Patent Description:
A vacuum circuit breaker (VCB) normally comprises a vacuum circuit interrupter and an actuator for operating the interrupter between open and closed states. Typically, the actuator comprises an electromagnetic device coupled to the contacts of the interrupter.

Conventional VCBs are considered to be relatively large and relatively expensive to manufacture. It would be desirable to provide an improved vacuum circuit breaker.

Japanese patent application <CIT> discloses a miniaturized vacuum switch having an elastic conductor for electrically connecting a movable electrode to a movable electrode side external circuit terminal and pressing the movable electrode to a fixed electrode side.

US patent application <CIT> discloses a pole part of a switchgear assembly in which the electrical terminals are provided in an insulating body.

A first aspect of the invention provides a vacuum circuit breaker as claimed in claim <NUM>.

Also disclosed is a vacuum circuit breaker comprising:.

In preferred embodiments said circuit breaker body is formed from a moldable material and wherein at least one of, and preferably each of, said first terminal and said second terminal are molded into said circuit breaker body. Preferably, the circuit breaker body is formed from plastic, preferably thermoplastic.

Advantageously, said hollow body has an annular internal surface that forms part of the internal surface of said internal chamber. Said annular internal surface of said hollow body may be flush or substantially flush with the internal surface of said circuit breaker body.

Typically, said first and second terminals are spaced apart along a pole axis of said circuit breaker body, said vacuum interrupter being at least partly located in a region of said internal chamber between said first and second terminals. the transverse cross-section of a region of said internal chamber defined by said second terminal is shaped and dimensioned to match the transverse cross-sectional shape and dimensions of transverse cross-section of said region in which the vacuum interrupter is at least partly located, or to define a space that is larger than the transverse cross-sectional shape and dimensions of region in which the vacuum interrupter is at least partly located.

Preferably a region of said internal chamber defined by said second terminal is shaped and dimensioned to match the transverse cross-sectional shape and dimensions of the vacuum interrupter, or to define a space that is larger than the transverse cross-sectional shape and dimensions of the vacuum interrupter.

Advantageously said circuit breaker body has an open end, said second terminal being located between said open end and said region in which said vacuum interrupter is at least partly located, said open end being shaped and dimensioned to allow said vacuum interrupter to pass through said open end.

Advantageously the internal chamber is shaped and dimensioned to allow passage of the vacuum interrupter along the internal chamber from an open end of the internal chamber to a desired location within the internal chamber.

Optionally an end of said vacuum interrupter is located within said hollow body.

Typical embodiments include an electrical connector device electrically connecting a movable contact of the vacuum interrupter to the second terminal, the electrical connector device being located within the internal chamber of the circuit breaker body, preferably within the hollow body of the second terminal. The internal chamber may be shaped and dimensioned to allow passage of the connector device along the internal chamber from an open end of the internal chamber to a desired location within the internal chamber.

Preferably a region of the internal chamber between the open end and a region defined by the second terminal is shaped and dimensioned to match the transverse cross-sectional shape and dimensions of the electrical connector device, and preferably also the vacuum interrupter, or to define a space that is larger than the transverse cross-sectional shape and dimensions of the electrical connector device, and preferably also of the vacuum interrupter.

Optionally said hollow body is cylindrical.

The internal chamber may be of substantially uniform transverse cross-section, at least in a region defined by said second terminal and region in which said vacuum interrupter is located.

The internal chamber may be of substantially cylindrical transverse cross-section.

In preferred embodiments the circuit breaker includes a pulling rod coupled to said vacuum interrupter for operation thereof, said pulling rod comprising a core located within a shell, the core being formed from heat-resistant material, preferably heat-resistant plastics, the shell being formed from impact resistant material, preferably impact-resistant plastics. Advantageously the core and the shell are formed from thermoplastics or thermosetting polymeric material.

Advantageously the core is formed from material, preferably moldable electrically insulating material, and most preferably plastics, having relatively high heat-resistance compared to the material from which the shell is formed, the shell being formed from material, preferably moldable electrically insulating material, and most preferably plastics, having relatively high impact-resistance compared to the material from which the core is formed.

Preferably the core and the shell are co-molded with one another.

Typically an end of said pulling rod is located within said hollow body.

In some embodiments the first terminal is located at the top of the body and provides a first electrical connection interface at the top of the body, preferably on the pole axis of the body, the second terminal including a stem projecting from said hollow body and projecting obliquely, preferably perpendicularly, from the pole axis to provide a second electrical connection interface that is laterally displaced from the pole axis, and wherein a notional perpendicular axis from the second electrical connection interface to the pole axis intersects the pole axis at a notional intersection point, the configuration of the circuit breaker being such that a notional triangle created by said first and second electrical connection interfaces and said notional intersection point is an isosceles right triangle, where a notional line between said first and second electrical connection interfaces forms the hypotenuse of the triangle.

Optionally the first terminal is located at the top of the body and provides a first electrical connection interface at the top of the body, preferably on the pole axis of the body, the second terminal including a stem projecting from said hollow body and projecting obliquely, preferably perpendicularly, from the pole axis to provide a second electrical connection interface that is laterally displaced from the pole axis, and wherein a first elongate external connector is connected to the first terminal at its connection interface, and a second elongate external connector is connected to the second terminal at its connection interface, wherein the external connectors extend parallel to each other but obliquely to the pole axis.

Advantageously the external connectors are of the same length.

Also disclosed is a pulling rod for a vacuum interrupter, said pulling rod comprising a core located within a shell, the core being formed from heat-resistant material, preferably heat-resistant plastics, the shell being formed from impact resistant material, preferably impact-resistant plastics. Preferably the core and the shell are formed from thermoplastics or thermosetting polymeric material.

In some embodiments, reduced weight and size characteristics of an indoor switching module can be achieved due to the design of the circuit breaker support insulation and its method of manufacture.

Preferred embodiments of the invention include support insulation made from electrically insulating material, for example thermoplastic material, into which the lower and upper terminals of the circuit breaker are incorporated, preferably by molding.

Advantageously, the lower terminal is annular in design.

Advantageously, the pole axis is inclined with respect to a notional inter-terminal axis extending between a respective reference point on each of the upper lower terminals, preferably such that the pole axis, said notional inter-terminal axis, and a lower terminal axis intersect to form a right isosceles triangle.

Preferred embodiments of the invention are able to provide a circuit breaker with relatively small dimensions for given current and insulation ratings, or a circuit breaker with relatively high current and insulation ratings for given dimensions.

Preferred embodiments facilitate a relatively low manufacturing cost for the circuit breaker.

Advantageously, the dimensions of a draw-out unit based on preferred circuit breakers embodying the invention are relatively small in comparison with conventional circuit breakers.

Advantageously, the cost of a draw-out unit based on preferred circuit breakers embodying the invention are relatively low in comparison with conventional circuit breakers.

Preferred embodiments exhibit an increased thermal stability and durability of the pulling rod insulator in comparison with conventional circuit breakers.

Further advantageous aspects of the invention will be apparent to those ordinarily skilled in the art upon review of the following description of a specific embodiment and with reference to the accompanying drawings.

An embodiment of the invention is now described by way of example and with reference to the accompanying drawings in which:.

Referring now to the drawings there is shown, generally indicated as <NUM> an electrical circuit breaker. The circuit breaker <NUM> is particularly intended for use in breaking an AC electrical power supply and so may be referred to as an AC circuit breaker. The circuit breaker <NUM> comprises a vacuum interrupter <NUM> and as such may be referred to as a vacuum circuit breaker (VCB). The vacuum interrupter <NUM>, which may also be referred to as a vacuum switching device, comprises a movable electrical contact (not visible) and a fixed (stationary) electrical contact (not visible) located in a vacuum chamber <NUM>, i.e. a chamber that is hermetically sealed and in vacuum, at least during use. The movable contact is movable between an open state, in which it is electrically and physically separate from the fixed contact and a closed state in which it makes electrical (and typically physical) contact with the second contact. The open state of the movable contact corresponds to the open, or breaking, state of the vacuum interrupter <NUM> and correspondingly of the circuit breaker <NUM> in which it interrupts current flow in whatever circuit (not shown) it is part of. The closed state of the contact corresponds to the closed, or making, state of the vacuum interrupter <NUM> and correspondingly of the circuit breaker <NUM>, in which current is able to flow between the fixed and movable contacts.

Movement of the contact between its open and closed states is effected by an actuator (not shown). The actuator may be of any suitable type, for example an electromagnetic actuator or any other mechanical, electrical or electro-mechanical actuator. The actuator is coupled to the movable contact of the vacuum interrupter <NUM> by a mechanical coupling mechanism, which in preferred embodiments comprises a pulling rod <NUM>, in particular an electrically insulating pulling rod, although in alternative embodiments it may take any other suitable form, e.g. a bellows coupling. The coupling mechanism couples the actuator to the movable contact to allow the actuator to move the contact between its open and closed states.

The vacuum interrupter <NUM>, and therefore the VCB <NUM>, typically operates in a normally closed state, i.e. with the movable contact in its closed state to allow current to flow between the contacts and so to flow in any given circuit (not shown) in which the circuit breaker <NUM> is installed during use. In such cases the VCB <NUM> may be configured to open automatically in response to detection of a fault condition, e.g. in response to detection of a current overload or short circuit, to protect the circuit into which it is incorporated during use. It achieves this by causing the actuator to move the movable contact to its open state in response to detection of the fault. To this end the VCB <NUM> typically includes, or is co-operable with, a controller (not shown) for effecting the open state upon detection of a fault. The controller typically comprises electrical and/or electronic circuitry that includes, or is connected to, one or more current sensors (not shown). The current sensor(s) are coupled in use to any convenient current conductor of the VCB <NUM> or circuit to which the VCB is connected. Upon detection of current, more particularly prospective current, above a threshold level by the sensor(s), the controller causes the VCB to open. In some embodiments, the VCB <NUM> can be reset, i.e. closed, manually or semi-manually (e.g. by manual activation of a user control (not shown)) and/or automatically in response to the VCB <NUM> detecting that the fault has gone, and/or after a threshold period of time has expired since activation. Circuit breakers that reset automatically are commonly known as reclosers.

Referring in particular to <FIG>, the circuit breaker <NUM> includes a first, or upper, electrical terminal <NUM> and a second, or lower, electrical terminal <NUM> by which the circuit breaker <NUM> can be electrically connected, in use, to an external electrical circuit or device (not shown). The first terminal <NUM> is electrically connected to the fixed contact of the vacuum interrupter <NUM>. The second terminal <NUM> is electrically connected to the movable contact of the vacuum interrupter <NUM>. The terminals <NUM>, <NUM> are formed from electrically conductive material, e.g. copper or other suitable metal or metal alloy.

The terminals <NUM>, <NUM> are supported by and typically incorporated into a body <NUM> of the circuit breaker <NUM>. The terminals <NUM>, <NUM> are mutually spaced apart along the pole axis P of the circuit breaker <NUM> (which in typical embodiments corresponds to the direction along which the movable contact of the interrupter <NUM> moves, and the direction of movement of the pulling rod). The body <NUM> defines an internal chamber <NUM> for housing and supporting the vacuum interrupter <NUM> and other components of the circuit breaker <NUM> as is described in further detail hereinafter. Conveniently, the chamber <NUM> is substantially circular in transverse cross section (i.e. the cross section that is perpendicular with the pole axis), although it may alternatively take other cross-sectional shapes. Typically, the upper terminal <NUM> is located at a first end <NUM> (or top) of the body <NUM>, and the lower terminal <NUM> is located between the first end <NUM> and a second end <NUM> (or bottom) of the body <NUM>. Advantageously, the second end <NUM> is open to allow insertion of circuit breaker components into the chamber <NUM> as is described in more detail hereinafter.

The body <NUM> is formed from an electrically insulating material, typically a dielectric material. In preferred embodiments the body is formed from a moldable material. For example the body <NUM> may be formed from plastic, preferably from thermoplastic material (e.g. comprised of one or more thermoplastics). Alternatively the body <NUM> may be formed from one or more thermosetting polymer or any convenient electrically insulating material.

Advantageously, at least one, but preferably both, of the terminals <NUM>, <NUM> is molded into the body <NUM>, i.e. incorporated into the body <NUM> during formation of the body by molding. Any suitable conventional molding process can be used, for example injection molding. Advantageously, the terminals <NUM>, <NUM> are incorporated into the body <NUM> such that at least some of, and preferably substantially all of, the external surfaces of the respective terminal <NUM>, <NUM> are in contact with a respective internal surface of the body <NUM>.

In preferred embodiments, the lower terminal <NUM> comprises a hollow annular body <NUM> that is preferably tubular in form, i.e. an open-ended sleeve-like structure. Typically, but not necessarily, the annular body <NUM> is substantially circular in transverse cross-section, i.e. the annular body <NUM> may be a hollow cylindrical structure. However, in alternative embodiments the annular body may have other (non-circular) cross-sectional shapes, preferably to match the shape of the chamber <NUM>. The annular body <NUM> is typically rigid, being formed from metallic or other conductive material. The annular body <NUM> is incorporated into the circuit breaker body <NUM> such that the internal surface <NUM> of the annular body <NUM> provides part of the internal surface of the chamber <NUM>. As such, the annular body <NUM> extends around the pole axis P. Preferably, the internal surface <NUM> of the annular body <NUM> is flush, or substantially flush, with the internal surface <NUM> of the chamber <NUM> that is provided by the body <NUM> itself. To this end, the annular body <NUM> may be provided in a recess formed in the body <NUM>. The external surface of the annular body <NUM> is covered by the body <NUM>. Advantageously, the annular body <NUM> is shaped and dimensioned to allow the vacuum interrupter to pass through it (i.e. the respective shapes and dimensions of the annular body <NUM> and the vacuum interrupter <NUM> are such that the vacuum interrupter is able to pass through the annular body <NUM>, and therefore to pass through the lower terminal <NUM>).

The lower terminal <NUM> typically also includes a connection stem <NUM>. The connection stem <NUM> is conveniently integrally formed with the annular body <NUM> but may otherwise be connected (at least electrically) to it. The connection stem <NUM> is typically rigid, being formed from metallic or other conductive material. The connection stem <NUM> extends from the annular body <NUM> in a direction that is non-parallel with, and preferably substantially perpendicular to, the pole axis P. The circuit breaker body <NUM> is shaped to cover the outer surface of the stem <NUM> except for at an end <NUM>, which is exposed to allow the stem <NUM>, and therefore the terminal <NUM>, to be connected to an external circuit or device. The end <NUM> of the stem <NUM> may be provided with a socket <NUM> or other suitable formation for this purpose.

The upper terminal <NUM> is typically located at the top end of the chamber <NUM> which conveniently corresponds to the top <NUM> of the circuit breaker body <NUM>. The terminal <NUM> may comprise a body <NUM> and a connection stem <NUM>. The body <NUM> may be annular, defining a socket <NUM> for receiving an electrical connector <NUM> to electrically connect the terminal <NUM> with the fixed contact of the vacuum interrupter <NUM>. The connection stem <NUM> conveniently extends from the body <NUM> in a direction substantially parallel with the pole axis P. The body <NUM> and stem <NUM> are typically rigid, being formed from metallic or other conductive material. The circuit breaker body <NUM> is shaped to cover the outer surface of the stem <NUM> except for at an end <NUM>, which is exposed to allow the stem <NUM>, and therefore the terminal <NUM>, to be connected to an external circuit or device. The end <NUM> of the stem <NUM> may be provided with a socket <NUM> or other suitable formation for this purpose. Advantageously, the upper terminal <NUM> screens the elements of the vacuum interrupter <NUM> with high electric field strength (e.g. triple points). It also facilitates reduction of the dimensions of the circuit breaker <NUM>.

An electrical connector device <NUM> (sometimes referred to as a current pickup) is provided for electrically connecting the movable contact of the vacuum interrupter <NUM> to the lower terminal <NUM>. The connector device <NUM> has a movable part <NUM> that is connected to the movable contact, and a fixed (stationary) part <NUM> that is connected to the lower terminal <NUM>. The movable part <NUM> is connected to the fixed part <NUM> by at least one, but typically a plurality of, flexible connectors <NUM> that allow relative movement between the fixed and movable parts <NUM>, <NUM>. Typically, the fixed part <NUM> is annular and is located around the movable part <NUM>. The fixed and movable parts <NUM>, <NUM> and the flexible connectors <NUM> are formed form any suitable conductive material. In the illustrated embodiment, the movable part <NUM> has a socket <NUM> for engaging an electrical connector <NUM> of the vacuum interrupter <NUM>, the connector <NUM> being electrically connected to the movable contact of the interrupter <NUM>. When the connector <NUM> is engaged with the movable part <NUM>, the electrical connection device <NUM> electrically connects the movable contact of the interrupter to the lower terminal <NUM> while accommodating movement of the movable contact.

In the illustrated embodiment, the pulling rod <NUM> is mechanically coupled to the movable contact via the electrical connector <NUM>, as can best be seen from <FIG>. In use, movement of the pulling rod <NUM> in the direction of the pole axis P causes a corresponding movement of the movable part <NUM> and of the movable contact.

Referring now in particular to <FIG>, it is shown how the circuit breaker <NUM> can readily be assembled, which simplifies the manufacturing process. <FIG> shows how the vacuum interrupter <NUM> can be inserted through the open end <NUM> of the circuit breaker body <NUM>, through the annular body <NUM> of the lower terminal <NUM>, and moved into engagement with the upper terminal <NUM> as indicated by arrow A. In this position the connector <NUM> of the vacuum interrupter <NUM> engages with the socket <NUM> to electrically connect the fixed contact to the terminal <NUM>. <FIG> shows how the electrical connector device <NUM> can be inserted through the open end <NUM> of the circuit breaker body <NUM>, into the annular body <NUM> of the lower terminal <NUM>, and moved into engagement with the vacuum interrupter <NUM> as indicated by arrow B.

The chamber <NUM> is shaped and dimensioned to receive the vacuum interrupter <NUM>, preferably providing an interference fit (also known as a friction fit or press fit) between the interrupter <NUM> and the internal surface of the chamber <NUM>. In typical embodiments, the external shape of the vacuum interrupter is substantially cylindrical and so the internal surface of the chamber <NUM> may be correspondingly shaped, at least in the region where the vacuum interrupter <NUM> is located in use. The chamber <NUM> is also shaped and dimensioned to allow passage of the vacuum interrupter <NUM> (advantageously in its normal use orientation) along the chamber <NUM> from the chamber end <NUM> (which is open to allow insertion of the interrupter <NUM> and other components) to its desired location during assembly of the circuit breaker <NUM>. Preferably, the chamber <NUM> is of substantially uniform transverse cross-section between its ends <NUM>, <NUM>, or at least between the lower terminal <NUM> and the upper terminal <NUM>, typically being substantially cylindrical, although it could take other shapes in alternative embodiments. In particular it is preferred that the transverse cross-section of the chamber <NUM> is substantially uniform in the region of the lower terminal <NUM> and in the region between the lower terminal <NUM> and the upper terminal <NUM> where the vacuum interrupter <NUM> is located in use. More generally, the shape and dimensions of the transverse cross-section of the chamber <NUM> in the region defined by the lower terminal <NUM> are such that the vacuum interrupter <NUM> is able to pass through the region defined by the lower terminal <NUM> into the region between the lower terminal <NUM> and the upper terminal <NUM>. To this end the region defined by the lower terminal <NUM> may be shaped and dimensioned (e.g. in transverse cross-section) to match the transverse cross-sectional shape and dimensions of the vacuum interrupter <NUM>, or to define a space that is larger than the transverse cross-sectional shape and dimensions of the vacuum interrupter <NUM>. One way to facilitate this is to make the chamber <NUM> cylindrical in transverse cross section, the vacuum interrupter typically also being cylindrical in transverse cross section. In the illustrated embodiment, the chamber <NUM> is uniformly cylindrical at least in the region of the lower terminal <NUM> and in the region between the lower terminal <NUM> and the upper terminal <NUM> where the vacuum interrupter <NUM> is located in use. Alternatively, the chamber <NUM> may be wider in the region of the lower terminal <NUM> than in the region between the lower terminal <NUM> and the upper terminal <NUM>. Optionally, the chamber <NUM> is shaped to provide a flared region at its end <NUM> (which may extend to the region of the lower terminal <NUM>), and the chamber <NUM> may have substantially uniform transverse cross section between the flared region and the other end <NUM>.

The chamber <NUM> is shaped and dimensioned to receive the electrical connector device <NUM>, preferably providing an interference fit (also known as a friction fit or press fit) between the fixed part <NUM> and the internal surface of the chamber <NUM>. Advantageously, the electrical connector device <NUM> is located (when the circuit breaker <NUM> is assembled) within the annular body <NUM> of the lower terminal <NUM>, and so the fixed part engages with the inside of the annular body <NUM> (which forms part of the chamber's internal surface). In typical embodiments, the external shape of the connector device <NUM> is substantially cylindrical and so the internal surface of the chamber <NUM> may be correspondingly shaped in the region of the annular body <NUM>. The chamber <NUM> is also shaped and dimensioned to facilitate passage of the connector device <NUM> (advantageously in its normal use orientation) along the chamber <NUM> from the open chamber end <NUM> to its desired location during assembly of the circuit breaker <NUM>. The shape and dimensions of the transverse cross-section of the chamber <NUM> from the open end <NUM> to the region defined by the lower terminal <NUM> are such that the electrical connector device <NUM> (and the vacuum interrupter <NUM>) is able to pass through open end <NUM> to the region defined by the lower terminal <NUM>. To this end the region between the open end <NUM> and the region defined by the lower terminal <NUM> may be shaped and dimensioned (e.g. in transverse cross-section) to match the transverse cross-sectional shape and dimensions of the electrical connector device <NUM> (and optionally the vacuum interrupter <NUM>), or to define a space that is larger than the transverse cross-sectional shape and dimensions of the electrical connector device <NUM> (and the vacuum interrupter <NUM>). In preferred embodiments, the shape and dimensions of the electrical connector device <NUM> and the vacuum interrupter <NUM> in transverse cross section are substantially the same.

The annular design of the body <NUM> of the lower terminal <NUM> creates a large heat-transfer surface, increasing heat dissipation from the vacuum interrupter <NUM> and other components of the circuit breaker <NUM>. Heat transfer is facilitated by low thermal resistance between the terminals <NUM>, <NUM> and the polymer material forming the body <NUM> into which the terminals are incorporated. This results in relatively high heat dissipation and increased the current rating of the circuit breaker <NUM> for given circuit breaker dimensions.

<FIG> shows the preferred pulling rod <NUM>. To reduce weight and cost, it is preferred to make the pulling rod <NUM> from plastics materials rather than, for example, metal. The pulling rod <NUM> must exhibit sufficiently high mechanical and electrical characteristics to suit the operation of the circuit breaker <NUM>. However, the maximum thickness provided by standard single-layer injection molding method is approximately <NUM>, which is not well suited to providing the required mechanical and electrical characteristics. In preferred embodiments, therefore the pulling rod <NUM> comprises an inner part <NUM>, or core, encased within an outer layer <NUM>, or shell, each being formed from a plastics material (preferably a thermoplastic or thermosetting polymer). Advantageously, the core <NUM> and shell <NUM> are formed from different plastics materials. Preferably, the core <NUM> is formed from a heat-resistant thermoplastic or thermosetting polymer and the shell <NUM> is formed from an impact-proof thermoplastic or thermosetting polymer. The materials are electrically insulating. In preferred embodiments, the core <NUM> is formed from material, preferably a moldable electrically insulating material, and most preferably plastics, having relatively high heat-resistance compared to the material from which the shell <NUM> is formed, whereas the shell <NUM> is formed from material, preferably a moldable electrically insulating material, and most preferably plastics, having relatively high impact-resistance compared to the material from which the core <NUM> is formed.

Advantageously, the pulling rod <NUM> may be formed by a multilayer injection molding process. The heat-resistant core <NUM> provides size stability at high temperatures, while the impact-proof shell <NUM> provides a relatively high resistance to the cyclic mechanical loads experienced during use. As a result, the pulling rod <NUM> exhibits sufficient mechanical and electrical characteristics while reducing the manufacturing cost of the pulling rod <NUM>.

One end of the pulling rod <NUM> may be provided with a mechanical connector <NUM>, preferably formed from a thermoplastic or thermosetting polymer or other electrically insulating material, for coupling the pulling rod <NUM> to the movable contact of the vacuum interrupter <NUM> to allow the actuator to move the movable contact. In the illustrated embodiment, part of the connector <NUM> is embedded in the pulling rod <NUM>, and part projects from the pulling rod <NUM> for coupling with the movable contact via the connector <NUM> of the vacuum interrupter <NUM>, which may include a socket for receiving the projecting part. The embedded part may be inserted into a socket in the pulling rod or co-molded with the pulling rod as is convenient. The opposite end of the pulling rod <NUM> may be provided with a mechanical connector <NUM>, a socket in the illustrated example, for coupling the pulling rod <NUM> to the actuator.

Referring in particular to <FIG>, in preferred embodiments the electrical connection device <NUM> is located within the hollow annular body <NUM> of the lower terminal <NUM>. Advantageously, all or part of one or more other components of the circuit breaker <NUM> may be located within the hollow annular body <NUM> of the lower terminal <NUM>. For example, in the illustrated embodiment, the lower end of the vacuum interrupter <NUM> and the upper end of the pulling rod <NUM> are located within the body <NUM>. This overlapping of circuit breaker components along the pole axis P serves to reduce the length of the circuit breaker <NUM> along the pole axis P and therefore to reduce the overall size of the circuit breaker. The annular body <NUM> also serves as an electrical shield to any component(s) located within it.

The resulting compact dimensions between the upper and lower terminals <NUM>, <NUM> can be too small to fit existing draw-out types of switchgear (not shown). However, the preferred configuration of the upper and lower terminals facilitates connection of the circuit breaker <NUM> to an external device (e.g. draw-out switchgear) having a spacing between its terminals that is greater than the distance between the exposed ends <NUM>, <NUM> of the upper and lower terminals <NUM>, <NUM> measured along the pole axis. The upper terminal <NUM> is located at the top of the body <NUM> such that the connection interface (or connection point) provided by its exposed end <NUM> is also at the top of the body, preferably located on the pole axis P. The exposed end <NUM> typically has a connection face that is perpendicular to the pole axis P. The upper terminal connection interface is indicated by the letter C in <FIG>. The stem <NUM> of the lower terminal <NUM> projects non-parallely, preferably perpendicularly, from the pole axis P such that the connection interface (or connection point) provided by its exposed end <NUM> is laterally displaced from the pole axis P. The exposed end <NUM> typically has a connection face that is perpendicular to the stem's longitudinal axis. The lower terminal connection interface is indicated by the letter A in <FIG>. A notional perpendicular axis (or straight line) from A to the pole axis P (which corresponds to the longitudinal axis of the stem <NUM> in preferred embodiments) intersects the pole axis P at point B (which may be described as notional). The shortest linear distance between A and C is greater than the shortest linear distance between C and B (along the pole axis P). The preferred configuration is that a notional triangle created by points A, B and C (i.e. where A, Band C are the apexes of the triangle, and where points A and C may be taken as a point, e.g. a central point, at the respective lower and upper connection interface) is an isosceles right triangle, where a notional (straight) line between points A and C forms the hypotenuse of the triangle. In alternative embodiments, the triangle may be an isosceles triangle but not necessarily an isosceles right triangle. By disposing the circuit breaker <NUM> with respect to the external device such that the pole axis P is obliquely disposed with respect to a relevant axis of the external device (e.g. the draw-out axis of a draw-out switchgear apparatus) the relevant spacing between the connection interfaces A, C is increased (in comparison to the distance from C to B).

A respective elongate external connector <NUM>, <NUM>, typically comprising an electrically conductive bar, bus, or other electrical conductor may be connected in use to each terminal <NUM>, <NUM> at the respective connection interface C, A. Preferably, the connectors <NUM>, <NUM> (more particularly their respective longitudinal axis) extend parallel to each other but obliquely to the pole axis P. The connectors <NUM>, <NUM> may have a connection (or end) face (for connection with the exposed ends <NUM>, <NUM>) that is obliquely disposed with respect to the longitudinal axis of the connector <NUM>, <NUM>. Points A and C may be centrally located on the respective connection face. The preferred configuration described above, in particular the creation of the notional isosceles triangle, allows the connectors <NUM>, <NUM> to be identical, or substantially identical, which reduces the overall cost of the system of which the circuit breaker is part.

For example in an electrical switchgear installation (not illustrated), provided that the circuit breaker <NUM> is inclined to the draw-in and out axis, the terminal distance (C to A) for a particular application can be increased up to the length of the hypotenuse of the right isosceles triangle created by three points: the upper terminal connection interface C; the lower terminal connection interface A; and the point of pole axis P and lower terminal axis intersection B.

The preferred circuit breaker body <NUM> can be arranged to provide the isosceles triangle between the upper and lower terminal connection interfaces/points. In some applications, including draw-out applications, this allows the same design of both upper and lower current-carrying bars <NUM>, <NUM> that are connected to the circuit breaker in use. This provides a manufacturing cost reduction due to less nomenclature and fewer different components.

It will be understood that circuit breakers embodying the invention need not necessarily be used with the isosceles triangle installation arrangement described above and illustrated in <FIG>. For example they may be used in installations where the current-carrying bars, or equivalent connectors, extend perpendicularly to the pole axis P. Similarly, the isosceles triangle installation arrangement described above and illustrated in <FIG> may be used with conventional circuit breakers (not illustrated) and is not restricted to use with the circuit breaker <NUM> described herein.

Advantages provided by preferred embodiments of the invention over conventional circuit breakers include: relatively low weight and small size of the circuit breaker and draw-out installations for given current and insulation ratings; or relatively high values of current and insulation ratings of the circuit breaker and draw-out installations for given circuit breaker dimensions. These lead to decreased costs and suitability for use in dimensionally constrained applications.

Further, any one or more of the electrical connection device <NUM>, the vacuum interrupter <NUM> and the pulling rod <NUM> are completely or partially located within the body <NUM> of the lower terminal <NUM>. This has the effect of shielding the electric field of these components, resulting in a relatively high dielectric strength between the lower terminal <NUM> and the earthed circuit breaker base, as will as allowing a reduction in the overall dimensions of the circuit breaker <NUM>.

It is also advantageous that the circuit breaker <NUM> can be assembled after formation of the body <NUM>.

The vacuum interrupter <NUM> is first inserted into the chamber <NUM> through the lower terminal <NUM>, then the current pickup <NUM> is inserted into the chamber <NUM> and is coupled to the moving part <NUM> of the vacuum interrupter <NUM>, and pressed into the inner face of the lower terminal. This simplifies the production of the circuit breaker, reducing manufacturing cost.

The combination of the design of the pulling rod <NUM> and the insulating body <NUM> increases the dielectric strength of the circuit breaker <NUM>. It also improves reliability and structural strength of the construction. Moreover, the terminals <NUM>, <NUM> embedded in the polymer body <NUM> act as efficient heat sinks, which makes it possible to increase rated currents, for given dimensions.

Claim 1:
A vacuum circuit breaker (<NUM>) comprising:
a first terminal (<NUM>);
a second terminal (<NUM>);
a vacuum interrupter (<NUM>) coupled between said first and second terminals and being operable to make or break an electrical connection between said first and second terminals; and
a body (<NUM>) formed from electrically insulating material and being shaped to define an internal chamber (<NUM>),
wherein said first and second terminals are supported by said body, and said vacuum interrupter is located in said internal chamber,
and wherein said first and second terminals (<NUM>, <NUM>) are spaced apart along a pole axis (P) of said circuit breaker body (<NUM>), said vacuum interrupter (<NUM>) being at least partly located in a region of said internal chamber (<NUM>) between said first and second terminals,
wherein the second terminal comprises a hollow body (<NUM>) that forms part of said internal chamber (<NUM>), characterized in that said part of said internal chamber (<NUM>) defined by said hollow body (<NUM>) of said second terminal (<NUM>) is shaped and dimensioned to match the transverse cross-sectional shape and dimensions of the vacuum interrupter (<NUM>), or to define a space that is larger than the transverse cross-sectional shape and dimensions of the vacuum interrupter, to allow passage of the vacuum interrupter (<NUM>) along the internal chamber (<NUM>) from an open end (<NUM>) of the internal chamber through said hollow body (<NUM>) to said region of the internal chamber (<NUM>).