AU632850B2

AU632850B2 - Electromagnetic machine

Info

Publication number: AU632850B2
Application number: AU62373/90A
Authority: AU
Inventors: Andrzej Witkowski; Janusz Zandler
Original assignee: Zw Engineering Pty Ltd
Current assignee: Zw Engineering Pty Ltd
Priority date: 1989-09-11
Filing date: 1990-09-11
Publication date: 1993-01-14
Anticipated expiration: 2010-09-11
Also published as: AU6237390A

Description

i_

AUSTRALIA

Patents Act 632~e) COMPLETE SPECIFICATION

(ORIGINAL)

Class Int. Class Application Number: Lodged: Complete Specification Lodged: Accepted: Published: Priority 0D Related Art: 0 e, o APPLICANT'S REF.: CAP of PJ 6290 Name(s) of Applicant(s): ZANDLER WITOCK ENGINEERING PTY LTD Address(es) of Applicant(s): Factory 4 9 Alick Street Brooklyn VIC 3012 0 Actual Inventor(s): 17n-.inrl A I I I WJkcoks('1 cvad ktJ Usz _76tnder 9 9 Address for Service is: PHILLIPS, ORMONDE AND FITZPATRICK Patent and Trade Mark Attorneys 367 Collins Street Melbourne, Australia, 3000 Complete Specification for the invention entitled: ELECTROMAGNETIC MACHINE The following statement is a ull description of this invention, including the best method of performing it known to -I

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a a a C a t CC 0 o a 4 C 45 CO C 4*4 0 a a 0e i a o a 00,0 00CC 04 ELECTROMAGNETIC MACHINE This invention relates to an electromagnetic machine, and in particular to an electromagnetic machine for operating as an electrical motor or generator involving AC or DC power. The invention is applicable to cylindrical, rotary-type electromagnetic machines, and it will be convenient to hereinafter describe the invention in relation to that exemplary application. It is to be appreciated, however, that the invention is not limited to that application.

Most electromagnetic motors and generators of the cylindrical, rotary-type include an outer stationary structure (stator) and inner rotatable structure (rotor), separated by an annular air gap. These structures form a magnetic circuit in which magnetic flux is produced, an electromotive force (emf) being generated by relative movement between the structures. In many machines, windings situated on the statiornav and rotatable structures produce the necessary ii;ay'etic flux for generating the emf by having electrical currents flow through them. In that regard, field windings on one structure produce the magnetic flux whilst the emf is generated in armature windings on the other structure.

Depending on whether the machine operates as motor or generator, then electric current will be provided to the armature windings to rotate the rotatable structure or the rotatable structure will be externally rotated, respectively, thereby generating the (back) emf. The location of those windings is usually selected depending 30 on whether the machine is a DC or AC motor or generator (as will be well appreciated by thobc skilled in this art) so that, for example in DC machines the field windings are on the stationary structure and the armature windings are on the rotatable structure. In some machines, windings on one of the structures have been substituted by permanent magnets.

These machines have generally incorporated stationary and rotatable structures wl ch are magnetically 39 hetropolar, i.e. have several magnetic pole positions of Ii L ~i

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3 alternating North and South polarity. More recently, machines have been developed in which the rotatable structure is homopolar, i.e. have pole positions of common N or S polarity, and the stationary structure is hetropolar. One example of such a machine is a "stepper" motor used for its advantageous characteristic or direct and precise positioning control. The homopolar structure may be produced by pole cores carrying field windings or one or more permanent magnets. Where the rotatable structure is homopolar then use of permanent magnet(s) has the advantage of avoiding the need for commutators and associated brush assemblies for connection to an external electrical circuit.

Whilst these prior machines can function generally satisfactorily, they are often of complex construction providing attendant high production costs.

It is an object of the present invention to provide a relatively simple and inexpensive, yet effective and efficient, electromagnetic machine.

With that in mind, the present invention provides an I 2. electromagnetic rotary machine, including: a stationary structure having a plurality of magnetic pole positions and electrical windings for magnetizing the pole positions; a S rotary structure mounted for rotary movement relative to the i stationary structure around a rotation axis extending through the rotary structure, the rotary structure having a plurality of magnetic pole positions; and, a magnetic device on the stationary structure for magnetizing the pole positions on the rotary structure, the pole positions of the stationary structure being homopolar and the pole positions of the rotary structure also being homopolar, with the pole positions of the stationary and rotary structures being of relatively opposite magnetic polarity, wherein, when the machine operates as an electric motor, the electrical windings are connected to an external source of electrical energy to provide electromagnetic fields creating motive forces between the pole positions of the stationary and rotary structures to cause rotation of the rotor structure thereby producing a mechanical energy output from the machine, and, when the machine operates as an electric generator, the rotor structure is connected to 4 n external source of mechanical energy to rotate the rotor f /7010E 4 structure and provide an electromotive force in the electrical windings thereby producing an electrical energy output from the machine.

Preferably, the magnetic pole positions are constructed and arranged so that magnetic fields generated between the pole positions have lines of useful magnetic flux extending in radial planes containing the rotation axis of the rotary structure.

The pole positions of the stationary structure are preferably constructed and arranged so that the electrical windings are electively energisable in rotational sequence.

The rotary structure preferably includes a rotor member composed of ferromagnetic material. The rotor member is preferably of a one piece solid construction.

The stationary structure preferably includes a housing.

S The housing is partially constructed of ferromagnetic material providing a path between the pole positions of the stationary and rotary structures along which lines of magnetic flux pass. Moreover, the housing is preferably partially constructed of non-ferromagnetic material to shield against magnetic flux passage. In one embodiment, the housing includes a ferromagnetic tubular casing surrounding the pole positions. A ferromagnetic end wall is at one end of the oo tubular casing and a non-ferromagnetic end wall at an opposite end of the tubular casing. With this arrangement, the S magnetic flux path extends through the tubular casing and the I one end wall of the housing.

The magnetic device preferably includes an electromagnet mounted to the stationary structure and axially spaced from V 30 the pole positions. The electromagnet is permanently o energised during operation of the rotary machine. In one embodiment, the magnetic device is mounted on the one end wall of the housing. Moreover, in this embodiment the rotary structure includes a rotor shaft and the magnetic device is ring shaped and extends circumferentially about the rotor shaft.

Preferably, switching means is operable to sequentially energise and de-energise the electrical windings. That switching means preferably includes at least one senoor S: 4-0- device. That device senses the rotary KW/7010E position of the rotary structure and, in accordance with the position sensed, initiates energisation and de-energisation of the respective electrical windings.

The following description refers to a preferred embodiment of the electromagnetic rotary machine of the present invention. To facilitate an understanding of the invention, reference is made in the description to the accompanying drawings where the machine is illustrated.

It is to be understood that the invention is not limited to the embodiment as hereinafter described and as illustrated.

In the drawings: Fig. 1 is a side sectional view through section I-I of Fig. 2 of the machine according to one preferred embodiment of the present invenhion; Fig. 2 is a cross-sectional view of the machine through Section II-II of Fig. 1 showing the machine in one operational position; and, Fig. 3 is a cross-sectional view of the machine similar to Fig. 2 but showing the machine in a subsequent operational position.

Referring to the drawings, and in particular Fig. i, S.rq there is generally shown rotary machine 1 having 0 :4 cylindrically-shaped outer stationary structure 2, and core-shaped inner rotary structure 3. Rotary structure 3 is located within stationary structure 2 and is rotatable on longitudinal rotation axis X, in a direction indicated I by arrow A.

O:oi Stationary structure 2 includes housing 4 having 30 tubular casing 5 and spaced apart end walls 6,7. Rotary structure 3 includes rotor member 8 carried by rotor shaft 9 extending through end walls 6,7 and journalled in bearings Stationary and rotary structures 2,3 also each include a plurality of magnetic pole positions 11,12.

Pole positions 11 are carried by and spaced apart about casing 5 whilst pole positions 12 are provided on rotor member 8. Pole positions 11,12 are shaped and sized so 39 that air gaps 13 are defined therebetween. Pole positions 1084E *t I *r I a, o aa a, 11 are homopolar and, in this embodiment, have a North polarity. Pole positions 12 are also homopolar and, in this embodiment have a South polarity. It should be appreciated that these polarities may be reversed.

In this embodiment, three pole positions 11 and four pole positions 12 are provided, although it should be appreciated that other equal or unequal pole positions 11,12 may be provided in alternative embodiments.

Pole positions 11,12 are constructed and arranged so that magnetic fields generated during machine operation produce "lines" of useful magnetic flux 0 which generally lie in radial planes containing rotation axis X. Thus, lines of magnetic flux 0 have paths extending from stationary structure pole positions 11 radially across air gaps 13 to rotary structure pole positions 12, returning through rotor member 8 and housing 4 to stationary structure pole positions 11.

Magnetic flux 0 is produced at pole positions 11 in a sequential arrangement. Moreover, that production of flux 0 is only for a segment of each rotation of rotary structure 3. That is, during each rotation of rotary structure 3, there is a sequential provision and removal of magnetic flux 0 at each pole position 11 so that magnetic flux 0 tends to "travel" about stationary structure 2. Sequential production of magnetic flux 0 occurs at individual pole positions 11 at each pole position in turn) in this embodiment, but may occur at multiple pole positions 11 at two or more pole positions concurrently) in an alternative embodiment.

30 In this embodiment, stationary structure 2 has an electrical winding 14 associated with each pole position 11 and which is selectively energisable to produce magnetic flux 0. Whether those windings 14 are energisable by externally applied current or internally induced current will depend on whether the machine operates as a motor or generator, respectively, as will be well appreciated by those skilled in the relevant art.

In this embodiment, energisation of windings 14 of 39 each pole position 11 occurs in a sequential arrangement ar 6I 1) o a a 1084E tI l 9t 4*~ St S 5 9 9: for a segment of each rotation of rotary structure 3.

That sequential energisation occurs at individual pole positions 11 (in this embodiment) or multiple pole positions 11 (in an alternative embodiment).

Each pole position 11 has pole face 15 of substantial concave arcuate extent about rotary axis.

That extent may be up to about 1800, although is substantially less than that in this embodiment.

In this embodiment (as shown), pole positions 11 are spaced apart about rotation axis X. Moreover, each pole position 11 includes a separate pole core 16 providing pole face However, in an alternative embodiment (not shown) those pole positions 11, and in particular their pole faces, may overlap one another circumferentially about axis X. That is, in this alternative embodiment pole positions 11 are not entirely circumferentially spaced apart, so that there is not an arcuate gap or separation between adjacent pole positions 11. The overlap extends entirely about rotary axis X. Moreover, the overlap is considerable in one embodiment, but as will be appreciated, may be related to the number of pole positions 11 provided (with the greater the number of pole positions, the less the overlap between adjacent pole positions). In one embodiment, where pole faces 15 each extend about 1800 then the overlap is about 1200 between pole faces 15 of adjacent pole positions 11.

In order to accommodate this circumferential overlap of pole positions 11, the windings 14 of adjacent pole 30 positions 11 are partially inter-wound with one another, or relatively radially spaced apart. Moreover, because of this overlapping, pole positions 11 do not each have discrete pole cores 16 with separate pole faces Rather, in this embodiment, each pole position 11 has a pole core zone with an associated pole face 15, a part of each pole core zone and pole face 15 also constituting part of a pole core zone and pole face 15 of at least one other pole position 11.

39 In one embodiment (not shown), pole positions 11 are i r:t

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1084E arranged in spaced apart groups about rotary axis X, with windings 14 of pole positions 11 in each group being connected for concurrent energisation. Two or more groups of pole positions 11 may be provided, with two or more pole positions 11 in each group. In one particular embodiment, there are three pairs of pole positions 11, pole positions 11 of each pair being arranged in spaced opposition about rotary axis X. Thus, where pole positions 11 each extend 1800 then successive pairs of pole positions 11 are phase shifted 600 (to overlap 1200) about rotary axis X.

Windings 14 of each pole position 11 lie generally in a circumferentially extending plane about rotary axis X. Within that general plane windings 14 extend at least substantially parallel to rotary axis X.

Each pole position 12 has pole face 17 of convex arcuate extent about rotary axis. That extent is equal -to that of pole faces 15, in this embodiment, although different extents may be selected in alternative embodiments. Each pole position 12 includes separate pole core 18 on rotor member 8 providing respective pole face 17.

In this embodiment rotor member 8 and pole cores 18 are of a unitary or one--piece, solid construction. Rotor member 8 and pole cores 18 are composed of ferromagnetic material such as steel, with pole positions 12 being magnetically induced by magnetic fields generated by electrical windings 14. In alternative embodiments (not shown), permanent magnets or energisable electrical windings may be positioned at pole cores 18 to increase the density of magnetic flux 0 and thereby increase magnetic forces between pole positions 11,12.

Each pole positon 11 is energised for the duration of movement of the point of maximum magnetic field strength Smax of a pole position 12 through an arcuate max distance d- Arcuate distance 4- includes the point of maximum magnetic field strength Nma x of respective pole max position 11. Thus, each pole position 11 is energised 39 whilst point Sax of pole position 12 moves an arcuate max L, 7 Qll 1084E -8distance Q, at least up to and possibly away from point N of that pole position 11.

max In this embodiment, each pole core 16 of pole positions 11 includes trailing edge 1.9 and leading edge whilst each pole core 18 of pole positions 12 includes trailing edge 21 and leading edge 22. Moreover, each pole position 11 is energised for the duration of movement of leading edge 22, of an approaching pole position 12, from adjacent trailing edge 19 to adjacent leading edge Machine 1 also includes switching means 23 operable to ensure appropriate sequential energisation and de-energisation of windings 14. That switching means 23 provides the timing for and duration of energisation of each of the pole position windings 14, as outlined above.

Switching means 23 is of any suitable construction well known to those skilled in the relevant art. In this embodiment, switching means 23 includes at least one sensor device 24 for sensing the rotary position of rotary structure 3 and, in accordance with the position sensed, generating signals which initiate energisation and de-energisation of respective windings 14.

In this embodiment, machine 1 further includes magnetic device 25 to further increase density of magnetic flux 0 and thus the magnetic forces between pole positions 11,12. Magnetic device 25 is spaced axially from pole positions 11,12 so that the lines of magnetic flux 0 extend axially from pole positions 12, passing magnetic device 25 to pole positions 11 of stationary structure 2.

30 In this embodiment, magnetic device 25 -s fixed on stationary structure 2. That mounting is through end wall 6. In an alternative embodiment (not shown), magnetic device 25 is mounted on, rotatable structure 3. That mounting is to rotor shaft 9.

In this embodiment, magnetic device 25 is an energisable electro-magnet 26. Magnet 26 may be particularly appropriate where it is mounted on stationary structure 2 (as shown) The power supply to electro-magnet 39 26 may be variable in order to vary the magnetic flux 84E -9density that in turn may be used to control the torque in the machine 1. In another embodiment (n't shown), magnetic device 25 is a permanent magnet.

Stationary and rotary structures 2,3 are composed of suitable materials to shield against or minimise magnetic flux leakage and distorted flux lines, whilst at the same time provide suitable paths for magnetic flux 0. To that end, stationary structure 2 is constructed at least in part of ferromagnetic material and at least in part of non-ferromagnetic material. In this embodiment, tubular casing 5 and end wall 6 is composed of ferromagnetic material to provide paths for magnetic flux 0, whilst end wall 7 is composed of non-ferromagnetic material.

Finally, it is to be appreciated that various modifications and/or alterations may be made to the machine without departing from the ambit of the present invention defined in the claims appended hereto.

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Claims

1. An electromagnetic rotary machine, including: a stationary structure having a plurality of magnetic pole positions and electrical windings for magnetizing the pole positions; a rotary structure mounted for rotary movement relative to the stationary structure around a rotation axis extending through the rotary structure, the rotary structure having a plurality of magnetic pole positions; and, a magnetic device on the stationary structure for magnetizing the pole positions on the rotary structure, the pole positions of the stationary structure being homopolar and the pole positions of the rotary structure also being homopolar, with the pole positions of the stationary and rotary structures being of relatively opposite magnetic polarity, wherein, when the machine operates as an electric motor, the electrical windings S are connected to an external source of electrical energy to jl provide electromagnetic fields creating motive forces between the pole positions of the stationary and rotary structures to cause rotation of the rotor structure thereby-, producing a mechanical energy output from the machine, and, when the machine operates as an electric generator, the rotor structure .o is connected to an external source of mechanical energy to o rotate the rotor structure and provide an electromotive force in the electrical windings thereby producing an electrical energy output from the machine. S 2. A rotary machine as claimed in claim 1, wherein the S magnetic pole positions are constructed and arranged so that magnetic fields generated between the pole positions have lines of useful magnetic flux extending in radial -)Zanes containing the rotation axis of the rotary structure.

3. A rotary machine as claimed in claim 1 or 2, wherein the pole positions of the stationary structure are constructed and arranged so that the electrical windings are selectively energisable in rotational sequence.

4. A rotary machine as claimed in any preceding claim, wherein the rotor member is of a one piece solid construction. A rotary machine as claimed in any preceding claim, wherein the magnetic device includes an electromagnet mounted to the stationary structure and axially spaced from the pole positions, the electromagnet being permanently energised KW/7010E 1 The claiias defining the invention are as follows: 1. An electromagnetic rotary machine, including: a stationary structure having a plurality of magnetic pole positions and electrical windings for magnetizing the pole positions; a rotary structure mounted for rotary movement relative to tIe stationary structure around a rotation axis extendin( through the rotary structure, the rotary structure having a plurality of magnetic pole positions; and, a magnetic device on the stationary structure for magnetizing the pole positions on the rotary structure, the pole positions of the stationary structure being homopolar and the pole positions of the rotary structure also being homopolar, with the pole positions of the stationary and rotary structures being of relatively opposite magnetic polarity, wherein, when the machine operates as an electric motor, the electrical windings are connected to an external source of electrical energy to provide electromagnetic fields creating motive forces between the pole positions of the stationary and rotary structures to cause rotation of the rotor structure thereby producing a S12' mechanical energy output from the machine, and, when the machine operates as an electric generator, the iotor structure is connected to an external source of mechanical energy to rotate the rotor structure and provide an electromotive force in the electrical windings thereby producing an electrical eneigy output from the machine. S 2. A rotary machine as claimed in claim 1, wherein the magnetic pole positions are consitructed and arranged so that magnetic fields generated between the pole positions have lines of useful magnetic flux extending in radial planes containing the rotation axis of the rotary structure. 3. A rotary machine as claimed in claim 1 or 2, wherein the pole positions of the stationary structure are constructed and arranged so that the electrical windings are selectively energisable in rotational sequonce. 4. A rotary machine as claimed in any preceding claim, .wherein the rotor member is of a one piece solid construction. A rotary machine as claimed in any preceding claim, wherein the magnetic device includes an electromagnet mounted to the stationary structure and axially spaced from the pole positions, the electromagnet being permanently energised KW/7010E I I- 12 during operation of the rotary machine.

6. A rotary machine as claimed in any one of claims 2 to wherein the stationary structure includes a housing partially constructed of ferromagnetic material providing a path between the pole positions of the stationary and rotary structures along which lines of magnetic flux pass, and partially constructed of non-ferromagnetic material to shield against magnetic flux passage.

7. A rotary machine as claimed in claim 6, wherein the housing includes a ferromagnetic tubular casing surrounding the pole positions, a ferromagnetic end wall at one end of the tubular casing and a non-ferromagnetic end wall at an opposite end of the tubular casing, the magnetic flux path extending through the tubular casing and the one end wall of the housing.

8. A rotary machine as claimed in claim 10, wherein the S magnetic device is mounted on the one end wall of the housilnq.

9. A rotary machine as claimed in claim 8, wherein the rotary structure includes a rotor shaft along which the rotation axis extends, and the magnetic device is ring shaped and extends circumferentially about the rotor shaft.

11. A rotary machine as claimed in claim 3 or any claim appended thereto, and further including switching means operable to sequentially energise and de-energise the electrical windings. 25 11. A rotary machine as claimed in claim 10, wherein the switching means includes at least one sensor device for sensing the rotary position of the rotary structure and, in accordance with the position sensed, initiate energisation and de-energisation of the respective electrical windings.

12. A rotary machine as claimed in any preceding claim, wherein the stationary structure has three pole positions and the rotary structure has four pole positions.

13. An electromagnetic rotary machine substantially as hereinbefore described with reference to what is shown in the accompanying drawings. DATED: 6 November, 1992 PHILLIPS ORMONDE FITZPATRICK SAttorneys for: ZANDLER WITOCK ENGINEERING PTY. LTD. )L KW/7010E C)