Title of Invention	ELECTRIC MACHINE WITH A WINDING FOR PRODUCING A ROTATING FIELD AND METHOD FOR PRODUCING THE WINDING
Abstract	The invention relates to an electric machine with a winding (20) for producing a rotating field with at least two coils for each phase and pair of poles, a first coil (1, 3, 5) of each phase being electrically turned through 180° in relation to a second oppositely wound coil (2, 4, 6) of this phase, wherein the coils of adjacent phases overlap and each first coil (1, 3, 5) of a phase is located in a first layer (41) and each second coil (2, 4/6) of a phase is located in a second layer (42), the second layer (42) surrounding the first layer (41). Furthermore, the invention relates to a method for producing the winding according to the invention.

Title of Invention

ELECTRIC MACHINE WITH A WINDING FOR PRODUCING A ROTATING FIELD AND METHOD FOR PRODUCING THE WINDING

Abstract

The invention relates to an electric machine with a winding (20) for producing a rotating field with at least two coils for each phase and pair of poles, a first coil (1, 3, 5) of each phase being electrically turned through 180° in relation to a second oppositely wound coil (2, 4, 6) of this phase, wherein the coils of adjacent phases overlap and each first coil (1, 3, 5) of a phase is located in a first layer (41) and each second coil (2, 4/6) of a phase is located in a second layer (42), the second layer (42) surrounding the first layer (41). Furthermore, the invention relates to a method for producing the winding according to the invention.

Full Text	FORM 2 THE PATENT ACT 1970 (39 of 1970) & The Patents Rules, 2003 COMPLETE SPECIFICATION (See Section 10, and rule 13) 1. TITLE OF INVENTION ELECTRIC MACHINE WITH A WINDING FOR AND METHOD FOR PRODUCING THE WINDING PRODUCING A ROTATING FIELD 2.APPLICANT(S) a) Name b) Nationality c) Address OERLIKON TEXTILE GMBH & CO. GERMAN Company LEVERKUSER STRASSE 65, D-42897 REMSCHEID, GERMANY KG PREAMBLE TO THE DESCRIPTION The following specification particularly describes the invention and the manner in which it is to be performed : - PATENTS ACT 1977 I, ASTRID TERRY, translator of 11, Bounds Oak Way, Tunbridge Wells, Kent. TN4 OUB, England, confirm that I am conversant with the English and German languages and I am a competent translator from one to the other. I declare to the best of my knowledge and belief that the attached English translation is a true and correct translation of the DE Patent No. 10 2007 038 601.1 Dated this 16th day of July 2008. The invention relates to an electric machine with a winding for producing a rotating field with at least two coils for each phase and pair of poles, a first coil of each phase being electrically turned through 180° in relation to a second oppositely wound coil of this phase. Furthermore, the invention relates to a method for producing the winding of the electric machine. A method for producing a winding for an electric motor, which has three phases, which are wound simultaneously on an iron core, is known from the US patent 4,847,982. The electric motor is designed as a three-phase motor, which either has six poles configured as iron bodies in order to configure the motor as a two-pole motor or which has twelve poles to configure it as a four-pole motor. The stator of the disclosed motor consists of an iron core and has three phase windings constructed from a plurality of coils on the poles to either form a two-pole or a four-pole motor, the coils being wound on the respective poles. The three phases are formed by a winding of a first coil in the clockwise direction, the iron body then being electrically turned through 180° before the respective second coil is wound anti-clockwise. The first and second coil are wound one after the other without interrupting the conductor material so owing to the simultaneous production of the coils, an accelerated winding of the winding body is possible. In this case, three coils are wound simultaneously onto salient poles of the iron body and, owing to the rotation 2 of the iron body through 180°, the winding of the next three coils can also take place in parallel. The described prior art shows a simple winding to be manufactured in an automated manner for producing a rotating field. The winding of concentrated coils around salient poles leads, however, to a rotating field strongly affected by harmonic waves. The harmonic waves in the rotating field of the machine lead to harmonics, in other words to multiples of the basic frequency in the current or in the voltage. This does not only lead to additional losses in the machine, but also in the connected electronics. To activate three-phase motors, for example, invertors with a voltage intermediate circuit are used. The capacitors of the voltage intermediate circuit are extraordinarily sensitive to current peaks, such as are caused by the harmonics. These lead to a reduction in the service life of the capacitors. It is therefore the object of the present invention to reduce the losses by an improved winding arrangement. This object is achieved by the electric machine with a winding for producing a rotating field according to claim 1. Furthermore, this object is achieved by a method for producing the winding of the electric machine according to the preamble of claim 8 in conjunction with the characterising features. Advantageous developments of the invention are disclosed in the dependent claims. 3 An electric machine is proposed with a winding for producing a rotating field with at least two coils for each phase and pair of poles, a first coil of each phase being electrically turned through-180° in relation to a second oppositely wound coil and wherein the coils of adjacent phases overlap and each first coil of a phase is located in a first layer and each second coil of a phase in a second layer, the second layer surrounding the first layer. The overlappings became visible, in particular in the region of the winding heads and are achieved by a larger winding step. Owing to the distribution according to the invention of the overlapping coils, symmetrical phase windings are produced. This ensures that no additional harmonics are produced through lack of symmetry. According to a preferred embodiment of the electric machine according to the invention, the first and the second coil of a phase are connected in series. This ensures that the same current also flows in the two coils. With a parallel connection, this would only be the case with identical resistances and inductances of the two part coils. According to a further embodiment of the electric machine according to the invention, the winding is an ironless air gap winding. The configuration as an air gap winding is particularly advantageous, because cogging torques can thus be avoided. Furthermore, remagnetisation losses and eddy current losses are reduced or eliminated entirely, depending on whether a magnetic return is present or not. This is of particular interest when operating the machine at high rotational speeds as 4 the remagnetisation losses increase proportionally with the frequency and the eddy current losses even increase proportionally to the square of the frequency. In an air gap winding, the possibility of distributing the magnetic field through pole shoes so in an air gap winding with concentrated coils the magnetic would be limited to the small region of the coil, is dispensed with. With the enlargement of the winding step air gap windings become sensible for the first time. According to a further embodiment of the electric machine according to the invention, the conductor material for the winding is litz wire and the litz wire consists of a plurality of individually insulated wires, which are twisted within the litz wire. The use of litz wire is advantageous for machines which are operated at high rotational speeds because the eddy current losses in the conductor material are reduced as a result. The losses are also reduced by the skin effect, also called current displacement. The losses are more sharply reduced, in this case, the smaller the cross section of the individual wire. The total cross section of the litz wire, in other words the number of parallel wires, is determined in this case by the necessary current requirement of the machine. The machine voltage, on the other hand, determines the number of windings of a phase winding. Furthermore, it is advantageous to twist the litz wire as the area enclosed by each wire with a winding is therefore on average the same. With non-twisted litz wire, these areas may differ, causing a deviation between the induced voltages and therefore equalising currents between the individual parallel wires, which in turn 5 produce undesired losses. The litz wire is in this case twisted such that the length of lay corresponds to the axial length of a winding, wherein the length of lay is the length over which the wires of the litz wire are twisted in relation to one another through 360°. According to a further embodiment, the electric machine is an electronically commutated direct current motor. An EC motor of this type consists of a stator winding for generating a rotating field and a permanently excited rotor. The stator winding is in this case fed by block-shaped currents. To produce the winding of a machine according to the invention in the form of an air gap winding with litz wire as the conductor material and three phases, an automatic winding system is used which is configured from a freely programmable two-axis CNC system with a triple needle winding head and a double tool carrier. A continuous forced guidance of the litz wire with a defined wire drawing is to be ensured in this case. With the winding pattern achieved by the method according to the invention, the three first coils are wound simultaneously with three separate litz wires and then the three second coils of the three phases. Advantageously, the winding of the coils takes place by means of a winding body, the winding body optionally having holding elements at the end around which the litz wires can be guided. The winding body already has the cylindrical form which the winding has to have for use in a rotating electric machine. The winding body is used, in this case, as a guide body for the litz wire, which can be introduced in the 6 handling system of a two-axis CNC machine. The end holding elements are merely used as auxiliary elements which can be attached to the winding body or can be formed thereon. The described winding body is primarily used when winding air gap windings and is then made of plastics material or a non-magnetically conductive metal. In a machine with iron the iron core which is present in any case is used as a winding body to guide the winding. Furthermore, the winding body for an air gap winding comprises a plurality of webs which are used to orient and position the litz wire. These webs are used as a winding aid in order to be able to wind the wire or the litz wire, analogously to the teeth or poles between the grooves of conventional iron core stators, around the latter. Once the winding has been completed by means of the winding body, the latter may optionally be removed again if no holding elements are provided which prevent this. If the winding body is not removed, the webs may also be used as a guide to introduce the winding body with the winding into a housing. This ensures that the connections of the winding are positioned in such a way that they can be connected to the printed circuit board with the power electronics. Alternatively to the use of a winding body, it may be advantageous for the winding to firstly be wound with an auxiliary device in one plane, whereupon the winding body configured in the plane is converted to the cylindrical form. The conversion of the winding to the cylindrical form takes place by means of a forming process, in which the winding arrangement of the litz wire, or the coils, is not changed. The 7 winding is merely converted from the plane to the cylindrical body so that, in this method, the use of a cylindrical winding body is not necessary. For insulation and to produce greater mechanical stability, it is particularly advantageous for the winding to be cast, the casting taking place by means of a hardenable material from the group of plastics materials, in particular a polyurethane. A polyurethane material or another material preferably with good heat conductivity, such as a cast resin allows the winding to optionally be cast in including the winding body, whereupon the casting material solidifies and forms a carrier body. The hardenable material is preferably a single-component or multi-component resin. Resins of this type have proven to be durable and easy to process. Thus, inter alia, plastics materials, such as polyester resin, epoxy resin, silicone resin or vinyl ester resin may also be used. Advantageously, each phase comprises two coils, which are electrically connected in series, the coils being wound from a continuous conductor material by means of a continuous winding. Firstly, all the first coils of- each phase are wound simultaneously, whereupon without an interruption of the respective conductor material, all the second coils are wound simultaneously. The invention will be described in more detail below with the aid of an embodiment shown in the drawings, in which: 8 Fig. 1 shows a winding pattern according to the invention for a three-phase winding with two coils electrically offset through 180° for each phase and pair of poles; Fig. 2 shows a view of the end faces of a winding body with a winding according to the invention with a pair of poles; Fig. 3 shows a side view of the winding body. The embodiment relates to an electronically commutated direct current motor for driving a spinning rotor of an open-end spinning machine. In this area of application, high rotational speeds are necessary so the winding is configured as an air gap winding with a twisted litz wire. Fig. 1 shows a winding pattern according to the invention with two coils electrically offset through 180° for each phase. The winding 20 shown is three-phase and shows the winding over a pair of poles. In a two-pole machine, the winding 20 shown is distributed over the entire machine, in other words over 360°. In a four-pole machine, in other words with two pairs of poles, the winding 20 shown is only over an area of 180°. Over the second pair of poles, the winding 20 is then repeated correspondingly. With p pairs of poles, 360°/ p are then still mechanically available for the winding pattern. The mechanical offset of the first and second coil of a phase is 180°/p here. 9 To produce the symmetrical winding 20 according to the invention, the first coils of each phase with the supply conductors la, 3a, 5a and the return conductors lb, 3b, 5b are firstly wound simultaneously and then, without interruption of the individual litz wires, the second coils of each phase with the supply conductors 2a, 4a, 6a and the return conductors 2b, 4b, 6b are wound. The start of the first coils la, 3a, 5a and the ends of the second coils 2b, 4b, 6b are guided out to be able to connect up the phases with power electronics. Fig. 2 shows the winding 20 according to the invention on a winding body 30 with six webs 31a to 31f and end holding elements 32a to 32f. The winding heads of the coils 1 to 6 can be seen in view of the end faces of the winding body. Furthermore, the supply conductors la to 6a and the return conductors lb to 6b are indicated. When producing the winding, firstly the coil 1 is wound around the webs 31a and 31b and the coil 3 is wound around the webs 31c and 31d and the coil 5 is wound around the webs 31 e and 31f. These three coils form the first coils of the three phases and are located in a first layer 41. The coil 2 is then wound around the webs 31d and 31e and the coil 4 around the webs 31f and 31a and the coil 6 around the webs 31b and 31c. The coils 2, 4 and 6 form the second coils of the three phases and are located in a second layer 42, which surrounds the first layer 41. The coil 2 is in this case rotated through 180° with respect to the coil 1 and oppositely wound. The same applies to the coil 4 and 3 and for coil 6 and 5. Fig. 3 shows a side view of the winding body 30 without a winding. In this case, the cylindrical base body 34 and one of the six webs 31a can be seen. The web 31a, on its 10 two end faces in each case has a holding element 32a and 33a. The other webs 31b to 31f, not shown here, are correspondingly each equipped on the two end faces with a holding element 32b to 32 f and 33b to 33f. A winding for three phases and with two coils for each phase and pair of poles was shown in the embodiment. Alternatively, other phase numbers are also possible. More than two coils can also be used for each phase and pair of poles. For example, the windings of one coil of the embodiment can be distributed on a plurality of web intermediate spacings. This increases the number of coils. Correspondingly the number of webs of the winding body has to be increased. A zone winding is thus obtained, which further reduces the harmonics. 11 CLAIM: 1. Electric machine with a winding (20) for producing a rotating field with at least two coils for each phase and pair of poles, a first coil (1, 3, 5) of each phase being electrically turned through 180° in relation to a second oppositely wound coil (2, 4, 6) of this phase, characterised in that the coils of adjacent phases overlap and in that each first coil (1, 3, 5) of a phase is located in a first layer (41) and each second coil (2, 4, 6) of a phase is located in a second layer (42), the second layer (42) surrounding the first layer (41). 2. Electric machine according to claim 1, characterised in that the first coil (1, 3, 5) and the second coil (2,4,6) of a phase are connected in series. 3. Electric machine according to any one of the preceding claims, characterised in that the winding (20) is an ironless air gap winding. 4. Electric machine according to any one of the preceding claims, characterised in that the conductor material for the winding is litz wire and in that the litz wire consists of a plurality of individual insulated wires, which are twisted together. 5. Electric machine according to any one of the preceding claims, characterised in that the electric machine is an electronically commutated direct current motor. 12 6. Electric machine according to any one of the preceding claims, characterised in that the winding is arranged on a cylindrical winding body, which has webs (31a-31f) with end holding elements (32a-32f, 33a-33f). 7 Electric machine according to any one of the preceding claims, characterised in that the winding is cast in a hardened material, in particular a polyurethane. 8. Method for producing the winding (20) of the electric machine according to any one of claims 1 to 5, characterised in that firstly the first coils (1, 3, 5) of each phase and then the second coils (2, 4, 6) of each phase are wound simultaneously. 9. Method according to claim 8, characterised in that the coils (1,3,5, 2, 4, 6) are wound on a cylindrical winding body (30), which has webs (31a-31f) with end holding elements (32a-32f, 33a-33f), around which the conductor material is guided. 10. Method according to claim 8, characterised in that the winding (20) is wound in one plane, and following this, the winding (20) formed in the plane is converted into a cylindrical form. 13 11. Method according to any one of claims 8 to 10, characterised in that the winding (20) is cast, the casting taking place by means of a hardenable material, in particular a polyurethane. 12. Method according to any one of claims 8 to 11, characterised in that the at least two coils are electrically connected in series and the first coil (1, 3, 5) and the second coil (2, 4, 6) are wound from a continuous conductor material by means of continuous winding. HIRAL CHANDRAKANT JOSHI AGENT FOR OERLIKON TEXTILE GMBH & CO. KG 14 Dated this 5th day of August 2008.

Full Text

FORM 2
THE PATENT ACT 1970 (39 of 1970)
&
The Patents Rules, 2003 COMPLETE SPECIFICATION
(See Section 10, and rule 13)

1. TITLE OF INVENTION
ELECTRIC MACHINE WITH A WINDING FOR AND METHOD FOR PRODUCING THE WINDING

PRODUCING A ROTATING FIELD

2.APPLICANT(S)
a) Name
b) Nationality
c) Address
OERLIKON TEXTILE GMBH & CO. GERMAN Company LEVERKUSER STRASSE 65, D-42897 REMSCHEID, GERMANY

KG

PREAMBLE TO THE DESCRIPTION

The following specification particularly describes the invention and the manner in which it is to be performed : -

PATENTS ACT 1977
I, ASTRID TERRY, translator of 11, Bounds Oak Way, Tunbridge Wells, Kent. TN4 OUB, England, confirm that I am conversant with the English and German languages and I am a competent translator from one to the other. I declare to the best of my knowledge and belief that the attached English translation is a true and correct translation of the DE Patent No. 10 2007 038 601.1

Dated this 16th day of July 2008.

The invention relates to an electric machine with a winding for producing a rotating field with at least two coils for each phase and pair of poles, a first coil of each phase being electrically turned through 180° in relation to a second oppositely wound coil of this phase. Furthermore, the invention relates to a method for producing the winding of the electric machine.
A method for producing a winding for an electric motor, which has three phases, which are wound simultaneously on an iron core, is known from the US patent 4,847,982. The electric motor is designed as a three-phase motor, which either has six poles configured as iron bodies in order to configure the motor as a two-pole motor or which has twelve poles to configure it as a four-pole motor.
The stator of the disclosed motor consists of an iron core and has three phase windings constructed from a plurality of coils on the poles to either form a two-pole or a four-pole motor, the coils being wound on the respective poles. The three phases are formed by a winding of a first coil in the clockwise direction, the iron body then being electrically turned through 180° before the respective second coil is wound anti-clockwise.
The first and second coil are wound one after the other without interrupting the conductor material so owing to the simultaneous production of the coils, an accelerated winding of the winding body is possible. In this case, three coils are wound simultaneously onto salient poles of the iron body and, owing to the rotation
2

of the iron body through 180°, the winding of the next three coils can also take place in parallel.
The described prior art shows a simple winding to be manufactured in an automated manner for producing a rotating field. The winding of concentrated coils around salient poles leads, however, to a rotating field strongly affected by harmonic waves.
The harmonic waves in the rotating field of the machine lead to harmonics, in other words to multiples of the basic frequency in the current or in the voltage. This does not only lead to additional losses in the machine, but also in the connected electronics. To activate three-phase motors, for example, invertors with a voltage intermediate circuit are used. The capacitors of the voltage intermediate circuit are extraordinarily sensitive to current peaks, such as are caused by the harmonics. These lead to a reduction in the service life of the capacitors.
It is therefore the object of the present invention to reduce the losses by an improved winding arrangement.
This object is achieved by the electric machine with a winding for producing a rotating field according to claim 1. Furthermore, this object is achieved by a method for producing the winding of the electric machine according to the preamble of claim 8 in conjunction with the characterising features. Advantageous developments of the invention are disclosed in the dependent claims.
3

An electric machine is proposed with a winding for producing a rotating field with at least two coils for each phase and pair of poles, a first coil of each phase being electrically turned through-180° in relation to a second oppositely wound coil and wherein the coils of adjacent phases overlap and each first coil of a phase is located in a first layer and each second coil of a phase in a second layer, the second layer surrounding the first layer.
The overlappings became visible, in particular in the region of the winding heads and are achieved by a larger winding step. Owing to the distribution according to the invention of the overlapping coils, symmetrical phase windings are produced. This ensures that no additional harmonics are produced through lack of symmetry.
According to a preferred embodiment of the electric machine according to the invention, the first and the second coil of a phase are connected in series. This ensures that the same current also flows in the two coils. With a parallel connection, this would only be the case with identical resistances and inductances of the two part coils.
According to a further embodiment of the electric machine according to the
invention, the winding is an ironless air gap winding. The configuration as an air
gap winding is particularly advantageous, because cogging torques can thus be
avoided. Furthermore, remagnetisation losses and eddy current losses are reduced
or eliminated entirely, depending on whether a magnetic return is present or not.
This is of particular interest when operating the machine at high rotational speeds as
4

the remagnetisation losses increase proportionally with the frequency and the eddy current losses even increase proportionally to the square of the frequency.
In an air gap winding, the possibility of distributing the magnetic field through pole shoes so in an air gap winding with concentrated coils the magnetic would be limited to the small region of the coil, is dispensed with. With the enlargement of the winding step air gap windings become sensible for the first time.
According to a further embodiment of the electric machine according to the invention, the conductor material for the winding is litz wire and the litz wire consists of a plurality of individually insulated wires, which are twisted within the litz wire. The use of litz wire is advantageous for machines which are operated at high rotational speeds because the eddy current losses in the conductor material are reduced as a result. The losses are also reduced by the skin effect, also called current displacement. The losses are more sharply reduced, in this case, the smaller the cross section of the individual wire. The total cross section of the litz wire, in other words the number of parallel wires, is determined in this case by the necessary current requirement of the machine. The machine voltage, on the other hand, determines the number of windings of a phase winding.
Furthermore, it is advantageous to twist the litz wire as the area enclosed by each
wire with a winding is therefore on average the same. With non-twisted litz wire,
these areas may differ, causing a deviation between the induced voltages and
therefore equalising currents between the individual parallel wires, which in turn
5

produce undesired losses. The litz wire is in this case twisted such that the length of lay corresponds to the axial length of a winding, wherein the length of lay is the length over which the wires of the litz wire are twisted in relation to one another through 360°.
According to a further embodiment, the electric machine is an electronically commutated direct current motor. An EC motor of this type consists of a stator winding for generating a rotating field and a permanently excited rotor. The stator winding is in this case fed by block-shaped currents.
To produce the winding of a machine according to the invention in the form of an air gap winding with litz wire as the conductor material and three phases, an automatic winding system is used which is configured from a freely programmable two-axis CNC system with a triple needle winding head and a double tool carrier. A continuous forced guidance of the litz wire with a defined wire drawing is to be ensured in this case. With the winding pattern achieved by the method according to the invention, the three first coils are wound simultaneously with three separate litz wires and then the three second coils of the three phases.
Advantageously, the winding of the coils takes place by means of a winding body,
the winding body optionally having holding elements at the end around which the
litz wires can be guided. The winding body already has the cylindrical form which
the winding has to have for use in a rotating electric machine. The winding body is
used, in this case, as a guide body for the litz wire, which can be introduced in the
6

handling system of a two-axis CNC machine. The end holding elements are merely used as auxiliary elements which can be attached to the winding body or can be formed thereon. The described winding body is primarily used when winding air gap windings and is then made of plastics material or a non-magnetically conductive metal. In a machine with iron the iron core which is present in any case is used as a winding body to guide the winding.
Furthermore, the winding body for an air gap winding comprises a plurality of webs which are used to orient and position the litz wire. These webs are used as a winding aid in order to be able to wind the wire or the litz wire, analogously to the teeth or poles between the grooves of conventional iron core stators, around the latter. Once the winding has been completed by means of the winding body, the latter may optionally be removed again if no holding elements are provided which prevent this. If the winding body is not removed, the webs may also be used as a guide to introduce the winding body with the winding into a housing. This ensures that the connections of the winding are positioned in such a way that they can be connected to the printed circuit board with the power electronics.
Alternatively to the use of a winding body, it may be advantageous for the winding to firstly be wound with an auxiliary device in one plane, whereupon the winding body configured in the plane is converted to the cylindrical form. The conversion of the winding to the cylindrical form takes place by means of a forming process, in which the winding arrangement of the litz wire, or the coils, is not changed. The
7

winding is merely converted from the plane to the cylindrical body so that, in this method, the use of a cylindrical winding body is not necessary.
For insulation and to produce greater mechanical stability, it is particularly advantageous for the winding to be cast, the casting taking place by means of a hardenable material from the group of plastics materials, in particular a polyurethane. A polyurethane material or another material preferably with good heat conductivity, such as a cast resin allows the winding to optionally be cast in including the winding body, whereupon the casting material solidifies and forms a carrier body. The hardenable material is preferably a single-component or multi-component resin. Resins of this type have proven to be durable and easy to process. Thus, inter alia, plastics materials, such as polyester resin, epoxy resin, silicone resin or vinyl ester resin may also be used.
Advantageously, each phase comprises two coils, which are electrically connected in series, the coils being wound from a continuous conductor material by means of a continuous winding. Firstly, all the first coils of- each phase are wound simultaneously, whereupon without an interruption of the respective conductor material, all the second coils are wound simultaneously.
The invention will be described in more detail below with the aid of an embodiment shown in the drawings, in which:
8

Fig. 1 shows a winding pattern according to the invention for a three-phase winding with two coils electrically offset through 180° for each phase and pair of poles;
Fig. 2 shows a view of the end faces of a winding body with a winding according to the invention with a pair of poles;
Fig. 3 shows a side view of the winding body.
The embodiment relates to an electronically commutated direct current motor for driving a spinning rotor of an open-end spinning machine. In this area of application, high rotational speeds are necessary so the winding is configured as an air gap winding with a twisted litz wire.
Fig. 1 shows a winding pattern according to the invention with two coils electrically offset through 180° for each phase. The winding 20 shown is three-phase and shows the winding over a pair of poles. In a two-pole machine, the winding 20 shown is distributed over the entire machine, in other words over 360°. In a four-pole machine, in other words with two pairs of poles, the winding 20 shown is only over an area of 180°. Over the second pair of poles, the winding 20 is then repeated correspondingly. With p pairs of poles, 360°/ p are then still mechanically available for the winding pattern. The mechanical offset of the first and second coil of a phase is 180°/p here.
9

To produce the symmetrical winding 20 according to the invention, the first coils of each phase with the supply conductors la, 3a, 5a and the return conductors lb, 3b, 5b are firstly wound simultaneously and then, without interruption of the individual litz wires, the second coils of each phase with the supply conductors 2a, 4a, 6a and the return conductors 2b, 4b, 6b are wound. The start of the first coils la, 3a, 5a and the ends of the second coils 2b, 4b, 6b are guided out to be able to connect up the phases with power electronics.
Fig. 2 shows the winding 20 according to the invention on a winding body 30 with six webs 31a to 31f and end holding elements 32a to 32f. The winding heads of the coils 1 to 6 can be seen in view of the end faces of the winding body. Furthermore, the supply conductors la to 6a and the return conductors lb to 6b are indicated. When producing the winding, firstly the coil 1 is wound around the webs 31a and 31b and the coil 3 is wound around the webs 31c and 31d and the coil 5 is wound around the webs 31 e and 31f. These three coils form the first coils of the three phases and are located in a first layer 41. The coil 2 is then wound around the webs 31d and 31e and the coil 4 around the webs 31f and 31a and the coil 6 around the webs 31b and 31c. The coils 2, 4 and 6 form the second coils of the three phases and are located in a second layer 42, which surrounds the first layer 41. The coil 2 is in this case rotated through 180° with respect to the coil 1 and oppositely wound. The same applies to the coil 4 and 3 and for coil 6 and 5.
Fig. 3 shows a side view of the winding body 30 without a winding. In this case, the
cylindrical base body 34 and one of the six webs 31a can be seen. The web 31a, on its
10

two end faces in each case has a holding element 32a and 33a. The other webs 31b to 31f, not shown here, are correspondingly each equipped on the two end faces with a holding element 32b to 32 f and 33b to 33f.
A winding for three phases and with two coils for each phase and pair of poles was shown in the embodiment. Alternatively, other phase numbers are also possible. More than two coils can also be used for each phase and pair of poles. For example, the windings of one coil of the embodiment can be distributed on a plurality of web intermediate spacings. This increases the number of coils. Correspondingly the number of webs of the winding body has to be increased. A zone winding is thus obtained, which further reduces the harmonics.
11

CLAIM:
1. Electric machine with a winding (20) for producing a rotating field with at least two coils for each phase and pair of poles, a first coil (1, 3, 5) of each phase being electrically turned through 180° in relation to a second oppositely wound coil (2, 4, 6) of this phase, characterised in that the coils of adjacent phases overlap and in that each first coil (1, 3, 5) of a phase is located in a first layer (41) and each second coil (2, 4, 6) of a phase is located in a second layer (42), the second layer (42) surrounding the first layer (41).
2. Electric machine according to claim 1, characterised in that the first coil (1, 3, 5) and the second coil (2,4,6) of a phase are connected in series.
3. Electric machine according to any one of the preceding claims, characterised in that the winding (20) is an ironless air gap winding.
4. Electric machine according to any one of the preceding claims, characterised in that the conductor material for the winding is litz wire and in that the litz wire consists of a plurality of individual insulated wires, which are twisted together.
5. Electric machine according to any one of the preceding claims, characterised
in that the electric machine is an electronically commutated direct current
motor.
12

6. Electric machine according to any one of the preceding claims, characterised in that the winding is arranged on a cylindrical winding body, which has webs (31a-31f) with end holding elements (32a-32f, 33a-33f).
7 Electric machine according to any one of the preceding claims, characterised
in that the winding is cast in a hardened material, in particular a polyurethane.
8. Method for producing the winding (20) of the electric machine according to any one of claims 1 to 5, characterised in that firstly the first coils (1, 3, 5) of each phase and then the second coils (2, 4, 6) of each phase are wound simultaneously.
9. Method according to claim 8, characterised in that the coils (1,3,5, 2, 4, 6) are wound on a cylindrical winding body (30), which has webs (31a-31f) with end holding elements (32a-32f, 33a-33f), around which the conductor material is guided.
10. Method according to claim 8, characterised in that the winding (20) is wound in one plane, and following this, the winding (20) formed in the plane is converted into a cylindrical form.
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11. Method according to any one of claims 8 to 10, characterised in that the winding (20) is cast, the casting taking place by means of a hardenable material, in particular a polyurethane.
12. Method according to any one of claims 8 to 11, characterised in that the at least two coils are electrically connected in series and the first coil (1, 3, 5) and the second coil (2, 4, 6) are wound from a continuous conductor material by means of continuous winding.
HIRAL CHANDRAKANT JOSHI AGENT FOR OERLIKON TEXTILE GMBH & CO. KG
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Dated this 5th day of August 2008.

ELECTRIC MACHINE WITH A WINDING FOR PRODUCING A ROTATING FIELD AND METHOD FOR PRODUCING THE WINDING

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