EP0008513A1

EP0008513A1 - Switch arrangement for three-phase electrical supply

Info

Publication number: EP0008513A1
Application number: EP79301601A
Authority: EP
Inventors: George Caton
Original assignee: Individual
Current assignee: Individual
Priority date: 1978-08-18
Filing date: 1979-08-07
Publication date: 1980-03-05
Also published as: AU4986479A

Abstract

A switch arrangement for making and breaking a three-phase electrical supply comprises an enclosure (1a, 2) wherein are situated three spaced fixed input terminals (11, 12,13) and output terminals (23, 24, 25) one for each phase. An elongated switch device (28) extends through the enclosure (1 a, 2) and is mounted for rotation therein. The device (28) has a housing (31) with three spaced switching input (36, 37, 38) and output terminals (40,41,42) switching means (55, 56, 57) are axially movable within the housing (31) to make or to break simultaneously electrical connections between the input and output contacts of each phase. The switch device (28) is rotatable between a first angular position wherein the fixed (11.12,13) and switching input terminals (36, 37, 38) and also the fixed (23, 24, 25) and switching output terminals (40, 41,42) are in electrical contact and a second angular position, wherein the fixed (11, 12, 13) and switching input terminals (36, 37, 38) or the fixed (23, 24, 25) and switching output terminals (40, 41,42) or both are out of electrical contact. The second position may be an isolated or earth position. An interlocking device (81, 86) prevents rotation of the switch device (28) unless the switching means (55, 56, 57) are in a position where the connections between the input and output are broken.

Description

This invention relates to a switch arrangement for use with a three-phase electrical supply. The arrangement finds utility in this field generally, but is particularly suitable for high power applications, that is for industrial or electrical supply distribution. The arrangement can incorporate either a conventional switch device or a circuit breaker device.
Conventional high power three-phase switchgear commonly comprises feeder circuits supplying current to three fixed input terminals, one.for each phase, and busbar circuits each connected to one of three fixed output terminals, one for each phase. Switching means are provided for connecting the input terminals to the output terminals, and the switching means may be a conventional switch device or, more commonly, a circuit breaker device.
It is a common requirement in such arrangements to incorporate integral means for connecting the feeder circuits to earth rather than to the busbar circuits. There is also a common requirement that both the feeder circuits and the busbar circuits may be isolated with no electrical connections made thereto. In known arrangements the switching means is contained in a movable housing which is separate from a stationary housing containing the feeder circuits and busbar circuits. When earthing of the feeder circuits or _. isolation of both circuits is required the movable housing has been withdrawn from the stationary housing, the earthing or isolation has been effected and then any required work on the earthed or isolated circuits carried out. Other arrangements employ series-connected isolating switches, usually in separate compartments, and these switches are often provided with alternative earthirgcontacts so that the feeder circuits may be isolated from the busbar circuits and subsequently connected to earth.
The objective of the present invention is to provide a simplified arrangement whereby isolation and/or earthing can be effected, and in general wherein two or more alternative switching positions are made possible i: a simple manner.
According to the present invention a switch arrangement for making and breaking a three-phase electrical supply comprises an enclosure wherein are situated three spaced fixed input terminals, one for each phase, three spaced fixed output terminals, one for each phase, and an elongated switch device extending through the enclosure and mounted for rotation therein; the switch device comprising a housing having on the outer surface thereof three spaced switching input terminals, one for each phase, and three spaced switch-, ing output terminals, one for each phase, each of the switching terminals being connected with a respective one of three input and three output contacts within the housing and switching means movable within the housing to make or break simultaneously electrical connections between the input and output contacts of each-phase; and means for rotating the switch device between a first angular position wherein the fixed input and the switching input terminals are in electrical contact and the fixed output and the switching output terminals are in electrical contact, and a second angular position wherein the fixed and switching input terminals or the fixed and switching output terminals, or both, are out of electrical contact.
With the switch device in the first angular position it will be seen that the switching means movable within the housing are operative to make or break the connection between the input terminals and the output terminals, so controlling the main supply, which will usually be from feeder circuits connected to the fixed input terminals, to busbar circuits or other means connected to the fixed output terminals, although other arrangements are, of course, possible. However, merely by rotating the switch device it can be moved to the second position, which may be one in which both the fixed input and switching terminals and the fixed output and switching terminals are out of electrical contact, so that in this position both the input and output are isolated. The switch device may further be rotated to a third position wherein the device connects the switching input terminals to the fixed input terminals and the switching output terminals to respective ones of three spaced earth terminals, one for each phase, so enabling the input to be earthed through operation _Qf the switching means. Obviously the isolating position may be omitted or the switch device may have more than two angular positions and may be designed to have an isolating position, an earthing position and one or more operating positions wherein fixed input terminals are connected to a selected one of a number of sets of fixed output terminals.
In one preferred embodiment the fixed input terminals are axially spaced apart on the enclosure, the fixed output terminals are axially spaced apart on the enclosure, the switching input terminals are axially spaced apart on the housing and the switching output terminals are axially spaced apart on the housing. The fixed input terminals are then preferably diametrically opposite to their associated fixed output terminals with respect to the axis of the arrangement, and the switching input terminals are diametrically opposite to their associated switching output terminals on the outer surface of the housing. A series of three axially spaced earth terminals are then desirably provided, angularly spaced-from the fixed output terminals and a series of three auxiliary fixed output terminals are provided diametrically opposite to the earth terminals, each auxiliary input terminal being electrically connected to an associated one of the main fixed input terminals. Thus, in a first angular position the diametrically opposite switching input and output terminals enable connections to be made between the fixed input and output terminals, and in a second angular position the diametrically opposite switching input and output terminals enable a connection to be made between the diametrically opposite auxiliary fixed input and earth terminals. In a third angular position the switching input and output terminals can lie out of alignment with any of the fixed terminals in an isolating^* position of the switch arrangement.
In a second preferred embodiment the fixed input . terminals are radially spaced apart on the enclosure, the fixed output terminals are radially spaced apart on the enclosure and are axially spaced from the fixed input terminals, the switching input terminals are radially spaced apart around the housing and the switching output terminals are radially spaced apart around the housing and are axially spaced from the switching input terminals. Desirably each fixed input terminal is axially aligned with its associated fixed output terminal, each switching input terminal is axially aligned with its associated switching output terminal, the fixed and switching input terminals lie in a first common radial plane and the fixed and switching output terminals lie in a second common radial plane.
A series of three radially spaced earth terminals are then desirably provided, in the same radial plane as the fixed output terminals and angularly spaced therefrom, and a series of three radially spaced auxiliary fixed input terminals are provided, in the same radial plane as the fixed output terminals, angularly spaced therefrom and in axial alignment with the associated earth terminals.
Thus, in a first angular position the axially aligned switching input and output terminals enable connections to be made between the axially aligned fixed input and output terminals, and in a second angular position the axially aligned switching input and output terminals enable a connection to be made between the axially aligned auxiliary fixed input and earth terminals. In a third angular position the switching input and output terminals can lie out of contact with any of the fixed terminals in an isolating position of the switch arrangement.
Preferably the switch arrangement includes a first interlock which prevents rotation of the switch device unless the switching means is in a position where the connections between the input and output contacts of each phase are broken. Preferably also the switch device is mounted so that it may be withdrawn axially from the assembly, for example for inspection, maintenance or replacement, and there is a second interlock that prevents such withdrawal unless the switch device is in an angular position such that the input and output terminals are isolated. The presence of these interlocks ensures safe operation of the switch arrangement.
Preferably the switching-means comprises an insulating carrier extending axially through the housing, the carrier carrying three axially spaced bridging contacts, each associated with a respective one of the input contacts and a respective one of the output contacts and the carrier being axially movable from a first limit position wherein each bridging contact electrically connects the associated input and output contacts, to a second limit position during which movement each bridging contact slides axially out of engagement with either or both of the associated input and output contacts to break the electrical connections.
By arranging the bridging contacts on an axially movable carrier and making and breaking the three phases by axial sliding movement of the bridging contacts, operation of the switch is effected merely by an axial push and/or pull operation of the carrier from one or both ends of the housing. By using this simple axial operation the frictional loss in opening and closing the switch is greatly reduced and the simple axial movement utilises the axial driving force to maximum advantage and increases the operational speed of the switch. The costly and cumbersome mechanical linkages hitherto used are replaced by a much simpler mechanism.
When opening a high power circuit by means of a switch or circuit breaker an arc is usually struck between the contacts as they open and this arc will maintain the current path through the switch or circuit breaker unless it is extinguished. In one form of switc device, therefore, preferably each input contact, and ir some cases also each output contact, has a main contact section and an arcing contact section and each bridging contact in moving from its first to its second limit position slides axially out of engagement first with the main contact section and then with the arcing contact section.
In order to solve the problem of quenching the arcs that are struck in this arrangement it is preferred that the interior of the housing is filled with an arc-quenching fluid, and the carrier carries three axially spaced pistons, each positioned so as to direct a stream of the fluid across the space between an associated bridging contact and arcing contact section as the bridging contact is moved out of engagement with the arcing contact section. The pistons may each be separate from the bridging contact, although it is possible for one or more of the pistons to be constituted by, or combined with, a bridging contact.
In order that the invention may be better understood specific embodiments thereof will now be described in more detail, by way of example only, with reference to the accompanying drawings in which:-

Figure 1 is an end elevation of a first embodiment with parts removed;
Figure 2 is a longitudinal cross-section through the assembly of Figure 1, on a reduced scale;
Figure 3 is a longitudinal cross-section through part of a second embodiment;
Figure 4 is a schematic end elevation of a third embodiment; ,
Figure 5 is an enlarged partial longitudinal cross-section through the assembly of Figure 4; and
Figure 6 is a schematic end elevation of a fourth embodiment.

As shown in Figures 1 and 2 a switch arrangement comprises an assembly having side members 1 and 2 and an end member 'la. Secured to the side members 1 and 2 are lower angle strips 3 and 4 respectively which support three cross bars 5, 6 and 7 of insulating material. Standing below the cross bars are three current transformers 8, 9 and 10, one for each phase of a three-phase electrical supply. A fixed input terminal 11, 12 and 13 respectively is mounted on each of the cross bars 5 to 7 and is electrically connected to the respective current transformer. The fixed input terminals each have an auxiliary fixed terminal such as 14 supported from the respective cross bar and electrically connected to the associated fixed input terminal.
Upper angle elements 15 and 16 are also secured respectively to the side plates 1 and 2 and support three upper cross bars 17 to 19 again of insulating material. Supported above the cross bars 17 are three output supply busbars 20, 21 and 22 respectively, one for each phase of the supply. The cross bars 17 to 19 support fixed output terminals 23, 24 and 25 respectively, each output terminal being electrically connected to one of the busbars. Three earth terminals such as 26 are mounted on carriers 27 on the side plate 2 and are electrically connected to earth through that side plate. Each earth terminal 26 lies in the same radial plane as its associated fixed input and output terminals and auxiliary terminal.
An end memeber 2a has angle elements 70 and 71 connected thereto, which are supported by slides 72 and 73 on angle elements 74 and 75 secured to the side members 1 and 2. An elongated switch device 2B extends through the enclosure and is mounted for rotation therein by bearings 29 and 30 supported by the end plates la and the end member 2a. The device fits axially loosely within bearing 29, but is axially secured to the bearing 30.
The switch device comprises a generally tubular housing 31 made of insulating material. The housing is closed at one end by an end assembly 32 incorporating a solenoid 33 and at the opposite end by an end assembly 34 incorporating a pressure-sealed tube 35, which extends through a solenoid 35a secured by means, not shown to the end plate la. The housing has three input switching terminals, 36, 37, and 38, one for each phase of the three-phase electrical supply, arranged along one side thereof, the terminals being shielded from each other and from the end assemblies by fins 39 extending partially round the circumference of the housing. Diametrically opposite to the terminals 36 to 38 the housing carries three output switching terminals 40, 41 and 42, one for each phase of the supply, and these terminals are similarly separated from each other and from the end assemblies by fins 43.
The input switching terminal 36 is electrically connected through the housing with an input contact 44, and the output switching terminal 40 is similarly connected through the wall of the housing to an output contact 45. In similar manner the input and output terminals 37 and 41 are connected respectively to input and output contacts 46 and 47, and the input and output terminals 38 and 42 are connected to respective input and output contacts 48 and 49.
Extending through the interior of the housing is an insulating carrier in the form of a shaft 50 which is supported for axial movement by linear bearings 51 and 52 housed in the respective end assemblies 32 and 34. The shaft 50 carries ferro-magnetic cores 53 and 54 at the respective ends thereof, and these cores co-operate with the respective solenoids 33 and 35a.
The shaft 50 carries three bridging contacts 55, 56 and 57. The contact 55 is designed electrically to connect the input and output contacts 44 and 45 of the first phase of the supply, the bridging contact 56 is designed electrically to connect the input and output contacts 46 and 47 of the second phase, and the bridging contact 57 is designed electrically to connect the input and output contacts 48 and 49 of the third phase. The switch is shown in this condition in Figure 1, with the shaft 50 in its extreme left-hand position. Each of the bridging contacts 55 to 57 is in the form of a disc which is dished and is split into two or more laminations, e.g. the inner part 55a and the outer part 55b of contact 55. The outer part 55b has an inturned rim 55c presenting a convex contact portion to the input and output contacts 44 and 45. The inner part 55a is of a spring material exerting an outward force on the outer part 55b to maintain the bridging contact in good electrical connection with the input and output contacts 44 and 45.
In addition to the bridging contacts 55 to 57 the shaft 50 also carries three pistons 58 to 60. Each piston is a close fit within the bore of the housing and comprises a rigid disc such as 58a formed with a series of holes 58b therethrough, which holes are covered by a flexible flap valve 58c. The interior of the housing is filled with an arc-quenching fluid, which may be either a liquid or a gas and is preferably sulphur hexafluoride.
A shaft 76 is secured to the ferro-magnetic core 53 and extends through a pressure seal 77 of the end assembly 32. At its free end the shaft 76 is pivoted at 77 to a lever 78 supported by a pivot 79 on a carrier 80 integral with or secured to the housing of the solenoid 33. A pin 81 is also pivoted to the lever 78 at 82, and the pin passes through a hole 83 in the carrier 80. The extreme end of the lever 78 is formed with an open slot 84 in which engages a pin fixed to the end of a link 85 which may be connected to auxiliary switches and/or indicators. An arcuate member 86 is secured towards the front of the housing, the member being shown in broken lines in Figure 1 so as not to obscure other detail. The member 86 is provided with three holes 87, 88 and 89, any one of which may be engaged by the pin 81. For convenience the pin 81 and the arrangement including lever 78 are not shown in Figure 1. The arcuate member 86 is also formed with a slot 90 and the carrier 80 has an extension 91 which normally lies behind the arcuate member 86, but can be aligned with the slot 90 to pass axially therethrough.
At the end of the housing of the switch device 28 adjacent to the pressure sealed tube 35 there is carried a radially extending plate 92 formed with a slot 93 therein. A bar 94 extends inwardly from the angle element 75 in a position to engage the slot 93. The bar 94 extends along the length of the side member 1 from the front thereof but terminates short of the solenoid 35a so that when the switch device 28 is in the fully home position as shown in Figure 2 the plate 92 lies between the end of the bar 94 and the solenoid 35a so that the bar and plate do not engage and the switch device is free to rotate. However, if the switch device lies to the left of the fully home position as shown in Figure 2 the plate 92 engages the slot 93 in the bar 94 to prevent rotation of the switch device 28.
Operation of the switch assembly will now be described. In the position shown in Figure 1 the switch device is shown in an angular position where it enables contact to be made between the fixed input terminals, ll, 12 and 13 and the fixed output terminals 23, 24 and 25. The bridging contacts 55 to 57 are shown in the closed position so that a circuit is made through the switch assembly for each phase of the electrical supply. In this position the lever 78 is pivoted fully clockwise and the pin 81 engages the hole 87 in the arcuate member 86 so preventing the switch device 28 from being rotated. Furthermore the part 91 engages behind the arcuate member 86 so that the switch device is also prevented from axial withdrawal from the assembly.
When it is required to break the electrical supply and open the switch the solenoid 33 is energised so driving the shaft 50 from the left-hand limit position shown in Figure 2 to a right-hand limit position (not shown). On such movement each of the bridging contacts 55 to 57 slides axially from the associated input and output contacts 44, 46 and 48 and 45, 47 and 49 respectively. As the bridging contacts move from the input and output contacts arcs are struck between those contacts and the movement of the associated pistons 58 to 60 forces a stream of the arc-quenching medium between the bridging contact and the contact sections to extinguish the arcs.
As the shaft 50 moves to its right-hand position the lever 78 is pivoted anti-clockwise so that the pin 81 is withdrawn from the hole 81 in the arcuate member 86. Thus, the switch device 28 is free to be rotated about the axis of the assembly and can be rotated from the central position shown in Figure 1 either anti-clockwise to an earthing position or clockwise to an isolating position. If moved to the earthing position the current transformers may then be earthed by energising the solenoid 35a, so moving the shaft 50 to the left and causing the bridging contacts again to make contact with the associated input and output contacts. During this movement of the shaft 50 the lever 78 is pivoted clockwise as shown in Figure 2 and the pin 81 engages the hole 88 in the arcuate membe,-86 so that the switch device 28 is again locked against rotation. Furthermore the part 91 is engaged behind the arcuate member 86 so that axial withdrawal of the switch device 28 is not possible.
If, however, the switch device 28 were rotated clockwise from the Figure 1 position into the isolating position it will be seen that the part 91 is then axially aligned with the slot 90 in the arcuate member 86. The switch device must have been in the open condition for it to have been rotated to this position and therefore the device may safely be withdrawn from the housing for replacement or maintenance as necessary. It will be noted that when the part 91 is in axial alignment with the slot 90 then the slot 93 in the plate 92 is in axial alignment with the bar 94 so that this does not hinder axial withdrawal of the device. This arrangement also acts as a safety device controlling replacement of the switch device, which cannot be inserted unless slot 93 and bar 94 are axially aligned and part 91 and slot 90 are axially aligned. This ensures that the device can only be inserted in the isolating position of the switch.
It will be understood that the switch device itself may take any one of a number of forms and that described is purely by way of example. Thus, the shaft need not be operated by two solenoids as described, but operation could be by way of a single solenoid only, operating in a push/pull manner. Alternatively the shaft 50 carrying the bridging contacts could be operated by hand or by pneumatic, hydraulic or mechanical actuating means, for example by an electric motor driving an operating screw. If required, operation may be by way of a spring assembly in either or both directions of the shaft, the springs being charged either by hand or by a power arrangement to give required operation when desired.
The actual arrangement of contacts within the interior of the switch device may be changed as desired. For example the device may comprise an elongated housing which contains three separate, individually sealed, single-pole vacuum modules, each of which makes and breaks the respective circuit by an axial movement of an operating member. The internal arrangement of each module may take any convenient form and each module may have an internal vacuum to prevent arcing or cause rapid extinction of any arc that may be struck, or may contain gas, oil or other arc quenching medium. The operating members of each module are then axially aligned and linked to each other by insulating connecting members within the housing, and are operated simultaneously by solenoids or other operating means at one or both ends of the housing.
A further alternative switch device is shown in Figure 3, the device being rotatably mountable in a terminal assembly somewhat similar to that shown in Figures 1 and 2,although in the terminal assembly the fixed and auxiliary input terminals lie in a different radial plane to the associated fixed output and earth terminals. In Figure 3 only two of the switching phases are shown, it being understood that a further phase is included in the broken away part of the centre of the Figure, which phase is of identical construction with those two shown in the Figure. The switch device shown in Figure 3 comprises an insulating housing 150 having end assemblies 151 and 152 in which are mounted solenoids l5la and 152a. A carrier 154 extends through the housing and is supported by sliding bearings 155 and 156 at the two ends thereof, the carrier having at its ends ferro- magnetic cores 157 and 158 co-operating with the solenoids. The carrier carries three bridging contact assemblies, which are identical for each of the three phases and only one will therefore be described. Similarly the fixed switching contacts are identical for each of the three phases and only one will be described.
Each phase incorporates a switching input terminal 159 and a switching output terminal 160. The switching input terminal is electrically connected through the housing to an input contact 161. This contact comprises an annular member 162 to which are secured and electrically connected a plurality of contacts such as 163 forming the main contact section of the input contact. The inner periphery of the annular member 162 has a high melting point alloy insert 164 which forms an arcing contact section of the input contact. An insulating shield 165 extends axially from the arcing contact section. The carrier 154 at this region of the device includes a disc 166 forming a piston, from which a number of rods 167 project axially and extend through bores 168 in the annular member 162. These rods support an electrically conducting sleeve 169 secured to an electrically conductive disc 170 having an annular insert 171. This insert is in sliding electrical contact with an annular output contact 172 connected through the wall of the housing with the switching output terminal 160. The disc 170 carries an axially extending electrically conductive probe 173.
To close the switch from the open position shown in Figure 3 the solenoid 152a is energised to drive the carrier from its right-hand limit position as shown to its left-hand limit position. During this movement, electrical contact is maintained between the part 170 of the bridging contact and the output contact 172. The probe 173 of the bridging contact engages the arcing contact section 164 of the input contact and then the sleeve 169 of the bridging contact engages the contacts 163 forming the main contact section of the input contact. Electrical connection is thus established between the switching input terminal 159 and the switching output terminal 160. In order to open the switch from this position the solenoid 157a is energised to drive the carrier 154 back to its extreme right-hand position. Contact between the sleeve 169 and the contact 163 forming the main contact section is first broken while still maintaining electrical connection between the probe 173 and the arcing contact section 164. When that contact is broken therefore an arc is struck between the section 164 and the probe 173. Movement of the core 157 and the piston 166 to the right however creates a flow of the arc quenching medium through the restricted space within the arcing contact section 164 and this flow between that section and the probe 173 extinguishes the arc. The main contact sections 163 are shielded from the arc by the insulating shield 165. On this opening action of the switch the section 170 of the bridging contact acts as the piston for driving the arc-quenching medium across the arc of the next adjacent phase and similarly the section 170 of the bridging contact of that phase acts as the piston for driving arc-quenching medium across the arcing contacts of the final phase.
The arrangement shown in Figure 3 may be modified by substituting for the solenoid arrangement shown any of the operating arrangements described with reference to Figure 1. Either the Figure 1 or the Figure 3 arrangement may also be modified by providing fluid relief arrangements within the wall of the housing or within the parts of the bridging contacts in order to ensure that pressure equalising is achieved while still obtaining the required flows of arc-quenching medium. For example, the housing may be formed by two concentric tubes defining an annular space therebetween, openings into the space from the interior of the inner tube being i provided at the ends of the tube and adjacent to each of the contacts. As with the Figure 1 embodiment, the embodiment shown in Figure 3 can be constructed as a vacuum switch or vacuum circuit breaker, the housing 50 then being sealed and evacuated.
In the embodiment shown in Figures 4 and 5 the switch arrangement comprises an enclosure 200 within which are situated three radially spaced fixed input terminals 201, 202 and 203. Three corresponding fixed output terminals such as 204 are each axially aligned with a respective one of the fixed input terminals. Three auxiliary fixed input terminals 205, 206 and 207 are located in the same radial plane as the fixed input terminals 201 to 203 and are radially spaced from those terminals. The fixed input terminals and auxiliary fixed input terminals are electrically connected as pairs by connectors 208, 209 and 209a. A set of three earth terminals (not shown) are provided on the enclosure in the same radial plane as the fixed output terminals 204, each earth terminal being axially aligned with a respective one of the auxiliary fixed input terminals 205 to 207.
An elongated switch device shown generally as 210 extends through the enclosure and is mounted for rotation therein by bearings such as 211. The switch device comprises a housing 213 in which is included three switching modules 213 to 215, one for each phase of the supply. The three modules are identical and only module 213 will be described in detail.
The module 213 is housed in an axial bore 216 within the housing 212 and extending through the housing into the bore is a switching input terminal 217 and a switching output terminal 218. The switching input terminal 217 is electrically connected to a fixed contact arrangement shown generally as 219 which includes a main contact 220 of tubular construction and with short axial splits at the free end to give flexibility and a tubular, probe-like arcing contact 221. The switching output terminal 218 is electrically connected to an annulus . 222 having a sliding contact 223.
The bore 216 also houses a moving contact formed by a conducting tube 224 which is in sliding engagement with the contact 223. The tube carries a main contact head 225 connected to the tube by radial spokes, and a sealing ring 226 is located between the head and the bore 216. The head 225 has a contact face 227 which can engage the inner surface of the main contact 220. The tube 224 also carries an auxiliary arcing contact 228 which can engage the outer surface of the end of the arcing contact 221, and an insulating shield 228a which slides around the fixed arcing contact 221,and which is of a streamlined shape. The tube 224 is connected by insulating links to an operating mechanism (not shown) which is located within the housing 212, the mechanism. being operative to move the shaft 224 axially and thus to move the contacts 227 and 228 from the solid line position in Figure 5 to the broken line position-in that Figure.
As already stated each module is identical in construction and each has its associated switching input terminal 217, 217a, 217b, and switching output terminal such as 218. The switching input terminals for modules 214 and 215 are shown as 217a and 217b in Figure 4: All the switching input terminals 217 lie in the same radial . plane as the fixed input terminals and auxiliary fixed input terminals, and all the switching output terminals 218 lie in the same radial plane as the fixed output terminals 204 and earth terminals. The shafts 224 of each of the three switch modules are moved axially by a common operating mechanism. This mechanism may take any suitable form.
It will readily be seen that when the switch device 210 is in the angular position shown in Figure 4 the fixed input terminals are connected with the switching input terminals and the fixed output terminals are connected with the switching output terminals. With the switch contacts 227 and 228 in the solid line position of Figure 5 a circuit is thus made through the switch arrangement for each phase. To break the circuit the shafts 224 are moved to the right so that electrical contact between the main contacts and then the arcing contacts is broken. During such movement the shield 228a and main contact head 225 operate as a piston within the bore 216 to compress gas or other medium within the bore and force it to flow in the opposite direction through the spaces between the spokes of the head 225 and therefore across and into the arc struck between the arcing contacts. This flow causes the arc to be quenched.
With the circuit broken in this manner the mode of operation of the switch arrangement may then be changed by rotating the switch device 210. Rotation in an anti-clockwise direction as shown in Figure 4 will cause the switching input terminals to make contact with the auxiliary fixed input terminals and will cause the switching output terminals to make contact with the earth terminals. Thus, if the switches for each phase are now closed the input circuits are connected to earth. Alternatively, if the switch device 210 were to be rotated clockwise from the direction shown in Figure 4 the switching input and switching output terminals would be moved to a position whereby they are electrically isolated from any of the terminals on the enclosure. The circuit inputs and outputs are thus isolated one from the other.
As with the embodiment of the invention described with reference to Figures 1 and 2 suitable interlocks may readily be built into this equipment to ensure that rotation of the housing cannot occur unless the circuits are open and so that axial withdrawal of the whole of the housing from the enclosure cannot be effected unless the housing has previously been rotated to the isolating position.
Figure 6 shows application of the invention to yet a different arrangement of circuit breaker having an elongated switch device shown generally as 229 having three switching modules 230 to 232 arranged in side by side relationship. Each of the modules may include a switching arrangement identical to that described in Figure 5 or of any other convenient form. Each module has a switching input contact 233, 234 and 235 respectively, all of which lie in a common radial plane, axially aligned with a respective switching output contact, which contacts also lie in a second common radial plane. The switch device shown in Figure 6 may be incorporated in a housing similar to that shown in Figures 4 and 5 and having fixed input terminals, auxiliary fixed input terminals, fixed output terminals and earth terminals.
In all embodiments of the invention it will be understood that the actual arrangement of the housing may be varied from that described, and that many different types of interlock means which will give the desired result may be designed.

Claims

1. A switch arrangement for making and breaking a three-phase electrical supply comprising an enclosure wherein are situated three spaced fixed input terminals, one for each phase, three spaced fixed output terminals, one for each phase, and an elongated switch device extending through the enclosure and mounted for rotation therein; the switch device comprising a housing having on the outer surface thereof three spaced switching input terminals, one for each phase, and three spaced switching output terminals, one for each phase, each of the switching terminals being connected with a respective one of three input and three output contacts within the housing, and switching means movable within the housing to make or break simultaneously electrical connections between the input and output contacts of each phase; and means for rotating the switch device between a first angular position wherein the fixed input and the switching input terminals are in electrical contact and the fixed output and the switching output terminals are-in electrical contact, and a second angular position wherein the fixed and switching input terminals or the fixed and switching output terminals, or both, are out of electrical contact.

2. A switch arrangement according to claim 1 in which the switch arrangement includes a first interlock which prevents rotation of the switch device unless the switching means is in a position where the connections between the input and output contacts of each phase are broken.

3. A switch arrangement according to claim 1 or claim 2 in which the switch device is mounted so that it may be withdrawn axially from the enclosure and including a second interlock that prevents such withdrawal unless the switch device is in an angular position such that the fixed input and output terminals are isolated from any other terminals.

4. A switch arrangement according to any one of the preceding claims in which the switch device is further rotatable to a third angular position in which the switching input terminals are electrically connected to the fixed input terminals and the switching output terminals are electrically connected to respective ones of three spaced earth terminals one for each phase.

5. A switch arrangement according to any one of the preceding claims in which the fixed input terminals are axially spaced apart on the enclosure, the fixed output terminals are axially spaced apart on the enclosure, the switching input terminals are axially spaced apart on the housing and the switching output terminals are axially spaced apart on the housing.

6. A switch arrangement according to claim 5 in which the fixed input terminals are diametrically opposite to the associated fixed output terminals with respect to the axis of the arrangement, and the switching input terminals are diametrically opposite to their associated switching output terminals on the outer surface of the housing.

7. A switch arrangement according to claim 6 in which three axially spaced earth terminals are situated within the enclosure, angularly spaced from the fixed output terminals, and a series of three auxiliary fixed input terminals are situated within the enclosure diametrically opposite to their associated earth terminals, each auxiliary input terminal being electrically connected to an associated one of the main fixed input terminals.

8. A switch arrangement according to any one of claims 1 to 4 in which the fixed input terminals are radially spaced apart on the enclosure, the fixed output terminals are radially spaced apart on the enclosure and are axially spaced from the fixed input terminals, the switching input terminals are radially spaced apart around the housing and the switching output terminals are radially spaced apart around the housing and are axially spaced from the switching input terminals.

9. A switch arrangement according to claim 8 in which each fixed input terminal is axially aligned with its associated fixed output terminal, each switching input terminal is axially aligned with its associated switching output terminal, the fixed and switching input terminals lie in a first common radial plane and the fixed and switching output terminals lie in a second common radial plane.

10. A switch arrangement according to claim 9 in which three radially spaced earth terminals are situated within the enclosure, in the same radial plane as the fixed output terminals and angularly spaced therefrom, and three radially spaced auxiliary fixed input terminals are situated within the enclosure in the same radial plane as the fixed output terminals, angularly spaced therefrom and in axial alignment with the associated earth terminals.

11. A switch arrangement according to any one of claims 1 to 7 in which the switching means comprises an insulating carrier extending axially through the housing, the carrier carrying three axially spaced bridging contacts, each associated with a respective one of the input contacts and a respective one of the output contacts and the carrier being axially movable from a first limit position wherein each bridging contact electrically connects the associated input and output contacts, to a second limit position during which movement each bridging contact slides axially out of engagement with either or both of the associated input and output contacts to break the electrical connections.

12. A switch arrangement according to claim 11 in which each of either or both of the input and output contacts has a main contact section and an arcing contact section and each bridging contact in moving from its first to its second limit position slides axially out of engagement first with the main contact section and then with the arcing contact section.