Unless otherwise indicated herein, the materials described in this section are not prior art to the claims in this application and are not admitted to be prior art by inclusion in this section.
The present disclosure is generally directed to bus connector assemblies for use with an electric power switching apparatus. More specifically, the present disclosure is generally directed to a bus connector for use with an electric power switching apparatus with isolation means such as a transfer switch or a circuit breaker. Such connector assemblies allow the switching apparatus to achieve a very high withstand current ratings. For example, the high withstand current rating may be 100,000 amperes or above. In one arrangement, the present disclosure relates generally to a connector assembly arrangement that may be used for interconnection between a device and a bus structure. More particularly, the connector assembly arrangement may be used in an isolation-bypass automatic transfer switch. However, aspects of the present disclosure may be equally applicable in other scenarios as well.
An automatic transfer switch is designed to provide a continuous source of power for critical loads by automatically transferring from a normal power source to an emergency power source when the normal power source falls below a preset limit. Automatic transfer switches are in widespread use in, e.g., airports, subways, schools, hospitals, military installations, industrial sites, and commercial buildings equipped with secondary power sources and where even brief power interruptions can be costly or perhaps even life threatening. Transfer switches operate, for example, to transfer a power consuming load from a circuit with a normal power supply to a circuit with an auxiliary power supply. A transfer switch can control electrical connection of utility power lines and the diesel generator to facility load buses. In certain installations, the transfer switch automatically starts a standby generator and connects the standby generator to the load bus upon loss of utility power. In addition, the transfer switch can automatically reconnect the utility power to the load bus if utility power is reestablished.
Automatic transfer switches are typically of two types: (i) an automatic transfer switch comprised of a single switching apparatus mounted in an enclosure; and (ii) an automatic transfer switch interconnected with a redundant switch (e.g., manual or automatic switch) mounted in a single enclosure or in multiple adjacent enclosures. This second configuration is typically referred to as a bypass-isolation transfer switch. Typically, one or both switches are provided with isolation means allowing disconnecting the switch from a bus structure and removal out of the enclosure.
A bus connector configured for receiving a bus is provided. In an example embodiment, the bus connector includes (i) a plurality of contact fingers configured to engage with the bus and (ii) a connector frame, wherein the connector frame is configured to hold the plurality of contact fingers. The plurality of contact fingers comprise a first set of contact fingers and a second set of contact fingers arranged at least substantially parallel to one another, wherein the first set and second set clamp the bus when the bus is inserted between the first set and the second set. The plurality of contact fingers includes contact fingers of a first length and contact fingers of a second length, wherein the second length is different than the first length.
In another example embodiment, the bus connector includes (i) a plurality of contact fingers configured to engage with the bus and (ii) a connector frame, wherein the connector frame is configured to hold the plurality of contact fingers. The plurality of contact fingers comprise a first set of contact fingers and a second set of contact fingers arranged at least substantially parallel to one another, wherein the first set and second set clamp the bus when the bus is inserted between the first set and the second set. Further, each set of contact fingers comprises (i) a plurality of contact fingers that create a first contact point at a first distance from the connector frame and (ii) a plurality of contact fingers that create a second contact point at a second distance from the connector frame different than the first distance.
In yet another example embodiment, the bus connector includes (i) a plurality of contact fingers configured to engage with the bus and (ii) a connector frame, wherein the connector frame is configured to hold the plurality of contact fingers. The plurality of contact fingers comprise a first set of contact fingers and a second set of contact fingers arranged at least substantially parallel to one another, wherein the first set and second set clamp the bus when the bus is inserted between the first set and the second set. Further, the plurality of contact fingers creates at least two different points of contact between the contact fingers and the bus when the bus is inserted into the bus connector.
The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the figures and the following detailed description.
a-c are top plan views of the bus connector of
a is a top plan view of the bus connector of
b is a magnified top plan view of the bus connector of
a is a top plan view of a first example contact finger and a second example contact finger of the bus connector of
b is a perspective view of the first example contact finger of
c is a perspective view of the second example contact finger of
In the following detailed description, reference is made to the accompanying drawings, which form a part hereof. In the drawings, similar symbols typically identify similar components, unless context dictates otherwise. The illustrative embodiments described in the detailed description, drawings, and claims are not meant to be limiting. Other embodiments may be utilized, and other changes may be made, without departing from the spirit or scope of the subject matter presented herein. It will be readily understood that the aspects of the present disclosure, as generally described herein, and illustrated in the figures, can be arranged, substituted, combined, separated, and designed in a wide variety of different configurations, all of which are explicitly contemplated herein.
1. Overview
As mentioned above, automatic transfer switches are typically of two types: (i) an automatic transfer switch comprised of a single switching apparatus mounted in an enclosure; and (ii) an automatic transfer switch interconnected with a redundant manual, or automatic, switch mounted in a single enclosure, or in multiple adjacent enclosures. The second configuration is typically referred to as bypass-isolation transfer switch. Typically, one or both switches are provided with isolation means allowing disconnecting the switch from a bus structure and removal out of the enclosure. The removable switch is typically provided with connectors that connect or disconnect a switch from the fixed bus structure within the enclosure. Although certain transfer switches or circuit breakers may utilize connectors of various designs, a connector designed to withstand very high short circuit forces can employ the electromagnetic forces to keep connector contacts closed by clamping onto the bus.
It would be desirable to provide a cost-effective connector design that is easy to assemble and install, scalable to different bus sizes, and configurable for different short circuit current levels. Further, there is also a general need for a connector with a low insertion force to reduce stress exerted onto the connector parts and to reduce the overall size and weight of isolation mechanism components.
An example bus connector in accordance with the present disclosure may include a plurality of contact fingers configured to engage with a bus. The plurality of contact fingers may include a first set of contact fingers and a second set of contact fingers arranged substantially parallel to one another, wherein the first set and second set clamp the bus when the bus is inserted between the first set and the second set. The bus connector may further include a connector frame, wherein the connector frame is configured to hold the plurality of contact fingers. Further, the plurality of contact fingers comprise contact fingers of a first length and contact fingers of a second length, wherein the second length is different than the first length. The bus may encounter a frictional force between the bus and the contact fingers as the bus is being inserted between the first set and the second set. The plurality of contact fingers may be arranged such that a total frictional force is distributed between (i) a first point of contact formed by the contact fingers of the first length and (ii) a second point of contact formed by the contact fingers of the second length.
Beneficially, the disclosed bus connector reduces the insertion force required to insert a moving bus into the bus connector. Further, the disclosed bus connector beneficially is easy to assemble and install, scalable to different bus sizes, and configurable for different short circuit current levels.
The disclosed bus connector may be used with an electric power switching apparatus. For example, the disclosed bus connector may be used with an electric power switching apparatus with isolation means such as a transfer switch, or a circuit breaker. In one arrangement, the present disclosure relates generally to a connector assembly arrangement that may be used for interconnection between a device and a bus structure (e.g., in an isolation-bypass automatic transfer switch). However, aspects of the present disclosure may be equally applicable in other scenarios as well.
2. Example Bus Connector
With reference to
In accordance with an example embodiment, the plurality of contact fingers 102 may include contact fingers of a first length and contact fingers of a second length different than the first length. For instance, as shown in
The first set 104 and the second set 106 are capable of outward deflection when the bus 11 is pushed inwardly with respect to the contact fingers. When the initial friction between the contact fingers 102 and the leading edge 11a of the moving bus 11 is overcome by an insertion force, the moving bus 11 slides in until fully engaged as shown in
As mentioned above, the first set 104 and second set 106 of contact fingers are at least substantially parallel to one another. In an example embodiment, the first set 104 and second set 106 of contact fingers arranged in parallel to each other with the mowing bus in between the contact fingers when fully engaged. This configuration is optimal for magnetic clamp-on force. Beneficially, by being at least substantially parallel, the contact fingers can clamp onto a generally flat moving bus. However, in general, the contact fingers may be arranged in any suitable formation to clamp a given bus.
Typically, higher currents require more contact fingers to withstand current without overheating. The basic configuration of the disclosed bus connector is beneficially scalable as needed for specific application requirements. For instance, the contact fingers and springs can be used in various multiples depending on how much current is passing through the connectors. Further, the contact springs can be used in parallel to multiply effective spring force exerted onto the contact fingers. Generally, higher finger forces allow for better electrical connections and higher currents without overheating components. Therefore, it is possible to lower the overall cost of a switch device by using fewer number and smaller sizes of connector components.
Returning to the figures,
In an example embodiment, the bus connector 13 may be pivoted to move about an axis, so as to allow the bus connector to pivot and align with moving bus 11. For example, as shown in
When the moving bus is inserted into the bus connector, an insertion force is applied to the bus. In order to initially overcome the frictional force between the contact fingers and the moving bus, the insertion force should be greater than the frictional force. As mentioned above, the plurality of contact fingers may include contact fingers of a first length and contact fingers of a second length different than the first length. By using contact fingers of different lengths, the initial insertion force required to insert a moving bus into a bus connector may be reduced. By having contact fingers of different lengths, this frictional force beneficially may be spread out or distributed among two (or perhaps more) contact points. As such, the initial insertion force required to initially overcome the frictional force between the contact fingers and the bus is reduced.
With reference to
In an example embodiment, each contact finger has a contact end having a protrusion extending towards its corresponding contact finger. These protrusions may act to create a point of contact between the contact finger and bus 11 when the bus is inserted. For instance, as illustrated in
In an example embodiment, the contact fingers may be arranged in a staggered arrangement that spreads out or distributes the total frictional force. For instance, the first set and the second set may each comprise contact fingers of the first length and contact fingers of the second length arranged in a staggered formation.
In the example illustrated bus connectors, each set 104, 106 of contact fingers includes (i) a plurality of contact fingers that create a first contact point at a first distance from the connector frame and (ii) a plurality of contact fingers that create a second contact point at a second distance from the connector frame different from the first distance. For instance, in the example embodiment depicted in
Further, the illustrated embodiments depict a connector bus having contact fingers of two different lengths. The initial insertion force required to overcome the frictional force can be further reduced by introducing additional contact fingers of different lengths (or, as discussed above, contact fingers of the same length that define additional different contact points). Thus, in accordance with an example embodiment, the plurality of contact fingers creates two or more different points of contact between the contact fingers and the bus when the bus is inserted into the bus connector. For example, three fingers of different lengths will result in three points of contact (e.g., P1, P2, P3) with each respective contact point resulting in one-third of the total frictional force. Other examples are possible as well.
3. Example Benefits of the Disclosed Methods and Systems
As described above, the proposed bus connector beneficially reduces the insertion force required to insert a moving bus into the bus connector. A reduced insertion force may beneficially reduce stress exerted on the bus connector components. Further, the disclosed bus connector beneficially is less complex to assemble and install, scalable to different bus sizes, and configurable for different short circuit current levels. From a manufacturing point of view, a scalable design with same components used in different configurations offers various advantages. For example, similar methods of assembly can be used. Further, the number of unique part numbers and unique parts in stock can be kept to minimum, thereby minimizing overall manufacturing costs.
4. Conclusion
While various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope being indicated by the following claims, along with the full scope of equivalents to which such claims are entitled. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to be limiting.
Number | Name | Date | Kind |
---|---|---|---|
4684191 | Feher | Aug 1987 | A |
5554040 | Sugiura | Sep 1996 | A |
5618187 | Goto | Apr 1997 | A |
6024589 | Hahn, IV | Feb 2000 | A |
6102754 | Capper | Aug 2000 | A |
6398580 | Lin | Jun 2002 | B2 |
8512057 | Haar | Aug 2013 | B2 |
8723038 | Sakai | May 2014 | B2 |
Number | Date | Country | |
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20150118878 A1 | Apr 2015 | US |