Referring to the exemplary drawings wherein like elements are numbered alike in the accompanying Figures:
An embodiment of the invention provides a bistable magnetic layout design for contactors using a DC control coil that allows for the reduction of DC control coil height. The magnetic circuit, as defined at least partially by a core, is modified by the inclusion of a permanent magnet, which aids in the pick-up and dropout of a contactor. Use of the permanent magnet allows use of a return spring with a lower spring constant. Use of a return spring with a lower spring constant reduces the required coil power consumption of the contactor, which accordingly allows use of a higher gauge (smaller diameter) coil conductor to thereby greatly reduce coil height.
In an embodiment, a single piece permanent magnet is used in the magnetic circuit. The permanent magnet is easy to manufacture and assemble, has a cylindrical shape with an inner bore, and rests on a coil bobbin surrounding an armature. The two flat surfaces of the cylinder define the two magnetic poles. The shape of the armature, defined in more detail below, enhances the operation of the electromagnet above and beyond other armatures that do not employ the features disclosed herein. In addition, the reduction of components reduces the overall cost of the apparatus, and provides for ease of assembly.
Referring now to
While an embodiment has been described having a single cylindrical permanent magnet with the magnetic poles on the flat faces, it will be appreciated that the scope of the invention is not so limited, and that the invention also applies to other permanent magnet arrangements, such as a plurality of stacked or segmented magnets, for example. While an embodiment has been described having a single stationary metallic projection as part of the stationary core, it will be appreciated that the scope of the invention is not so limited, and that the invention also applies to other arrangements of stationary cores, such as a multi-piece assembly comprising segments, for example.
In an embodiment, the armature 150 is biased toward the first position, as depicted in
While an embodiment has been described using a compression spring disposed between the flat plate and the top of the core to provide a biasing force, it will be appreciated that the scope of the invention is not so limited, and that the invention also applies to other biasing means, such as an extension spring disposed between the top of the core and the top of the armature, or a torsion spring disposed between the side of the core and the armature, for example. While an embodiment has been depicted providing an air gap via physical separation, it will be appreciated that the scope of the invention is not so limited, and that the invention also applies to other structures that provide an air gap, such as a non-magnetic separator disposed between the armature and the magnet, for example.
In an embodiment, the bottom 154 of the armature 150 and the projection 133 define sets of opposing pole faces 20, 22, 24, 26 configured to nestle with each other in response to the armature 150 being in the second position. The bottom 154 of the armature 150 comprises a recess 156, the projection 133 comprises a projection 132, and the projection 132 is configured to nestle within the recess 156. In another embodiment, the bottom 154 of the armature 150 comprises a projection 155, the projection 133 comprises a recess 135, and the projection 155 is configured to nestle within the recess 135. In another embodiment, the bottom 154 of the armature comprises a first recess 156 and a first projection 155, the projection 133 comprises a second recess 135 and a second projection 132, the first projection 155 is configured to nestle within the second recess 135; and the second projection 132 is configured to nestle within the first recess 156. In another embodiment, the sets of opposing pole faces 20, 22, 24, 26 comprise tapered surfaces 20, 22, 24, 26 configured to nestle with each other. In an embodiment, the tapered surfaces 20, 22, 24, 26 have an included angle θ of about 60 degrees. As used herein, the term about refers to variation that may result from manufacturing, material, and design tolerances to accommodate a variety of desired operating characteristics.
While embodiments of the invention are described and illustrated having the bottom 154 of armature 150 tapered radially outward, and the projection 133 of stationary core 110 tapered radially inward, such that the armature 150 nestles over the projection 133, it will be appreciated that the scope of the invention is not so limited, and that the tapering may be reversed such that the armature nestles within the projection.
Referring now to
In an embodiment, the armature 150 is biased toward the first position, as depicted in
Referring now to
Referring now to
Referring now to
In an embodiment, it is desirable to size the bore 165 of the permanent magnet 160 so as to prevent any local circulation of flux between the magnet 160 and the extension arm 151 of the armature 150. Also, it is desirable to size the depth 161 of the permanent magnet 160 so as to prevent any local circulation of flux between the magnet 160 and the top 130 of the core 110.
In an embodiment, in response to the coil windings 115 being in an energized state, an attractive electromagnetic force between the armature 150 and the projection 133 will be created, as well as an attractive electromagnetic force between the flat plate 117 and the top 120 of the core 110. The increase in mating surface area between the projection 133 and the armature 150 discussed above provides for an increase in the attractive force. The coil windings 115, armature bottom 154, projection 133, and the flat plate 117 are configured such that this attractive force will be greater than the sum of the forces provided by the spring 118 and the permanent magnet 160 to bias the armature 150 to the first position. Accordingly, in response to the coil windings 115 being in an energized state, the armature 150 shifts toward the second position (as depicted in
As the armature begins to move from the first position in
Because the magnet 160 allows for the use of a smaller spring 118, as described above, there is a reduced biasing force opposing the disposition of the armature 150 in the second position in response to the coil windings 115 being in the energized state. Furthermore, as described above, in response to the armature 150 moving toward the second position, the magnet 160 provides a force to attract the bottom 154 of the armature 150 toward the projection 133. The magnet 160 also provides an attractive force between the flat plate 117 and the top 120 of the core 110. Therefore, the current flow through the coil windings 115 required to maintain the armature 150 in the second position is reduced. As the current flow through the coil winding 115 conductor is reduced, a higher gauge (smaller diameter) conductor may be used for the coil windings 115. Use of smaller diameter conductor within the coil windings 115 likewise allows the coil to be configured having smaller overall dimensions.
An embodiment of the invention provides a bistable magnetic layout design for contactors using DC control coils. The design allows for the reduction of DC control coil height. The embodiment includes the magnetic circuit having the cylindrical shaped movable armature 150 with the extension arm 151. The extension arm 151 moves through the bore 165 of the permanent magnet 160. The permanent air gap 162 between the permanent magnet 160 and the armature top 152 is kept when the contacts 50, 51 of the contactor are open. This ensures that during the pick-up condition the electromagnetic force on the armature 150 is greater than the sum of the return spring force and the permanent magnet force. The bottom 154 of the armature 150 is tapered to increase the vertical component of the electromagnet force.
The fixed core 110 consists of a U shaped magnetic circuit, a top plate, and the tapered projection 133 with an inner cutout axially aligned with the armature 150. The enhanced polar surface of the armature 150, the inner-core of the armature 150, and the projection 133 in the fixed core 110 ensure enough resultant magnetic flux to provide proper pick up of the contactor. As the armature 150 approaches the tapered projection 133 during the pick-up condition, the permanent magnet 160 also aids the electromagnet coil windings 115 in pick-up.
During the dropout condition, the return spring 118 provides the initial bias. As the armature 150 travels a certain distance toward the projection 133, the permanent magnet 160 aides it in dropout. Thus the return spring 118 can have a lower spring constant for dropout, reducing the required coil power consumption of the contactor, and thereby allowing use of smaller diameter coil conductor to reduce coil height.
As disclosed, some embodiments of the invention may include some of the following advantages: ability to reduce the size of the biasing spring; ability to reduce coil power consumption; ability to reduced the size of the coil; ability to reduce apparatus cost; and ease of assembly.
While the invention has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best or only mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims. Also, in the drawings and the description, there have been disclosed exemplary embodiments of the invention and, although specific terms may have been employed, they are unless otherwise stated used in a generic and descriptive sense only and not for purposes of limitation, the scope of the invention therefore not being so limited. Moreover, the use of the terms first, second, etc. do not denote any order or importance, but rather the terms first, second, etc. are used to distinguish one element from another. Furthermore, the use of the terms a, an, etc. do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced item.