Rotary electrical machines

Abstract

A rotary electrical machine (1) has at least one stator (23). The stator is provided with at least one radial channel (107) for ducting cooling air. The channel (107) extends between a first position (113) at or substantially near the rim (109) of a winding region of the stator (23) and a second position (119) at or substantially near the center (51) of the winding region. The machine (1) has cooling means (91-97) for causing cooling air to enter the radial channel (107) via the second position (119) and exit via the first portion (113). The stator may have electrical windings arranged as coil sectors (183-197) disposed substantially equi-angularly in a generally circular pattern. At least some of the coil sectors are wound in a generally spiral fashion when viewed axially. A rotor (13), for the machine may have a plurality of equi-angularly spaced magnets (127), which are generally circular but with a cut-away portion, when viewed axially.

Description

In the axial machine 1 according to the invention, as shown in FIG. 1, each of six disc-shaped rotors 3, 5, 7, 9, 11, 13 is respectively alternately interleaved with five disc-shaped stators 15, 17, 19, 21, 23. The rotors each comprise a plurality of radially spaced magnets 25, 27, etc. The magnets are retained by respective hoops 29, etc. The rotors are mounted on a central drive shaft 31 by means of respective integral bosses 33, 35, 37, 39, 41, 42.

The drive shaft 31 passes through respective central stator openings 43, 45, 47, 49, 51. The stators are joined to form a unitary assembly block 55 so that each is provided with a plurality of radially arranged air holes 57, 59, 61, 63, 65, etc., communicating with respective peripheral air channels 67, 69, 71, 73, 75, 77, etc.

A closed path for the magnetic field resulting from the magnets 25, 27, etc., is maintained by keeper discs 79, 81 at either end of the machine.

The drive shaft 31 passes outwardly of the block 55 through a first casing end piece 83 having a first bearing 85 and through a second casing end piece 87 having a second bearing 89. After the drive shaft 31 emerges from the first end piece 83 it is connected to cooling fan 91.

After the drive shaft 31 emerges through the second end piece 87, it is connected to a coupling 101 for connecting it to another component such as a turbine (not shown).

The construction of each stator is substantially the same but for convenience, a description will be given only of the stator 23 which is adjacent the second end piece 87. Details of the means of stator cooling are also shown in FIG. 1. The stator windings will be explained further hereinbelow with reference to FIGS. 5A-5C.

Referring again to FIG. 1, the stator 23 comprises a winding assembly 103 provided with a plurality of radial channels 105, 107, etc., extending between the periphery 109 of the stator and the central opening 51. At the periphery 109, the channels 105, 107, etc., have respective inlets 111, 113, etc., which communicate with axial channels 115, etc., formed in the stator assembly block 55, to receive air from the cooling fan 91.

At the central opening 51, the radial stator channels 105, 107 have respective outlets 117, 119, etc., which communicate with the air channels 77 by means of spaces 121, etc., between each stator and its respective rotor 11, 13, etc.

In use, as the drive shaft 31 rotates the cooling fan 91 forces air through the axial channels 115, etc., and passes radially outwardly through the stator-rotor spaces 121, etc., over the magnets 33, etc., and the retention hoops 29, etc., before emerging through the peripheral air channels 77, etc., formed in the stator assembly block 55, finally emerging through exit air holes 67, etc. As mentioned above in this way, the cooling air cools the stators first, before passing over the magnets and retention hoops of the rotors. Moreover, the same effect can be achieved by drawing air from the air intake 97, by connecting the air holes 67, etc., to a remote pump. In principle, such a pump could also be connected to the drive shaft 31.

The stator assembly shown in FIG. 2 of the drawings is structurally identical to that shown in FIG. 1. However, in this case, the evacuation compressor 91 causes air to be sucked into the peripheral air channels 69, etc. through the air holes 59, etc. The air flows through the air channels 69, etc and thence through each of the channels formed by the rotor-stator spaces 121, etc., passing over the magnets 25, etc. and the retention hoops, 29, etc. The air then passes radially inwardly through the inlets 117, 119, etc of the stators 23, etc and exits through the outlets 111, 113, etc. The air passes through the diffuser 95, finally emerges from air outlet 97.

In this way, the cooling air cools the magnets 25, etc. and retention hoops 29, etc of the rotors first, before passing through the radial channels in the stators and then being drawn away from the stator assembly.

Referring now to FIGS. 3 and 4, each rotor has the same construction as the rotor 23 adjacent second end piece 27. This rotor, 23, etc., is in accordance with the third aspect of the present invention and comprises a generally annular spider 123 the centre of which is joined to the drive shaft 31. Eight equi-angularly spaced magnets 125, 127, 129, 131, 133, 135, 137, 139, 141 are disposed around the spider in respective holes 143, 145, 147, 149, 151, 153, 155, 157 therein, formed to correspond to the shapes of, and to receive the respective magnets.

In this example, each of the magnets 125, etc., has the same shape. However, this is not essential. For simplicity, reference is made only to one magnet 125. As viewed in the axial direction, it is circular in shape except for a cut-away portion defined by a convex edge 159, etc., contiguous with the periphery 161 of the spider 123. These magnets may be fashioned in this shape by taking conventional button magnets and grinding the periphery to produce the convex-edge 159, etc., defining the cut-away portion. The magnets are retained by a reinforced carbon fibre retention hoop 163 which is placed over the spider periphery 161, for example as described in GB-A-2 261 327.

Note that other shapes of magnet may be chosen to give improved output if the benefit outweighs the cost considerations.

The winding assembly of each stator is the same. Thus, for convenience, a description will be made here only of the assembly 103 of the stator 23 closest to the second end piece 87 and with reference to FIGS. 5A-5C.

The windings are made in three planes 165, 167, 169 overlapping relative to the axis and each is provided with a respective connection 171, 173, 175 (with respective counter-connections 177, 179, 181) for a three-phase electrical output (denoted X, Y, Z).

The windings are each formed into eight respective coil sectors 183, 185, 187, 189, 191, 193, 195, 197. It will be appreciated that each set of windings in the respective planes 165, 167, 169 are formed on or within respective laminar supports 199, 201, 203.

Each coil sector 183, etc., is substantially of similar shape. For convenience, this will be described here only with reference to one such sector 183. The sector is generally spiral in shape with the wiring spiralling from the middle 205 to the periphery 207 thereof. The radially outermost part 209 adjacent the stator periphery 109 is generally rounded. The innermost part 211 adjacent the opening 51 is inwardly pinched but has a flat part 213 facing the opening.

In the light of this disclosure modifications of the described embodiment, as well as other embodiments, all within the scope of the present invention as defined by the appended claims, will now become apparent to persons skilled in the art.

Claims

1. A rotary electrical machine comprising at least one substantially disc-shaped stator and at least one substantially disc-shaped adjacent rotor, a space being provided between said stator and said rotor, the stator being provided with at least one set of at least two substantially parallel radial channels for ducting of cooling air, the set of radial channels extending between a first position at or substantially near the rim of a winding region of the stator and a second position at or substantially near the centre of the winding region, the electrical machine further comprising cooling means for causing cooling air to pass through the set of radial channels and to pass through said space between said stator and said rotor.

2. A machine according to claim 1, wherein said cooling air enters the radial set of channels via the first position and exits via the second position.

3. A machine according to claim 2, wherein said cooling air passes through the space between the stator and the rotor after exiting the set of radial channels.

4. A machine according to claim 1, wherein said cooling air enters the set of radial channels via the second position and exits via the first position.

5. A machine according to claim 4, wherein said cooling air passes through said space between the stator and the rotor before entering the set of radial channels.

6. A machine according to claim 1, wherein said cooling means is arranged to subject one position of the at least one set of radial channels to a reduced pressure to suck the cooling air through the set of radial channels from the other position.

7. A machine according to claim 1, wherein said cooling means is arranged to provide pressurised cooling air to the at least one set of radial channels at one position to blow the cooling air through the set of radial channels to the other position.

8. A machine according to claim 1, further comprising a drive shaft and the cooling means comprises an evacuation compressor actuable by the drive shaft.

9. A machine according to claim 1, wherein the cooling means comprises a pump.

10. A machine according to claim 1, wherein the cooling means comprises a cooling fan.

11. A machine according to claim 1, wherein the at least one stator comprises electrical windings.

12. A machine according to claim 1, wherein the at least one rotor has a plurality of substantially equi-angularly spaced magnets.

13. A machine according to claim 1, wherein the at least one set of radial channels follows a substantially straight path between the first and second positions.

14. A machine according to claim 1, wherein the at least one set of radial channels follows a curved or meandering path between the first and second positions, the general direction of the channels being radial.

15. A rotary electrical machine comprising at least one stator, the stator being provided with at least one set of radial channels for ducting of cooling air, said radial channels extending between a first position at or substantially near the rim of a winding region of the stator and a second position at or substantially near the centre of the winding region, the electrical machine further comprising cooling means for causing cooling air to enter the radial channels via the second position and exit via the first position each set of radial channels comprising at least two substantially parallel radial channels.

16. A machine according to claim 15, wherein the at least one stator comprises at least three electrical windings.

17. A machine according to claim 16, wherein at least one radial channel of a set of radial channels being disposed between adjacent windings.