Patent Description:
Vacuum interrupters are widely used in utility power transmission systems, power generation units and power-distribution 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. In this respect, it is a challenge to provide stable and reliable mechanisms to transmit the motion from a driving unit to a contact rod of the vacuum interrupter and an associated bypass switch connected to the electrical contacts, and with respect to interacting components to keep wear low.

<CIT> provides 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.

<CIT> relates to a switching system for a step transformer having at least two adjacent taps and a pair of terminals shiftable between the taps has a pair of fixed contacts normally connected to the terminals, a vacuum interrupter connected between the terminals and displaceable between an open-circuit position and a closed-circuit position, a pair of movable contacts each engageable with a respective one of the fixed contacts and forming therewith a respective bypass switch, and a cam rotatable about a cam axis and having a contact face and an axially oppositely facing interrupter face each formed with a respective operating formation.

Aspects of the present disclosure relate to a vacuum interrupter module comprising a vacuum interrupter assembly and a bypass switch assembly for a power diverter switch that enables secure and reliable switching of electrical contacts of the vacuum interrupter and an associated bypass switch and contributes to an enhanced life of the vacuum interrupter module. Further aspects of the present disclosure relate to a corresponding power diverter switch and load tap changer including such a vacuum interrupter module. The invention is defined by the attached set of claims.

According to a first aspect, a vacuum interrupter module for a tap changer comprises an insulation plate having a first main side and a second main side opposite of the first main side, a vacuum interrupter assembly, a bypass switch assembly, and a control cam. The vacuum interrupter assembly comprises a vacuum interrupter and a driving mechanism coupled with the vacuum interrupter, the vacuum interrupter and the driving mechanism being arranged on the first main side of the insulation plate. The bypass switch assembly comprises two bypass contacts, each one mechanically connected to a corresponding bypass lever, the two bypass contacts and the two corresponding bypass levers being arranged on the first main side of the insulation plate. The control cam is arranged on the first main side of the insulation plate and configured to actuate both the driving mechanism and, through the corresponding bypass levers, the two bypass contacts.

Due to the described configuration of the vacuum interrupter module, both the vacuum interrupter assembly and the bypass switch assembly can be controlled by a single control cam, thus enabling a simple mechanical set-up and perfect phase synchronization between the respective electrical switching components. At the same time, their arrangement on a common side of the insulation plate means that essentially all mechanical components subject to wear are easily accessible in a mounted position. In particular, no transmission system is required on the second main side. Consequently, the disclosed vacuum interrupter module enables secure and reliable switching of electrical contacts of the vacuum interrupter and bypass contacts and contributes to better maintenance and thus an enhanced life of the vacuum interrupter module.

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 module of the present disclosure it is possible to counteract the aforementioned adverse effects at least. Due to the simple and compact design of the common control cam that controls the movement of both the vacuum interrupter and bypass contacts, their relative movements can be synchronized and the overall part count of the module can be reduced, making the individual parts more accessible for maintenance.

According to an embodiment of the first aspect, the control cam has a first cam profile and a second cam profile arranged on two opposite sides of the control cam, wherein the first cam profile is used for control of the vacuum interrupter assembly via the driving mechanism, and the second cam profile is used for control of the two bypass contacts via the corresponding bypass levers. Thus, the two different motions can be designed and controlled individually, but operated synchronized in phase.

According to a second aspect, a power diverter switch comprises a vacuum interrupter module according to the first aspect and a selector switch assembly electrically coupled with electrical contacts of the vacuum interrupter module.

According to a third aspect, a tap changer, in particular a transformer load tap changer, comprises a plurality of power diverter switches and at least one insulation shaft, mechanically connecting the control cam of each one of the plurality of power diverter switches and configured to transmit an incoming motion.

Such a configuration of a power diverter switch and a tap changer comprising an improved vacuum interrupter module enables secure and reliable switching or separation of electrical contacts of the vacuum interrupter and the bypass contacts. As a result, the power diverter switch and tap changer according to the second and third aspect, respectively, also exhibit the improved characteristics of the vacuum interrupter module according to the first aspect 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.

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 <NUM> of the insulation plate <NUM>, a bypass switch assembly <NUM> and a vacuum interrupter assembly <NUM> is mounted. A back-side <NUM> 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> as detailed later with respect to <FIG>.

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 interrupter modules <NUM> further includes, for each phase winding, the bypass switch module <NUM>, and may further include, for each phase winding, a selector switch assembly (not visible in <FIG>). The selector switch assembly can be configured to make connections between taps, while the bypass switch assembly <NUM> 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 assembly <NUM> 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 driving mechanism <NUM> further includes a damping unit <NUM>, configured to hydraulically dampen the movement of the driving rod by means of the fluid, in which the entire assembly is immersed.

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>, respectively.

As shown in <FIG>, a first cam profile <NUM> is formed at a first main side of the essentially circular control cam <NUM>. In the described embodiment the first main side corresponds to the top side of the control cam <NUM> facing away from the insulation plate <NUM> and towards the driving mechanism <NUM>. The first cam profile <NUM> establishes an almost rectangular guiding pathway, surrounding a central hole <NUM> for connecting the control cam <NUM> to a drive shaft. The pathway can also be described as four quarter circles <NUM> with alternating smaller and larger radii, and four connecting C-shaped portions <NUM>. As shown in <FIG>, a first cam follower <NUM> engages with the first cam profile <NUM> to control the vacuum interrupter assembly <NUM>. In particular, the first cam follower <NUM> is attached to the driving rod <NUM> and moves the driving rod <NUM> inside the guiding tube <NUM> along the longitudinal axis L, thereby charging the spring accumulator of the driving mechanism <NUM> formed by two springs <NUM> arranged between the driving rod <NUM> and the guiding tube <NUM>.

The vacuum interrupter assembly <NUM> is configured such that, when the driving rod <NUM> is driven towards the vacuum interrupter <NUM>, the electrical contacts of the vacuum interrupter <NUM> are closed. Inversely, the vacuum interrupter assembly <NUM> is configured such that, when the piston <NUM> is driven away from the vacuum interrupter <NUM>, the electrical contacts of the vacuum interrupter <NUM> are opened.

As shown in <FIG>, a second cam profile <NUM> is formed at an opposite second main side of the circular control cam <NUM>, in the described embodiment the bottom side facing towards the insulation plate <NUM>. The second cam profile <NUM> establishes an almost D-shaped guiding pathway, also surrounding the central hole <NUM>. The pathway can also be described as two semicircles <NUM> with different radii, and two connecting S-shaped portions <NUM>. As shown in <FIG>, two second cam followers <NUM> engage, on opposite sides of the central hole <NUM>, with the second cam profile <NUM> to control the bypass switch assembly <NUM>. To this end, the second cam followers <NUM> are attached to the bypass levers <NUM>, which in turn open or close the bypass contacts <NUM> depending on whether the respective second cam follower <NUM> is in a part of the guiding pathway with a smaller or larger distance from the central hole <NUM>.

As still shown in <FIG>, each bypass lever <NUM> comprises a first part <NUM> and a second part <NUM>. The first part <NUM> in turn comprises a first arm <NUM> and a second arm <NUM>, arranged at around <NUM> degrees with respect to a connecting axis of rotation <NUM>. The second cam follower <NUM> is attached to an end of the first arm <NUM>. One end of the second part <NUM> is movable attached by means of bearings to an end of the second arm <NUM>. The other end of the second part is attached to a movable part of the bypass contact <NUM> with a bronze sleeve. At least one of the first part <NUM> or second part <NUM> is made from an insulating material, such as a polymer material, and is used to interrupt an electrical connection between the bypass contacts <NUM> and the other sub modules in the vacuum interrupter module, in particular the control cam <NUM> and the drive mechanism <NUM> attached thereto.

<FIG> further shows that the inner electrical contacts of the two bypass contacts <NUM> are electrically connected by means of a conductive copper bar <NUM>, arranged below the insulation plate <NUM> (not shown in <FIG>). As shown in <FIG>, this the conductive bar <NUM> is connected to a common electrical connector of a power diverter switch. Further conductive bars <NUM> and <NUM> connect the respective outer electrical contacts of the two bypass contacts <NUM> with corresponding connections of the vacuum interrupter <NUM> and two electrical connections of the actual tap changer.

Referring now to <FIG>, there is shown a schematic drawing of one of the electrical circuits <NUM> of the tap changing assembly connected to a regulating winding <NUM> in a plus-minus configuration. The electrical circuit <NUM> is arranged into first and second branch circuits <NUM>, <NUM> and generally includes a selector switch assembly <NUM>, the bypass switch assembly <NUM> and the vacuum interrupter assembly <NUM> comprising a vacuum interrupter <NUM>.

The selector switch assembly <NUM> comprises movable first and second contact arms <NUM>, <NUM> and a plurality of stationary contacts <NUM> which are connected to the taps of the winding <NUM>, respectively. The first and second contact arms <NUM>, <NUM> are connected to reactors <NUM>, <NUM>, respectively, which reduce the amplitude of the circulating current when the selector switch assembly <NUM> is bridging two taps. The first contact arm <NUM> is located in the first branch circuit <NUM> and the second contact arm <NUM> is located in the second branch circuit <NUM>. The bypass switch assembly <NUM> comprises first and second bypass switches <NUM>, <NUM>, with the first bypass switch <NUM> being located in the first branch circuit <NUM> and the second bypass switch <NUM> being located in the second branch circuit <NUM>. Each of the first and second bypass switches <NUM>, <NUM> is connected between its associated reactor <NUM>, <NUM> and the main power circuit. The vacuum interrupter <NUM> is connected between the first and second branch circuits <NUM>, <NUM> and comprises a fixed contact and a movable contact enclosed in a bottle or housing having a vacuum therein.

The first and second contact arms <NUM>, <NUM> of the selector switch assembly <NUM> can be positioned in a non-bridging position or a bridging position. In a non-bridging position, the first and second contact arms <NUM>, <NUM> are connected to a single one of a plurality of taps on the winding <NUM> of the transformer. In a bridging position, the first contact arm <NUM> is connected to one of the taps and the second contact <NUM> is connected to another, adjacent one of the taps.

In <FIG>, the first and second contact arms <NUM>, <NUM> are both connected to tap <NUM> of the winding <NUM>, i.e., the first and second contact arms <NUM>, <NUM> are in a non-bridging position. In a steady state condition, the contacts of the vacuum interrupter <NUM> are closed and the contacts in each of the first and second bypass switches <NUM>, <NUM> are closed. The load current flows through the first and second contact arms <NUM>, <NUM> and the first and second bypass switches <NUM>, <NUM>. Substantially no current flows through the vacuum interrupter <NUM> and there is no circulating current in the reactor circuit.

<FIG> shown <NUM> further switching states during the switch from the initial tap, i.e. tap <NUM>, to a neighboring tap, i.e. tap <NUM>. All states shown in <FIG> are controlled by a single drive mechanism, and in particular by the control cam <NUM> as described above.

In a first stage shown in <FIG>, an upper or first bypass switch <NUM> opens, i.e. by opening one of the two bypass contacts <NUM>. Then, in a second stage shown in <FIG>, the vacuum interrupter <NUM> is opened. In a third stage shown in <FIG>, the upper or first contact arm <NUM> moves to tap <NUM>. In a fourth stage shown in <FIG>, the vacuum interrupter <NUM> is closed. In a fifth stage shown in <FIG>, the upper or first bypass switch <NUM> closes. In a sixth stage shown in <FIG>, a lower or second bypass switch <NUM> opens. In a seventh stage shown in <FIG>, the vacuum interrupter <NUM> is opened again. In an eighth stage shown in <FIG>, the lower or second contact arm <NUM> moves to tap <NUM>. In a ninth stage shown in <FIG>, the vacuum interrupter <NUM> is closed again. In a tenth stage shown in <FIG>, the lower or second bypass switch <NUM> closes. At this stage, the tap changer <NUM> has successfully changed from tap <NUM> to tap <NUM>, with both contact arms <NUM>, <NUM> connected to the same electrical potential, similar to the initial stage shown in <FIG>. Further details of the electrical connections and potential states of a tap changer are described in <CIT>, whose content is included by reference herein.

<FIG> show the opening of the disclosed vacuum interrupter module <NUM> for the upper or first bypass switch <NUM> from different perspectives. <FIG> show the opening of the disclosed vacuum interrupter module <NUM> for the lower or second bypass switch <NUM> from different perspectives. In particular, <FIG> and <FIG> show perspective view onto the vacuum interrupter module <NUM>, and <FIG> and <FIG> show a top view onto the front side <NUM> of the insulation plate <NUM>.

<FIG> shows a perspective view of a power diverter switch <NUM>, comprising the vacuum interrupter module <NUM> mounted on top of a selector switch assembly <NUM>. As can be seen therein, the movable parts of the two assemblies are connected to be driven by a common drive. In the disclosed embodiment, the driving connection is formed by a second insulation shaft <NUM>, which in addition to the mechanical connection fulfills the functions of a cardan mechanism to compensate minimal positional displacements between the two assemblies <NUM> and <NUM>. Still referring to <FIG>, three electrical connections <NUM>, <NUM>, and <NUM> connect the conductive bars <NUM> to <NUM> with the respective electrical contacts of the selector switch assembly <NUM> as shown in and explained with reference to <FIG>.

The described vacuum interrupter module <NUM> provides a beneficial robustness and contributes to reduced manufacturability and maintenance criteria. Inter alia, this is achieved by the single, common control cam <NUM> as well as the arrangement of essentially all moveable components of the vacuum interrupter module <NUM> on the upper front side <NUM> of the insulation plate <NUM>. The use of a common control cam <NUM> simplifies to synchronize the various mechanical movements required and at the same time helps to reduce the part count. The arrangement of essentially all moveable parts on a more accessible front side <NUM> facilitates their maintenance and, if necessary, replacement due to wear.

Claim 1:
A vacuum interrupter module (<NUM>) for a tap changer, comprising:
- an insulation plate (<NUM>) having a first main side and a second main side opposite of the first main side, the second main side carrying copper bars used for a schematic connection of the vacuum interrupter module (<NUM>);
- a vacuum interrupter assembly (<NUM>) comprising a vacuum interrupter (<NUM>) and a driving mechanism (<NUM>) coupled with the vacuum interrupter (<NUM>);
- a bypass switch assembly (<NUM>), comprising two bypass contacts (<NUM>), each one mechanically connected to a corresponding bypass lever (<NUM>); and
- a control cam (<NUM>),
characterized in that
- the control cam (<NUM>) is configured to actuate both the driving mechanism (<NUM>) and, through the corresponding bypass levers (<NUM>), the two bypass contacts (<NUM>); and
- the vacuum interrupter assembly (<NUM>) comprising the vacuum interrupter (<NUM>) and the driving mechanism (<NUM>), the bypass switch assembly (<NUM>) comprising the two bypass contacts (<NUM>) and the two corresponding bypass levers (<NUM>), and the control cam (<NUM>) are arranged on the first main side of the insulation plate (<NUM>), such that essentially all mechanical components subject to wear are easily accessible in a mounted position of the vacuum interrupter module (<NUM>).