AU2014202614B2

AU2014202614B2 - A device for cooling flameproof alternators

Info

Publication number: AU2014202614B2
Application number: AU2014202614A
Authority: AU
Inventors: Giuliano Res
Original assignee: Individual
Current assignee: Individual
Priority date: 2013-05-13
Filing date: 2014-05-13
Publication date: 2018-08-30
Anticipated expiration: 2034-05-13
Also published as: AU2014202614A1

Abstract

A device for improved air cooling of a flameproof alternator having a fan, stepped cooling grooves in the alternator housing, a cowling and outer sleeve for directing the airflow. The stepped cooling grooves provide increased thermal cooling surface area, make use of the spiralling nature of the incoming air movement to provide increased air turbulence for improving the thermal transfer and direct the exiting air into a generally conical pattern N '~~NN 4k ~ / ~ Na ~NN (N~' 1 kN~N t N\N / k~ ~ N et j~.ve I N>jN -~ N> 'JNN~~ v WN> N~ p ~NN\ ~ / <hNA. \ N -' / wt~ / \ C ~<N< t~ U V~ J I,, It F 'ure 2

Description

BACKGROUND OF THE INVENTION [0001] The present invention relates to improvements in alternators and more particularly relates to an assembly integrated with an alternator which more efficiently cools the alternator during use and results in increased efficiency of the alternator. The invention further relates to an assembly which is integrated into an alternator body and which improves air flow and heat dissipation from the alternator. The present invention further relates to improvements in cooling alternators which are used in particular though not exclusively, in dangerous environments such as occurs in underground mining and which reduces the danger of explosion by improved cooling characteristics.

PRIOR ART [0002] Alternators are widely used in industry and mining environments. An alternator converts the mechanical power from a rotating shaft into electrical power and heat. The electric power generated is used to drive electrical equipment. Efficiency of alternators is limited by various operational factors including fan cooling loss, bearing loss, iron loss, copper loss, and the voltage drop in the diode bridges. Efficiency is also reduced by overheating. Fans used to cool an alternator contribute to the inefficiency. Efficiencies can range from 60%- 90% depending upon the environment in which the alternator is operating, its application, the type of alternator and the type of construction. Large AC generators used in power stations run at carefully controlled speeds and have no constraints on size or weight. They have very high efficiencies as high as 98%.

[0003] The design of an alternator involves trade-offs between such features as cost, size, weight and efficiency. The efficiency of common alternators is only around 50-60% so significant heat is generated. Mining industry standards require that machines and machine components used in the mining and petrochemical industries are

2014202614 14 Aug 2018 flameproof and/or intrinsically safe. Heat reduction is important to reduce the risk of combustion particularly in environments where sparks can cause fire and explosion.

[0004] A flameproof device must be able to withstand an internal explosion and any air passages between the internal space and the outside must meet specific flame-path requirements such as a maximum 0.3 mm gap over a minimum 12.5 mm distance. Intrinsically safe devices ensure internal temperatures remain low, even in fault conditions, and so do not pose an ignition hazard. Flameproof alternators need to meet additional requirements of the mining and petrochemical environments. The trade-offs involved with flameproof designs typically lead to a brushless design to avoid sparks, copper wires and an electro-magnet. Each of these trade-offs tend to be detrimental to efficiency due to heating. Heat dissipation is therefore a major concern in the design of flameproof alternators and is, for a given size alternator, a major limiting factor in the output power capacity of the alternator. Current flameproof alternators typically have a fan that blows cooling air over the smooth outside surface of a bronze cylindrical housing. The size of the housing is chosen, in part, to provide adequate surface area for the required air cooling capacity. Housing design has traditionally been restricted to a cylindrical generally smooth body. Without formations which increase the heat transfer surfaces cooling capacity and consequently efficiency is reduced.

[0005] Alternators heretofore devised and utilized are known to consist basically of familiar, expected and obvious structural configurations, notwithstanding the plurality of designs encompassed by the prior art which have been developed for the fulfillment of the objectives and requirements of alternator power generation. While these devices fulfill their respective functions, particular objectives and requirements, the aforementioned prior art does not disclose an alternator which includes an integrated cooling assembly with a large surface area relative to the outer surface area of a cylindrical housing for heat transfer and therefore cooling.

2014202614 14 Aug 2018

THE INVENTION [0006] The present invention provides improvements in alternators which more efficiently cools the alternator during use and results in increased efficiency of power output. The invention further relates to an assembly which is integrated into an alternator body and which improves air flow and heat dissipation from the body of the alternator. The present invention further relates to improvements in cooling alternators which are used in particular though not exclusively, in dangerous environments such as occurs in underground mining and which reduces the danger of explosion by improved cooling characteristics.

[0007] The present invention provides an alternative housing construction for an alternator which increases heat transfer by either ventilation through the casing wall or through use of formations which increase the surface area of the heat transfer region thereby increasing cooling during use of the alternator and enabling increased output power capacity for a given alternator size and at minimal cost. The present invention provides improvements in alternators which are particularly useful in dangerous environments such as occurs in underground mining and which reduce the danger of explosion by an alternative housing geometry contributing to improved cooling characteristics.

[0008] The general purpose of the present invention, which is described herein in detail, is to provide a new alternator housing which while possessing many of the attributes of the known alternator housings has the additional advantages along with novel features that result in a new, advantageous and more efficient alternator which is not anticipated, rendered obvious, suggested, or even implied by any of the prior art devices, either alone or in any combination thereof.

[0009] Accordingly, one objective of the subject invention is to provide an alternator which possesses a housing geometry which statically improves air flow about the alternator during operation to dissipate heat generated. A further objective of the invention is to provide a cover assembly for an alternator which is relatively simple in

2014202614 14 Aug 2018 construction, and which increases efficiency of operation without comprising known functions.

[0010] In one broad form the present invention comprises:

an alternator comprising an outer housing, which receives and retains therein an inner housing, forming therebetween an air passage;

a cooling fan connectable to the inner housing, a cowling for retaining the fan; characterized in that the inner housing includes a plurality of spaced apart formations arranged to increase a contact area between air passing through the passage and the formations; wherein each said formations include radially disposed and axially aligned grooves spaced around the inner housing; each said grooves having at least one stepped region along the groove; the outer housing and formations on the inner housing co -operating to increase air turbulence and retard spiraling air entering the passage.

[0011] In another broad form the present invention comprises:

an inner housing for an alternator, the alternator comprising an outer housing, which receives and retains therein an inner housing, the inner housing including a cooling fan connectable to the inner housing, a cowling for retaining the fan;

characterized in that the inner housing includes a plurality of spaced apart formations arranged to increase a housing/air thermal contact area between air passing through the passage and the formations; wherein each said formations include radially disposed and axially aligned grooves spaced around the inner housing; each said grooves having at least one stepped region along the groove; the outer housing and formations on the inner housing co -operating to increase air turbulence and retard spiraling air entering the passage.

[0012] The present invention provides a useful alternative to the known devices and although the invention will be described with reference to its application in alternators it will be recognised that the alternator assembly has a variety of applications not limited to that described.

2014202614 14 Aug 2018 [0013] The present invention provides an alternative to the known prior art and the shortcomings identified. The foregoing and other objects and advantages will appear from the description to follow. In the description reference is made to the accompanying representations, which forms a part hereof, and in which is shown by way of illustration specific embodiments in which the invention may be practiced. These embodiments will be described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that other embodiments may be utilized and that structural changes may be made without departing from the scope of the invention. In the accompanying illustrations, like reference characters designate the same or similar.

BRIEF DESCRIPTION OF THE DRAWINGS [0014] The present invention will now be described in broad detail according to preferred but non limiting embodiments wherein;

Figure 1 is an exploded view of the alternator according to a preferred embodiment showing the cowling and outer sleeve separated from the main alternator subassembly.

Figure 2 shows an abbreviated exploded view of the alternator cylindrical housing, the fan and the cowling.

Figure 3 shows an exploded enlarged view of the alternator according to the embodiment of figure 1.

Figure 4 shows a perspective view of the inner housing showing the cooling formations along the length of the housing.

Figure 5 shows the inner housing with casing abbreviated and including the cooling fan.

DETAILED DESCRIPTION

2014202614 14 Aug 2018 [0015] The present invention is a low cost integrated cooling device for flameproof alternators. Although the invention will be described according to preferred embodiments it will be appreciated that other variants are contemplated which may take any desired shape, since its function is primarily is to provide sufficient cooling.

[0016] Figure 1 is an exploded view of the alternator 1 according to a preferred embodiment. Alternator 1 comprises an inner housing 2 which retains alternator windings (obscured) and a cooling fan 3 mounted on shaft 4. Cowling 5 provides a protective recess to retain fan 3 and to allow air to be drawn through grill 6. An outer sleeve 7 is provided which receives and retains therein inner housing 2. The diameter of outer sleeve 7 relative to the outside diameter for inner housing 2 results in an air gap formed between inner housing 2 and outer sleeve 7. As outer sleeve 7 is separated from the main alternator subassembly via the air gap, in particular the inner housing 2, air travels under the action of fan 3 longitudinally along the length of the inner housing 2 until it exits.

[0017] Cylindrical outer sleeve 7 is mounted over the cylindrical inner housing 2 to guide the air and maintain turbulent flow in the gap between the cylindrical housing 2 and the inside of the outer sleeve 7. Cowling 5 is mounted over the fan 3 to direct the airflow through the gap between the outer sleeve 7 and the cylindrical housing 2. Air turbulence improves the thermal transfer from the metal to the air and in so doing helps maintain a lower surface temperature on the inner housing 2.

[0018] In a preferred embodiment of the present invention in wall 8 of inner housing 2 there are provided a series of stepped grooves 10. These are cut into the alternator's cylindrical inner housing 2 to increase the surface area for cooling and improve air turbulence while maintaining the required explosion proof characteristics. Air is drawn in by bi-directional fan 3 and, along with a cowling 5, is forced into the cooling gap between the cylindrical inner housing 2 and the outer sleeve 7. The stepped design of the machined stepped grooves 10 helps to increase the turbulence compared with a, non-stepped or non existent groove.

2014202614 14 Aug 2018 [0019 ] The fan 3 is designed to maximize the airflow with a series of interleaved large flat blades 9 and small flat blades 11. The large blades 9 are based on a commonly known impeller blade design. The small blades 11 have abbreviated S-shaped regions. The small blades 11 prevent air currents that oppose the air currents desirable for the efficient operation of the large blades 9. The cowling 5 has a flare-down shape 12 on the periphery of the central intake grill 6. This flare- down formation 6 is designed to impede reverse air currents that would result in air escaping from under the cowling 5 and reducing the effectiveness of the fan 3 and cowling operation. The cowling 5 also acts as a safety barrier. The cylindrical inner housing 2 is preferably machined from a thick tube of brass. Brass characteristics combine good strength, good machinability and reasonable cost along with a high thermal conductivity. In other embodiments other materials with these suitable characteristics may be used.

[0020 ] Air is drawn in to the fan 3 and expelled backwards in a spiraling fashion from the cowling 6. As the air is forced through the cooling air gap in the spiral it passes along and across the stepped grooves 10 which produce turbulent mini air currents inside the stepped grooves 10 as well as increasing turbulence in the cooling air gap in general. The air heats up as it passes through the air gap, cooling the cylindrical housing 2 and exiting the rear of the alternator. As the air passes towards the rear of the alternator 13 the stepped grooves 10 impede and slow down the spiraling action of the airflow. Just as air exits the stepped grooves 10 it engages a sloped formation 14 which directs air radially outwards in a conical shape in such a way that the air exits the alternator in a generally conical, rather than cylindrical, fashion. The conical air exit pattern has a lower backpressure and therefore better airflow in installations with a surface behind and near the alternator compared with a more cylindrically shaped exit pattern.

[0021 ] Figure 2 shows with corresponding numbering an abbreviated exploded view of the alternator cylindrical inner housing 2, the fan 3 and the cowling 5. In this case fan 3 is separated from the inner housing 2.

[0022] Figure 3 shows an exploded enlarged view of the alternator 1 according to the embodiment of figure 1 but in this case the inner housing 2 is shown abbreviated to

2014202614 14 Aug 2018 expose the inside surface 15.

[0023] Figure 4 shows in isolation a perspective view of part of the inner housing 2 showing the cooling formations along the length of the housing. Housing 2 comprises a plurality of radially disposed formations 10 equally spaced apart about the circumference. Each formation 10 shown in figure 4 has the same geometry but it will be appreciated that various internal geometries for the cooling formations may be adopted along the length of the inner housing 2. In this embodiment, formation 10 comprises inclined regions 17, 19 and 21. Intermediate those regions are plateaus 18, 20 and 22. Air is blown in the direction of arrow 23. As a result of the geometry of the formations 10 and the various steps in each formation, turbulent and a spiral flow travels along the length of the inner housing 2 resulting in heat transfer from the alternator windings to the outside of inner housing 2.

[0024] Figure 5 shows an enlarged view of the inner housing 2 with casing abbreviated to expose inside 15 of alternator 1. In this view the cooling fan 3 is attached. In this view inner housing 2 is fitted with end collar 32 which includes ramped formations 33 and 34. Ramped formation 34 aligns with groove 35. Groove 35 comprises plateaus 25, 27, 29 and 31. Steps 30 28 and 26 cascade downwardly away from the fan 3. Air flows in the direction of arrow 36 and as the air exits from groove 35 it engages ramp 34 and is blown upwards. This air enters the space between the inner housing 2 and outer housing 7 ( see figure 1). Providing the various surface areas in stepped formation and generating spiral flow contributes to heat exchange and therefore cooling of the alternator and increased efficiency. This is particularly beneficial in hazardous environments.

[0025] According to one preferred embodiment has a fan and electronics design so as to operate with the input shaft spinning in either direction. In other embodiments a unidirectional fan may be used. Similarly, in other embodiments the internal design of the various coils, magnets and electronics may be designed for a specific input shaft spin direction. To reduce overall cost the machined scrap brass is recovered and sold as scrap. In another preferred embodiment the design feature to increase thermal transfer

2014202614 14 Aug 2018 surface area and increase turbulence replaced the stepped grooves 10 with press-fit fins that are inserted into matching grooves to ensure good thermal contact between the fins and the cylindrical housing.

[0026] The design and construction may be variously modified, without departing from the spirit and scope of the invention, as defined in the claims. For example, the assembly may be made of different materials of construction and but may be made in other forms and shapes such as longer cylinders. It will be recognized by persons skilled in the art that numerous variations and modifications may be made to the invention as broadly described herein, without departing from the overall spirit and scope of the invention.

2014202614 19 Jul 2018

Claims

THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:

1. An alternator comprising an outer housing, which receives and retains therein an inner housing, forming therebetween an air passage;

a cooling fan connectable to the inner housing, a cowling for retaining the fan; characterized in that the inner housing includes a plurality of spaced apart formations arranged to increase a contact area between air passing through the passage and the formations; wherein each said formations include radially disposed and axially aligned grooves spaced around and recessed below an outer surface of the inner housing; each said grooves having at least one stepped region along the groove; the outer housing and formations on the inner housing co -operating to increase air turbulence and retard spiraling air entering the passage.
2. An alternator according to claim 1 wherein the formations increase an outer surface area of the inner housing
3. An alternator according to claim 2 wherein the cowling engages and closes the outer housing.
4. An alternator according to claim 3 wherein the air passage between the outer and inner housings is a cylindrical channel.
5. An alternator according to claim 4 wherein the cowling co -operates with the fan to force air into the air channel in said spiral direction.
6. An alternator according to claim 5 wherein the groove formations are substantially channel shaped in cross section.
7. An alternator according to claim 6 wherein, the grooves are elongated and evenly spaced about a wall circumference of the inner housing.
8. An alternator according to claim 7 wherein, each groove includes therein at least 10

2014202614 19 Jul 2018 one ramped formation.
9. An alternator according to claim 8 wherein each groove has a base and side walls providing contact areas for the spiraling airflow.
10. An alternator according to claim 9 wherein, each groove includes a plurality of cascading steps with the ramped formation providing a riser for each step.
11. An alternator according to claim 10 wherein the cascading steps are disposed along the base of each groove.
12. An alternator according to claim 11 wherein, the alternator is flameproof and the inner housing is flame proof.
13. An inner housing for an alternator, the alternator comprising an outer housing, which receives and retains therein an inner housing, the inner housing including a cooling fan connectable to the inner housing, a cowling for retaining the fan;

characterized in that the inner housing includes a plurality of spaced apart formations arranged to increase a contact area between air passing through the passage and the formations; wherein each said formations include radially disposed and axially aligned grooves spaced around the inner housing; each said grooves having at least one stepped region along the groove; the outer housing and formations on the inner housing co -operating to increase air turbulence and retard spiraling air entering the passage.
14. An inner housing according to claim 13 wherein the formations increase the outer surface area of the inner housing
15. An inner housing according to claim 14 wherein the cowling engages and closes the outer housing.
16. An inner housing according to claim 15 wherein the grooves each comprise

2014202614 19 Jul 2018 elongated channels defining sidewalls and a base.
17. An inner housing according to claim 16 wherein the outer and inner housings are cylindrical and co -operate to form an air passage between the cylindrical outer housing and the inner housing.
18. An inner housing according to claim 17 wherein the cowling co -operates with the fan to force air into the air channel in said spiral direction.
19. An inner housing according to claim 18 wherein the grooves each include a plurality of said stepped regions which are disposed along the base of each groove.
20. An inner housing according to claim 19 wherein, the inner and outer housings are flameproof.