WO2004064229A1

WO2004064229A1 - Winding method

Info

Publication number: WO2004064229A1
Application number: PCT/NZ2004/000002
Authority: WO
Inventors: David Howell; Daniel Gadd
Original assignee: Wellington Drive Technologies Limited
Priority date: 2003-01-14
Filing date: 2004-01-05
Publication date: 2004-07-29
Also published as: NZ523624A

Abstract

A method and apparatus for placing substantially cylindrical coil windings on the stator or rotor of a distributed winding motor or alternator is disclosed. A single or multi-phase winding (14) in coplanar form is trapped at the inner periphery and drawn into the gap between, typically, a stator (12) and a form without wire guides on the stator or form. As it is drawn in, it is converted to a cylindrical winding. Coplanar winding (14) may be trapped by pins (4) on turret (6) at each winding pole point and as turret (6) and stator (12) are pressed into mould (1) the winding is drawn in and converted to a cylindrical form.

Description

WINDING METHOD

TECHNICAL FIELD

This invention relates to the production of windings for dynamoelectric machines. In particular, the invention relates to methods of providing windings on a stator of a dynamoelectric machine.

BACKGROUND ART

For good electric motor efficiency, it is important that windings be accurately located on the motor stator. It is also important that the maximum possible proportion of the available winding space be filled with windings. Most existing motor designs are either concentrated winding (salient pole) or distributed winding (slotless) types. Concentrated winding designs are distinguished by the presence of slots in the magnetic stator core. These slots are absent in distributed winding designs, although many such machines have slots formed from nonmagnetic material superimposed on the magnetic core. Both distributed winding and concentrated winding types often rely on these slots to locate the windings. However the slot shape for concentrated winding pole machines makes achieving a high slot fill difficult, and complex multi-stage winding machines are commonly used to achieve this.

For distributed winding machines, slots are generally formed by wire guides rather than the shape of the stator backiron. The wire guides, which serve no purpose other than locating the coils, take up space which could usefully be filled with windings. Elimination of these guides would thus allow more winding area, and hence improved motor efficiency. Furthermore, the gaps provided by wire guides are usually shallow, which makes insertion of the winding easier, but makes retention of the windings, and even distribution of the windings across the gap, more difficult.

Existing techniques for winding and placing coils using a two step process, whereby coils are wound in a substantially planar configuration and then pressed into or around the stator. However these techniques rely upon slots in the stator to guide and locate the wires during insertion and thus are not ideal for distributed winding machines. Single-step techniques which wind the wires directly in place also exist, but these also rely upon stator slots for positioning. Further, both types of technique generally rely either on inherent wire stiffness, tension in the end turns, or additional components, to retain the windings in the slots, which also is not ideal for distributed winding machines An insertion technique which does not inherently require slots in the stator is described in GB2076710. However this technique pushes the coils into place rather than drawing them, and thus is only applicable to windings having sufficient stiffness to maintain their shape without assistance, i.e. windings made of relatively heavy gauge wire.

OBJECT OF THE INVENTION

It is an object of the present invention to provide an improved method of providing windings for dynamoelectric machines which will at least go some way toward overcoming disadvantages associated with known methods, or which will at least provide the public with a useful choice.

DISCLOSURE OF THE INVENTION

Accordingly in one aspect the invention may broadly be said to consist in a method of providing a winding on a distributed winding stator of a dynamoelectric machine, the method including the steps of providing winding material having at least one phase winding in a substantially co-planar configuration, and

transforming the winding material to a substantially cylindrical configuration for provision about a surface of the stator or rotor by drawing it into place without the aid of wire guides.

A method as described above, wherein the substantially co-planar configuration has a general inner peripheral boundary and a general outer peripheral boundary, and the method includes the step of

moving the outer boundary both radially and axially relative to the inner boundary to provide the inner boundary and the outer boundary at substantially the same diameter so that the winding material forms a substantially cylindrical configuration.

A method as described above, wherein the method includes the step of providing an inner boundary engagement means to engage with parts of the windings along or adjacent to the inner boundary of the winding material.

A method as described above wherein the method includes the step of providing a mould having a hollow cylindrical surface and a corresponding cylindrical turret on which the engagement means are provided. A method as described above wherein the method includes the step of providing a stator form and placing the form on a turret over the inner periphery of the winding material and over the engagement means whereby the inner periphery of the winding material is held in place between the turret and form by the engagement means.

A method as described above, wherein the method further includes the steps of pressing the form into the mould to thereby draw the winding material into a gap between the outside of the stator form and the inside of the mould.

A method as described above, wherein the form is pressed into the mould until the winding material forms a substantial cylinder about the stator form.

A method as described above, wherein the windings may include thermobondable wire and a current may be passed through the coils to bond the winding to the stator form.

A method as described above, wherein one or both of the stator form and mould either comprises a part of the stator, or simply comprises a substantially cylindrical member which may be used to merely support the winding material during forming. In the case where both parts are purely support forms, the free standing form that is produced may be applied to a stator or a rotor or may simply have backiron wrapped around it to be used as an external stator of an internal rotor machine, while in the case where both parts form a part of the stator, the resulting assembly may be self-supporting without the use of thermobondable wire or other wire location means.

A method as described above, wherein the inner boundary engagement means either comprises part of the turret or part of the stator form.

In a further aspect the invention may broadly be said to consist in a distributed winding stator for a dynamoelectric machine, the stator having windings provided on a surface of the stator in accordance with the method of the invention.

DRAWING DESCRIPTION

An example of an embodiment of the invention will be described with reference to the drawings in which Figure 1 shows diagrammatic cross sections and plan views of a plunger, main mould and turret for use in accordance with the invention

Figure 2 is a section and planned view of the components of figure 1 assembled ready for use with windings

Figure 3 is a diagrammatic cross section of the windings being introduced to the mould

Figure 4 is a diagrammatic cross section showing the windings partially pressed into the mould

Figure 5 is a diagrammatic cross section showing the windings fully pressed within the mould including a lower face plunger

Figure 6 shows a diagrammatic cross section as shown in figure 5 with the lower face plunger at a full extent of travel.

Figure 7 is a plan view of one version of a completed stator

Figure 8 is a diagrammatic cross-section of the stator of figure 7 along line A- A

Figure 9 is a detail of the corner of the stator of figure 8

DESCRIPTION OF PREFERRED EMBODIMENT

Referring to figure 1, a main mould 1 is shown. It is substantially cylindrical in form and is lined with a low friction material such as mylar or PTFE. It will be appreciated that although item 1 is shown and referred to as being a mould, it could also be a component of the finished stator, for example if the machine is an internal rotor design the mould may be formed from a cylindrical lamination stack lined with insulation. Also shown in figure 1 is a turret having a number of pins 4 which are located at the top of the turret. Each pin 4 is biased either directly or indirectly into the upright position as shown in the figure so that the pin protrudes upwardly away from the body of the turret. The preferred biasing arrangement is the use of springs 10.

Also shown in figure 1 is a face pressing plunger 8 which has an outside dimension that can be accommodated within the mould 1. Turning now to figure 2, the mould 1 and turret are shown located together, the turret being provided within another part of the mould 1. The turret is biased into position near the top of mould 1 by springs 10. Immediately above the turret is a stator form for a dynamoelectric machine. The stator is generally referenced 12. It will be appreciated that although item 12 is referred to as being a stator, it could be another part of a dynamoelectric machine such as a rotor, or this item could simply provide a cylinder for forming windings rather than comprising a stator in itself. Therefore, item 12 may need further material apart from windings attached to it to form a true stator or rotor of a dynamoelectric machine.

As can be seen in figure 2, there is an arrangement of windings generally referenced 14 provided in an annular form having a general outer peripheral boundary 16 and inner peripheral boundary 18. The windings comprise prewound phase strings which are ready for placement about an appropriate former such as the stator form 12. The windings 14 are arranged so that the innermost point of each coil (these points for each coil together forming the inner boundary 18) is looped over one of the pins 4. Therefore, the number of pins 4 corresponds to the number of wire guides or slots in a more conventional motor (which equals the number of phases multiplied by the number of poles).

The winding coils are placed on the stator as follows. Firstly, the windings are placed in a series of generally rectangular coils in a "star" pattern, upon the horizontal top of the mould. The inner corners of each coil are hooked over the pins 4 as mentioned above. It will be seen that other coil shapes could be adopted.

The coils are prewound in strings on a bobbin type winding machine and placed in a star pattern, or alternatively may be directly wound into the star pattern. Adaptations of existing stator coil "fall winding" machines are suitable for this purpose. It will be appreciated that other methods may also be used.

Turning now to figure 3, the stator form 12 has now been pressed down onto the pins 4. The spring force holding the turret in the mould is higher than the sum of the spring forces on the retractable pins, so that the retractable pins are initially pushed down as shown in figure 3 without any substantial movement of the turret. This traps the inner ends of the coils between the pins, stator and turret as the pins retract.

Turning to figure 4, it will be seen that the stator is now pressed down further into the mould. As the stator continues to be pressed down, the coils are drawn into the gap between the outside of the stator and the inside of the mould. It should be noted that pins 4 do not act to guide the windings, but are intended to act as the agent which allows the wire to be drawn into the stator. Guiding of the windings is unnecessary as the size of the gap between stator and mould ensures that the windings cannot cross or otherwise entangle during drawing.

In figure 5, the stator has been fully pressed into the mould, and the windings now form a substantial cylinder about the outside of the stator form. As can be seen, when the stator is nearly pushed home into the mould, the upper ends (i.e. the "upper" end turns of the coils), which were at the outer edges of the star pattern shown in figure 2, are unable to be pulled into the gap between the stator and the mould. This is because they cross over each other and are bulkier than the sides of the coils. Therefore, as the stator is pressed into the mould, the coils are stretched down the side of the stator and this pulls the coils straight.

The upper edge of the mould can be chamfered or otherwise shaped to promote neat forming of the upper end turns of the windings.

As can be seen from figure 5, the face pressing plunger is now introduced to the bottom of the mould.

In figure 6, the plunger is shown being pressed up home into the base of the stator form. This presses the lower end turns, which are trapped behind the pins, into a controlled shape.

Once the stator has been fully pressed home, the windings (provided thermobondable wire has been used) can be set off by passing a current through the coils. After a period of cooling, which is short due to good thermal contact between the windings and the mould, the finished stator can be removed from the mould.

While the plunger is shown as having projections which will assist in maintaining the windings in line during pressing these are not essential, and a stator without projections will also act as required provided the tolerances are correct.

It will be appreciated that for an external rotor machine the stator form 12 shown in the drawings will typically have backiron and insulation provided on it.

It will further be appreciated that in instances where accurate forming of the end turns is not required, the pins 4 may be fixed to the turret rather than retractable. It will further be appreciated that the pins, whether retractable or not, may alternatively be placed on the plunger or stator form rather than the turret. If the pins need not be retractable, the turret may then be completely eliminated.

It will further be appreciated that the windings before pressing, though shown here as a set of coils laid out in a star pattern, may alternatively be formed in any generally annular shape which allows the inner part of the annulus to be hooked over the pins

A variation of this technique is to use wire which is not thermobondable, and to fix the wires in place with epoxy while still in the mould. For rapid production the section of the mould which is in contact with the finished stator may be removable from the machine, so that the epoxy pouring and setting may happen while further stators are being formed.

A further variation is to replace the stator with a plunger coated with PTFE or another low friction material. After forming the windings as in the method above, it will be seen that it is possible to remove the plunger from the windings, to form an electrical free-standing "self supporting" winding. This self supporting winding can then have backiron wrapped around the outside of it and be used as the external stator of an internal rotor dynamoelectric machine. Alternatively the backiron may be pre-wound and placed either in the mould (for an internal rotor machine) or around the plunger (for an external rotor machine), along with a layer of insulating material, before pressing. The winding thus conforms closely to the backiron after pressing , and may be removed after setting off as a single assembly.

Still a further variation as shown in figure 7 is to place in the mould (for external rotor machines) or on the plunger (for internal rotor machines) a stator lining of a non-conductive material (typically a polymer). Upon pressing the winding, the winding is contained between the stator and stator insulation, and thus does not require bonding or epoxy to retain its form. A stator for an internal rotor machine, constructed using this method, is shown in figures 1, 8 and 9 where windings 14 are drawn between a backiron 90 with insulation 91 and a stator liner 92.

It will be seen that the invention provides improved method of placing coils on a distributed winding type stator (and possibly with other stator or rotor arrangements) so as to eliminate the need for wire guides, while still providing central placement accuracy, rapid operation and very efficient area utilisation. It will also be seen that this method does not prevent the use of wire guides, but only renders them unnecessary. INDUSTRIAL APPLICABILITY

The invention lies in the field of electrodynamic machines and relates to an alternative method of producing a distributed winding type machine and the machine so wound. As such the product is an electrodynamic machine of industrial applicability.

Claims

WHAT WE CLAIM IS:

1. A method of providing a winding for a distributed winding rotor or stator of a dynamoelectric machine, including the steps of providing a winding material having at least one phase winding in a substantially co-planar configuration, characterised in that the winding material is transformed to a substantially continuous cylindrical configuration for provision about a surface of the stator or rotor by drawing it into place without the aid of wire guides.

2. A method as described as claimed in claim 1, characterised in that the substantially co-planar configuration has a general inner peripheral boundary and a general outer peripheral boundary, and the method includes the step of moving the outer boundary both radially and axially relative to the inner boundary to provide the inner boundary and the outer boundary at substantially the same diameter so that the winding material forms a substantially cylindrical configuration.

3. A method as claimed in claim 2, characterised in that the method includes the step of providing an inner boundary engagement means to engage with parts of the windings along or adjacent to the inner boundary of the winding material.

4. A method as described in claim 2 characterised in that the method includes the step of providing a mould having a hollow cylindrical surface and a corresponding cylindrical turret on which the engagement means are provided.

5. A method as described in claim 3 characterised in that the method includes the step of providing a stator form and placing the form on a turret over the inner periphery of the winding material and over the engagement means whereby the inner periphery of the winding material is held in place between the turret and form by the engagement means.

6. A method as claimed in Claim 5, characterised in that the method further includes the steps of pressing the form into the mould to thereby draw the winding material into a gap between the outside of the stator form and the inside of the mould.

7. A method as claimed in Claim 6 characterised in that the engagement means retract as the form is pressed into the mould.

8. A method as claimed in Claim 3 or 7, characterised in that the form is pressed into the mould until the winding material forms a substantially cylindrical winding about the stator form.

9. A method as claimed in Claim 5, characterised in that the winding includes thermobondable wire and a current is passed through the coils to bond the winding to the stator form.

10. A method as claimed in Claim 8, characterised in that the stator form either comprises a part of the stator , or comprises a substantially cylindrical member which may be used to support the winding material during forming or for transfer to a rotor or stator.

11. A method as claimed in Claim 10, characterised in that the inner boundary engagement means are formed as part of the stator form

12. A method as claimed in Claim 8, characterised in that the mould either comprises a part of the stator, or comprises a substantially cylindrical member which may be used to support the winding material during forming or for transfer to a rotor or stator.

13. A distributed winding stator for a dynamoelectric machine, the stator having windings provided by drawing a co-planar winding into place on the rotor or stator as a substantially cylindrical winding.

14. A stator for a dynamoelectric machine as claimed in Claim 13, characterised in that the windings are substantially located between male and female parts of the stator suitable for use as formers during the winding assembly.