IES20090970A2 - An alternator - Google Patents

Abstract

An alternator (1) of modular construction which has rotor comprising one or more disc-shaped rotor plates (2). Each rotor plate (2) carrries a number of permanent magnet arranged in a circular array. Each rotor plate 92) has complementary stator plate (4) which comprises one or more disc-shaped stator plates (4). Each stator plate (4) carries a plurality of coils arranged in a circular array, wherein each coil is demountably secured within a radial pocket (7) in the stator plate (45). the stator plates (4) are clamped together between end castings (40,41) by means of the screws (21,23). The stator plates (2) are mounted spaced-apart on the drive shaft (3) and extend radially outwardly from the drive shaft (3), each rotor plate (2) overlapping with at least one stator plate (4). <Figure 1>

Description

Field of Invention This invention relates to alternators and in particular, to alternators for use with wind turbines.

Background of Invention An Alternator is an electromechanical device that converts mechanical energy to electrical energy in the form of alternating current (AC). Usually most of the alternators use radial flux magnetic field but axial alternators are also known.

The conventional alternators have stator having multiple stator plates wherein more than one coils are placed in various ways. The ways and manner in which coils are placed and retained in the stator plate(s) has different consequences and meanings, such as manufacturing ease, repair and maintenance freedom, and overall lifespan of the alternator.

One of the features of an ideal alternator is that it should have strong and rigid stator plate structure, with surety that the coils can be installed or removed as individual parts.

One of the disadvantages of the state of art is that it is not easy to cure defect, if any, in an individual coil in stator, The present invention is directed, inter alia, towards achieving some ideal features in the structure of stator of an alternator.

Statement of Invention According to the invention, there is provided an alternator of modular construction including a rotor comprising one or more disc shaped rotor plates, each rotor plate carrying a number of permanent magnets arranged in a circular array, and a complementary stator IE 0 9 09 70 -2comprising one or more disc shaped stator plates, each stator plate carrying a plurality of coils arranged in a circular array, wherein each coil is de-mountably secured within a radial pocket on the stator plate.

An advantage of the invention is that symmetrical moulding of the coil retention plates allows back to back assembly of same parts and this cancels out possible manufacturing distortion. This kind of assembly results in a very strong and very rigid structure. This is a cost effective arrangement due to ease of manufacture and reduced raw material requirement.

Another advantage of foe invention is that the individual coils, or alternatively coils incorporating iron cores, are encapsulated to achieve accurately dimensioned and hermetic sealing against hostile environments.

Another advantage of the invention is that very accurate positioning and retention of the encapsulated coils within the stator plates can be achieved, which in turn promotes rigidity.

A further advantage of the invention is that the encapsulated coil in the moulded stator plates can be installed or removed as individual parts. Therefore, in the event of coil’s failure, the entire stator plate does not have to be removed and changed as is the case with the prior arts.

Another advantage of the invention is the method of manufacturing stator plates (Pressure Injection Moulded Structural Foam) is very cost effective and dimensionally predictable as compared to the existing state of art, for example, the traditional method of encapsulating the coil array as one piece to form a stator plate.

In one embodiment of the invention, each stator plate has an injection moulded structural foam body which may comprise of two symmetrical injection moulded structural foam discs. -3IE 09 09 7 0 In another embodiment, each coil wilh or without iron core is encapsulated within a high thermal conductivity epoxy resin to form a dimensionally accurate and reproducible assembly or component.

In another embodiment, a stack of annular stator plates are clamped together between associated end covers, a rotor drive shaft being rotatably mounted between the end covers and passing through a central opening in each stator plate, a number of rotor plates mounted spaced-apart on the drive shaft, each rotor plate extending radially outwardly from the drive shaft and overlapping with at least one stator plate.

In a ftirther embodiment, each encapsulated coil is de-mountably secured within the pocket by means of a pair of resilient wedge elements mounted between the coil and a side wall of the pocket.

In another embodiment of the invention, a pair of annular disc is used to clamp together moulded pockets to retain coils and to form a stator plate.

In another embodiment, each wedge element has a resilient bifurcated head.

Conveniently, complementary interchangeable formations are provided on each wedge element and on a side wall of the pocket for releasably retaining the wedge element in engagement with the pocket. The interchangeable formations may be provided by serrations on the wedge element and on the side wall ofthe pocket.

Brief description of the drawings The invention will be more clearly understood by the following description of some embodiments thereof, given by way of example only, with reference to the accompanying drawings, in which; Fig. 1 is an exploded perspective view of an alternator according to the invention; Fig. 2 is the detail perspective view of a rotor plate forming portion of the alternator; IE 0 9 0 9 7 0 .4.

Fig. 3 is a detail exploded perspective view of a stator plate assembly forming portion of the alternator; Fig, 4 is a detail perspective view of the stator plate; Fig. 5 is a detail perspective view of the stator plate; and Fig. 6 is an enlarged detail perspective view showing portion of the stator plate.

Detailed Description of the Invention Referring to the drawings, there is illustrated an alternator according to the invention indicated generally by the reference numeral 1. The alternator 1 has a number of disc shaped rotor plates 2 which are keyed onto a drive shaft 3. Each rotor plate 2 carries a number of permanent magnets arranged in a circular array. A number of complementary stator plates 4 are mounted between rotor plates 2. Each stator plate 4 carries a plurality of encapsulated coils with or without iron cores. 5 arranged in a circular array for co-operation with the magnets on the rotor plates 2. Each coil 5 is demountably secured within a radial pocket on the stator plate 4, Referring in particular to Fig. 3 to Fig. 6, each stator plate 4 has an injection moulded structural foam body formed in two parts comprising a pair of annular disc 10 which clamp together to form the stator plate 4. Each disc 10 has a central opening ll.A number of radial pockets 7, in this case nine, are formed in the stator plate 4. An encapsulated coil 5 is mounted in each pocket 7. Each encapsulated coil 5 can be readily easily inserted into one of the pockets 7 to form the circular array of the encapsulated coils 5 in the stator plate 4.

A pair of plastic wedges 12 (Fig. 6) are mounted at a mouth of each pocket 7 to retain the coil 5 therein. These wedges 12 can be released to allow a coil 5 to be removed for inspection or replacement if necessary. Each wedge 12 co-operates with a tapered shoulder portion 14 at an outer end of the coil 5 and with a side wall 15 at a mouth of pocket 7. -5IE 090970 Coraplementary serrations 16, 17 in the side wall 15 and on the wedge 12 co-operate to retain wedge 12 in place. A resilient bifurcated head 18 on the wedge 12 allows the wedge 12 to snap into engagement with the pocket 7 when the coil 5 has been loaded in the pocket 7.

A number of through holes 20, 21 in the stator plate 4 receives clamping 22,23 (Fig. 1) for clamping the stator plates 4 together. Preferably metal bushings are mounted in these holes 20,21. Conveniently, the bushing can be mounted in the mould during the moulding of each annular disc 10 for moulding in situ.

Each coil 5 comprises of a metal coil encapsulated in a high thermal conductivity epoxy. Each end of the coil terminates in an electrical contact 30 at an outer end of the coil 5.

Each rotor plate 2 is an aluminium casting heat treated to increase its tensile strength. 15 A number of neodymium magnets 35 are mounted on each rotor plate 2 as shown in Fig.2. Where a rotor plate 2 is mounted between a pair of stator plates 4 magnets 35 are provided on both sides of the rotor plate 2. Rotor plate 2 at an outer end of the track of the stator plate will only have magnets on an inside face adjacent the coils 5.

A pair of end casting 40, 41 form end covers which have centrally mounted bearings (not shown) between which the drive shaft 3 is rotatably supported.

Mounting feet 42 project outwardly from each end casting 40, 41 for mounting the alternator 1 on a support frame or chassis.

A stack of stator plates 4 are clamped together between the end castings 40, 41 by means of the bolts 21,23 which extend through the end castings 40,41 and the stator plates 4. The stator plates 2 are mounted spaced-apart on the drive shaft 3 and extend radially outwardly from the drive shaft 3, each rotor plate 2 overlapping with at least one stator plate 4.

IE Ο 9 Ο 9 7 Ο -6It will be appreciated that any suitable number of stator plates 4 and associated rotor plates 2 may be provided in the stack between the end casting 40, 41. This conveniently allows alternators of different size to be constructed from essentially the same elements. It will further be appreciated that should individual coils 5 fail they can be readily easily and quickly replaced.

It is envisaged that die rotor plates could be made of various other materials. For example, they could be injected moulded in a reinforced polymer such as glass filled polycarbonate or nylon.

An arrangement of the ducts or windows, fins and baffles in the rotor plates and the stator plates create an air flow that is beneficial to coil cooling.

The invention is not limited to the embodiments hereinbefore described which may 15 be varied in both construction and detail.

Claims (5)

1. Claiins

1. An alternator including a rotor comprising one or more disc-shaped rotor plates, each rotor plate carrying a number of permanent magnets arranged in a circular array, and a complementary stator comprising one or more disc-shaped stator plates, each stator plate carrying a plurality of coils arranged in a circular array, wherein each coil is demountably secured within a radial pocket on the stator plate.

2. An alternator according to claim 1, wherein each stator plate of stator has an injection moulded structural foam body comprising of two symmetrical injection moulded structural foam discs.

3. An alternator according to claim 1, wherein each coil with or without iron core in the stator plate is encapsulated within high thermal conductivity epoxy block,

4. An alternator according to Claim 1, wherein the coils are inserted into the pockets contained in annular moulded structural foam to form a circular array of coils in the stator plate.

5. An alternator according to claim 1, wherein each coil in a stator plate is demountably secured within the pocket by means of a pair of resilient wedge elements mounted between the coil and side wall of the pocket