum interrupter module <NUM> safely carries the current between the tap and a main power circuit. A drive system is configured to move a selector switch, the bypass switch module and the vacuum interrupter module <NUM>.

The control cam <NUM> is coupled with the vacuum interrupter assembly <NUM> and is configured to drive the driving mechanism <NUM> to open and close the electrical contacts of the vacuum interrupter <NUM> (see <FIG>). The driving mechanism <NUM> includes a driving rod <NUM> and a guiding tube <NUM> enclosing the driving rod <NUM> such that the driving rod <NUM> is axially movable inside the guiding tube <NUM> along a longitudinal axis L of the vacuum interrupter assembly <NUM>.

The respective vacuum interrupter assembly <NUM> further comprises a damping unit <NUM> coupled with the driving mechanism <NUM> and comprising a first chamber <NUM>, a second chamber <NUM> and a piston <NUM> arranged there between with respect to the longitudinal axis L (see <FIG> and <FIG>). The chambers <NUM>, <NUM> are coupled with each other hydraulically and limited by the guiding tube <NUM>, the piston <NUM> and a first disc <NUM> and a second disc <NUM> all arranged axially with respect to the longitudinal axis inside the guiding tube <NUM>. The piston <NUM> is coupled with the driving rod <NUM> axially movable along the longitudinal axis L such that in interaction with the fluid the damping unit <NUM> provides hydraulic damping both when opening and when closing the electrical contacts of the vacuum interrupter <NUM> due to movement of the driving rod <NUM> and the piston <NUM> along the longitudinal axis L.

According to the cross section view of the embodiment as illustrated in <FIG> the vacuum interrupter module <NUM> further comprises one or more driving springs <NUM>, a locking mechanism <NUM>, an adjusting system <NUM> and a locking system <NUM>. The driving springs <NUM> accumulate the needed energy to provide proper switching speed of the vacuum interrupter module <NUM>. The locking mechanism <NUM> and the locking system <NUM> are used for defining the two positions of the vacuum interrupter <NUM>. Further, the locking system <NUM> is clamping the vacuum interrupter <NUM> toward the insulation plate <NUM>. The adjusting system <NUM> is configured to adjust a contact gap and to provide solution for axial discrepancies during assembling of the vacuum interrupter module <NUM> and the vacuum interrupter assembly <NUM>. The damping unit <NUM> is configured to provide reliable damping when the driving rod <NUM> is closing the vacuum interrupter <NUM> and when the driving rod <NUM> is opening the vacuum interrupter <NUM>.

The <FIG> and <FIG> each shows an enlarged perspective view of the damping unit <NUM> of the corresponding vacuum interrupter assembly <NUM> as circled in dashed lines in <FIG>. The damping unit <NUM> is configured such that it provides more damping when closing the electrical contacts of the vacuum interrupter <NUM> than when opening the same. Such a higher hydraulic damping force is achieved by the two different chambers <NUM>, <NUM> and the discs <NUM>, <NUM> comprising different orifices <NUM> and <NUM>, respectively.

The discs <NUM>, <NUM> and the piston <NUM> realizes washers or bushings including a respective central opening the driving rod <NUM> is extending through. The discs <NUM> and <NUM> are fixedly connected to an inside surface of the guiding tube <NUM> whereas the piston <NUM> is fixedly connected to an outside surface of the driving rod <NUM>. Additionally, the inner surface of the guiding tube <NUM> and/or the outer surface of the driving rod <NUM> can comprise edges, protrusions and/or grooves to enable precise and stable arrangement of the discs <NUM>, <NUM> and the piston <NUM>, respectively.

The first disc <NUM> comprises two orifices <NUM> and the second disc <NUM> comprises two orifices <NUM> each defining a fluid passage out and into the first chamber <NUM> and the second chamber <NUM>. The orifices <NUM> and <NUM> of the first and the second disc <NUM> and <NUM> all are circularly limited and a respective diameter of the orifices <NUM> of the first disc <NUM> is smaller than a respective diameter of the orifice <NUM> of the second disc <NUM>. According to the illustrated embodiments, the first disc <NUM> is arranged closer to the vacuum interrupter <NUM> than the second disc <NUM>. The discs <NUM> and <NUM> are arranged inside the guiding tube <NUM> at opposite sides of the piston <NUM> with respect to the longitudinal axis L.

The vacuum interrupter assembly <NUM> is configured such that when the piston <NUM> is driven towards the first disc <NUM> the electrical contacts of the vacuum interrupter are closed. Consequently, the vacuum interrupter assembly <NUM> is configured such that when the piston <NUM> is driven towards the second disc <NUM> the electrical contacts of the vacuum interrupter are opened.

Thus, the first disc <NUM> and its orifices <NUM> are configured to provide a predetermined hydraulic damping when closing the electrical contacts of the vacuum interrupter <NUM>. Accordingly, the second disc <NUM> and its orifices <NUM> are configured to provide a predetermined hydraulic damping when opening the electrical contacts of the vacuum interrupter <NUM>.

Moreover, the guiding tube <NUM> comprises two recesses penetrating a wall of the guiding tube <NUM> defining a first channel <NUM> and a second channel <NUM> from the inside to the outside of the guiding tube <NUM>. The first channel <NUM> is associated to the first chamber <NUM> and the second channel <NUM> is associated to the second chamber <NUM> such that a fluid passage is defined by the orifices <NUM> of the first disc <NUM>, the first channel <NUM>, the second channel <NUM> and the orifices <NUM> of the second disc <NUM>. Due to movement of the driving rod <NUM> and the piston <NUM> a volume of one chamber <NUM>, <NUM> is reduced whereas a volume of the other camber <NUM>, <NUM> is increased. The piston <NUM> then closes the first channel <NUM> when closing the electrical contacts of the vacuum interrupter <NUM> and closes the second channel <NUM> when opening the electrical contacts of the vacuum interrupter <NUM>.

A size of the piston <NUM> as well as a size and a location of the first and the second channel <NUM>, <NUM> in the wall of the guiding tube <NUM> are configured in coordination with each other to provide a predetermined hydraulic damping force in interaction with the fluid and a size of the orifices <NUM> and <NUM> in the discs <NUM> and <NUM>. For example, a size of the orifices <NUM> of the first disc <NUM>, a size of the orifices <NUM> of the second disc <NUM> and a size of the first and the second channel <NUM> and <NUM> are configured in coordination with a viscosity of the fluid inside the tank <NUM>. For example, the discs <NUM> and <NUM>, the piston <NUM> and the channels <NUM> and <NUM> are arranged and sized so that the piston <NUM> nearly closes both the first channel <NUM> and the second channel <NUM> in a middle position between the discs <NUM>, <NUM> and the volume of the chambers <NUM> and <NUM> is roughly the same. Such a state might be illustrated in <FIG>.

The piston <NUM> may have a thickness of a few millimeters, <NUM> for example, with respect to the longitudinal axis L. The thickness of the piston <NUM> is beneficially adapted to a stroke of the movable electrical contacts of the vacuum interrupter <NUM>, which has a value of <NUM>, for example. Thus, a movable distance of the piston <NUM> inside the guiding tube <NUM> should also be adapted to the aforementioned stroke such that the piston can move reliably.

For example, when moving the driving rod <NUM> and the piston <NUM> in the closing direction, a lower speed is desired. A size of the orifices <NUM> of the first disc <NUM> and/or a size of the orifices <NUM> of the second disc <NUM> are configured to be smaller than a size of the first and/or the second channel <NUM>, <NUM> on the periphery of the guiding tube <NUM> to reach a more smooth movement. With respect to an end opening position, the second channel <NUM> is closed by the piston <NUM> and the first channel <NUM> is predetermined opened in part. Thus, the piston <NUM> covers only one channel, i.e. an area of fluid leakage is larger, therefore at this point the speed is higher.

If the movement the piston <NUM> is continued to close the electrical contacts it will close the first channel <NUM> and the second channel <NUM> then is opened in part, predetermined, to reach a desired braking effect, as an oil flow will be only through the two small orifices <NUM> of the first disk <NUM>. At the end closing position the second channel <NUM>, placed on the periphery of the guiding tube <NUM> is opened in part, thus preventing any braking effect that would be formed by a vacuum in the second chamber <NUM> inside the guiding tube <NUM> when moving the piston <NUM> towards the second disk <NUM>. When moving in the opening direction again, the sequence is the same but the speed is higher, and the orifices <NUM> of the second disk <NUM> are larger than the ones in the first disk <NUM>.

For example, a respective center of the first and the second channel <NUM>, <NUM> can have a distance of <NUM> from each other, wherein the first and the second channels <NUM>, <NUM> may comprise a diameter of <NUM> each. Thus, with respect to a start opening position which is equivalent to the end closing position the second channel <NUM> might be covered by the piston <NUM> such that a fluid-permeable area is reduced to <NUM> left with respect to the <NUM> diameter, for example.

Thus, with respect to a start closing position which is equivalent to the end opening position the first channel <NUM> might be covered by the piston <NUM> such that a fluid-permeable area is reduced to the half, viz. <NUM> left with respect to the <NUM> diameter, for example.

The damping unit <NUM> is implemented in the guiding tube <NUM> of the driving mechanism <NUM> in the power diverter switch. The damping unit <NUM> merely comprises three elements and some adaptions on the guiding tube <NUM> and the driving rod <NUM> of the vacuum interrupter assembly <NUM>. Inter alia, the exact positions of the holes or channels <NUM>, <NUM> in the wall of the guiding tube <NUM> enables to provide an exact moment of the damping force and with default of the diameter of the orifices <NUM>, <NUM> it is possible to achieve a desired reactance of the fluid - respectively damping force. Due to such a configuration, the damping unit <NUM> enables to beneficially influence the opening and closing speeds of the vacuum interrupter <NUM> and reduce unwanted bouncing effects during closing of the vacuum interrupter <NUM>.

The described vacuum interrupter assembly <NUM> provides a beneficial robustness and contributes to reduced manufacturability and maintenance criteria. Inter alia, this is achieved due to the specifically configured damping unit <NUM> which is immersed in a dielectric fluid. The electrical contacts of the vacuum interrupter <NUM> are opened and closed by the means of the driving mechanism <NUM> and the damping unit <NUM> is implemented in the driving mechanism <NUM>. The damping unit <NUM> according to the illustrated embodiments is configured to provide more damping force when the driving rod <NUM> is closing the vacuum interrupter <NUM> than when the driving rod <NUM> is opening the vacuum interrupter <NUM>. This can be achieved by the two hydraulic chambers <NUM>, <NUM> and the discs <NUM>, <NUM> with different orifices <NUM>, <NUM>.

Claim 1:
Vacuum interrupter assembly (<NUM>) for a power diverter switch, comprising:
- a vacuum interrupter (<NUM>) which is configured to open and close associated electrical contacts in a vacuum,
- a driving mechanism (<NUM>) which is coupled with the vacuum interrupter (<NUM>) and which is configured to drive opening and closing of the electrical contacts of the vacuum interrupter (<NUM>), wherein the driving mechanism (<NUM>) includes a driving rod (<NUM>) and a guiding tube (<NUM>) enclosing the driving rod (<NUM>) such that the driving rod (<NUM>) is axially movable inside the guiding tube (<NUM>) along a longitudinal axis (L) of the vacuum interrupter assembly (<NUM>),
- a damping unit (<NUM>) coupled with the driving mechanism (<NUM>) and comprising a first chamber (<NUM>), a second chamber (<NUM>) and a piston (<NUM>) arranged there between with respect to the longitudinal axis (L), wherein the chambers (<NUM>, <NUM>) are coupled with each other hydraulically and limited by the guiding tube (<NUM>) and the piston (<NUM>), and wherein the piston (<NUM>) is coupled with the driving rod (<NUM>) axially movable along the longitudinal axis (L) such that in interaction with a fluid the damping unit (<NUM>) provides hydraulic damping both when opening and when closing the electrical contacts of the vacuum interrupter (<NUM>) due to movement of the driving rod (<NUM>) and the piston (<NUM>), characterized in that the damping unit (<NUM>) further comprises
a first disc (<NUM>) and a second disc (<NUM>) fixedly arranged to the guiding tube (<NUM>) at opposite sides of the piston (<NUM>) with respect to the longitudinal axis (L) limiting the first and the second chamber (<NUM>, <NUM>) respectively, wherein the first disc (<NUM>), the second disc (<NUM>) and the piston (<NUM>) all are arranged axially with respect to the longitudinal axis (L) inside the guiding tube (<NUM>) and enclosing the driving rod (<NUM>) such that the first disc (<NUM>) and the second disc (<NUM>) are connected to the guiding tube (<NUM>) and the piston (<NUM>) is connected to the driving rod (<NUM>) and all are arranged radially between the guiding tube (<NUM>) and the driving rod (<NUM>).