WO2011136854A1

WO2011136854A1 - Radial gap motor-generator

Info

Publication number: WO2011136854A1
Application number: PCT/US2011/000750
Authority: WO
Inventors: Christopher W. Gabrys
Original assignee: REVOLUTION ELECTRIC MOTOR COMPANY Inc; Revolution Electric Motor Co Inc
Current assignee: REVOLUTION ELECTRIC MOTOR COMPANY Inc; Revolution Electric Motor Co Inc
Priority date: 2010-04-28
Filing date: 2011-04-28
Publication date: 2011-11-03
Anticipated expiration: 2012-10-28

Abstract

A radial gap motor-generator includes a rotor that rotates about an axis of rotation, and a stator that is stationary and magnetically exerts torque upon the rotor. The rotor is constructed of two concentric, radially spaced apart ferromagnetic cylinders, to which has magnets are attached to drive magnetic flux radially back and forth across the radial gap between the ferromagnetic cylinders forming a magnetic airgap therebetween. The stator is located between the ferromagnetic cylinders and has windings having an active region and end turn regions. The windings traverse axially in the active region and traverse circumferentially in the end turn regions. The windings are wound from wire formed from a bundle of individually insulated conductor strands that are electrically connected in parallel but are electrically insulated between each other along their length in the magnetic airgap. The bundle is diametrally compressible and elastic.

Description

Radial Gap Motor-Generator

This invention pertains to motor-generators for converting between electrical and mechanical energy, and more particularly to a radial gap motor-generator that provides increased efficiency per cost while allowing for a standard frame diameter and size. The motor-generator construction can further achieve a high power density and operate more efficiently over a wide speed and power range. This relates to and claims priority for US SN 61/343,477 filed April 28, 2010 and titled "Radial Gap Motor-Generator."

Background of the Invention

Electric motors and generators convert between electric and rotary mechanical power. Motors currently consume more than 50% of electrical power produced, and the cost of electric power is projected to increase significantly in the coming years. There is a great desire to increase the efficiency of electric motors for saving energy and reducing pollution to the environment.

The efficiency of electric motors can potentially be increased by reducing the resistive and magnetic induced losses. Magnetic losses include both hysteresis and eddy current losses and are the result of changing magnetic field through different parts of the motor.

One type of electrical machine that can provide for reduced magnetic induced losses is an air core construction. Air core motors and generators place the windings within a magnetic airgap, and not in slots cut into an iron stator as in conventional electrical machines. However, air core motors and generators have suffered from higher costs as a result of the required magnet and copper amounts. Some designs have also required a non-standard size, making them difficult to use for replacement. It is desirable to provide new motors and generators with increased efficiency per cost that can also be made to utilize standard frame sizes.

Summary of the Invention

The invention provides a radial gap motor-generator with higher efficiency per cost. The motor-generator comprises a rotor that rotates about an axis of rotation, and a stator that is stationary and magnetically exerts torque upon said rotor. The rotor is constructed of two concentric, radially spaced apart ferromagnetic cylinders, whereby magnets attached to the ferromagnetic cylinders drive magnetic flux radially back and forth between the

ferromagnetic cylinders forming a magnetic airgap therebetween. The stator is located between the ferromagnetic cylinders and comprises windings having an active region and end turn regions, wherein the windings traverse axially in the active region and traverse circumferentially in the end turn regions. The windings are wound from wire formed from a bundle of individually insulated conductor strands, wherein the strands are electrically connected in parallel but are electrically insulated between each other along their length in the magnetic airgap, and wherein the bundle is diametrally compressible and elastic. The windings are supported by a low electrical conductivity form such that all phases of the windings lie against each other and in a single radial layer in the active region, and the wires are separated from each other by a form outside of the magnetic airgap, ensuring that the wires are held straight in the active region.

Typically in air core motor-generators, increased copper windings volume results in higher efficiency from reduced resistive losses. We have found that less copper volume but with more copper per windings volume, giving a greater copper windings density, can increase efficiency. The result is partially achieved as a function of reducing the magnetic airgap thickness. We have found that reducing the magnetic airgap will more than proportionally increase the magnetic flux density for a given ratio of magnet thickness to airgap thickness. This higher than proportion increase in flux density can advantageously allow for use of a shorter winding active region with production of the same back emf, and lower winding resistance.

Flexible winding wire would typically tend to make winding an accurate and rigid armature difficult, because the flexible windings wire is easy to form, although it does not hold its position as well as solid wire. However, the flexible multi-strand construction does make the wire diametrally compressible and elastic, and therefore can be clamped in a fixed position by pushing wire into a reduced opening slot of a form. In a preferred embodiment, the form clamps the wires where they are separated. The wires are preferably separated at a location outside of the magnetic airgap. The clamping does not cause need for an increased magnetic airgap because it is outside of the magnetic airgap.

Several findings and parameters support the increased efficiency per unit cost of the new motor-generators. The thinner airgap from haying all the phase windings lie in a single radial layer, is found to yield an unproportional ly higher flux density per magnet volume, even with the same ratio of magnet thickness to airgap thickness. In addition, we have found that windings near the circumferential ends of the poles do not contribute to back emf and power conversion. If magnet is included at the ends of the poles, it does no significant work and primarily provides only leakage flux. In examination of the back emf generation of the motor-generator windings, a three phase wye connected armature is found to produce the peak voltage when two of three phases are circumferentially centered together with the center of a pole. The wye connection is preferred because it eliminates circulating currents and their losses that can occur in a delta winding connection. Further, the additional windings over the width of a pole add winding resistance and resistive loss. Maximum windings density in the active region is further achieved when the wires lie against each other and in a single radial layer in the active region. The highest winding density supports a thinner air gap and resulting higher flux density, as well as the lowest resistance of windings to best take advantage of the flux distribution for power conversion. The higher flux density reduces the windings length required for the desired back emf and in turn reduces the phase resistance. Windings of flexible wire can be accomplished for these armatures with the clamping of the wires outside the active region where the magnetic airgap is not affected.

In one embodiment of the invention, the wires are clamped by being compressed in the circumferential direction of the motor-generator and being expanded in the radial direction of the motor-generator, and the radial expansion occurs outside the magnetic airgap. In this configuration, the clamps can be located just outside or near the ends of the active region and accurately hold the wires to lie side-by-side and straight in the axial direction when in the active region. The active region is the portion of the windings that receives the flux and is in a direction that causes generation of back emf.

The efficiency of the motor-generator is maintained high with the use of the wire formed of a bunch of multiple individually insulated strands. Wire constructed in this manner reduces the eddy current losses that would otherwise be significant in a larger solid conductor wire. A drawback is that the wire has a lower packing factor than a solid conductor wire, and resultantly has a higher resistance per length for a given cross-sectional area of copper. An additional advantage of the wire construction is that wire can be made diametrally compressible and elastic, and also facilitates the clamping of the wires where separated. The diametral elasticity of the wire can be increased by several means. In one embodiment, the diametral elasticity is increased by having an outer sheath over the strand bundle. The sheath will tend to keep the wire from changing shape without compression force applied. In another embodiment, the diametral elasticity of the wire is increased by twisting of the strands wherein strands are twisted in one direction and groups of strands are assembled together by twisting in the opposite direction.

The construction of the air core armature results in a single radial layer of the multiple phase windings in the active region. At the end turn regions, the windings of different phases overlap. A drawback of the design is that it can make assembly of the armature into the rotor difficult. The end turn regions are radially thicker than the active region, so inserting the thicker end turn region through the narrow airgap can be difficult. To overcome the issues of assembly, in one embodiment the form has clamps for the wires where separated and the clamps are located at one end turn region with a greater diameter than clamps located at the other end turn region. Once wound, the armature end turns at one end of the armature can be made to have a reduced diameter while the end turns at the opposite can have an increased diameter. The armature can be inserted into the space between the ferromagnetic cylinders and magnets on one cylinder inserted later.

It is desirable to utilize the minimum amount of magnet material for attaining the greatest power conversion. Magnet material at locations that do not contribute to significant work is preferably omitted. Magnet material at the circumferential ends of the poles contributes to leakage and is preferably not included. In a further embodiment of the invention, the magnets are circumferentially spaced apart on the ferromagnetic cylinders but have a pole arc length that is equal to or greater than the width of the wires of two phases in the active region. If the magnet arc length is at least equal to or greater than the width of two phases, then the maximum utilization of the windings can occur and all wires contribute to production of back emf simultaneously. Additionally, the circumferential width of a single phase winding in the active region is approximately equal to 1/3 the pole pitch of the rotor, and the magnets have circumferential width that is between 60% and 85% of the pole pitch of the rotor. This minimizes the magnet for high power density and efficiency.

The armature form can be constructed as continuous thin walled tube that provides structural support for the windings along their length, including in the active region. In some cases, it can be desirable to further increase the performance of the motor-generator per unit cost by reducing the magnetic airgap even further. In this case, the form material can be eliminated in the active region. In an additional embodiment, the form comprises two separate pieces with one located at each end turn region and the wires achieve structural integrity by being bonded together with each other in the active region. The forms can be spaced apart by tooling to hold the active region windings straight during winding. The active region wires can be bonded together while on the tooling and the tooling later removed to allow an even thinner armature and allow further reduced magnetic airgap.

The form facilitates winding of the high efficiency armatures using the flexible windings. In a preferred embodiment, the form has holding features for the wires where the wires are separated such that each holding feature holds a single wire. As the windings are wound, each holding feature satisfactorily clamps an individual wire and allows rapid continuation of the winding process until complete. The lowest cost construction of the rotor consists of utilizing radially magnetized magnets attached to ferromagnetic cylinders. The magnets drive the magnetic flux radially across the magnetic airgap and circumferentially through the cylinders. In some cases, it may be desirable, such as for inertia reduction, to utilize non-ferromagnetic cylinders. In this case the magnets can be magnetized in a Halbach array configuration. This construction conducts the flux circumferentially by circumferential magnetized magnets as well as radially across the magnetic airgap by radial magnetized magnets. The drawback of using non- ferromagnetic cylinders and a Halbach magnet array are more expensive magnets and more difficult rotor assembly.

The winding process of the motor-generators can simplify construction and electrical connections. For a twenty pole, three-phase motor, it is possible to have only three windings and only six coil ends. This is in contrast to sixty coil ends if constructed from coils wound independently and later assembled. In a preferred embodiment, the windings are attached to a low electrical conductivity form such that all phases of the windings lie in a single radial layer in the active region, the windings are separated from each other by clamps of the form at a location outside of the magnetic airgap and the windings are wound by successively bending the wire into a winding pattern and pushing the wire into the clamps. For example, a wire can be inserted into a clamp, then pulled straight across the active region, inserted into a second clamp, bent into an end turn, inserted into a third clamp and pulled across the active region in the opposite direction and inserted into a fourth clamp, repeatedly.

Controlling the spacing of the wires in the active region allows the armatures to be wound both densely and accurately. By the combination of compressible wire and having features to space the wires to be located outside the magnetic airgap allows the magnetic airgap to be made as thin as possible and allows the maximum windings density. In another embodiment, the windings are attached to a low electrical conductivity form such that wires lie adjacent to each other inside the magnetic airgap in a single radial layer containing three phases, and at a position in the end turn regions wires of a single phase are spaced apart from each other by the form, and wires of different phases radially overlap in the end turn regions.

Description of the Drawings

The invention and its many advantages and features will become better understood upon reading the following detailed description of the preferred embodiments in conjunction with the following drawings, wherein:

Fig. 1 is a schematic drawing of an air core motor-generator in accordance with the invention; Fig. 2 is a schematic end view of the rotor in the air core motor-generator of Fig. 1 in accordance with the invention;

Fig. 3 is a comparison plot of magnetic pole flux density versus airgap for both radially thick and radially thin magnets.

Fig. 4A is a schematic drawing of the armature form in the air core motor-generator of

Fig. 1 in accordance with the invention;

Fig. 4B is a schematic drawing of the armature form shown in Fig. 4A with one winding attached;

Fig. 5 is a developed side view of a section of the completed wound armature in the air core motor-generator of Fig. 1 in accordance with one embodiment of the invention;

Fig. 6 is a cross-sectional view of the active length region of the armature in the air core motor-generator of Fig. 1 in accordance with the invention;

Fig. 7 is a cross-sectional view of the clamping portion of the armature in the air core motor-generator of Fig. 1 showing the circumferentially compressed wires in the end turn region in accordance with the invention;

Fig. 8 is an electrical schematic of the three phase wye connected phase windings of the armature in the air core motor-generator of Fig. 1 in accordance with the invention;

Fig. 9 is a rotor and armature cross section of an air core motor-generator of prior art;

Fig. 10 is a simplified magnetic pole flux plot of the prior art air core motor-generator of Fig. 9;

Fig. 11 is an cross-sectional axial end view of an enlarged section of a rotor and armature of an air core motor-generator in accordance with the invention;

Fig. 12 is a simplified magnetic pole flux plot of the air core motor-generator of Fig. 11 in accordance with the invention;

Fig. 13 is a comparison of magnet weight between an equivalent rated three phase prior air core motor of Fig. 9 with three wire layers in the armature, and a new motor in accordance with the invention;

Fig. 14 is a comparison of copper weight between an equivalent rated prior air core motor Fig. 9 and a new motor in accordance with the invention;

Fig. 15 is a comparison of electrical efficiency between an equivalent rated prior air core motor Fig. 9 and a new motor in accordance with the invention; Fig. 16 is a comparison of efficiency of several different 1 HP induction motors and a new motor in accordance with the invention;

Fig. 17 is a cross-section of the active region of an air core motor-generator in accordance with the invention;

Fig. 18 is a cross-section of alternate configuration active region of an air core motor- generator in accordance with the invention;

Fig. 19 is a cross-section of a second alternate configuration active region of an air core motor-generator in accordance with the invention;

Fig. 20 is a schematic drawing of an alternate configuration armature form, with one winding attached for an air core motor-generator in accordance with the invention; and

Fig. 21 is a side view of the alternate configuration of completed wound armature in the air core motor-generator of Fig. 1 in accordance with the invention;

Description of the Preferred Embodiments

Turning to the drawings, wherein like reference characters designate identical or corresponding parts, Fig. 1 shows an air core motor-generator 30 comprised of a rotor 31 and a stator 32. The rotor 31 is constructed of two concentric spaced apart steel cylinders 33, 34. Magnets 35, 36 attached to the cylinders 33, 34 drive magnetic flux radially back and forth between the cylinders and define a magnetic airgap 37 therebetween. Magnets 35, 36 may be attached to one or both cylinders 33, 34. The cylinders 33, 34 are coupled together at one end by a hub 38 that connects to a shaft 39. Air cooling passages 40 may be prpvided in the hub

38 to facilitate air flow and cooling through the airgap 37. Located inside the magnetic airgap 37 is an air core armature 41 that magnetically exerts torque on the rotor 31. The shaft

39 is journaled for rotation by bearings 42, 43 that are supported by housing end plates 44, 45. The end plates 44, 45 are attached together and aligned by an outer housing tube 46. Windings 47 from the armature 41 connect to a variable frequency drive 49 through inductors 48 when operated as a motor. Input power 50 powers the VFD 49 to provide synchronous power to the motor 30.

A schematic end view drawing of the rotor in the air core motor-generator of Fig. 1 is shown in Fig. 2. The rotor 31 is constructed of nested cylinders 33, 34 such that the whole magnetic path rotates, and a circumferentially varying magnetic flux does not pass through a stationary steel stator, as in conventional slot wound motor-generators. The benefits of this construction include the elimination of eddy current and hysteresis losses that would otherwise occur in a steel stator. Radial magnets 35, 36 are attached to the cylinders 33, 34 to drive flux radially back and forth between the cylinders 33, 34, and the flux is conducted circumferentially through the cylinders 33, 34 to complete the flux loop. In an alternate construction, with typically significantly higher costs, the magnets could be magnetized in a Halbach magnet array and the cylinders are no longer required to conduct flux

circumferentially. In such an arrangement, the cylinders could be made thinner and of non- ferromagnetic material, if desired.

In the design and testing of air core motor-generators, we have found that a significant improvement in the efficiency or power density per cost can be achieved by reducing the magnetic airgap thickness even while reducing the amount of magnet utilized. A comparison plot 55, in Fig. 3,of magnetic pole flux density versus airgap for both radially thick and radially thin magnets, shows the average pole flux density versus airgap thickness for both thick magnets 51 (0.188" thick) and thin magnets 52 (0.125" thick) of a given motor design. A surprising finding is that the flux density can be significantly increased by reducing the magnetic airgap thickness, even when the ratio between magnet thickness and airgap thickness is held constant and the amount of magnet utilized is also reduced. The magnetic flux density does not stay constant for constant ratios of magnet thickness to airgap thickness. For example, the flux density measurement 54 is for 0.125" thick magnets with a 0.200" airgap thickness and flux density measurement 53 is for 0.188" thick magnets with a 0.300" airgap thickness. Both configurations 53, 54 have the same ratio of magnet thickness to airgap thickness, yet surprisingly the thinner magnets with thinner magnetic airgap provide a 16% higher magnetic flux density, or 0.64T versus 0.55T.

It is therefore desirable to reduce the magnetic airgap thickness to the minimum possible value through construction. Instead of winding multiple phase windings in multiple layers, it is preferable to wind the multiple phase windings in a single layer. A net effect of increased flux density can thereby reduce the required amount of both windings for achieving the desired back emf and the required amount of magnet. A schematic drawing of an armature form 60 in the air core motor-generator of Fig. 1 in accordance with the invention is shown in Fig 4A. The form 60 is preferably constructed from a low electrical conductivity material and preferably non-magnetic material such as a strong rigid plastic such as polycarbonate. The form 60 comprises a tube 61 with a mounting section 62 that transfers torque from the windings (shown in Figs. 4B and 5) to the housing. Mounting holes 63 can be utilized for attachment. The form 60 further includes clamps 64, 65 that separate the wires of the windings at locations outside the magnetic airgap to facilitate clamping the wires in position. A schematic drawing of the armature form 60, with one winding 66 attached, in the air core motor-generator of Fig. 1, is shown in Fig. 4B. The form 60 can support the windings 66 during the winding process. The windings 66 comprise an active region 67 that traverses axially, receives magnetic flux and generates back emf, and two end turn sections 68, 69 that traverse circumferentially. In the active region 67, the windings of all phases lie juxtaposed together in a single radial layer. The windings of multiple phases overlap at the end turn sections 68, 69.

A developed side view of a portion of the completed wound armature in the air core motor-generator of Fig. 1 in accordance with the invention is shown in Fig. 5. The armature 41 is wound with wires 66 such that they have a single layer active region 67 for receiving magnetic flux and producing back emf. The windings 66 further include end turns 68 and 69 that travel circumferentially to connect wires in the active region 67. Outside of the magnetic airgap, clamps 64, 65 separate and squeeze the wires circumferentially and expand the wires radially to hold the wires 66 in place while still allowing the wires 66 to lie next to each other in the active region 67. The form tube 61 connects the clamps 64, 65 at each end of the armature 41.

A cross-sectional view of the active length region of the armature in the air core motor-generator of Fig. 1 in accordance with the invention is shown in Fig. 6. The armature 41 comprises wires 66 with diameter 80 that are a bundles of individually insulated strands. The wires 66 lie against each other in the active region as they run in an axial direction.

A cross-sectional view of the clamping portion of the armature in the air core motor- generator of Fig. 1 in accordance with the invention is shown in Fig. 7. The armature 41 comprises wires 66 with diameter 80 that are spaced apart from each other by clamps 64 at the cantilevered end of the armature form 60. The clamps 64 have a width 81 that squeezes the wires 66 in the circumferential direction of the motor-generator to the small thickness 81 of the clamps and expands them in the radial direction shown by the vertical arrow 85 in Fig. 7.

An electrical schematic 90 of the phase windings of the armature in the air core motor-generator of Fig. 1 in accordance with the invention is shown in Fig. 8. The schematic shows a wye connection of the three phase windings 91, 92, 93. The voltage 94 across two legs 91, 93 is the sum of two phases since the current 95 flows through both.

A rotor and armature cross section of an air core motor-generator 100 of prior art is shown in Fig. 9. The motor-generator 100 comprises rotor magnets 101, 102 that are attached to ferromagnetic backirons 103, 104. The magnets 101, 102 drive magnetic flux back and forth across the airgap 105. Located in the airgap 105 is an aircore armature 106. The armature 106 utilizes a plastic form 1 10 and has three phase windings 107, 108, 109 that are located in three layers across the airgap 105.

A simplified magnetic pole flux plot of the air core motor-generator of Fig. 9 of prior art is shown in Fig. 10. The flux plot 120 shows the pole pitch 121, which is the length between the circumferential centers of adjacent magnets. The magnets produce an airgap flux density profile 122. The pole pitch of the outer magnets is somewhat greater than the pole pitch of the inner magnets; the pole pitch of the motor is the average of the inner pole pitch and the outer pole pitch. The peak flux density 123 has an approximate flux width 124 and a deadband 125 where the flux density is reduced due to circumferential leakage. Also shown is the width of two phases 126, which is wider than the pole pitch 121. In the deadband 125, the two phases 126 do not produce significant added back emf yet the windings in the deadband 125 increase resistive losses. Beyond the deadband 125, the extra width of the two phases 127 generates negative back emf that reduces power conversion and efficiency further.

An enlarge section of a rotor and armature cross section of an air core motor- generator 130 in accordance with the invention is shown in Fig. 11. The motor-generator 130 comprises rotor magnets 131, 132 that are attached to ferromagnetic backirons 133, 134. The magnets 131, 132 drive magnetic flux back and forth across the airgap 135. Located in the airgap 135 is an aircore armature 136. The armature 136 utilizes a plastic form 140 and has three phase windings 137, 138, 139 that are located in a single layer across the airgap 135.

A magnetic pole flux plot of the air core motor-generator of Fig. 1 1 is shown in Fig. 12. The flux plot 150 shows the pole pitch 151. The magnets produce flux density profile 152 with a peak flux density 153 and approximate flux width 154. Also shown is the width of two phases 155. The width of two phases 155 is less than the pole pitch 151 and preferably approximately equivalent to the flux width. The magnets 131, 132 are

circumferentially spaced apart on the cylinders but have a pole arc length that is equal to or greater than the width of the wires of two phases in the active region.

A comparison of magnet weight between an equivalent rated prior air core motor and a new motor in accordance with the invention is shown in Fig. 13. The chart 160 shows theprior 1 HP air core motor of Fig. 9 utilized 6.82 lbs of NdFeB magnet. The new 1 HP motor of Fig. 11 utilizes only 2.19 lbs of NdFeB magnet.

A comparison of copper weight between an equivalent rated prior air core motor and a new motor in accordance with the invention is shown in Fig. 14. The chart 170 shows the prior 1 HP air core motor utilized 2.69 lbs of copper. The new 1 HP motor utilizes only 0.56 lbs of copper.

A comparison of electrical efficiency between an equivalent rated prior air core motor and a new motor in accordance with the invention is shown in Fig. 15. The electrical efficiency does not include the bearing and windage losses. The chart 180 shows the prior 1 HP air core motor provided an electrical efficiency of 97.2%. The new 1 HP motor provides an electrical efficiency of 99.1%

A comparison of efficiency different 1 HP induction motors and a new motor in accordance with the invention is shown in Fig. 16. The chart 190 compares single phase conventional induction motor 191, single phase premium efficiency 192, three phase conventional 193, three phase premium 194 and the new motor 195.

A cross-section of the active region of an air core motor-generator in accordance with the invention is shown in Fig. 17. The active region 67 comprises wires 66 traversing axially that are supported by tube portion 61 of the armature form 60. The wires 66 have a diameter 200 and have a total radial armature thickness 201 of the wires 66 and form tube 61.

A cross-section of alternate configuration active region of an air core motor-generator in accordance with the invention is shown in Fig. 18. The active region 67 comprises wires 66 traversing axially that are supported by the armature form tube 61. After winding, the wires 66 are compressed to a thinner radial thickness 210 by either tooling or an outer band. The armature has a total radial thickness 211.

A cross-section of a second alternate configuration active region of an air core motor- generator in accordance with the invention is shown in Fig. 19. The active region 67 comprises wires 66 that are compressed after winding into a reduced radial thickness 220. The active region 67 does not contain the form so the thickness of the windings 220 is equal to the armature total radial thickness 221. The wires 66 are preferably bonded together to make the active region 67 rigid for operation of the motor-generator. A reinforcing band 68, 69 of fiberglass or the like can be bonded to radial inner and/or outer surface of the band of wires 66 during compression to the radial thickness 221 if desired for higher power applications.

A schematic drawing of an alternate configuration armature form, with one winding attached for an air core motor-generator in accordance with the invention is shown in Fig. 20. The form 60' is preferably constructed from a low electrical conductivity material and preferably non-magnetic material such as rigid, heat resistant, dimensionally stable plastic. The form 60' comprises a mounting section 62 that transfers torque from the windings to the housing. Mounting holes 63 can be utilized for attachment. The form 60' further includes clamps 64, 65 that separate the wires of the windings at locations outside the magnetic airgap.

The form 60' can support the windings 66 during the winding process. The windings 66 are bonded together in the active region to become rigid and allow for operation of the motor-generator without the armature contacting the rotor.

A side view of another alternate configuration of completed wound armature in the air core motor-generator of Fig. 1 in accordance with the invention is shown in Fig. 21. The armature 240 is wound with wires 66 such that they have a single layer active region 67 for receiving magnetic flux and producing back emf. The windings 66 further include end turns 70 and 72 that travel circumferentially to connect wires in the active region 67. Outside of the magnetic airgap, clamps 64, 65 separate and squeeze the wires 66 axially and expand the wires radially to hold the wires in place while still allowing the wires 66 to lie next to each other in the active region 67. The form tube 61 connects the clamps 64, 65 at each end of the armature 240.

Obviously, numerous modifications and variations of the described preferred embodiment are possible and will occur to those skilled in the art in light of this disclosure of the invention. Accordingly, I intend that these modifications and variations, and the equivalents thereof, be included within the spirit and scope of the invention as defined in the following claims, wherein I claim:

Claims

1. A radial gap motor-generator comprising:

a rotor that rotates about an axis of rotation, and a stator that is stationary and magnetically exerts torque upon said rotor;

said rotor is constructed of two concentric, radially spaced apart ferromagnetic cylinders, whereby magnets attached to said ferromagnetic cylinders drive magnetic flux radially back and forth between said ferromagnetic cylinders forming a magnetic airgap therebetween; said stator is located between said ferromagnetic cylinders and comprises windings having an active region and end turn regions, wherein said windings traverse axially in said active region and traverse circumferential ly in said end turn regions;

said windings are wound from wire formed from a bundle of individually insulated conductor strands, wherein said strands are electrically connected in parallel but are electrically insulated between each other along their length in said magnetic airgap, said bundle being diametrally compressible and elastic;

said windings are supported by a low electrical conductivity form such that all phases of said windings lie in a single radial layer in said active region, said wires lie against each other in said active region and are separated from each other by said form at a location outside of said magnetic airgap.

2. A brushless motor-generator as described in claim 1 wherein: said form clamps said wires where said wires are separated.

3. A brushless motor-generator as described in claim 2 wherein:

said wires are clamped by being compressed in the circumferential direction of said motor- generator and being expanded in the radial direction of said motor-generator, said radial expansion occurring outside said magnetic airgap.

4. A brushless motor-generator as described in claim 2 wherein:

said diametral elasticity of said wire is increased by having an outer sheath over said bundle.

5. A brushless motor-generator as described in claim 2 wherein:

said diametral elasticity of said wire is increased by twisting of said strands wherein strands are twisted in one direction and groups of strands are assembled together by twisting in the opposite direction.

6. A brushless motor-generator as described in claim 2 wherein:

said form has clamps for said wires where separated and said clamps are located at one end turn region with a greater diameter than clamps located at the other end turn region.

7. A brushless motor-generator as described in claim 1 wherein:

said magnets are circumferentially spaced apart on said ferromagnetic cylinders and have a pole arc length that is equal to or greater than the width of the wires of two phases in said active region.

8. A brushless motor-generator as described in claim 1 wherein:

said magnets have circumferential width that is between 60% and 85% of the pole pitch of the rotor, and the circumferential width of a single phase winding in the active region is approximately equal to 1/3 of the pole pitch of the rotor.

9. A brushless motor-generator as described in claim 1 wherein:

a single phase winding in said active region has a width that is approximately equal to 1/3 the pole pitch of said rotor.

10. A brushless motor-generator as described in claim 1 wherein:

said form comprises two separate pieces with one located at each end turn region and said wires achieve structural support by being bonded together with each other in said active region.

11. A radial gap motor-generator comprising:

said rotor is constructed of two concentric, radially spaced apart cylinders, whereby magnets attached to said cylinders drive magnetic flux radially back and forth between said cylinders forming a magnetic airgap therebetween;

said stator is located between said cylinders and comprises windings having an active region and end turn regions, wherein said windings traverse axially in said active region and traverse circumferentially in said end turn regions;

said windings are attached to a low electrical conductivity form such that wires lie adjacent to each other inside said magnetic airgap in a single radial layer containing three phases, and at a position in the end turn regions wires of a single phase are spaced apart from each other by said form, and wires of different phases radially overlap in said end turn regions

12. A brushless motor-generator as described in claim 11 wherein: said form clamps said wires where said wires are separated.

13. A brushless motor-generator as described in claim 12 wherein:

14. A brushless motor-generator as described in claim 12 wherein:

the diametral elasticity of said wire is increased by having an outer sheath over said bundle.

15. A brushless motor-generator as described in claim 12 wherein:

the diametral elasticity of said wire is increased by twisting of said strands wherein strands are twisted in one direction and groups of strands are assembled together by twisting in the opposite direction.

16. A brushless motor-generator as described in claim 12 wherein:

the wires are clamped across their diameters to the form at a portion outside the magnetic airgap.

17. A brushless motor-generator as described in claim 12 wherein:

said form has clamps for said wires where separated and said clamps are located at one end turn region with a . greater diameter than clamps located at the other end turn region.

18. A brushless motor-generator as described in claim 11 wherein:

said magnets are circumferentially spaced apart on said cylinders but have a pole arc length that is equal to or greater than the width of the wires of two phases in said active region.

19. A brushless motor-generator as described in claim 11 wherein:

said magnets have circumferential width that is between 60% and 85% of the pole pitch of the rotor and that the circumferential width of a single phase winding in the active region is approximately equal to 1/3 of the pole pitch of the rotor.

20. A brushless motor-generator as described in claim 11 wherein:

the width of a single phase winding in said active region is approximately equal to 1/3 the pole pitch of said rotor.

21. A brushless motor-generator as described in claim 1 1 wherein:

22. A brushless motor-generator as described in claim 11 wherein:

said form has holding features for said wires where said wires are separated such that each said holding feature holds a single wire.

23. A radial gap motor-generator comprising:

said windings are attached to a low electrical conductivity form such that all phases of said windings lie in a single radial layer in said active region, said windings are separated from each other by clamps of said form at a location outside the axial ends of said magnetic airgap and said windings are wound by successively bending said wire into a winding pattern and pushing said wire into said clamps.

24. A brushless motor-generator as described in claim 23 wherein: said form clamps said wires where said wires are separated.

25. A brushless motor-generator as described in claim 24 wherein:

26. A brushless motor-generator as described in claim 24 wherein:

27. A brushless motor-generator as described in claim 24 wherein:

28. A brushless motor-generator as described in claim 24 wherein:

29. A brushless motor-generator as described in claim 23 wherein:

30. A brushless motor-generator as described in claim 23 wherein:

31. A brushless motor-generator as described in claim 23 wherein:

32. A brushless motor-generator as described in claim 23 wherein:

33. A brushless motor-generator as described in claim 23 wherein:

two phases together are less than the width of 1 pole pitch when centered on a pole, whereby no portion of the windings will produce a negative back emf component that could reduce the power capability and efficiency of said motor-generator.

34. A brushless motor-generator as described in claim 23 wherein:

said wires lie against each other and in a single radial layer in the active region for high windings density in the active region.

35. A brushless motor-generator as described in claim 23 wherein:

two phases of said windings have a width that is less than said pole pitch and

approximately equivalent to said flux width.

36. A radial gap motor-generator comprising:

said rotor is constructed of two concentric, radially spaced apart cylinders, whereby magnets attached to said cylinders drive magnetic flux radially back and forth between said cylinders forming a magnetic airgap therebetween; said stator is located between said cylinders and comprises windings having an active region and end turn regions, wherein said windings traverse axially in said active region and traverse circumferentially in said end turn regions;

said windings are supported by a low electrical conductivity form such that all phases of said windings lie in a single radial layer in said active region, said wires lie against each other in said active region and are separated from each other by said form near the axial ends of said active region;

wires of different phases radially overlap in said end turn regions and the width of a single phase winding in said active region is approximately equal to 1/3 the pole pitch of said rotor.

37. A brushless motor-generator as described in claim 36 wherein:

said magnets are circumferentially spaced apart on said ferromagnetic cylinders but have a pole arc length that is equal to or greater than the width of the wires of two phases in said active region.