MX2011008493A - Motor control center and bus assembly therefor. - Google Patents

Abstract

A bus assembly is provided for a motor control center (MCC). The MCC includes an enclosure, an electrical switching apparatus, such as a circuit breaker, which is removably coupled to the enclosure, and at least one subunit. The bus assembly includes a horizontal bus, a number of vertical buses, and a number of short circuit protective devices (SCPDs), such as fuses or circuit breakers. The horizontal bus is electrically connected to the circuit breaker, each vertical bus electrically connects a corresponding subunit to the horizontal bus, and each SCPD is disposed between the horizontal bus and a corresponding one of the vertical buses. The SCPDs reduce the peak current level and arc flash energy experienced by the subunits, and relatively quickly clear the arcing event.

Description

CENTER OF CONTROL OF ENGINES AND ASSEMBLY OF CONNECTING BARS FOR THE SAME Countryside The disclosed concept generally refers to engine control system and, more particularly, to engine control centers. The disclosed concept also refers to connector bar assemblies for motor control centers.

Background Information Motor control centers are used, for example, in some commercial and industrial applications to distribute electric power to a variety of loads (e.g., without limitation, relatively high power electric motors, pumps, and other loads).

Figure 1, for example, shows a portion of a motor control center 10. The motor control center 10 includes a multi-compartment housing 12 for receiving a plurality of motor control modules 14, 16, 18, 20 , 22, 24, commonly referred to as "buckets". Typically, each bucket (see, e.g., bucket 22 of Figure 1; also shown in Figure 2) is a removable sub-unit, which is pulled out by pulling it out, having it or being installed behind a 26. The door 26 is preferably coupled to the housing 12 by hinges 28 (shown in phantom line drawing in Figure 1) to allow access to motor control components of the tray 22 while it is installed in the housing 12 For example and without limitation, the door 26 allows access to a circuit breaker assembly 30, a blade indicator 32, a shutter indicator 34, and a line contact actuator 36. When the tray 22 is fully installed and electrically connected behind the door 26 of the housing 10, an operator can operate a disconnection handle 38. In a de-energized state of the motor control center 10, the operator can operate an isolation feature by moving a c orredera 40 and inserting a handle 42 through a hole 43 in the door 26 to access the line contact actuator 36 to move several line contacts (see, for example, the blade contacts 46, 48, 50 of the trough 22 of FIG. 2) to an isolated position outside (see FIG. 2) electrical contact with a connector bar assembly 60 (partially shown in phantom line drawing in FIG. 2; see also FIG. 3) of the motor control center 10.

A portion of a circuit diagram for the motor control center 10, according to current industry standard practice, is shown in Fig. 3. In the example of Fig. 3, the motor control center 10 is for a relatively low voltage system (e.g., without limitation, up to 600 V), including a main three phase busbar assembly 60 having a horizontal bus bar 62, which is powered by a main circuit breaker 30 and with capacity nominal, for example and without limitation, up to 3,200 A. More specifically, the motor control center 10 is made of a series of structures, each housing a vertical connector bar 64 of nominal capacity typically, for example and without limitation, 300, 600, 800 or 1,200 A. Sub-units, for example in the form of motor control starting units 70 or feeder units (not shown) of various sizes and different configurations, s or electrically connected to the vertical connector bars 64 by a suitable electrical connector assembly (indicated generally by reference 66 in Figure 3) such as, for example and without limitation, a male / female blade connector assembly. According to the applicable safety rules, the connecting rod assembly 60 of the motor control center 10 has a nominal capacity such as to support arcing events with an associated short circuit current level of around 42, around 65 and around 100 kA, for a time duration of around 50 ms for products of NEMA capacity, and up to 1 second for products with IEC capacity. The main circuit breaker 30 typically provides short circuit protection for the motor control center 10. The quench time to extinguish the arcing event is about 50 ms (e.g., about three cycles) for a NEMA application. The motor control centers 10 are described in greater detail, for example, in the patent applications US 2009/0086414, 2008/0258667, 2008/0023211 and 2008/0022673, of the same applicant as the present one, incorporated in the preference by reference.

Safety is a primary concern in the electrical industry. A point of focus refers to electrical safety with respect to uncontrolled arc scintillation events within motor control centers. Arc scintillation is a dangerous condition associated with the explosive release of energy from an electric arc (eg, arcing event). This failure can be the result of many factors including, for example and without limitation, tools that are dropped, accidental contact with electrical systems, accumulation of conductive dust, corrosion, or improper work procedures. A relatively minor event initiated within a motor control center sub-unit, for example, caused by a scintillation to ground, can rapidly propagate into a phase-to-phase fault and then a three-phase arc-forming fault, to scale total, the arc potentially jumping to the line side of the circuit breaker or fuse of the sub-unit. Therefore, the arc scintillation energy can be considerable and pose a serious safety hazard.

There is room for improvement in the motor control centers, and in connector bar assemblies for them.

Compendium These and other needs are met by means of embodiments of the disclosed concept, which are directed to an assembly of connecting rods for a motor control center where, among other benefits, the assembly of connecting rods limits the arc scintillation energy, with This reduces short circuits and other electrical voltages on the components of the motor control center and the connector bars, which in turn allow the implementation of sub-unit configurations and connector bus assemblies for more compact motor control centers.

As an aspect of the disclosed concept, an assembly of busbars for a motor control center is provided. The motor control center includes a housing, an electrical switch apparatus removably coupled to the housing, and at least one sub-unit. The connecting rod assembly comprises: a horizontal connecting rod structured to be electrically connected to the electric switch apparatus; several vertical connecting rods, each structured to connect electrically to a corresponding sub-unit of the at least one sub-unit of the horizontal connecting rod; and various short circuit protective devices, each being disposed between the horizontal connecting rod and a corresponding connecting rod of the vertical connecting rods.

The motor control center may be structured to support an arcing event. The arcing event may have an associated peak current level and associated arc scintillation energy, where each of the short circuit protective devices is structured to reduce the peak current level and arc scintillation energy experienced by the arc. the sub-unit. The motor control center may have a nominal capacity to withstand the arcing event for a predetermined duration, wherein the short circuit protective devices are structured to extinguish the arcing event from a corresponding connecting rod of the vertical connector bars faster than the predetermined duration.

The various short circuit protective devices can be several circuit breakers or fuses. The short-circuit protection devices can be plug-in modules that are removably connected to the horizontal connector bar.

Also disclosed is an engine control center that incorporates the aforementioned connector bar assembly.

Brief Description of the Drawings A full understanding of the disclosed concept can be achieved from the following description of the preferred embodiments when read in conjunction with the accompanying drawings, in which: Figure 1 is an isometric view of a portion of a motor control center; Fig. 2 is an isometric view of one of the buckets of the motor control center of Fig. 1, also showing a portion of the bus bar assembly for motor control center in phantom line drawing; Figure 3 is a schematic diagram for the motor control center and the busbar assembly for the same of Figure 2; Figure 4 is a schematic diagram of a motor control center and an assembly of busbars therefor, according to an embodiment of the disclosed concept; Y Figure 5 is a schematic diagram of a motor control center and an assembly of link bars for the same, according to another embodiment of the disclosed concept.

Description of Preferred Forms of Realization As used herein, the term "engine control center" refers to any known or suitable low voltage control equipment, including, but not limited to, switchboards.

As used herein, the term "low-voltage control equipment" refers to any known or suitable electrical device having a horizontal busbar that feeds a series of vertical busbars and electrical switching devices or sub-units and expressly includes , but without limitation, motor control centers and switchboards.

As used herein, the statement that two or more parts are "connected" or "coupled" will mean that the parts are joined either directly or joined through one or more intermediate portions. In addition, as used herein, the manifestation that two or more parties are "joined" will mean that the parties are directly united.

As used herein, the term "several" will mean one or an integer greater than one (i.e., a plurality).

Figures 4 and 5 show schematic diagrams of an assembly of link bars 100 for a motor control center 200 according to the disclosed concept. The engine control center includes a housing 202 (partially shown in simplified form in Figures 4 and 5, see also, for example and without limitation, housing 12 of Figure 1), an electrical switch apparatus such as, for example and without limitation, a circuit breaker 204, which is removably coupled to the housing 202, and at least one sub-unit 300, 302, 304, 306.

The connector rod assembly 100 preferably includes a horizontal connector bar 102 electrically connected to the aforementioned electrical switch apparatus (e.g., without limitation, a circuit breaker 204). Several vertical connecting rods 104, 106, 108, 110 (four are shown in the examples and are described herein) electrically connect with corresponding sub-units 300, 302, 304, 306 with the horizontal connecting rod 102. Several of the devices short circuit protectors (SCPDs) 120, 122, 124, 126 (four are shown in the examples and described herein) are employed between the horizontal connecting rod 102 and corresponding vertical connecting bars 104, 106, 108, 110. In the non-limiting example of Figure 4, the connector bar assembly 100 includes four vertical connector bars 104, 106, 108, 110 having sub-units 300, 302, 304, 306 and being connected by means of SCPDs 120, 122, 124, 126, respectively, to the horizontal connecting rod 102. However, it will be appreciated that any alternative, known or suitable number and / or configuration of vertical connecting rods, sub-units and / or SCPDs can be employed, without depart from the scope of the disclosed concept. For example and without limitation, in Figures 4 and 5 the sub-units are starting units 300, 302, 304, 306, although other types and / or configurations of sub-units may be used (e.g., without limitation, power units (not shown)).

Among other benefits, each of the SCPDs 120, 122, 124, 126 is structured to protect the corresponding vertical connecting rod 104, 106, 108, 110 and the associated starting unit 300, 302, 304, 306, respectively. More specifically, the SCPDs 120, 122, 124, 126 limit the arc scintillation energy, thereby providing the motor control center 200 with improved arc scintillation protection. That is, the motor control centers 200 are typically structured to support certain arcing events having associated electrical current levels, including a peak current level and an associated arc scintillation energy. In addition, the motor control center 200 has a nominal capacity to withstand such an arcing event for a predetermined duration. According to the disclosed concept, each of the SCPDs 120, 122, 124, 126 reduces the peak current levels and arc scintillation energy experienced by the associated sub-units 300, 302, 304, 306 (e.g., without limitation, starter units) and rapidly extinguishes the arcing event of the corresponding vertical connecting rod 104, 106, 108, 110.

In a non-limiting example, which is provided solely for purposes of illustration and is not intended to limit the scope of the disclosed concept, the engine control center 200 is a relatively low voltage, three-phase system (e.g., up to about 600 V) having a three-phase horizontal busbar 102 with rated capacity of up to about 3,200 A, and being powered by a primary or main circuit breaker 204 with a rated capacity of about 3,200 A. The typical rated vertical busbar ratings are 300, 600, 800 and 1,200 A. The motor control center 200 has a rated capacity to withstand a short circuit current of a level typically in the range of about 42, about 65 and about 100 kA for a duration of time of around 50 ms for NEMA products, and up to 1.0 second for IEC products. The actual theoretical peak current levels for such motor control centers 200 can approach up to 231 kA, or more. The extinction time for such a system to extinguish the arcing condition is around 50 ms (eg, about three cycles) for a NEMA application. The SCPD (see, for example, SCPD 120) limits the peak current level to about 50 kA, and an extinction time of about half a cycle (e.g., without limitation, about 8 ms). Accordingly, the arc scintillation energy associated with the arcing event can be advantageously predicted as being limited to a level of about 1.2 Cal / cm2. Therefore, it will be appreciated that the assembly of connector bars 100 disclosed, and in particular the short circuit protective devices (e.g., without limitation, the SCPDs 120, 122, 124, 126) for them, substantially reduce the levels of arch scintillation energy of the state of the art and thereby considerably improve the arc scintillation protection for the motor control center 200.

Preferably, each of the short circuit protective devices (see, for example, SCPD 120) is in the form of a plug-in module removably connected to the horizontal connector bar 102 of the connector bar assembly. In the example of figure 4, the plug-in modules are fuses 120, 122, 124, 126, which are removably electrically connected to the horizontal connecting rod 102 and / or the corresponding vertical connecting rod (see, for example , the vertical connecting rod 104) by means of any known electrical connector (s) or suitable (s) 130, 140 (e.g., without limitation, male / female electrical connectors (not shown)) .

As previously noted, it will be appreciated that any number, type and / or configuration of alternative short circuit protective device 120, 122, 124, 126, known or suitable, may be employed without departing from the disclosed concept. For example and without limitation, in the example of Figure 5, the connector bar assembly 100 'employs SCPDs which are circuit breakers 120', 122 ', 124', 126 'that provide the above-mentioned protection against short circuit and scintillation from arc to a corresponding vertical connecting rod 104, 106, 108, 110 and associated sub-unit (s) 300, 302, 304, 306 (e.g., without limitation, feeder units; boot units (shown)), respectively. Preferably, but not necessarily, the circuit breakers 120 122 ', 124', 126 ', such as the fuses 120, 122, 124, 126 discussed hereinabove with respect to the example of Figure 4, form modules that they are electrically connected removably between the horizontal connecting rod 102 and the corresponding vertical connecting rod (see, for example, the vertical connecting rod 104) by suitable electrical connectors 130 ', 140'.

The SCPDs 120, 122, 124, 126 (FIG. 4), 120 ', 122', 124 ', 126' (FIG. 5) also provide an advantageous security feature insofar as the units can be removed from a rack (v. gr., to be removed) and placed on the shelf while the operator is securely positioned behind a dead front door of the motor control center 200. Specifically, the door acts as a barrier protecting the operator from arc twinkling. and the associated effects of the outbreak. In other words, the disclosed SCPD concept can be implemented with various security features of the shelf systems described, for example and without limitation, in publications US 2009/0086414, 2008/0258667, 2008/0023211 and 2008/0022673, which are incorporated herein by reference.

In addition to the aforementioned benefits, it will be appreciated that, by reducing the mechanical and electrical stresses of the short circuit on the vertical busbars 104, 106, 108, 110 and other components of the motor control center 200, the disclosed concept achieves the capacity of develop relatively compact connector and sub-unit bar configurations. By way of example and without limitation, typically electrically insulated structural supports (e.g., clamps) (not shown, but generally well known) are typically required for vertical connector bars 104, 106, 108, 110 of the control center of engines 200. Traditionally, relatively expensive materials have been employed such as, for example, polyester reinforced with high strength glass or thermoset plastic material known or suitable for providing the required electrical insulation as long as they are capable of withstanding the arc scintillation energy and the associated forces of the pop. With reduced forces (eg, without limitation, up to 25% reduction or more) achieved by the assembly of connector bars 100 disclosed, more readily available and cost-effective materials such as, for example, can be employed. example and without limitation, thermoplastic materials, to provide the necessary electrical insulation. Additionally, the placement (eg, spacing) of the structural support (e.g., without limitation, steel clamps (not shown, but generally well known)) is dictated by the different nominal ratings of the connector bars. (e.g., without limitation, 42, 65, 100 kA). In other words, to support the higher associated forces, more clamps are typically added as the nominal capacity of the connector bars increases. For example and without limitation, for a nominal capacity of 42 kA, the clamps are generally arranged (eg, spaced apart) to about 18 inches (45.72 cm); for a nominal capacity of 65 kA the clamps are arranged at about 12 inches (30.48 cm) apart, and for 100 kA the clamps are arranged at about every 6 inches (15.24 cm). However, the reduced forces associated with the disclosed motor control center 200 and the assembly of link bars 100 therefor allow for 42 kA clamp configuration (e.g., without limitation, every 18 inches (45.72 cm )) becomes standard.

Therefore, it will be appreciated that the sub-units 300, 302, 304, 306 of the engine control center (e.g., without limitation, feeder units; starting units (shown)), the SCPDs 120, 122, 124 , 126 (FIG. 4), and vertical connector bar structures 104, 106, 108, 110 can be configured narrower. For example and without limitation, the nominal capacity category of DKSY2 component series recognized by UL can be used to establish the appropriate compact configuration. In this way, as an example, for requirements of a system of 100 kA to 480 V and the most demanding systems of 600 V, the starting units 300, 302, 304, 306 of the motor control center and the feeder units (not shown) can use a circuit breaker of lower rated capacity, and for 600 V systems, the need for an additional current limiting accessory can be eliminated.

Although specific embodiments of the disclosed concept have been described in detail, those skilled in the art will appreciate that various modifications and alternatives to those details may be developed in light of the overall teachings of the disclosure. Accordingly, the particular arrangements disclosed are intended to be illustrative only and not limiting as to the scope of the disclosed concept, to which the full scope of the appended claims and any and all equivalents thereof must be given.

Claims (20)

1. A connector bar assembly for a motor control center, said motor control center including a housing, an electrical switch apparatus removably coupled to said housing, and at least one sub-unit, said connector bar assembly comprising: a horizontal connector bar structured to be electrically connected to said electrical switch apparatus; several vertical connector bars, each structured to connect electrically to a corresponding sub-unit of said at least one sub-unit to said horizontal connecting rod; Y several short-circuit protective devices, each one arranged between said horizontal connecting rod and a corresponding connecting rod of said vertical connecting rods.

2. The connector bar assembly of claim 1, wherein said motor control center is structured to support an arcing event; wherein said arc-forming event has a peak current level and associated arc scintillation energy; and wherein each of said short circuit protective devices is structured to reduce the peak current level and the arc scintillation energy experienced by said at least one subunit.

3. The connector bar assembly of claim 2, wherein said short circuit protective devices limit the peak current level to about 50 kA.

4. The connector bar assembly of claim 2, wherein said motor control center has a nominal capacity to support said arcing event for a predetermined duration; and wherein said short circuit protective devices are structured to extinguish said arcing event of said corresponding connecting rod of said vertical connecting rods more rapidly than said predetermined duration.

5. The connector bar assembly of claim 4, wherein said short circuit protective devices are structured to extinguish said arcing event in about 8 ms.

6. The connector bar assembly of claim 1, wherein said various short circuit protective devices are plural circuit breakers.

7. The connector bar assembly of claim 1, wherein said various short circuit protective devices are plural fuses.

8. The connector bar assembly of claim 1, wherein said plural short circuit protective devices are plural plug-in modules removably connected to said horizontal connector bar.

9. The connecting rod assembly of claim 1, wherein said plural vertical connecting rods are a plurality of vertical connecting rods; wherein said at least one subunit is a plurality of subunits; wherein said various short circuit protective devices are a plurality of short circuit protective devices; and wherein each of said short circuit protective devices is disposed between said horizontal connecting rod and a corresponding connecting rod of said vertical connecting rods in order to electrically connect a corresponding sub-unit of said subunits to said horizontal connecting rod.

10. The connector bar assembly of claim 1, wherein said electrical switch apparatus is a circuit breaker.

11. An engine control center, comprising: a housing; an electrical switch apparatus removably coupled to said housing; at least one sub-unit; Y A connector rod assembly comprising: a horizontal connecting rod connected to said electrical switch apparatus, several vertical connecting rods, each electrically connecting a sub-unit of said at least one sub-unit to said horizontal connecting rod, and several short-circuit protective devices, each one arranged between said horizontal connecting rod and a corresponding connecting rod of said vertical connecting rods.

12. The motor control center of claim 11, wherein said motor control center is structured to support an arcing event; wherein said arc-forming event has a peak current level and associated arc scintillation energy; and wherein each of said short circuit protective devices is structured to reduce the peak current level and the arc scintillation energy experienced by said at least one subunit.

13. The motor control center of claim 12, wherein said short circuit protective devices limit the peak current level to about 50 kA.

14. The motor control center of claim 12, wherein said motor control center has a rated capacity to support said arcing event for a predetermined duration; and wherein said short circuit protective devices are structured to extinguish said arcing event of said corresponding connecting rod of said vertical connecting rods more rapidly than said predetermined duration.

15. The motor control center of claim 14, wherein said short circuit protective devices are structured to extinguish said arcing event in about 8 ms.

16. The motor control center of claim 11, wherein said various short circuit protective devices are several circuit breakers.

17. The motor control center of claim 11, wherein said various short circuit protective devices are plural fuses.

18. The motor control center of claim 11, wherein said various short circuit protective devices are plural plug-in modules removably connected to said horizontal connecting rod.

19. The motor control center of claim 11, wherein said plural vertical connecting rods are a plurality of vertical connecting rods; wherein said at least one subunit is a plurality of subunits; wherein said various short circuit protective devices are a plurality of short circuit protective devices; and wherein each of said short circuit protective devices is disposed between said horizontal connecting rod and a corresponding connecting rod of said vertical connecting rods in order to electrically connect a corresponding sub-unit of said subunits to said horizontal connecting rod.

20. The motor control center of claim 11, wherein said electrical switch apparatus is a circuit breaker.