Patent Application
20160260571
The field of the invention relates generally to fusible circuit protection devices, and more specifically to fusible disconnect switch devices configured for higher voltage direct current (DC) industrial applications.
Fuses are widely used as overcurrent protection devices to prevent costly damage to electrical circuits. Fuse terminals typically form an electrical connection between an electrical power source and an electrical component or a combination of components arranged in an electrical circuit. One or more fusible links or elements, or a fuse element assembly, is connected between the fuse terminals, so that when electrical current flowing through the fuse exceeds a predetermined limit, the fusible elements melt and opens one or more circuits through the fuse to prevent electrical component damage.
A variety of fusible disconnect switch devices are known in the art wherein fused output power may be selectively switched from a power supply input. Existing fusible disconnect switch devices, however, have not completely met the needs of the marketplace and improvements are desired. In particular, higher voltage, direct applications present additional demands on fusible switch disconnect devices that are not well met by existing fusible disconnect devices.
Non-limiting and non-exhaustive embodiments are described with reference to the following Figures, wherein like reference numerals refer to like parts throughout the various views unless otherwise specified.
The fusible switching disconnect device 30 may be configured as a compact fusible switching disconnect device such as those described further below that advantageously combine switching capability and enhanced fusible circuit protection in a single, compact switch housing 32. As shown in
The switch contacts 36, 38 are movable between opened and closed positions to electrically connect or isolate the line-side connecting terminal 34 and the fuse contact terminal 40 and hence connect or disconnect the load-side circuitry 24 from the line-side circuitry 22 when desired. When the fusible switching disconnect device 30 is connected to energized line-side circuitry 22, and also when the switch contacts 36, 38 are closed as shown in
When the overcurrent protection fuse 44 is subjected to a predetermined electrical current condition when the switch contacts 38, 38 are closed, however, the overcurrent protection fuse 44, and specifically the fusible element (or fusible elements) therein is configured to permanently open or fail to conduct current any longer, creating an open circuit between the fuse contact terminals 40 and 42. When the overcurrent protection fuse 44 opens in such a manner, current flow through the fusible switching disconnect device 30 is interrupted and possible damage to the line-side circuitry 22 is avoided. In one contemplated embodiment, the fuse 44 may be a rectangular fuse module such as a CUBEFuse™ power fuse module commercially available from Bussmann by Eaton of St. Louis, Mo. In other embodiments, the overcurrent protection fuse 44 may be a cylindrical fuse such as a Class CC fuse, a so-called Midget fuse, or an IEC 10×38 fuse also available from Bussmann by Eaton.
Because the overcurrent protection fuse 44 permanently opens, the overcurrent protection fuse 44 must be replaced to once again complete the current path between the fuse contact terminals 40 and 42 in the fusible switching disconnect device 30 such the power can again be supplied to the load-side circuitry 24 via the fusible switching disconnect device 30. In this aspect, the fusible switching disconnect device 30 is contrasted with a circuit breaker device that is known to provide overcurrent protection via a resettable breaker element. At least in part because the device 30 does not involve or include a resettable circuit breaker element in the circuit path completed in the switch housing 32, the fusible switching disconnect device 30 is considerably smaller than an equivalently rated circuit breaker device providing similar overcurrent protection performance.
As compared to conventional arrangements wherein fusible devices are connected in series with separately packaged switching elements, the fusible switching disconnect device 30 is relatively compact and can provide substantial reduction in size and cost while providing comparable, if not superior, circuit protection performance.
When the compact fusible switching disconnect devices 30 are utilized in combination in a panelboard 26, current interruption ratings of the panelboard 26 may be increased while the size of the panelboard 26 may be simultaneously reduced. The compact fusible disconnect device 30 may advantageously accommodate fuses 44 without involving a separately provided fuse holder or fuse carrier that is found in certain types of conventional fusible switch disconnect devices. The compact fusible disconnect device 30 may also be configured to establish electrical connection to the fuse contact terminals 40, 42 without fastening of the fuse 44 to the line and load-side terminals with separate fasteners, and therefore provide still further benefits by eliminating certain components of conventional fusible disconnect constructions while simultaneously providing a lower cost, yet easier to use fusible circuit protection product 30.
Presently available compact fusible disconnect devices such as Compact Circuit Protection (CCP) devices available from Bussmann by Eaton of St. Louis, Mo. provide the functionality and benefits described thus far in relation to the switch housing 32 and the associated terminals and contacts, but are nonetheless limited in some aspects for particular applications involving higher voltage direct current (DC) power systems. More specifically, presently available compact fusible disconnect devices of otherwise similar type can safely break a DC circuit having a voltage potential of about 125 VDC or less. For DC power systems operating above 125 VDC, the arc energy associated with electrical arcing as the switch contacts 36, 38 are opened or closed increases considerably and exceeds the ability of presently available compact fusible disconnect devices to reliably withstand. Compact fusible disconnect devices are now desired that may operate not only at 125 VDC and above, but also at much higher DC voltages such as 400 VDC, 600 VDC and even 1000 VDC. Improvements are therefore desired.
To address arcing concerns of 125 VDC operation and above, the compact fusible disconnect device 30 of the invention includes a set of magnets 48 arranged to provide an arc deflecting force to more quickly extinguish the arc and its intensity as switching occurs in the switch housing 32. In contemplated embodiments, the set of magnets 48 includes a first pair of magnets 48a and a second pair of magnets 48b arranged to provide an arc deflecting force proximate each of the switch contacts 36 and 38. Also in contemplated embodiments, the first pair of magnets 48 and the second pair of magnets 48 are arranged to provide oppositely directed arc deflection forces proximate each switch contact 36 and 38. By providing two switch contacts 36, 38, the electrical arc is divided over the two locations corresponding to each contact 36 and 38, and via the pairs of magnets 48a, 48b providing the arc deflecting force on each respective contact 36 and 38, electrical arcing is less severe and shorter in duration than it otherwise would be, allowing the compact fusible disconnect device 30 to safely and capably operate to disconnect the line-side circuitry 22 and electrically isolate the load-side circuitry 24 at much higher operating DC voltages beyond the capability of known fusible switch disconnect devices. Voltage potentials as high as 1000 VDC may be reliably and safely disconnected by virtue of the set of magnets 48. In other embodiments, DC voltage potential breaking may still be improved, but to a lesser extent, by providing one pair of magnets instead of two.
A line-side fuse clip 60 may be situated within the switch housing 52 and may receive one of the terminal blades 58 of the fuse module 54. A load-side fuse clip 62 may also be situated within the switch housing 52 and may receive the other of the fuse terminal blades 58. The line-side fuse clip 60 may be electrically connected to a line-side terminal 63 including a stationary switch contact 64. The load-side fuse clip 62 may be electrically connected to a load-side terminal 66.
A rotary switch actuator 68 is further provided on the switch housing 52, and is mechanically coupled to an actuator link 70 that, in turn is coupled to a sliding actuator bar 72. The actuator bar 72 carries a pair of switch contacts 74 and 76. A load-side terminal 78 including a stationary contact 80 is also provided. Electrical connection to power supply or line-side circuitry 22 may be accomplished in a known manner using the line-side terminal 78, and an electrical connection to load-side circuitry 24 may be accomplished in a known manner using the load-side terminal 66. A variety of connecting techniques are known (e.g., box lug terminals, screw clamp terminals, spring terminals, and the like) and may be utilized. The configuration of the line and load-side terminals 78 and 66 shown are exemplary only, and in the example of
Disconnect switching may be accomplished by rotating the switch actuator 68 in the direction of arrow A, causing the actuator link 70 to move the sliding bar 72 linearly in the direction of arrow B and moving the switch contacts 74 and 76 toward the stationary contacts 64 and 80. Eventually, the switch contacts 74 and 76 become mechanically and electrically engaged to the stationary contacts 64 and 80 and a circuit path may be closed through the fuse 54 between the line and load terminals 78 and 66 when the fuse terminal blades 58 are received in the line and load-side fuse clips 60 and 62. This position, wherein the movable switch contacts 74 and 76 are mechanically and electrically connected to the stationary switch contacts 64 and 80 is referred to herein as a closed position wherein the fusible disconnect switch device 50 electrically connects the line-side circuitry 22 and the load-side circuitry 24 through the fuse 54.
When the actuator 68 is moved in the opposite direction indicated by arrow C in
As such, by moving the actuator 68 to a desired position to effect the opened or closed position of the switch contacts, the fuse 54 and associated load-side circuitry 24 may be connected and disconnected from the line-side circuitry 22 while the line-side circuitry 22 remains “live” in full power operation.
Additionally, the fuse module 54 may be simply plugged into the fuse clips 60, 62 or extracted therefrom to install or remove the fuse module 54 from the switch housing 52. The fuse housing 56 projects from the switch housing 52 and is open and accessible so that a person can grasp the fuse housing 56 by hand and pull it in the direction of arrow B to disengage the fuse terminal blades 58 from the line and load-side fuse clips 60 and 62 such that the fuse module 54 is completely released from the switch housing 52. Likewise, a replacement fuse module 54 can be grasped by hand and moved toward the switch housing 52 to engage the fuse terminal blades 58 to the line and load-side fuse clips 60 and 62.
Such plug-in connection and removal of the fuse module 54 advantageously facilitates quick and convenient installation and removal of the fuse 54 without requiring separately supplied fuse carrier elements and without requiring tools or fasteners common to other known disconnect devices. Also, the fuse terminal blades 58 project from a lower side of the fuse housing 56 that faces the switch housing 52. Moreover, the fuse terminal blades 58 extend in a generally parallel manner projecting away from the lower side of the fuse module 54 such that the fuse housing 56 (as well as a person's hand when handling it) is physically isolated from the conductive fuse terminals 58 and the conductive line and load-side fuse clips 60 and 62. The fuse module 54 is therefore touch safe (i.e., may be safely handled by hand without risk of electrical shock) when installing and removing the fuse 54.
Additionally, the disconnect device 50 is rather compact and can easily occupy less space in a fusible panelboard assembly, for example, than conventional in-line fuse and circuit breaker combinations. In particular, CUBEFuse™ power fuse modules occupy a smaller area, sometimes referred to as a footprint, in the panel assembly than non-rectangular fuses having comparable ratings and interruption capabilities. Reductions in the size of panelboards are therefore possible, with increased interruption capabilities.
In ordinary use, the circuit is preferably connected and disconnected at the switch contacts 64, 74, 76 and 80 rather than at the fuse clips 60 and 62. Electrical arcing that may occur when connecting/disconnecting the circuit may be contained at a location away from the fuse clips 60 and 62 to provide additional safety for persons installing, removing, or replacing fuses. By opening the disconnect module 50 with the switch actuator 68 before installing or removing the fuse module 54, any risk posed by electrical arcing or energized metal at the fuse and housing interface is eliminated. The disconnect module 50 is accordingly believed to be safer to use than many known fused disconnect switches.
The disconnect switching device 50 includes still further features, however, that improve the safety of the device 50 in the event that a person removes the fuse module 54 without operating the actuator 68 to disconnect the circuit through the fuse module 54.
As shown in
In the exemplary embodiment shown, the fuse housing 56 includes a recessed guide rim 84 having a slightly smaller outer perimeter than a remainder of the fuse housing 56, and the guide rim 84 is seated in the switch housing receptacle 82 when the fuse module 54 is installed. It is understood, however, that the guide rim 84 may be considered entirely optional in another embodiment and need not be provided.
The switch housing receptacle 82 further includes a bottom surface 86, sometimes referred to as a floor, that includes first and second openings 88 formed therein and through which the fuse terminal blades 58 may be extended to engage them with the line and load-side fuse clips 60 and 62. In the example shown, the assembly further includes an interlock element 92 that is in turn coupled to the switch actuator 68 via a positioning arm or link 94. As the switch actuator 68 is rotated in the direction of arrow C to open the switch contacts 74 and 76, the link 94 pulls the interlock element 92 along a linear axis in the direction of arrow E away from the line-side fuse clip 60. In this state, the slidable plug-in connection of the fuse 54 and specifically line-side terminal blade 58 to the line-side fuse clip 60 is permitted, as well as removal of the line-side terminal blade 58 from the line-side fuse clip 60.
When the switch actuator 68 is rotated in the direction of arrow A, however, to the closed or “on” position wherein the switch contacts 74 and 76 are engaged with the stationary contacts 64 and 80, the interlock element 92 is slidably moved toward the line-side fuse clip 60 along the linear axis in the direction of arrow F toward the line-side fuse clip 60. An end of the interlock element is passed through an opening in the line-side terminal blade 58 as this happens and the line-side terminal blade 58 becomes effectively locked in place and frustrates any attempt to remove the fuse 54.
The switch actuator 68 simultaneously drives the sliding bar 72 along a first linear axis (i.e., a vertical axis in
As seen in
When electrical current I flows through the conductor 105 in a direction normal to the plane of the page of
Above the conductor 105 in the example illustrated in
F=IL×B (1)
It should now be evident that the magnitude of the force can be varied by applying different magnetic fields, different amounts of current, and different lengths (L) of conductor 105. The orientation of the force F is shown to extend in the vertical direction in the plane of the page of
Briefly, Fleming's Left Hand Rule illustrates that when current flows in a wire (e.g., the conductor 105) and when an external magnetic field (e.g., the magnetic field B illustrated by lines 106) is applied across that flow of current, the wire experiences a force (e.g., the force F) that is oriented perpendicularly both to the magnetic field and also to the direction of the current flow. As such, the left hand can be held so as to represent three mutually orthogonal axes on the thumb, first finger and middle finger. Each finger represents one of the current I, the magnetic field B and the force F generated in response. As one illustrative example, and considering the example shown in
By orienting the current flow I in different directions through the magnetic field B, and also by orienting the magnetic field B in different directions, forces F extending in directions other than the arrow L can be generated. Within the switch housing 52 of the device 50 (
The polarity of the magnets 102, 104 in each magnet pair 100a, 100b may be reversed or oppositely directed relative to one another to produce magnetic fields extending in opposing directions and hence generating oppositely directed forces Fa and Fb as determined by the relationship (1) set forth above. For example, the first pair of magnets 102a, 104a impose a first magnetic field having a first polarity and hence generates a magnetic field acting in a first direction (e.g., toward the top of the page in
The arrangement shown in
In contemplated embodiments the magnets 102a, 102b, 104a and 104b are permanent magnets, and more specifically are rare earth magnets such as neodymium magnets. In the example of
One of the housing pieces 52a is illustrated in
In combination the housing pieces 52a, 52b enclose and protect the internal components shown in
The magnets 102a, 102b, 104a and 104b may be fastened or secured in place in the pockets 120 in any known manner, and the magnets may be strategically selected in size and type, and also arranged and spaced relative to one another to produce a magnetic field of a desired strength between the magnets in each magnet pair. In general, stronger magnets 102a, 102b, 104a and 104b and therefor stronger magnetic fields may be desired as the DC voltage level of the circuit being opened and closed increases through the device 50. The magnets 102a and 104a used in the first magnet pair 100a may be the same or different type as the magnets 102b and 104b in the second magnet pair 100b. Likewise, the magnetic field strength established by the first magnet pair 100a may the same or different from the magnet pair 100b.
In the arrangement shown in
The switch housing 52 in the embodiment of
The embodiment of
In certain contemplated embodiments, the magnets 102a, 104a could be applied entirely outside the switch housing 52 and held in place via magnetic attraction. Some care should be taken, however, if the magnetic strength is insufficient to reliably hold the magnets in place, as the magnetic arc defection could be compromised if the magnets were removed or displaced in a manner that would impair the desired Lorentz force from being established to deflect an arc.
The benefits and advantages of the inventive concepts are now believed to have been amply illustrated in relation to the exemplary embodiments disclosed.
An embodiment of a fusible disconnect switch device has been disclosed including: a nonconductive switch housing configured to accept an overcurrent protection fuse; a current path defined in the nonconductive switch housing, the current path comprising: a first fuse contact member and a second fuse contact member, the first fuse contact member and the second fuse contact member configured to complete an electrical connection through the overcurrent protection fuse; and a first switch contact connected to the first fuse contact member; a rotary actuator configured to move the first switch contact between an opened position and a closed position to complete or open the current path; and a first magnet and a second magnet disposed about the first switch contact, wherein the first and second magnets establish a first magnetic field therebetween and wherein the first switch contact is in the magnetic field.
Optionally, the current path further may include a second switch contact spaced from the first switch contact in the nonconductive switch housing. The first and second switch contacts may be mounted stationary in the nonconductive switch housing. The fusible disconnect switch may further include third and fourth magnets disposed about the second switch contact, wherein the third and fourth magnets establish a second magnetic field therebetween and wherein the second switch contact is in the second magnetic field. The first magnetic field may have a first polarity, and the second magnetic field may have a second polarity opposite to the first polarity. The first and second magnets may be permanent magnets, and more specifically may be rare earth magnets, and even more specifically may be neodymium magnets.
The fusible disconnect switch device may also include a sliding actuator bar, with the first and second movable switch contacts coupled to the sliding actuator bar. The sliding actuator bar may be movable along a first axis. The first magnetic field may be established along a second axis perpendicular to the first axis. The first and second magnet may be disposed on a first side of the sliding actuator bar, and the device may further include third and fourth magnets situated on a second side of the sliding actuator bar.
The overcurrent protection fuse may include a pair of terminal blades insertable into the switch housing along an insertion axis. The first magnetic field may be established along a second axis perpendicular to the insertion axis.
The fusible switch disconnect device may also include a third magnet, the first magnet and the third magnet extending generally coplanar to one another.
The fusible switch disconnect device of claim 14, wherein the first magnet and second magnet respectively extend in spaced apart but parallel planes, and wherein the at least one switch contact is disposed between the first magnet and the second magnet. The first and second magnets may be internal to the nonconductive switch housing. The nonconductive switch housing may define at least one pocket that receives at least one of the first and second magnets. The current path may further include a line-side terminal and a load-side terminal for establishing a respective electrical connection to line-side and load-side circuitry. The first and second magnets may be situated proximate the line-side terminal. At least one of the line-side terminal and load-side terminal may include a panel mount clip.
The fusible switch disconnect device may further include a nonconductive terminal cover movable by the rotary switch actuator between a first position and a second position. The fusible switch disconnect device of claim may also include a switch interlock shaft coupled to the switch actuator. Each of the first and second fuse contact members comprises a fuse clip configured to engage a terminal blade of the overcurrent protection fuse.
An embodiment of a fusible disconnect switch device has also been disclosed including: a nonconductive housing defining an exterior fuse receptacle and a first terminal blade opening and second terminal blade opening formed through the housing; a line-side terminal in the nonconductive housing; a line-side fuse terminal proximate the first terminal blade opening; at least one switch contact associated with at least one of the line-side terminal and the line-side fuse terminal; a switch actuator selectively positionable to move the switch contact between a closed position completing an electrical path from the line-side terminal to the line-side fuse terminal and an open position disconnecting the line-side contact from the line-side fuse terminal; and at least one pair of magnets imposing a magnetic field across the at least one switch contact.
Optionally, the fusible switch disconnect device may also include a retractable fuse insertable into the fuse receptacle, the fuse including a first terminal blade and a second terminal blade, the first terminal blade passing through the first terminal blade opening and establishing a line-side electrical connection to the line-side fuse terminal. The fuse may project from the fuse receptacle when the first terminal blade is passed through the first terminal blade opening. The retractable fuse may be a rectangular fuse module. The fuse may be open and accessible on an outer surface of the housing.
The at least one switch contact may include a first switch contact associated with the line-side terminal and a second switch contact associated with the line-side fuse terminal, and wherein the at least one pair of magnets comprises a first pair of magnets and a second pair of magnets spaced from one another, the first pair of magnets imposing a first magnetic field across the first switch contact and the second pair of magnets imposing a second magnetic field across the second switch contact. The first magnetic field may have a first polarity, and the second magnetic field may have a second polarity opposite to the first polarity. The at least one pair of magnets may comprise permanent magnets. The at least one pair of magnets may also be rare earth magnets. The at least one pair of magnets may also be neodymium magnets.
An embodiment of a fused disconnect switch has also been disclosed including: a nonconductive housing defining a fuse receptacle and first and second fuse contact members in the fuse receptacle; a line-side terminal carrying a first stationary contact; a line-side fuse terminal proximate the first terminal blade opening and comprising a second stationary contact; a switch actuator selectively positionable between a closed position and an open position; a sliding bar coupled to the actuator and carrying first and second movable switch contacts, the first and second switch contacts completing an electrical path from the line-side terminal to the line-side fuse terminal when the switch is in the closed position and disconnecting the line-side contact from the line-side fuse terminal when the switch actuator is in the opened position; and at least one pair of magnets imposing a magnetic field proximate at least one of the first and secondary stationary contacts, wherein an arc deflecting force is generated when the electrical path is disconnected.
Optionally, the at least one pair of magnets may comprise a first pair of magnets and a second pair of magnets, the first pair of magnets imposing a first magnetic field proximate the first stationary contact and the second pair of magnets imposing a second magnetic field proximate at least one of the first and secondary stationary contacts. The first magnetic field may have a first polarity, and the second magnetic field may have a second polarity opposite to the first polarity. The first and second pairs of magnets may include a first and second pair of permanent magnets. The first and second pairs of permanent magnets may include a first and second pair of rare earth magnets, and the first and second pair of rare earth magnets may include a first and second pair of neodymium magnets.
This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.
