Multiple height, high density horizontal low voltage motor control center

A reduced form factor component support is provided for motor control centers and similar packaged electrical systems. The reduced form factor component support may be used with smaller components, such as small motor starters, motor drives, and so forth. Electrical connections with standard bus bars in the enclosure are made through special connectors mounted on subplates in the rear of the enclosure, or by an invertible stab housing that can allow the reduced form factor component support to share conventional slots in a bus cover, thereby providing access to the supply power in the enclosure.

BACKGROUND

The present invention relates generally to the field of packaged electrical systems. More particularly, the invention relates to an arrangement for a motor control center (MCC) providing a reduced height form factor component support and a mechanism for interconnecting the component support with line and load conductors in an enclosure.

A range of applications exist for packaged electrical and electronic components, particularly power electronic components such as those used to power loads in industrial applications. In one type of packaged system, typically referred to as an MCC, various switch gear, control devices, protective circuit devices, programmable logic controllers, motor drives, and so forth are housed in a large enclosure that may be subdivided into compartments. The enclosure is supplied with power by power buses that extend generally in a plane toward the rear of the enclosure. The individual compartments typically house associated circuitry that may be withdrawn from the enclosure for servicing and replacement. Compartmentalizing such systems greatly enhances the ability to service the system components, and also serves to isolate the system components from one another. Thus, where access or service is required for components within one compartment of the enclosure, that compartment alone may be opened and the component support withdrawn for the necessary service.

Typical MCCs include access to power bus structures at certain locations in the rear section of the enclosure. For example, there may be multiple locations in the rear of the enclosure where component supports (sometimes referred to as “buckets”) may be slid into place and plugged into the power buses. Conventional enclosures, for example, may include a dozen rows of slots through which stab contacts extend when the component supports are placed in the enclosure. However, because access to the power buses is limited, only component supports at locations corresponding to the slot locatinos are provided, with no access to the power buses at intermediate locations. Consequently, all component supports must be configured to interface with the power buses at one or the other of the access points provided by the slots.

While much of the switchgear, protective circuitry, and power control devices used in MCCs may be large and require ample space for housing them, a number of components have been substantially reduced in size in recent years. For example, certain motor starters and motor controllers are now packaged in relatively small units, substantially smaller than the volume provided by a standard compartment in an MCC enclosure. However, due to the relative universality of the enclosure designs, enclosures have not been developed that can accommodate smaller form factor compartments. In particular, even smaller components must, at present, be provided in compartments that could accommodate much larger components, resulting in a reduction in the space efficiency and power density of the overall system.

It would be advantageous, therefore, to provide an improved technique for housing electrical components in MCCs and similar systems. There is a particular need for a reduced form factor component support and compartment in such systems, as well as mechanisms for interfacing such components with existing slotted bus bar access panels.

BRIEF DESCRIPTION

The present invention provides a novel approach to configuration of component supports for MCCs and similar systems designed to respond to such needs. In general, the invention provides an electrical system that includes an electrical enclosure having buses for routing electrical power to component units. A bus cover has stab openings therein for receiving stabs for electrically coupling component units to the buses. Component units in the system may be disposed in the electrical enclosure and support electrical power components.

In one implementation of the invention, the component units or supports have an invertible stab housing secured to a rear wall thereof. The stab housing can be mounted to the component unit with stabs extending from an upper position or from a lower position depending upon the location of the available stab openings in the bus cover. Thus, reduced form factor component supports can be provided that share stab openings by appropriately positioning the stab housing of each unit in lower and upper positions such that the stabs extend through the bus cover in a shared arrangement.

In an alternative configuration, the invention provides a system that includes a similar electrical enclosure, but with an interface fixedly secured in the enclosure. The interface serves to couple the conventional bus bar structure on a rear side thereof and provides pluggable connections on a front side thereof for routing power to two component units when mounted in the enclosure. The component units may then include mating electrical plugs that interface with the pluggable connections within the enclosure. The interface may be formed as a subplate affixed within a rear portion of the enclosure and supporting the pluggable connection.

More generally, the invention provides a reduced, 3.25 inch form factor component form unit for MCCs. The reduced form factor unit may be configured to support power electronic components, and is fitted within a correspondingly dimensioned compartment of an MCC enclosure.

DETAILED DESCRIPTION

Turning now to the drawings, and referring first toFIG. 1, a packaged electrical system10is illustrated generally as including an enclosure12in which a range of electrical and electronic components, switchgear, and so forth are housed. The system10may be configured as an MCC, such as for industrial control of motors and other loads. It should be noted that, as used herein, the terms “motor control center” and “MCC” should include any suitable type of industrial, marine, commercial and other enclosure in which supports are provided for components in a compartmentalized fashion and interface with bus structures provided in the enclosure. In a conventional MCC, for example, the enclosure defines a shell14that encloses an internal volume16in which compartments18are subdivided. Each compartment typically has standard dimensions, particularly various standard heights. Depending upon the associated components to be mounted in each compartment, the enclosure will be provided with doors20that permit individual compartments to be opened for access to the components located therein. As in the illustrated embodiment, each compartment may be separated by shelves (shown partially broken away inFIG. 1to show connections along the rear wall). Moreover, for routing of power conductors, load conductors, and so forth, a wireway may be provided in the enclosure, such as the vertical wireway shown to the right of the enclosure inFIG. 1.

The enclosure12includes a series of power buses22(shown in dashed lines inFIG. 1) that route three phases of electrical power to the various compartments. As will be appreciated by those skilled in the art, the buses22are provided behind a bus cover24that limits access to the buses when energized. Slots26are provided in pairs, with a number of such rows of such slots being provided for plugging component supports into electrical contact with the buses. In general, conventional component supports will include stabs that extend through the slots26to make contact with the buses22.

The arrangement shown inFIG. 1is particularly adapted for plug-in receipt of component supports by means of receptacles28for data and control power, and connectors30for line and load connections. As will be appreciated by those skilled in the art, in many applications, power and data are provided to each component support at various levels. These levels may include low level power and data connections for the exchange of input and output data, monitoring and control instructions, and so forth via a known data exchange protocol, such as DeviceNet. Moreover, power may be provided at a control power level, such as 24 vdc or 110 vac for operation of certain of the devices, such as relays and contactors. Such data and control power is provided in the enclosure ofFIG. 1via receptacles28.

Because the compartments illustrated inFIG. 1are of a reduced form factor, as described in greater detail below, interfacing with the standard slot locations in the bus cover24is generally not feasible. That is, the reduced height form factor of the compartments results in locations for the connectors that are between conventional locations of the slots26in the bus cover. To nevertheless accommodate the components, connectors30are provided on subplates32that are secured within the enclosure over the bus cover24. Electrical connections are made on a rear side of the subplates32directly to the buses, and wiring then routes power to connectors30. In a present embodiment, as described in greater detail below, the connectors may be provided for both line connections (incoming power) and load connections (outgoing power) for each component support. Moreover, the connectors may be configured for accommodating both three-wire three phase power and four-wire three phase power, with one receptacle being unwired when the connectors are used with three-wire three phase power.

The compartments thus configured receive reduced form factor component supports as indicated at reference numeral34. As will be appreciated by those skilled in the art, such component supports are typically configured as slide-in units or drawers that support multiple components36that are wired together as subassemblies or sub-circuits. In the embodiment illustrated inFIG. 1, a mating connector38is provided on a rear wall of the component support34. The connector38is designed to interface with connectors30within the compartment when the component support is slid into place.

A number of standard dimensions are currently available for component supports in MCCs and similar systems. In particular, the smallest component support generally available currently is a 6.5 inch form factor. The present arrangement for interfacing the component support with buses in the enclosure permits a reduction in the height by a factor of 2. Thus, in a present embodiment, component support34has a 3.25 inch form factor. Such reduced form factor component supports are believed to be particularly useful for housing smaller components and circuits such as motor starters, motor controllers, and so forth.

FIG. 2illustrates, in somewhat greater detail, the arrangement ofFIG. 1for two reduced form factor compartments. As shown inFIG. 2, slides40are provided within the enclosure for supporting the component support on a shelf that subdivides the enclosure into compartments. The subplate32, then, is fixed (mechanically bolted or screwed) in place toward the rear of the compartment over the bus cover described above (see,FIG. 1). The data and control power receptacles28are provided adjacent to the subplate32. The subplate32includes line-side plugs42that are connected (stabbed or wired) to the buses routed in the rear of the enclosure (see,FIG. 1) and provide for connections to the power source, typically the power grid. Load-side plugs44are provided and are routed to wiring that extends to the load, such as an electric motor or any other suitable load driven by the components within the compartment.

Various mechanical features of the subplate and connector30facilitate plug-in operation. For example, an alignment pin46may be provided in the connector arrangement, along with an alignment receptacle48. As described below, the pin46and receptacle48may interface with similar arrangements on the connector on the rear of the component support to ensure proper alignment of the connectors when the component support is slid into place and the connections made. Similarly, alignment holes50may be provided in the subplate32. These alignment holes are intended to receive pins, described below, that again facilitate the alignment of the component support with the subplate prior to making of the contacts between the connectors.

FIG. 3is a diagrammatical representation of the electrical connections made by the subplate32supporting the connectors30. In general, the line-side connector is electrically coupled to buses within the enclosure. Where a neutral bus is provided, this bus also may be connected to the connector via stabs or hard-wiring (see, dashed lines inFIG. 3). Similarly, the load-side connector30is wired to conductors for transmitting controlled output power to the load controlled by the components within the component support. Connector30is mechanically held by the subplate32which serves as a mechanical support and to facilitate alignment and plugging of the component support connector into connector30.

As the component support34approaches the subplate30as illustrated inFIG. 3, pins52extending from a rear surface of the component support34enter into alignment holes50in the subplate. The component support34is thus guided into place such that the mating connector38may make contact with the appropriate conductors of the connector30and supply power to the components36of the component support.

An exemplary arrangement for the foregoing connectors on the component support and subplate is illustrated inFIG. 4. To the left of the diagram inFIG. 4, the mating connector38on the rear of the component support34is illustrated. Load-side plugs54are provide in the connector for routing three phase power to a load. Similarly, line-side plugs56are provided for receiving three phase power from the buses of the enclosure. Neutral line-out58and line-in60connections are provided to accommodate neutral connections where four-wire three phase power is employed. On an opposite side of the connector, the connections illustrated inFIG. 4are hard-wired to components within the component support34.

The connections on the subplate32are essentially the mirror image of those on the rear of the component support. That is, the connector30includes line-side plugs62that interface with the receptacles56on the component support. Similar load-side plugs64interface with the load-side receptacles54of the component support. Where four-wire three phase power is employed, neutral in66and neutral out68connections are provided. As will be appreciated by those skilled in the art, any suitable connectors may be used for the reduced form factor component supports provided herein. Moreover, the designations as “plug” and “receptacle” may be reversed where desired, with receptacles being provided in the connector of the subplate and plugs being provided on the component support.

FIG. 5illustrates an alternative configuration for a reduced form factor component support in accordance with the invention. In the embodiment ofFIG. 5, the component supports34are made to interface directly with shared slots70in the enclosure12. Slots70are essentially identical to slots26described above with reference toFIG. 1. However, slots70will be shared in the enclosure by the positioning of a divider or intermediate shelf72between the reduced form factor component supports34. To facilitate contacting the bus bars22behind the bus cover24, an invertible stab housing74is provided. As will be appreciated by those skilled in the art, such stab housings are generally insulated enclosures that can be mounted on the rear of a component support and provide insulated hard-wired connections on the interior of the component support, with stabs76extending rearwardly from the stab housing. The stabs76are configured to enter through slots70and to make connections with bus bars22positioned behind the bus cover24. The invertible stab housings74are designed such that stabs76are in close proximity to an edge of the housing. That is, when positioned in a first position as illustrated in upper component support34ofFIG. 5, the stabs will exit near a lower edge of the component support, as indicated generally by reference numeral78. In an inverted position, as indicated by reference numeral80, the same housing can provide for stabs that exit near an upper edge of the component support. As the reduced from factor component supports are mounted in the enclosure, then, the stabs76of each stab housing will enter into engagement with bus bars72through shared slots70in the bus cover.

This sharing of slots is illustrated in somewhat greater detail inFIG. 6. As noted above, the invertible stab housing74provides for stabs that can exit either near a lower edge of a component support or an upper edge of a component support, as indicated by reference numerals78and80, respectively. The stabs76, then, generally align with one another and are positioned sufficiently close to one another such that the stabs can enter into the shared slots70to complete connections with the buses22disposed behind the bus cover24.