The present invention generally relates to the field of electrical switchboards and panel boards and more particularly to an alignment arrangement for a circuit breaker cradle configured to mount in a switchgear enclosure.
Switchgear assemblies and switchboards and panel boards are general terms which cover metal enclosures, housing switching and interrupting devices such as fuses and circuit breakers, along with associated control, instrumentation and metering devices. Such assemblies typically include associated bus bars, interconnections and supporting structures used for the distribution of electrical power. Low voltage switchgear and switchboards operate at voltages of up to 600 volts and with continuous currents up to 5000 amps or higher. Such devices are also designed to withstand short circuit currents ranging up to 200,000 amps (3 phase RMS symmetrical).
Typical switchgear equipment is composed of a lineup of several metal enclosed sections. Each section may have several circuit breakers stacked one above the other vertically in the front of the section with each breaker being enclosed in its own metal compartment. Each section has a vertical or section bus which supplies current to the breakers within the section by short horizontal branch busses, also referred to as run-in busses. The vertical bus bars in each section are supplied with current by a horizontal main bus bar that runs through the lineup of metal enclosed sections. A typical arrangement includes bus bars for each electrical phase of a multi-phase system which may include three power phases and a neutral.
Circuit breakers used in switchgear enclosures may be of a stationary or a draw out construction. In a stationary construction, the circuit breaker is bolted to the structure both mechanically and electrically and is not removable without the use of tools. A draw out construction of a circuit breaker typically is removable without the use of tools. However, draw out breakers use plug-in electrical connections to the switchgear bus, generally referred to as primary disconnects, and are located at the rear wall of the circuit breaker compartment. In addition, the circuit breaker may have plug-in connections for control and communication wiring typically called secondary disconnects. In order to function properly, the draw out circuit breaker must rack in and out of the circuit breaker compartment without binding and with proper alignment of the primary and secondary disconnects to insure proper engagement for good electrical connection.
Thus there is a need for a switchgear enclosure for electrical equipment having at least one circuit breaker compartment for receiving a circuit breaker that will align the circuit breaker properly with the primary disconnects and secondary disconnects in the enclosure. There is a further need for an alignment arrangement for a circuit breaker cradle configured to mount in a switchgear enclosure that would align the cradle horizontally and vertically in the switchgear enclosure and align the cradle properly front to back within the switchgear enclosure. There is a further need for a circuit breaker cradle to be self aligning for installation in a switchgear enclosure.
There is provided an enclosure for electrical equipment. The enclosure includes a pair of substantially parallel support members. At least one mounting base is coupled to the members, with the mounting base defining a first notch in the mounting base and a second notch in the mounting base. A cradle is configured to mount in the enclosure, with the cradle having a rear end defining a pair of mounting flanges, with each flange having at least one alignment tab corresponding to the respective notch. Wherein the cradle is supported in the enclosure and aligned in the enclosure by engaging the tabs with the notches and the cradle is aligned front to back by the flanges contacting the mounting base. Additional mounting bases can be installed with additional alignment tabs defined on the cradle corresponding to the additional mounting base notches. The circuit breaker cradle can be electrically grounded to the enclosure by metallic fasteners securing the cradle to the mounting base and extending into the frame members of the enclosure.
There is further provided an alignment arrangement for a circuit breaker cradle configured to mount in a enclosure. The enclosure includes a mounting base. The alignment arrangement includes a first cradle alignment notch defined in one end of the mounting base. A second cradle alignment notch is defined in another end of the mounting base. A first alignment tab is defined on one edge of the cradle and positioned on the cradle to align with the first cradle alignment notch. A second alignment tab is defined on another edge of the cradle and positioned on the cradle to align with the second cradle alignment notch. The two alignment tabs will mate and interlock with the two notches in the mounting base to align the cradle horizontally and vertically in the enclosure.
There is additionally provided a method for installing a circuit breaker in a switchgear enclosure, with the switchgear enclosure having a pair of vertical frame members. The method comprises the steps of providing a mounting base defining a first cradle alignment notch in one end of the mounting base and a second cradle alignment notch defined in another end of the mounting base. Coupling the mounting base to each of the vertical frame members. Providing a circuit breaker cradle, with the cradle having a rear end defining a pair of mounting flanges. Each mounting flange has at least one alignment tab with the tabs corresponding to the alignment notches. Coupling the circuit breaker cradle to the mounting base and each vertical frame member wherein the cradle is aligned horizontally and vertically by the tabs mating and interlocking with the notches and the cradle is aligned front to back by the flanges contacting the mounting base. Installing a circuit breaker in the cradle. Another embodiment of the method, the circuit breaker is a draw-out circuit breaker. Another embodiment of the method includes the steps of providing fasteners and installing the fasteners in the flanges, through the mounting base, into the vertical frame members, wherein the cradle is electrically grounded.
There is further provided an enclosure for enclosing electrical equipment. The enclosure includes a pair of spaced apart support members. At least one mounting base is coupled to the support members, the base including first and second alignment features. A cradle, including a third and fourth alignment feature, is alignable and engageable with the first and second alignment features respectively. The cradle is then aligned and supported in the enclosure when the alignment features are engaged.
Before describing the exemplary embodiments of an arrangement for aligning a circuit breaker cradle in a switchgear enclosure, several comments are appropriate. Switchgear assemblies and panel board assemblies typically include vertical (section) bus bars to distribute electric power within the enclosures. In a short circuit condition, extreme magnetic forces are created in the bus bars as a result of short circuit currents up to and including 200,000 amps symmetrical RMS flowing through each bus bar. In a three phase power system (typically) as a certain circuit current flows through such bus bars, magnetic forces between adjacent bus bars tend to move such bus bars laterally (perpendicular) to the current flow. The circuit breakers are installed in the switchgear enclosures to react to short circuit conditions and open the circuits to minimize damage to the enclosure and related electrical equipment.
One type of circuit breaker is referred to as a draw-out circuit breaker. A draw-out circuit breaker typically has plug in electrical connections to the bus bars in the enclosure and are typically referred to as primary disconnects. The primary disconnects are located on the rear wall of the circuit breaker compartment. Additional control wiring and communication wiring plug-in connections may also be provided and are referred to as secondary disconnects.
A draw-out circuit breaker compartment typically includes guide rails to locate and support the breaker in a racking mechanism for moving the breaker along the rails between the disconnect, test and connection positions. The circuit breaker compartments may also have additional features such as shutters and interlocks. The draw-out circuit breaker rails, racking devices and additional features may be housed in a separate framework referred to as a circuit breaker cradle 40. The circuit breaker cradle 40, when assembled into the switchgear enclosure 10, becomes a part of the circuit breaker compartment 15.
Referring now to the figures,
The mounting base 22, typically is a molded piece composed of electrically insulating material, such as thermoplastic, or glass reinforced polyester, or other suitable electrically insulating material that has a characteristic of the appropriate strength for the intended use. The alignment notches 28, 30 in the mounting base 22 are one component of the alignment arrangement 20.
The circuit breaker cradles 40 are secured to the respective mounting bases 22, 62 with fasteners 50, such as screws or the like. The fasteners 50 are configured to extend through the mounting flanges 44 and into the mounting base 22, 62. The fasteners are also configured to pass through clearance holes formed in the mounting base and coupled to the frame members 12 of the enclosure to electrically ground the cradle 40 to the enclosure 10.
With the circuit breaker cradle 40 installed in the circuit breaker compartment 15, a draw-out circuit breaker CB can be installed in the circuit breaker cradle 40 in the circuit breaker compartment 15. (See
It should be understood that the size of the circuit breaker cradle 40 and the respective mounting bases 22, 62 are dependent upon the type of circuit breaker CB to be installed in the cradle 40 within the circuit breaker compartment 15. However, the alignment arrangement 20 described above will function with any appropriately side components described herein.
For purposes of this disclosure, the term “coupled” means the joining of two components (electrical or mechanical) directly or indirectly to one another. Such joining may be stationary in nature or movable in nature. Such joining may be achieved with the two components (electrical or mechanical) and any additional intermediate members being integrally formed as a single unitary body with one another or with the two components or the two components and any additional member being attached to one another. Such joining may be permanent in nature or alternatively may be removable or releasable in nature
Thus, there is provided an alignment arrangement for a circuit breaker cradle to self-align and mount in a switchgear enclosure. The foregoing description of embodiments have been presented for purposes of illustration and description and is not intended to be exhaustive nor to be limited to the precise forms disclosed and modifications and variations are possible in light of the above teaching and may be acquired by practice of the invention. The embodiments are chosen and described in order to explain the principles and practical application to enable one skilled in the art to utilize the alignment arrangement in various embodiments and various modifications that are suited to the particular use contemplated. It is intended that the scope of the alignment arrangement be defined by the claims appended hereto and their equivalents.