Patent Application
20090128273
The invention relates to inductors. More specifically, the invention relates to an apparatus for winding wire around an inductor core.
High power inductors require large diameter wire that is difficult to bend. In addition, many inductors, such as a common mode inductor, have multiple phases that must be electrically insulated from one another and from the magnetic core of the inductor. Typically, the phases of the inductor are isolated by using wire that is insulated with some type of rubber material. However, this insulating material adds to the stiffness of the wire and, as a result, the wire is more difficult to bend when wrapping the wire around the inductor core.
In addition, the insulation material around a wire adds to the total diameter of the wire, making the wound inductor larger than it would be if bare, uninsulated wire were used. When winding insulated wire around the magnetic core of the inductor, the wire bulges out away from the core, making the outer diameter of the inductor much larger than it should be. Also, use of rubber insulation reduces the ability of the wire to dissipate heat that is generated when the inductor is in use.
Toroids are often the geometry of choice in designing inductor cores. Toroids offer the smallest size (by volume and weight) and lower electromagnetic interference (EMI) than other shapes used for inductor cores. Toroidal geometry leads to near complete magnetic field cancellation outside of its coil, so the toroidal inductor has less EMI when compared against other inductors of equal power rating. Toroids also have the highest effective permeability of any core shape because they can be made from one piece of material. However, toroidal inductor cores have the particular disadvantage of being difficult to wind. Also, using insulated wire can create difficulty inserting wire into the inner diameter of a toroidal inductor core, and it increases friction between the various turns of the wire.
Therefore, there is a need in the art for a high power inductor that avoids the need for using insulated wire, thereby avoiding the problems resulting from the use of insulated wire. However, the different phases of the wire must still be electrically insulated from each other and from the magnetic core.
The invention is an electrically insulating bobbin surrounding the magnetic core of an inductor. The bobbin is made from an electrically insulating material that isolates the turns of an uninsulated wire that is wound around the magnetic core of the inductor. The turns of the uninsulated wire are electrically insulated from each other and from the inductor core.
a shows a modular component of an alternate embodiment of the invention.
b shows a modular component of an alternate embodiment of the invention.
When the upper bobbin 110 and lower bobbin 120 are placed together, channels 112 form continuous, helical channels that extend from wire inlet 160 on upper bobbin 110, wrapping around the core seven times, to wire outlet 170 on lower bobbin 120. Thus, wire can be placed in channel 112, beginning at wire inlet 160 and ending at wire outlet 170, and the wire can be wrapped around inductor core assembly 130, creating multiple turns of wire around inductor core assembly 130. When positioned in channels 112, wire 140 travels in a helical path around inductor core assembly 130. Wire inlet 160 and wire outlet 170 open up and spread out to allow insulating sheathing to be placed over the wires to isolate them from each other.
In the embodiment of the invention shown in
Similarly, another wire is positioned at wire inlet 160b and wound through channel 112b until it reaches wire outlet 170b, while a third wire is positioned at wire inlet 160c and wound through channel 112c until it reached wire outlet 170c. These three wires in combination create three phases of seven windings each around inductor core assembly 130. Channels 112a, 112b and 112c are designed so that all of the turns of the three phases are evenly distributed around inductor core assembly 130. Even distribution of the turns provides electrical and magnetic balance to inductor assembly 100.
While the embodiment of the invention shown in
In addition, while the embodiment of the invention shown in
After upper bobbin 110 and lower bobbin 120 have been positioned around inductor core assembly 130, the bobbins are wound with wires 140 (see
When wires 140 are positioned in channels 112, they are only isolated on three sides of the wire by channel floors 113 and channel walls 114. To completely insulate wire 140, the entire inductor assembly 100 may be potted in an electrically insulating compound to completely isolate the wires from each other. This compound should also be thermally conductive to allow heat to be dissipated from inductor assembly 100.
Upper bobbin 110 and lower bobbin 120 may each be made as a single piece, as shown in
a and
Each of turn sections 210 and inlet/outlet section 220 are made individually and then bonded together to form upper and lower bobbins. Thus, for example, upper bobbin 110 could be assembled by connecting six turn sections 210 and one inlet/outlet section 220 to form the fully assembled upper bobbin 110. Similarly, lower bobbin 120 could be assembled by connecting six turn sections 210 and one inlet/outlet section 220. When connected together, turn sections 210 and inlet/outlet sections 220 form continuous channels 112 that form continuous, helical channels that extend around an inductor core.
Of course, as noted previously, the number of turns and phases of this particular embodiment is purely exemplary. Any number of turns and phases of an inductor could be used and still come within the scope of this invention. Turn section 210 and inlet/outlet section 220 could be designed to create any number of turns and any number of phases and still fall within the scope of the invention.
The invention is a bobbin for winding wire around an inductor core. The bobbin is made from an electrically insulating material and provides channels through which an uninsulated wire may be wound. Each of the channels have a channel floor that insulates the wire from a magnetic inductor core, and also have insulating walls that electrically insulate the wires from each other. Because the inductor may be wound with uninsulated wire, it is easier to wind the wire, the inductor can be made more compactly, and it is easier to remove excess heat from the inductor. Also, the total size and weight of the inductor is generally smaller than an inductor wound with insulated wire. Moreover, use of the insulating bobbin leads to more consistent assembly of inductors, because the channels of the bobbin guide the location of the wires. Finally, the elimination of insulation around the wires eliminates a thermal interface, resulting in improved heat dissipation, particularly when the wound conductor is covered with a potting material.
Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.
