Abstract:
In accordance with the embodiment a folded electromagnetic coil comprises an electrically conducting wire looped and folded many times such that two or more semicircular sections are formed with approximately the same centerline and the same coil opening such that a supported-magnet can pass unobstructed though the coil center.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     None 
     FEDERAL SPONSORED RESEARCH 
     Not applicable 
     SEQUENCE LISTING OF PROGRAM 
     Not applicable 
     BACKGROUND 
     1. Field 
     This application relates to electromagnetic coils used in electric generators, electric motors, and other electrical equipment. 
     2. Prior Art 
     Most electric generators and electric motors use electromagnetic coils to either convert mechanical motion into electricity (generator) or convert electricity into mechanical motion (motor). These electromagnetic coils are generally made of electrically conductive and insulated wire either wound into a winding without a metal core (coreless) or wound into a winding around a ferromagnetic material (core) such as iron or steel. These coils consist of a single wire wound in many approximately parallel loops (turns) that are flat and unfolded. 
     It is well known in the art that an electrical current passing through a wire induces a magnetic field that uniformly circles the wire in a plane perpendicular to the direction of current. However, when many wire loops are formed into a coil (winding), current flow creates a magnetic field from each wire that extends to pass through the coil center, concentrating the magnetic field along the coil centerline. The concentrated magnetic field at the coil center can be many times more than the magnetic field elsewhere around the coil. 
     However, the coreless electromagnetic coil used in some rotating generators or motors cannot take advantage of the concentrated magnetic field as described above. This is simply due to the circular shape of the coil blocks a radial support of the magnet, or the magnet itself, passing through the coil center, or the converse of the coil passing around a magnet on its centerline. Linear generators and motors are an exception because the magnet can have linear support along the coil centerline without interfering with linear motion of either the magnet or coil. 
     Therefore, coreless electromagnetic coils loose the benefit of the concentrated magnetic field at the coil center to avoid the rotating part (rotor) of a generator or motor colliding with the fixed part (stator) of the generator or motor. For example, a fixed arrangement of coreless coils (stator) can be positioned to one or both sides of magnets on a rotor such that the rotor&#39;s rotation causes the magnet centers to momentarily align with the coil centers but the magnets do not pass through the coil centers. 
     To keep cost and complexity low, coreless electromagnetic coils are often found in simple wind turbines where the wind forces blades to rotate magnets across fixed electromagnetic coils (as described above), generating electricity. Without ferromagnetic cores, the generator is simpler and less expensive, but the power produced is much lower than generators that have electromagnetic coils with ferromagnetic cores. 
     Coils with ferromagnetic cores take advantage of the concentrated field at coil center, but at a price of more complexity and expense. The coil wire is wrapped around a ferromagnetic core forming an electromagnet with a north or south-pole at the ends, depending on the direction of the current through the coil. If the current direction is reversed, the magnetic poles reverse. 
     The literature describes many types of generators and motors using electromagnetic coils with cores. In general, the core of electromagnetic coil is positioned opposite a magnet such that a relative movement induces a magnetic field in the core. That relative movement can be either coils rotating about fixed magnets, or magnets rotating about fixed coils. The magnets can be permanent, electromagnet, or an electrically conducting cage as in an inductive motor. Furthermore, a circular pattern of coils can be fixed or rotate on the inside or outside of a circular pattern of fixed or rotating magnets. Whatever the arrangement, there are advantages and disadvantages of using ferromagnetic cores in the electromagnetic coils of generators and motors. 
     The primary advantage is that the core enables access to the concentrated magnetic field in the coil center such that a relative motion of the core and magnet generates more current than a coreless coil. 
     The disadvantages are more complexity and expense than a coreless coil. In addition, to the added cost of the cores, the introduction of ferromagnetic cores cause a problem called torque cogging, or just cogging. The magnet and core inherently attract each other, and considerable force must be expended to separate them or the rotor will not rotate. This is called cogging, and it is a major problem for generators. For example, considerable wind energy is lost to a wind turbine before the wind is strong enough to overcome cogging and self-start the generator. Cogging also causes instability, vibration, noise, and damage to generators. Since cogging is such a problem, considerable design and operational tradeoffs from optimum performance are made to reduce it. These tradeoffs generally reduce power output, increase cost, and add complexity. 
     Furthermore, induction generators use electromagnetic coils with cores to control the rotation of the rotor such that a force causing rotation to exceed a prescribed speed generates electrical power. Induction generators have an advantage of generating grid ready power, even when the external force varies. However, to produce useful power, this range of variation can be narrow, forfeiting energy outside the range. Another disadvantage is that the electronics is more complex, and some of the generated power is consumed by the generator itself, in order to keep the coils charged. 
     Therefore, prior art generators and motors have significant disadvantages. 
     SUMMARY 
     In accordance with the embodiment a folded electromagnetic coil comprises an electrically conducting wire looped and folded many times such that two or more semicircular sections are formed with approximately the same centerline and same coil opening such that a supported-magnet can pass unobstructed though the coil center. 
    
    
     
       DRAWING 
       FIGS.  1 - 10   
       In the drawings, closely related figures have the same number but different alphabetical suffixes. 
         FIG. 1  shows an isometric view of the folded electromagnetic coil. 
         FIG. 2  shows an end view of the folded electromagnetic coil as viewed along the coil centerline. 
         FIG. 3  shows a cross section view of the magnetic field from the folded electromagnetic coil as viewed from a horizontal plane cutting through the centerline and wires of the two semicircle sections. The crosses are wires in which current is moving into the page; the dots are wires in which current is moving out of the page. 
         FIG. 4  shows an isometric view of the folded electromagnetic coil embodiment with a magnet and support passing along the coil centerline. 
         FIG. 5  shows an end view of the folded electromagnetic coil with a magnet passing along the coil centerline. 
         FIG. 6  shows a cross section view of the magnetic field emanating from a magnet. 
         FIGS. 7A-E  shows side views of the folded electromagnetic coil as one magnet, north-pole leading, momentarily passes different locations along the coil centerline. 
         FIG. 8  shows a side view of the folded electromagnetic coil as one magnet, south-pole leading, momentarily passes in between the first and second semicircle coil sections. 
         FIGS. 9A-B  shows side views of the folded electromagnetic coil as three magnets, alternate-poles leading, momentarily pass different locations along coil centerline. 
         FIGS. 10A-B  shows side views of the folded electromagnetic coil as one magnet, north-pole leading, is forced by alternating current to move along the coil centerline. 
     
    
    
     REFERENCE NUMERALS 
     
         
           20  folded electromagnetic coil 
           22  wire 
           24  first semicircle section of coil 
           26  second semicircle section of coil 
           28  coil centerline 
           30  coil opening 
           32  electric current 
           34  coil magnetic-field 
           40  magnet 
           42  magnet support 
           44  magnet centerline 
           46  magnet magnetic-field 
           48  electronic controls 
       
    
     DETAILED DESCRIPTION 
     FIGS.  1 - 3   
     The embodiment of the folded electromagnetic coil  20  is illustrated in a  FIG. 1  (isometric) and  FIG. 2  (end view) and consists of wire  22 . Wire  22  is electrically conductive and may be covered with electrical insulation material. Coil  20  is made from wire  22  wrapped into many loops that are folded to form a first semicircle section  24  and a second semicircle section  26  that have approximately the same coil centerline  28  and approximately the same coil opening  30  with respect to coil  20  not completely encircling coil centerline  28 . Centerline  28  can be linear, curved, or other shapes. Coil opening  30  can be any circular subsection. 
     When a changing electric current  32  passed through coil  20 , it induces a magnetic-field  34  that concentrates at the center of coil  20  as shown in  FIG. 3 . 
     Operation—FIGS.  4 - 6   
     Because coil  20  does not completely surround centerline  28 , magnet  40  with support  42  can pass along centerline  28  unobstructed (or coil  20  can pass around magnet  40 ) as shown in  FIG. 4  (isometric) and  FIG. 5  (end view). Magnet  40  can be permanent or electromagnetic with a north and south-pole, a magnet centerline  44 , and magnetic-field  46  surrounding it as shown in  FIG. 6 . Magnet  40  can pass along coil centerline  28  with its north-pole leading through coil  20 , or its south-pole leading through coil  20 , or both north/south leading through coil  20  at the same time, or any other orientation of poles relative motion of magnet  40  and coil  20  along centerline  28 . 
     Support  42  can be any shape or material to support a plurality of magnets  40  in linear or rotational motion through a plurality of coils  20 . A portion, all, or none of support  42  may pass through coil  20  depending on the size and shape of magnet  40 . For example, magnet  40  may be sized and shaped to pass through coil  20  without support  42 . 
     Example of Operation in an electric generator—FIGS.  7 - 9   
     To generate electricity with the folded electromagnetic coil  20 , an external force such as a wind turbine moves magnet  40  through coil  20  along coil centerline  28  (or moves coil  20  around magnet  40  on coil centerline  28 ). As described below, current  32  is generated in alternating directions as magnet  40  passes through centerline  28 . 
     When magnet  40 , with north-pole leading, momentarily passes half way into first semicircle section  24 , its magnetic field  46  induces current  32  that flows counterclockwise as shown in  FIG. 7A . 
     When magnet  40  momentarily passes to the center of first semicircle section  24 , its magnetic field  46  induces current  32  in first semicircle section  24  but equally in opposite directions such that current  32  sums to zero as shown in  FIG. 7B . 
     When magnet  40  momentarily passes in between first and second semicircle section  24 ,  26 , its magnetic field  46  induces current  32  that flows clockwise through both sections  24 , 26  such that current  32  from section  24 , 26  are in the same direction and add as shown in  FIG. 7C . 
     When magnet  40  momentarily passes to the center of second semicircle section  26 , its magnetic field  46  induces current  32  in second semicircle section  24  but equally in both directions, producing a sum of zero current as shown in  FIG. 7D . 
     When magnet  40  momentarily passes half way into second semicircle section  26 , its magnetic field  46  induces current  32  that flows counterclockwise as shown in  FIG. 7E . 
     When magnet  40 , with south-pole leading, passes in between first and second semicircle section  24 ,  26 , its magnetic field  46  induces current  32  that flows counterclockwise through both sections  24 , 26  such that current  32  adds as shown in  FIG. 8 . It should be noted that current  32  is in the opposite direction of the same magnet location of  FIG. 7C  with north-pole leading. 
     Thus, when a first magnet  40 A, south pole leading, momentarily passes into the center of a second coil  20 B and a second magnet  40 B, north-pole leading, momentarily pass into the center of a first coil  20 A, their magnetic fields  46  are in opposite direction yet both generate current  32  in a clockwise direction such that current  32  from both coils  20 A,  20 B as connected are in the same direction and add as shown in  FIG. 9A . 
     When a second magnet  40 B, north pole leading, momentarily passes into the center of second coil  20 B and a third magnet  40 C, south-pole leading, momentarily pass into the center of first coil  20 A, their magnetic fields  46  are again in opposite directions and in this situation both generate current  32  in a counterclockwise direction such that current  32  from coils are in the same direction and add as shown in  FIG. 9B . 
     Thus, a plurality of magnets  40 , with alternating poles leading, passing through a plurality of coils  20  can generate alternating current  32  in the same direction such that current  32  increases linearly with an increase in magnets  40  and coils  20 . Current  32  can also be increased by moving magnets  40  faster through coils  20  and increasing the number of loops in coil  20 . 
     Example of Operation in an Electric Motor—FIG.  10   
     The folded electromagnetic coil  20  can also produce mechanical force of a motor when current  32  is introduced into coil  20  from an external source such as a battery or an electric power plant. Current  32  induces coil magnetic-field  34  as shown in  FIG. 3 . With precise timing, electronic controls  48  reverse the direction of current  32  causing a reverse in the direction of coil magnetic field  34  such that magnet  40  can be alternately pulled and pushed to move continuously along coil centerline  28 . 
     When an external current  32  is sent counterclockwise through coil  20 , coil magnetic-field  34  and magnet magnetic-field  46  are in opposite directions, pushing magnet  40 , with north-pole leading, along centerline  28  from first semicircle section  24  to second semicircle section  26  as shown in  FIG. 10A . Furthermore, non-symmetric coil magnetic-field  34  around magnet  40 , due to coil opening  30 , causes a pushing force on magnet  40  in a direction through the middle of coil opening  30  and perpendicular to coil centerline  28 . If oriented against gravity, this force could be used to magnetically levitate coil  20  relative to magnet  40  or vice versa. 
     When an external current  32  is subsequently sent clockwise through coil  20 , coil magnetic-field  34  and magnet magnetic-field  46  again are in opposite directions, pushing magnet  40 , with north-pole leading, along centerline  28  from second semicircle section  24  to outside coil  20  as shown in  FIG. 10B . Again, non-symmetric coil magnetic-field  34  around magnet  40  causes a pushing force on magnet  40  in a direction through the middle of coil opening  30  and perpendicular to coil centerline  28 . 
     Advantages 
     From the description above, a number of advantages of my folded electromagnetic coil become evident: 
     (a) Produces the same amount of power (current times voltage) as a coil with a ferromagnetic core but avoids the added complexity and costs of a core. A similar size, coreless electromagnet coil produces much less power. 
     (b) Enables total avoidance of clogging, since there is no ferromagnetic core for the magnets to attract. Consequently, generators and motors with folded electromagnetic coils do not lose power to reduce cogging as is necessary in generators and motors using coils with ferromagnetic cores. Also, the instability, noise, and damage associated with cogging are avoided. 
     (c) Enables the generator to work at all ranges of external force, avoiding lost power when the generator is not rotated within a certain range as with induction generators. 
     (d) Enables the electronics for a more productive generator to be very simple and inexpensive. This is particularly beneficial for wind, hydro, and wave turbines. 
     (e) Enables a motor to be less complicated and less expensive than existing motors, yet operate more efficiently and powerfully with full control of rotation velocity and torque. 
     (f) With simpler and less expensive generators and motors coupled with more power output, clean power from wind, hydro, and wave become more cost-efficient. 
     (g) The motor force perpendicular to the centerline could be used to magnetically levitate the rotor, further increasing efficiency by avoiding friction and lowering costs by eliminating bearings and other anti-friction components and maintenance. 
     CONCLUSIONS, RAMIFICATIONS, AND SCOPE 
     Accordingly, the reader will see that the folded electromagnetic coil can be used to generate electricity more efficiently than other electromagnetic coils, yet more simply and at lower cost. Cost-effective power generation is a critical parameter for clean power sources such as wind, hydro, and wave power to gain acceptance over conventional coal and oil power plants that pollute our environment. 
     Likewise, simpler and less expensive motors enable their greater use, improving quality of life and higher productivity all over the world. These high-efficiency, coreless coils may also enable frictionless motors, adding to even better performance. 
     Although the description above contains many specificities, these should not be construed as limiting the scope of the embodiment but as merely providing illustrations of some of the presently preferred embodiment. For example, larger or smaller magnets can be used to have more or fewer magnets and magnetic poles in a semicircle section. 
     Thus, the scope of the embodiment should be determined by the appended claims and their legal equivalents, rather than by examples given.