Low voltage direct current (LVDC) distribution systems are emerging in a number of industrial, commercial, and residential applications. Typically LVDC distribution systems involve the use of many power electronic converters on either the distributed power generation or the electric and electronics load side. An example of industrial LVDC distribution systems is the DC data center. In traditional AC data centers, multiple power conversion stages are required to convert utility AC power to DC load power and to ensure that the power supplied to the servers is not interrupted with battery energy storage. By using a LVDC distribution system some DC data centers have been able to eliminate up to two power conversion stages, improving the energy conversion efficiency of the power distribution system.
For residential and commercial settings, another example of LVDC distribution is a local DC grid connecting DC photovoltaic power generation systems, battery energy storage systems, plug-in electric vehicles, and DC electronics and appliances. Traditionally, photovoltaic cells in photovoltaic power generation systems produce DC power that must be converted to AC power before being distributed across the electrical grid. Batteries supply the electricity to fuel electric vehicles in on-board energy storage applications, or provide the backup power and the load peak shaving/shifting services in stationary storage applications. Consequently, batteries are charged with DC power but need additional AC/DC converters in an AC grid system. Other consumer appliances and electronics (e.g., televisions, computers, monitors, printers, and LED lighting) use DC power and require conversion of the AC power delivered by the traditional AC power distribution system to DC power to function properly. The local DC grid enables the direct use of photovoltaic power with better efficiency and minimal power conversion hardware. The DC plug and socket outlet device connects the equipment, appliances or electronics to the LVDC distribution system and delivers the power for end use.
Accordingly to one aspect, a direct current (DC) socket for reducing DC arcing may include a receptacle configured to receive one or more prongs of a DC plug of an electrical device. The receptacle includes one or more supply terminals to supply a DC power from a DC power source to the electrical device via the DC plug. Each of the supply terminals is configured to contact a corresponding prong of the DC plug within a contact region of the receptacle while the DC plug is connected to the DC socket, and an electromagnet positioned in the receptacle and configured to produce a magnetic field within the contact region of the receptacle to reduce a DC arc generated between the supply terminals and the prongs in response to disconnection of the DC plug from the DC socket.
In some embodiments, the electromagnet is configured to produce the magnetic field in response to contact between the one or more prongs of the DC plug and the supply terminals of the receptacle. The magnetic field produced by the electromagnet is proportional to a load current supplied to the electrical device by the DC socket.
In some embodiments, the electromagnet may include a core made of a ferromagnetic material, and one or more coils positioned on the core configured to generate the magnetic field in response to a coil current.
In some embodiments, the core may include a base having a first end and a second end, a first column extending from the first end of the base, a second column extending from the second end of the base parallel to the first column, and a central column extending from the base parallel to the first column and the second column and positioned between the first column and the second column. The first column and the central column define a first gap therebetween and the second column and the central column define a second gap therebetween. In some embodiments, the one or more coils may include a first coil positioned on the first column around a first coil section of the first column and configured to generate a first magnetic field. The first column includes a first exposed section above the first coil section configured to direct the first magnetic field across the first gap to the central column, and a second coil positioned on the second column around a second coil section of the second column and configured to generate a second magnetic field. The second column includes a second exposed section above the second coil section configured to direct the second magnetic field across the second gap to the central column. In some embodiments, the first gap and the second gap are each sized to receive a supply terminal of the one or more supply terminals coupled to the corresponding prong of the DC plug. In some embodiments, the one or more coils of the electromagnet are electrically coupled in series with the electrical device.
In some embodiments, the core may include a base having a first base end a second base end, a top extending parallel to the base having a first top end a second top end, a central column extending from the base to the top. The central column connects the base to the top between the first and second ends of the base and the first and second ends of the top. The top further includes a first top column extending toward the base at the first top end, and the base includes a first base column extending towards the top at the first base end. The top further includes a second top column extending toward the base at the second top end, and the base includes a second base column extending toward the top at the second base end. In some embodiments, the one or more coils may include a single coil configured to generate the magnetic field. The single coil is positioned on the central column and extends from the base to the top. The first top column and the first base column cooperate to define a first gap and the second top column and the second base column cooperate to define a second gap. The first gap and the second gap are each sized to receive a supply terminal of the one or more supply terminals coupled to the corresponding prong of the DC plug. In some embodiments, the first top column and the first base column are configured to cause the magnetic field to pass from the first top column, across the first gap, to the first base column, and the second top column and the second base column are configured to cause the magnetic field to pass from the second top column, across the second gap, to the second base column. In some embodiments, the single coil is electrically coupled in parallel with the DC power source from which the electrical device receives the DC power.
In some embodiments, the DC socket may include an arc chute positioned in the receptacle and configured to redirect the DC arc generated between the supply terminals and the prongs in response to disconnection of the DC plug from the DC socket. The DC socket may include a shutter to selectively prevent access to the supply terminals.
According to another aspect, a method for reducing DC arcing of a DC socket may include delivering, by the DC socket, a DC power to a DC plug of an electrical device connected to the DC socket. Delivering the DC power may include energizing an electromagnet of the DC socket to generate a magnetic field within the DC socket, and reducing, by the generated magnetic field, a DC arc generated within a receptacle of the DC socket in response to disconnection of the DC plug from the DC socket.
In some embodiments, energizing the electromagnet may include energizing the electromagnet with a load current supplied to the electrical device by a DC power source via the DC plug and the DC socket. The electromagnet generates the magnetic field proportional to the load current delivered to the electrical device. Reducing the DC arc within the receptacle of the DC socket may include reducing an energy of the DC arc and reducing a time duration of the DC arc. Energizing the electromagnet of the DC socket may include energizing the electromagnet of the DC socket to generate a time invariant magnetic field. In some embodiments, energizing the electromagnet of the DC socket may include energizing a coil of the electromagnet that is electrically coupled in parallel with a DC power source from which the DC power is received. In some embodiments, energizing the electromagnet of the DC socket may include energizing a coil of the electromagnet that is electrically coupled in series with the electrical device.
The concepts described herein are illustrated by way of example and not by way of limitation in the accompanying figures. For simplicity and clarity of illustration, elements illustrated in the figures are not necessarily drawn to scale. Where considered appropriate, reference labels have been repeated among the figures to indicate corresponding or analogous elements.
While the concepts of the present disclosure are susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and will be described herein in detail. It should be understood, however, that there is no intent to limit the concepts of the present disclosure to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives consistent with the present disclosure and the appended claims.
References in the specification to “one embodiment,” “an embodiment,” “an illustrative embodiment,” etc., indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may or may not necessarily include that particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to effect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described. Additionally, it should be appreciated that items included in a list in the form of “at least one of A, B, and C” can mean (A); (B); (C); (A and B); (A and C); (B and C); or (A, B, and C). Similarly, items listed in the form of “at least one of A, B, or C” can mean (A); (B); (C); (A and B); (A and C); (B and C); or (A, B, and C).
The disclosed embodiments may be implemented, in some cases, in hardware, firmware, software, or any combination thereof. The disclosed embodiments may also be implemented as instructions carried by or stored on one or more transitory or non-transitory machine-readable (e.g., computer-readable) storage media, which may be read and executed by one or more processors. A machine-readable storage medium may be embodied as any storage device, mechanism, or other physical structure for storing or transmitting information in a form readable by a machine (e.g., a volatile or non-volatile memory, a media disc, or other media device).
In the drawings, some structural or method features may be shown in specific arrangements and/or orderings. However, it should be appreciated that such specific arrangements and/or orderings may not be required. Rather, in some embodiments, such features may be arranged in a different manner and/or order than shown in the illustrative figures. Additionally, the inclusion of a structural or method feature in a particular figure is not meant to imply that such feature is required in all embodiments and, in some embodiments, may not be included or may be combined with other features.
Referring now to
In general, the magnetic field generated by the electromagnet 120 reduces the DC arc when the one or more prongs 128 separate from the one or more supply terminals 118. As a result, both DC arcing duration time and DC arcing energy may be reduced, and the damage to the electrical contacts and the potential safety hazards due to DC arcing may be mitigated.
The DC power source 110 may be configured as any type of DC power supply capable of energizing one or more DC electrical devices 114. In some embodiments, the DC power source 110 includes an AC-to-DC converter connected to an AC power distribution system (e.g., an AC grid). The DC power source 110 may include any type of energy sources (e.g., generators, fuel cells, or photovoltaic cells), any type of electrical energy transmission systems, and/or any type of energy storage devices such as, for example, batteries or super capacitors.
The DC socket 112 includes a receptacle 116 configured to receive the DC plug 126. The connection and interaction between the DC plug 126 and the DC socket 112 is shown illustrative in
In the illustrative embodiment, the receptacle 116 is embodied as a housing having one or more apertures (not shown) in which the supply terminals 118 are positioned. The apertures are sized to receive the one or more prongs 128 of the DC plug 126. In some embodiments, the apertures of the receptacle 116 are configured to maintain the electrical connection between the prongs 128 of the DC plug 126 and the supply terminals 118 of the DC socket 112 by creating an interference fit between the apertures and the prongs 128. Additionally or alternatively, the supply terminals 118 may be formed to receive the prongs 128 and maintain an electrical connection between components through an interference fit. For example, the prongs 128 may be configured as male electrical connectors and the supply terminals 118 may be configured as female electrical connectors or vice versa.
The location of the supply terminals 118 in the receptacle 116 defines one or more contact regions in which the supply terminals 118 and the prongs 128 physically contact each other to form an electrical connection when the DC plug 126 is connected to the receptacle 116 and in which a DC arc may form when the prongs 128 are disconnected from the supply terminals 118. The supply terminals 118 and the prongs 128 may be configured to mate together, couple with each other, or otherwise contact each other in the contact region of the receptacle 116 in any suitable manner. For example, the supply terminals 118 and the prongs 128 may overlap each other, be received by one another, or use some other physical mechanism to ensure electrical contact between each other.
The illustrative receptacle 116 also includes one or more electromagnets 120 configured to produce one or more magnetic fields to reduce DC arcing between the supply terminals 118 and the prongs 128, which may be generated when prongs 128 are disconnected from the supply terminals 118. The electromagnet 120 includes one or more coils 122 and one or more cores 124. In the illustrative embodiment, the electromagnet 120 includes a single core 124, made of a ferromagnetic material such as iron, with one or more coils 122 positioned on the core 124. The one or more coils 122 include electrical wires coiled around the core 124 that form a solenoid coil. The one or more coils 122 are positioned on the core 124 to generate a magnetic field in response to a coil current. The core 124 is configured to concentrate the magnetic field at specific locations and generally strengthen the magnetic field at those locations. In the illustrative embodiments, the electromagnet(s) 120 are configured to produce a magnetic field across one or more gaps formed in the electromagnet core 124, which correspond to the contact region of the receptacle 116 (i.e., the region in which the prongs 128 of the DC plug 126 contact the supply terminals 118). In some embodiments, the electromagnet 120 produces the magnetic field in response to the DC prongs 128 being in contact with the supply terminals 118 of the receptacle 116 such that a DC current flows through the coils 122 of the electromagnet 120.
The electrical device 114 may be configured as any electrical device configured to run on DC power. For example, the electrical device 114 may be embodied as an electric vehicle, a computer, a television, an LED, a DC motor, or other DC-powered device. It may also be embodied as a DC-AC power inverter for an AC-powered device, such as a motor driver. As discussed above, the electrical device 114 includes the DC plug 126 configured to connect to the receptacle 116 of the direct current socket 112. Additionally, the electrical device 114 may include various electrical circuits 130. The electrical circuits 130 of the electrical device 114 may be embodied as any electrical circuitry designed to accomplish the various functions of the electrical device 114. The particular electrical circuits 130 included in the electrical device 114 may depend on the type of electrical device 114 and its intended function. Again, as discussed above, the DC plug 126 includes the one or more prongs 128 configured to interact with the supply terminals 118 of the DC socket 112 and establish an electrical connection to supply DC power to the electrical device 114 from the DC power source 110.
While the illustrative system 100 includes the DC socket 112 incorporated in, or otherwise connected to, the DC power source 110, the DC socket 112 may be incorporated in the electrical device 114 and the DC plug may be connected to or incorporated in the DC power source 110 in other embodiments. For example, an electric vehicle may include a DC socket configured to receive a DC plug associated with a charging station that is connected to the DC power source 110. In such an example, the DC arc reducing system is incorporated into the DC socket included in the electrical device 114 (i.e., the electric vehicle). In some embodiments, the DC socket 112 includes an arc chute. The arc chute may be positioned in the receptacle to be near the one or more contact regions. The arc chute is configured to redirect a DC arc generated between a supply terminal 118 and a DC prong 128 and thereby dissipate the DC arc. In some embodiments, the socket 112 may include a shutter to prevent unwanted access to the supply terminals 118 and thereby prevent the risk of electric shock hazard.
Referring now to
The first column 224 and the central column 232 are spaced apart from one another and cooperate to define a first gap 236 therebetween. Similarly, the second column 228 and the central column 232 are also spaced apart from one another and cooperate to define a second gap 238 therebetween. In the illustrative embodiment, the first and second gaps 236, 238 are sized to receive both the supply terminals 118 and the prongs 128. In particular, the first and second gaps 236, 238 are sized to receive the supply terminals 118 and the prongs 128 while they are coupled together forming an electrical connection between the DC power source 110 and the electrical device 114. As such, the first and second gaps 236, 238 correspond to the contact region of the DC receptacle 116 in the illustrative embodiment of
In the illustrative embodiment, each prong 128 is configured to mate with a corresponding supply terminal 118 through an interference fit. Each prong 128 is illustratively formed as a rigid metal blade 240 with a leading edge 242 and each supply terminal 118 is made of a flexible metal beam 244 shaped to receive the corresponding metal blade 240. Each flexible beam 244 is shaped to form a slot 246 configured to receive the metal blade 240 and includes a leading edge 248. When the metal blade 240 is inserted into the slot 246, the flexible beam 244 is configured to exert a pinching force on the metal blade 240. The pinching force maintains the electrical connection between the flexible beam 244 and the blade 240. Of course, other connection mechanisms may be used in other embodiments to electrically connect the prongs 128 and the supply terminals 118.
As shown in
Referring now to
In the illustrative embodiment of
Additionally, because the load current is used to excite the electromagnet 120, the generated magnetic field can reduce DC arcs in either direction. For example, for the charging and discharging operation of a residential battery energy storage system, at different times the power flows either out of the socket or back into the socket. When the current direction reverses in the discharging operation, the magnetic field generated by the electromagnet 120 also reverses direction. Therefore, the direction of the force applied to stretch the arc remains the same.
Referring now to
As the magnetic fields pass through the first gap 236 and the second gap 238, a Lorenz force 426 is produced that pushes the arc current up and out of the electromagnet 120. In the illustrative embodiment, the current passing through the supply terminal 118/prong 128 positioned in the first gap 236 flows out of the plane of the page, as shown by the dots on the supply terminal 118/prong 128 in
Referring now to
The first base gap surface 532 and the first top gap surface 540 are spaced apart and define a first gap 546 sized to receive the supply terminals 118 and the prongs 128. Similarly, the second base gap surface 536 and the second top gap surface 544 are spaced apart and define a second gap 548 sized to receive the supply terminals 118 and the prongs 128. As such, the first and second gaps 546, 548 correspond to the contact region of the receptacle 116 in the illustrative embodiment of
The coil 514 is positioned on the central column 528 and extends from the base 516 to the top 522. In the illustrative embodiment, the coil 514 is made of a conductive wire, such as copper wire, that is wound around the central column 528 to form a solenoid structure.
Referring now to
In the illustrative embodiment, the coil 514 of the electromagnet 120 is connected in parallel with the DC power source 110 and the electrical device 114, when the electrical device 114 is connected to the DC socket 112. In some embodiments, the DC arc protection system 500 includes a sensor configured to generate sensor data indicative of when an electrical device 114 is connected to the DC power source 110 via the DC socket 112. When the sensor data indicates that an electrical device 114 is connected, the DC power source 110 will supply power to the coil 514 of the electromagnet 120 (e.g., via activation of a switch in series with the coil 514).
Referring now to
Similar to what was described above, as the magnetic fields pass through the first gap 546 and the second gap 548, a Lorenz force 734 is produced that pushes the arc current out of the electromagnet 120. In the illustrative embodiment, the current passing through the supply terminal 118/prong 128 positioned in the first gap 546 flows into the plane of the page, as shown by the x's on the supply terminal 118/prong 128 in
Referring to
Graph 900 illustrates the arcing time duration of a DC arc plotted against the load current delivered from the DC power source 110 to the electrical device 114. Plot 910 of graph 900 shows the time duration in milliseconds (ms) of the DC arc formed as the prongs 128 are disconnected from the supply terminals 118 in a DC socket 112 having no DC arc protection (i.e., having no electromagnet 120). Plot 920 of graph 900 shows the time duration of a DC arc formed in a DC socket 112 having an electromagnet 120 having a strength of about 18 mT electromagnet. As is shown by comparison of the plot 910 and the plot 920, generation of a magnetic field in the contact region of the DC socket 112 reduces the time duration of the DC arc.
Referring now to
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