Switchgear assembly with front accessible slide-in fixed power switch

[0002] 1. Field of the Invention

[0003] This invention relates to switchgear assemblies which house electric power switches such as circuit breakers, transfer switches and the like. More particularly, it relates to such switchgear assemblies in which the power switch is connected to the power buses in the switchgear cabinet by fixed connections.

[0004] 2. Background Information

[0005] Switchgear assemblies include power switches, such as circuit breakers, transfer switches and the like, housed in metal cabinets together with sections of power buses between which the switches can be connected. In low voltage switchgear, that is 600 volts or lower, the power switches may be either draw-out mounted of fixed mounted in the metal cabinets. Draw-out mounted power switches are provided with quick disconnects on a rear face so that the power switches are automatically connected to the power buses as the switches are inserted into the cabinet from the front and automatically disconnected as they are withdrawn. Some users prefer or require that the power switches be fixed mounted, that is, secured to the power buses by fixed connections such as bolts, for instance.

[0006] In existing switchgear, there are few similarities in the assemblies and methods by which these differing constructions are mounted. The desirable goal of accommodating the same breaker arrangements despite mounting methods has for the most part not been achieved, and therefore, has historically led to different design concepts for each.

[0007] Present construction methods for fixed mounting power switches involve mounting the power switch on a bare frame or chassis utilizing holes provided in the molded power switch housing. Side accessibility is required to effect this mounting technique as well as to make the connections with the buses. As completed switchgear assemblies typically have a number of switchgear cabinets or sections arranged side by side, the side accessibility needed mandates that the power switches be installed and connected to the power buses before the units are joined side by side. This also makes it difficult to change or replace a fixed mounted power switch after the vertical sections are coupled together. The methods for changing these power switches in the field are quite involved due to the accessibility required for making the primary bus and housing connections.

[0008] There is a need, therefore, for an improved method and arrangement for fixed mounting power switches and switchgear assemblies.

[0009] More particularly, there is a need for such an improved method and apparatus which does not require side access to the vertical sections or cabinets of the switchgear assembly, so that the power switches do not necessarily have to be installed before coupling of the vertical sections.

[0010] There is a further need for such an improved method and apparatus in which the power switches can be easily removed and replaced in the field.

[0011] There is also a need for such an improved apparatus and method which also permits the power switches to be arranged in the cabinets similarly to the draw-out power switches.

[0012] These needs and others are satisfied by the invention which is directed to a switchgear assembly in which the power switches are insertable into the switchgear cabinets through front openings and the power switches have power conductors projecting rearward from the switch housing with terminal sections extending vertically beyond the housing so that they are accessible through the front opening for connection to bus members mounted in the cabinet rearward of the front openings. The bus members have sections projecting forward toward the front opening of the cabinet and vertically extending terminal sections which are secured by fixed connectors to the vertical sections of the power conductors. In a preferred arrangement, the power switches have a first set of power conductors with terminal sections extending vertically above the switch housing for connection to a first set of bus members and a second set of power conductors with terminal sections extending downward below the switch housing for connection to a second set of bus members.

[0013] Typically, the power switches are vertically stacked in a front compartment of the switchgear cabinet. Behind the front compartment is a middle compartment in which a vertical set of bus members are mounted. These vertical bus members have extensions extending forward with terminal sections extending vertically upward for engagement with the upwardly extending terminal sections of the first set of power conductors on the power switches. The bus members also include a set of runbacks with the first set extending from the rear compartment, through the middle compartment, into the forward compartment and having vertically downwardly extending terminal sections which engage the vertically downwardly extending second set of power conductors on the at least one circuit breaker. A second set of runbacks is secured to the second set of power conductors on a rear face of the bottom circuit breaker. This second set of runbacks is attached to the power switch external to the cabinet and is insertable through the front opening with the bottom circuit breaker to extend through the middle compartment and into the rear compartment for connection in the rear compartment to a set of power cables.

[0014] The means which mount the power switches in the cabinets engage the sides of the housings on the power switches and include substantially horizontal upwardly facing mounting surfaces on mounts extending along the sides of the cabinets. The power switches have downwardly facing generally horizontal mounting surfaces on the sides of the housing which engage the upwardly facing horizontal surfaces so that the power switch may slide into the cabinet through the front access opening. Preferably, these mounts comprise mounting panels that have generally horizontally extending slots forming the substantially horizontal upwardly facing mounting surfaces. The housing has substantially horizontally extending lateral projections on each side forming the downwardly facing generally horizontal mounting surfaces. These lateral projections on the housing slide into the generally horizontally extending slots in the mounting panels. The slots in the mounting panels have blind ends which form stops against which the projections on the housing seat to position the housing relative to the power buses. Preferably, these blind ends of the slots are formed by lateral offsets in the mounting panels. The mounts further include locking members engaging the mounting panels and preventing forward movement of the housing in the slots. These locking members are preferably brackets having tabs which block forward movement of the lateral projections on the housing in the side slots. Also, most preferably, the tabs on the mounting brackets extend transversely into the slots on the mounting panels and engage slits in the mounting panel extending from the slots. This mounting arrangement provides easy installation and removal, but yet provides secured mounting to resist the forces generated by short circuit currents and interruption of the same.

[0015] Accordingly, it is an object of the invention to provide a switchgear assembly with an improved arrangement for fixed-mounting of the power switches.

[0016] More particularly, it is an object of the invention to provide such switchgear in which the connections of the power conductors on the switches to the power buckles are accessible through the front opening.

[0017] Thus, it is another object of the invention to provide switchgear assembly in which the power switches can be fixed-mounted within the switchgear cabinets without the need for side access so that the power switches can be easily installed and removed without disassembling the switchgear assembly.

[0018] An additional object of the invention is to provide such switchgear in which the fixed-mounted power switches are readily slid into place within the sub-switchgear cabinets and easily and securely maintained in place.

[0019] It is still another object of the invention to provide a switchgear assembly for fix-mounted power switches, which is similar to the arrangement for draw out power switches.

[0020] A full understanding of the invention can be gained from the following description of the preferred embodiments when read in conjunction with the accompanying drawings in which:

[0021] FIG. 1 is a side elevation view with side panels removed of a section of a switchgear assembly incorporating the invention.

[0022] FIG. 2 is an exploded isometric view taken from the front of a portion of a switchgear assembly of FIG. 1.

[0023] FIG. 3 is an exploded isometric view similar to FIG. 2 looking forward.

[0024] FIG. 4 is an exploded isometric view similar to FIG. 2 but showing the arrangement for installing the bottom circuit breaker.

[0025] FIG. 5 is a fragmentary isometric view looking upward on engagement of a locking bracket with a mounting panel only in accordance with the invention.

[0026] FIG. 6 is an isometric view of a circuit breaker installed in a cell of the switchgear cabinet.

[0027] The switchgear assembly 1 includes a metal cabinet 3 with a side panel (not shown) removed. A number of similar cabinets or sections 3 mounted side by side form the switchgear assembly 1.

[0028] The cabinet or section 3 is divided into a forward compartment 5, a middle compartment 7 and a rear compartment 9. The forward compartment 5 is divided into a number of vertically stacked cells 11 in which power switches 13 are mounted. In the exemplary switchgear assembly 1, the power switches 13 are power circuit breakers; however, other types of power switches, such as transfer switches, isolation switches and the like also can be mounted in one or more of the cells 11. Typically, the power circuit breakers 13 are three phase breakers and are connected between three phase power buses 15 including a set of vertical buses 17 mounted in the middle compartment 7. This vertical three phase bus 17 is connected to similar vertical buses in adjacent compartments by horizontal buses 19a-cand 21a-c. Each of the circuit breakers 13 is connected to the vertical bus 17 by another bus member in the form of a stab 23 which extends through a barrier 25 into the forward compartment. Each of the circuit breakers 13 is connected to a second set of bus members in the form of runbacks 27 which extend from the forward compartment 5 through the middle compartment 7 and into the rear compartment 9 where they are connected to sets of power cables such as indicated at 29.

[0029] Turning also to FIGS. 2 and 3, the circuit breakers 13 are inserted into the cells 11 through front openings 31 and supported by mounts formed by sheet metal side panels 35. The side panels 35 have slots 37 extending horizontally from a front edge to form an upwardly facing generally horizontal support surface 39. The circuit breakers 13 have molded housings 41 with molded projections 43 extending laterally from each side. Groves 45 and the lower surfaces of these projections 43 form generally horizontal downwardly facing support surfaces 47 which engage and slide along the support edge 39 on the side panels 35. The slots 37 arc flared at 37fto help guide the projections 43 into the slots 37. A lateral offset 49 in the side panels 35 forms a positive rear stop for the projections 43. The projections 43 and therefore the circuit breakers are locked in place by locking brackets 51land 51r.

[0030] As best seen in FIG. 5, the left bracket 51is a planar member with a pair of tabs 53. The rear most tab 53 engages a slit 55 in the side panel which extends downward from the slot 37. This tab 53 is sized so that when seated in the slit 55 it extends upward to the slot 37 forming a forward stop for the projection 43 on the side of the circuit breaker housing. The locking bracket 51is secured by screws to 57 to a vertical member 59 which is part of the switchgear cabinet 3. In a similar fashion, the locking bracket 51rhas tabs 53 which engage a slit 55 in the slot 37 in the right side panel 35. The second tab 53 bears against a notch in the panel 35. This right side bracket is secured by screws (now shown) to another panel 61 which forms part of the cabinet structure. With the projections 43 thus firmly confined within the slots 37, the circuit breaker 13 is secured as shown in FIG. 6 against movement including any response to the sizable magnetic forces which can be generated during short circuit interruption.

[0031] The circuit breakers 13 are secured to the power buses 15 by fixed connections. As can be seen in FIG. 3, the circuit breakers 13 have a first or upper set of three phase power conductors 63a-63cprojecting from a rear face 65 of the housing 41 and a second or lower set of three phase power conductors 65a-c. The upper conductor 63a-63chave terminal sections 67a-67cextending vertically upward beyond housing 41 (see FIG. 1). For all of the circuit breakers 13 except the lower most circuit breaker, the lower set of power conductors have terminal section 69a-69cextending vertically downward beyond the housing 41. As best seen in FIG. 2, the tabs 23a-23bconnected to the vertical bus 17 similarly have terminal sections 71a-71cextending vertically upward above the housing 41 of the circuit breaker and abutting the terminal sections 67 on the upper set of power conductors of the circuit breakers. These terminal sections 65a-65cand 71a-71chave aligned apertures for fasteners 72 (only one shown) which fixedly connect the terminal sections 65a-65cto 71a-71c. Terminal section 73a-73cextending vertically downward from the runbacks 27 are similarly secured to the terminal sections 69a-69con the lower power conductors of all of the circuit breakers except the bottom circuit breaker. As the terminal sections 67a-67cand 69a-69care above and below, respectively, the housing 41 of the circuit breaker 13, they are accessible through the front openings 31 for securing the fastener 72. Preferably, self-retaining fasteners are retained on the terminal sections 67a-67cand 69a-69c.

[0032] While there can be room below the bottom most circuit breaker 13 for securing terminal sections such as 69a-69cto confronting terminal sections on the lower most runbacks 27, the space is at floor level and very difficult to operate in. Therefore, it is preferred as shown in FIG. 4 that runbacks 27a-27cbe connected to the lower set of power conductors 65a-65con the lower most circuit breaker 13, prior to insertions of the circuit breaker into the cell 11. For this purpose, a connecting member 75 secured to the power conductor 65a-65chas flanges which abut flanges 77 on the forward ends of the runbacks 27a-27c. Then, as the circuit breaker is inserted into the bottom cell 11 the runbacks 27a-27care passed through the barrier 25 into the middle compartment 7 and extend into the rear compartment 9 as the circuit breaker seats 13 in the slots 37. The connections for the terminal sections 67a-67con the upper set of power conductors for the lower circuit breaker are then made in the same manner as described above.

[0033] The switchgear assembly 1 includes a combination arch shield/wire tray 79 above each circuit breaker 13 as shown in FIG. 6. An example of such a device is described in commonly known U.S. patent application Ser. No. 09/325,514 filed on Jun. 3, 1999 and titled “Combined Arc Shield/Wire Tray for Switchgear and Switchgear Assemblies Incorporating Same”. The arc shield section 81 disperses arc gases which are exhausted through arc vents 83 (see FIG. 4) in the circuit breaker housing 41 during interruption of short circuit currents. The forward wire tray section 85 houses terminations for the secondary or control wiring (not shown) for the circuit breaker 13 which is made accessible through access doors 87 in the front of the circuit breaker. These unitary arc shield/wire trays 79 must be easily removable to gain access to the fixed connections between the circuit breaker power conductors and the buses. Accordingly, the sheet metal combined arc shield/wire trays 79 are provided with upwardly extending flanges 89 on either side with inwardly directed terminal flanges 91. These terminal flanges 91 engage outwardly directed support flanges 93 on the lower edge of the side panel 35 in the cell 11 above. The unitary arc shield/wire tray 79 for the upper most cell 11 can be removed through a movable top panel 95 on the forward compartment 5 (see FIG. 1).

[0034] The invention provides an installation for fixed mounting circuit breakers in switchgear which requires minimum modifications from a typical draw out circuit breaker arrangement. It provides for sliding the fixed mounted circuit breakers into the respective cells in the switchgear forward compartment and for locking them securely in place. Most importantly, it provides for easy access through the front opening through which the circuit breaker is installed for securing the power conductors on the circuit breaker to the switchgear buses. In a preferred arrangement, the runback for the lower set of power conductors on the rear face of the circuit breaker can be secured to the circuit breaker before insertion into the switchgear cabinet. While in the preferred embodiment, this is only done with the bottom circuit breaker, it should be evident that any or all of the other circuit breakers in the vertical stack can also have the runback mounted before installation.

[0035] While specific embodiments of the invention have been described in detail, it will be appreciated by those skilled in the art that various modifications and alternatives to those details could be developed in light of the overall teachings of the disclosure. Accordingly, the particular arrangements disclosed are meant to be illustrative only and not limiting as to the scope of invention which is to be given the full breadth of the claims appended and any and all equivalents thereof.