GB2375897A

GB2375897A - Sealed generator

Info

Publication number: GB2375897A
Application number: GB0202332A
Authority: GB
Inventors: Vincent Peter Smith
Original assignee: Individual
Current assignee: Individual
Priority date: 2001-02-02
Filing date: 2002-02-01
Publication date: 2002-11-27
Anticipated expiration: 2022-02-01
Also published as: GB0202332D0; GB2375897B; GB0102615D0

Abstract

The present invention provides a electric generator comprising a casing (1) defining a sealed enclosure for a stator (17) and a plurality of permanent magnets (29) carried by a rotor (15). The rotor magnets (29) define a plurality of poles (even in, number) and rotating within the stator. The stator laminations 19 are skewed with respect to one another by up to 10 degrees, and are disposed within the casing and in heat transmitting contact therewith. The generator is provided with cooling means comprising a fan (41) mounted outside the enclosure for rotation with the rotor shaft and arranged to pass air over fins 3. The windings are connectable to a terminal block which has a plurality of terminals which allow the stator windings to be connected in one of a plurality of configurations to give a desired output format.

Description

Title : The Electric Generator DESCRIPTION The present invention relates to a brushless electric generator.

There is a demand for an electric generator that can generate a useful power output when driven at relatively low speeds. For example, it would be useful to be able to generate power to supply the electrical loads of domestic premises from a water or wind turbine. Such a source of electric power could be used as an alternative to or as a supplement to drawing electrical power from a means supply grid. However, despite the interest in generating energy from renewable energy sources a suitable generator is not available off the shelf.

Most generators have the magnetic field electrically generated by providing the rotor with field windings. Electrical current is supplied via brushes.

It is necessary to cool the windings and to achieve this the casing is ventilated.

Most often a fan is provided within the casing for drawing air over the windings of the rotor. However, this has the disadvantage of allowing dirt to enter the housing. For example, it causes premature wear of the brushes supplying the current to the field windings. The present invention aims to provide a solution to this problem.

Accordingly, the present invention provides a brushless electric generator comprising a casing defining a sealed enclosure for a stator and a plurality of permanent magnets carried by a rotor, the rotor having a rotor shaft journalled for rotation with respect to the casing and serving as an imput shaft, permanent magnets defining a plurality of poles (even in number) and rotating within the

stator, the stator comprising a plurality of axial laminations, each having a plurality of grooves therein which together define a plurality of axially extending recesses to receive stator windings, the laminations being skewed with respect to one another by up to 10 degrees, and being disposed within the casing and in heat transmitting contact therewith, the generator being provided with cooling means comprising a fan mounted on the rotor shaft outside the enclosure for rotation with the rotor shaft and arranged to pass air over formations which increase the surface area of the casing, and wherein the windings are connectable to a terminal block which has a plurality of terminals which allow the stator windings to be connected in one of a plurality of configurations to give a desired output format.

The use of a permanent magnet avoids the need for brushes, and by incorporating the magnets into the rotor rather than the stator, the voltage output can be taken from the stator. Since the stator is in contact with the casing cooling of the casing serves to cool the generator and can be achieved with the externally mounted fan allowing the stator rotor assemby to be completely sealed. The fan is conveniently housed within a cowling disposed at one end of the casing and the formations which provide increased surface area of the casing are conveniently provided by a plurality of fins. Air drawn into one end of the cowling can be passed over the fins by the action of the fan or vise versa.

It is preferred to provide at least six poles. There will be a corresponding number of stator windings. There will be twelve reconnectable ends in the case of a six pole generator. The connector block allows any desired output format to

be wired, for example three'phase four wire series star, three phase four wire parallel star, or single phase two or three wire zig-zag. The latter connection is preferred. I prefer to use a 6 degrees skew on the stator laminations. The rotor comprises a central shaft, to which the magnets are secured. The magnets are spaced apart circumferentially by spacers between the magnets. Aluminium end caps are used. It is preferred to use neodinium magnets.

The present invention will now be described further by way of example only with reference to the accompanying drawings; in which :- Figure 1 is a partially broken away perspective view of a generator according to the invention, Figure 2 is a longitudinal section of the generator of Figure 1, Figure 3 is a section taken on line 3 3 of Figure 2, Figure 4 is a perspective view of the rotor which leads to the generator of Figure 1, and Figure 5 is a perspective view of the stator used in the embodiment of Figure 1.

Referring to the drawings, a generator according to the invention comprises a cylindrical casing 1, carrying a plurality of outwardly extending external cooling fins 3, and having opposite end plates 5,7. The end plates are bolted to the casing by fixing means 9. Bearings 11 are mounted in each of the end plates and a rotor 15 is mounted in the bearings for rotation with respect to the casing. The end plates carry sealing rings 13 for sealing the interior of the casing from the atmosphere. The sealed internal compartment of the casing

accommodates the stator 17. The stator comprises a plurality of thin annular discs 19 which are laminated together. The discs have a plurality of recesses 21 formed in the inner bore 23. In the preferred embodiment the recesses are aligned with one another so that they define a skew angle of 6 degrees from a line parallel to the longitudinal axis X. Stator windings are received in the recesses 21 and are wound around the assembled discs 19 in a conventional manner not illustrated. The stator assembly is immersed in varnish in the usual way and provides insulation on the stator windings to class f (155 C). The stator is an interference fit within the casing to achieve good heat transmitting contact between the stator and the casing. This can be achieved by cooling the stator and heating the casing to allow assembly of the components. The assembly is coated in varnish and baked for the required time to cure the varnish. The present invention is described with respect to a six pole generator. The stator is provided with six pairs of magnets 29. The pairs are separated by aluminium spacer bars 31 screwed to a central core of the rotor 15 using stainless steel countersunk head screws 33. End caps 35 made of aluminium are bolted to the core of the rotor using cap head screws 37. It is advantageous to have the cap head screws project from the end caps to aid air circulation within the housing.

An input end of the stator is provided with a key way 39 to receive a suitable drive coupling. The other end of the stator shaft carries a multi-bladed fan 41. A cowling 43 is mounted to one end of the casing and covers the fan 41. One end of the cowling has an open mesh 45 through which air can be drawn into the cowling and the cowling is dimensioned to fit around an exterior of the fins 3.

The air is forced out between the cowling and the fins through passages denoted by arrows 47 which are defined between the body of the casing between adjacent fins and the cowling.

The housing is provided with a mounting flange for a hollow housing 49 which has a releasable lid 51. The housing 49 has an outlet along one side for the electrical connections. The housing 49 can be mounted in any one of any four orientations according to the preferred location of the outlet 53. Mounted within the housing is a connector block to which the windings of the stator are connected and to which the output wires are connected.

In the case of a six pole motor as described herein there are twelve connectable ends from the stator wiring and these are wired in any desired configuration. The terminal block has seven terminals to facilitate connection in any desired configurations. The casing has mounting feet 54 to provide for foot mountings. The feet can be removably mounted to the casing and the end plate 5 can be changed for one which allows for direct coupling via a flange. The environmental protection is to IP55 which renders it suitable for harsh damp environments-such as water turbine installations.

The generator can be used in conjunction with a suitable transformer where a D. C. output is required.

Claims

1. A brushless electric generator comprising a casing defining a sealed enclosure for a stator and a plurality of permanent magnets carried by a rotor, the rotor having a rotor shaft journalled for rotation with respect to the casing and serving as an input shaft, permanent magnets defining a plurality of poles (even in number) and rotating within the stator, the stator comprising a plurality of axial laminations, each having a plurality of grooves therein which together define a plurality of axially extending recesses to receive stator windings, the laminations being skewed with respect to one another by up to 10 degrees, and being disposed within the casing and in heat transmitting contact therewith, the generator being provided with cooling means comprising a fan mounted on the rotor shaft outside the enclosure for rotation with the rotor shaft and arranged to pass air over formations which increase the surface area of the casing, and wherein the windings are connectable to a terminal block which has a plurality of terminals which allow the stator windings to be connected in one of a plurality of configurations to give a desired output format.

2. A brushless electric generator as claimed in claim 1 in which the stator rotor assemby is completely sealed.

3. A brushless electric generator as claimed in claim 1 or 2 in which the fan is housed within a cowling disposed at one end of the casing and

the formations which provide increased surface area of the casing are provided by a plurality of fins.

4. A brushless electric generator as claimed in claim 1,2 or 3 when comprising at least six poles.

5. A brushless electric generator as claimed in anyone of claims 1 to 4 in which the terminal block allows the output format to be wired, in three phase four wire series star, three phase four wire parallel star, or single phase two or three wire zig-zag.

6. A brushless electric generator as claimed in anyone of claims 1 to 5 in which the starter rotor laminations are skewed at 6 degrees.

7. A brushless eletric generator as claimed in anyone of the preceding claims in which the rotor comprises a central shaft, to which the magnets are secured.

8. A brushless electric generator as claimed in any preceding claims in which the magnets are spaced apart circumferentially by spacers between the magnets.

9. A brushless electric generator as claimed in anyone of claims 1 to 8 in which aluminium end caps are used.

10. A brushless electric generator as claimed in anyone of claims 1 to 9 in which neodinium magnets are used.

11. A brushless electric generator as claimed in anyone of the preceding claims and further comprising opposite end plates bolted to the casing by fixing means and bearings mounted in each of the end plates.

12. A brushless electric generator as claimed in claim 11 in which the end plates carry sealing rings for sealing the interior of the casing from the atmosphere.

13. A brushless electric generator as claimed in anyone of the preceding claims in which the stator is an interference fit within the casing to achieve good heat transmitting contact between the stator and the casing.

14. A brushless electric generator as claimed in anyone of the preceding claims in which there is a pair of magnets for each pole and the pairs are separated by aluminium spacer bars screwed to a central core of the rotor using stainless steel countersunk head screws.

15. A brushless electric generator as claimed in claim 9 in which the end caps are bolted to the core of the rotor using cap head screws whose heads project from the end caps to aid air circulation within the housing.

16. A brushless electric generator as claimed in claim 12 in which the terminal block has seven terminals.

17. A brushless electric generator constructed and arranged substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.