WO2014012549A2

WO2014012549A2 - A canned electric machine and use hereof

Info

Publication number: WO2014012549A2
Application number: PCT/DK2013/050221
Authority: WO
Inventors: Lars Skovlund Andersen
Original assignee: Johnson Controls Denmark Aps
Priority date: 2012-07-16
Filing date: 2013-07-03
Publication date: 2014-01-23
Also published as: WO2014012549A3; DK201270430A

Abstract

The invention relates to a canned electrical machine (1) comprising at least one rotor (4) as a rotating part, at least one stator (5) as a stationary part with electrical windings (6) and structures such as iron laminates and/or similar flux conducting structures (7, 8) enabling the flux to be established and conducted wherein said rotor and stator interact by magnetic flux and hence forces via at least one airgap (12), and a can (9)segregating said electrical machine (1) in two separate compartments (10, 1). The can (9) is placed away from said airgap (12) that separates said at least one rotor (4) from said at least one stator (5). The invention also relates to use of a canned electrical machine as driving or driven member for compressors, turbines, pumps, decanters, expanders or similar machinery such as a driving member for an ammonia compressor.

Description

A CANNED ELECTRIC MACHINE AND USE HEREOF

Background of the invention The invention relates to a canned electric machine according to the preamble of claim 1 and use hereof.

Description of the Related Art Canned electrical machines such as motors or generators are used as driving or driven members for compressors, turbines, pumps, decanters, expanders etc. when the machinery comprises substances or medias desired not to inflict on the basic behavior of the electrical machines. The can of a canned electrical machine is located in the airgap between stator and rotor and separates the substances or medias from sensitive electrical parts of the machine often carrying all or part of the pressure difference and variance.

The can is usually either made in a non-magnetic metal introducing parasitic eddy current losses further implying limitations based on dissipating the hereby generated heat or plastic (eventually reinforced by e. g. fibres) most likely significantly increasing the airgap as well as causing mechanical problems over time e.g. if the rotor tears the can due to debris contaminating in the substance handled or deflection or worn bearings imply contact.

The object of the invention is therefore to provide for a canned electrical machine without the above disadvantages. The invention

The invention provides for a canned electrical machine wherein said can is placed away from said airgap that separates said at least one rotor from said at least one stator.

Hereby is ensured that a can does not cause any mechanical problems in relation to the rotor of the machine. Further, as the airgap may be designed without a can it is possible to establish a significantly smaller distance between the stator and rotor e.g. an airgap distance similar to conventional electrical machines without can. The smaller airgap distance ensures an efficient machine design with a higher torque and lower power losses. In an aspect of the invention, said can is placed in said at least one stator. Hereby is achieved an advantageous embodiment as the can will handle pressure and any pressure deflection better as an integrated part in the stator compared to an exposed airgap position. In another aspect of the invention, said can is placed in-between segments of said stator laminates and/or similar flux conducting structures. The stator location ensures a higher support of the can and a low damage risk which allows use of very thin material in establishing the can. Further, the location of the very thin can between stator laminates will reduce the parasitic eddy current losses to a minimum.

In an aspect of the invention, said stator segments comprise one side - iron laminates and/or similar flux conducting structures - segment non-airgap side - including the electrical live parts and another side - iron laminates and/or similar flux conducting structures - segment airgap side - including stator tops facing the airgap. Hereby is ensured that the stator side with delicate electrical live parts is protected by the can from the handled substances or medias of the machine as present in the airgap and the other side of the stator. Further, an advantageous cooling effect of this other stator side is achieved by the flow of handled substances or medias which is already used for cooling the airgap and rotor.

In a further aspect of the invention, said can is placed substantially concentrical to said airgap. Hereby is achieved similar and symmetrical forces and pressures on the can surface which ensures that no can part faces excessive loads compared with other parts and is in danger of rupturing.

In an even further aspect of the invention, said compartment on said stator side is filled with a substantially non-compressible fluid compatible with said live electrical parts such as transformer oil. Hereby is achieved an advantageous embodiment of the invention.

In an aspect of the invention, said stator structure delineation/pressure carrying structure to ambient can withstand the pressure and pressure variations, the machinery is exposed to. Hereby is achieved an advantageous embodiment of the invention.

In an aspect of the invention, said at least one can is made of flexible material such as very thin sheets of un-magnetic metal or polymer foils. Hereby is achieved a can which can adapt to pressure variations while having significantly reduced / no parasitic eddy current losses by use of thin and high resistance materials.

In an aspect of the invention, said can is made of flexible material, such as polymer or metal materials e.g. material of Polyoxymethylene (POM) or silicone rubber for example in fiber reinforced configurations or stainless steel material e.g. a highly corrosion-resistant high-performance alloy enabling said can to adapt to variation in motor dimensions due to deflection of the mechanical structure and volume change of said fluid due to temperature, pressure and force impacts. Further, is achieved an advantageous and power efficient machine by the reduction in parasitic eddy current losses. In an aspect of the invention, said can is made of flexible material, such as polymer material, coated with thin layer(s) of non-permeable materials such as glass, metals, ceramics etc. for example using physical vapor deposition (PVD) or chemical vapor deposition (CVD) in the coating process. Hereby are achieved advantageous material choices with the thin, non-permeable and well-defined coating layer(s) which provide the physical characteristics for the can while the material to be coated with layer(s) in the coating process gives rigidity, strength and flexibility to the can.

In an aspect of the invention, said machine is to drive or to be driven by machinery handling substances and medias desired not to be inflicted by or inflicting the electrical live parts of said electrical machine e.g. ammonia, water or water vapor, corrosive, aggressive and/or toxic substances and medias, substances and medias not to be contaminated as well as vacuum. Hereby is achieved an advantageous invention for handling corrosive, aggressive and/or toxic substances and medias. In an aspect of the invention, the thickness of said flexible material is in a range of 50-1000 μπι. Hereby is achieved an advantageous embodiment of the invention wherein the material thickness range ensures a durable can with low parasitic eddy current losses. In an aspect of the invention, said can is axially sealed to adjacent housing by means of squeezing the said can between at least one tightening element and O-ring grooved in adjacent housing and/or said O-ring sealing is made in tandem having a tracing track connected to ambient in-between. In another aspect of the invention, said machine is an electrical machine with salient poles e.g. in stator and/or rotor of a switched reluctance motor. The use of a can away from an airgap established between salient poles is especially advantageous as can attachment to salient poles in an airgap usually is very demanding and may create pressure deflections.

The invention also relates to use of a canned electrical machine according to any of claims 1 to 14 as driving or driven member for compressors, turbines, pumps, decanters, expanders or similar machinery such as a driving member for an ammonia compressor.

Hereby is ensured advantageous use of the invention in demanding applications with machinery handling corrosive, aggressive and/or toxic substances and medias. Figures

The invention will be described in the following with reference to the figures in which illustrates an axial cross sectional view of an embodiment canned electric machine according to the invention, fig. 2 illustrates the embodiment of a canned electric machine in sectional view perpendicular to the axial view

fig. 3a illustrates a 3D cross sectional view of an embodiment of a canned electric machine according to the invention, and fig. 3b illustrates an enlargement of a part in the canned electric machine as illustrated in fig. 3a.

Detailed description of the invention

Fig. 1 illustrates an axial cross sectional view B-B of an embodiment of a canned electric machine 1 according to the invention. The canned electric machine 1 may for example be a canned switched reluctance (SR) electrical motor. The canned electrical machine 1 comprises a pressure carrying structure 14 as the housing surface toward the ambient or exterior environment 15.

The axial cross sectional view illustrates the rotor 4 of the machine 1 located on a shaft 2 which drives or is driven by adjacent machinery. The adjacent machinery may for example be compressors, turbines, pumps, decanters, expanders or similar machinery and handling corrosive, aggressive and/or toxic substances and medias such as ammonia, water or water vapor. The handled substances and medias may also be substances and medias which are not to be contaminated e.g. in a cleanroom environment or to uphold food standards as well as being vacuum.

The stator 5 of the machine 1 is separated from the rotor by an airgap 12 dividing the electric machine into a motor compartment - stator side 10 and a motor compartment - rotor side 11 if the machine 1 for example is a SR electrical motor. The stator 5 is made in iron laminates and/or similar flux conducting structures and comprises electrical live parts 3 which include the electrical windings 6.

The stator 5 is divided into two segments: An iron laminates and/or similar flux conducting structures - segment non-airgap side 7 i.e. a segment outwardly facing the pressure carrying structure 14 and an iron laminates and/or similar flux conducting structures - segment airgap side 8 i.e. a segment inwardly facing the airgap 12.

The segment non-airgap side 7 of the stator 5 comprises the electrical live parts 3 and are separated from the segment airgap side 8 by a can 9 i.e. a can 9 placed in- between the two segments 7, 8. The can 9 may for example be placed substantially concentrical to the airgap 12.

The segment non-airgap side 7 of the motor compartment - stator side 10 may for example be filled with a substantially non-compressible fluid 13 compatible with said live electrical parts 3 such as transformer oil.

The segment airgap side 8 and the rotor 4 of the machine 1 may endure the substances or medias mentioned above while the can 12 protects the segment non- airgap side 7. The segment airgap side 8 and the rotor 4 are cooled by flow of the substances or medias such as ammonia whereas the segment non-airgap side 7 may be cooled by a cooling medium flowing in cooling pipes 16 stretching through the iron laminates and/or similar flux conducting structures. The can 12 may be made of a flexible polymer material e.g. a material of Polyoxymethylene (POM) or silicone rubber for example in fiber reinforced configurations.

The flexible can material may also be made of a metal foil such as stainless steel material e.g. Hastelloy or the like highly corrosion-resistant high-performance alloys.

Further, the can may be made of flexible material, such as a polymer material, coated with thin layer(s) of non-permeable materials e.g. glass, metals, ceramics etc. for example using physical vapor deposition (PVD) or chemical vapor deposition (CVD) in the coating process. Fig. 2 illustrates the embodiment of a canned electric machine in a cross sectional view C-C perpendicular to the axial view of fig. 1. Fig. 2 especially illustrates the salient poles in stator 5 of the electrical machine 1 such as a switched reluctance motor. The stator poles also comprises the electrical windings 6 in the iron laminates and/or similar flux conducting structures - segment non-airgap side 7 separated from the iron laminates and/or similar flux conducting structures - segment airgap side 8 by the can 9.

The can 9 is illustrated as placed substantially concentrical to the airgap 12 in the stator 5.

The iron laminates and/or similar flux conducting structures - segment airgap side 8 comprises a plurality of stator tops 17 facing the airgap 12 on one side and the can 9 on the opposite side. The can 9 may be squeezed by means of spacers 18, separating the stator tops 17. The polygon shape of the can ensures hereby that no rotation of the parts will occur. The openings between the plurality of stator tops 17 may be closed with the spacers 18 e.g. made in a plastic material. The spacers and stator tops may be shaped as blocks to form an interlocking jigsaw puzzle type of connection.

Fig. 3a illustrates a 3D cross sectional view of an embodiment of a canned electric machine 1 according to the invention.

The cross sectional view especially illustrates a hollow rotor motor type to be used for cantilever (overhung) assembly to adjacent machinery (a bearing less motor type as implied in the figure). Fig. 3b illustrates an enlargement of a part in the canned electric machine as illustrated in fig. 3a.

The part includes a section of the can 9 located in between the iron laminates and/or similar flux conducting structures - segment non-airgap side 7 and the iron laminates and/or similar flux conducting structures - segment airgap side 8 / stator tops 17. The stator tops 17 also face the airgap 12 as well as the rotor 4.

The figure also shows an embodiment of axially sealing the can 9 wherein the section of the can 9 is illustrated as stretching toward and being sealed to the end shield 20 of the canned electrical machine 1 via an O-ring sealing 21 including at least one tightening element and O-ring such as two O-rings 21.

A tracing track for the substances or medias may be located between the two O-rings in a further embodiment of the invention in order to trace any leakage and avoid any mixture of substances or medias caused by e. g. diffusion in the O-rings.

The invention has been exemplified above with reference to a specific example of motor type as well as specific examples of material choices for the can. However, it should be understood that the invention is not limited to the particular examples described above but may be designed and altered in a multitude of varieties within the scope of the invention as specified in the claims.

List

1. Canned electrical machine

2. Adjacent machinery access (Driven or driving)

3. Electrical live parts

4. Rotor

5. Stator

6. Electrical winding

7. Iron laminates and/or similar flux conducting structures - segment non-airgap side

8. Iron laminates and/or similar flux conducting structures - segment airgap side

9. Can

10. Motor compartment - stator side

11. Motor compartment - rotor side

12. Airgap between rotor and stator

13. Filling fluid

14. Pressure carrying structure

15. Ambient

16. Cooling pipes

17. Stator tops

18. Spacers e.g. in a plastic material

19. Tracing track for tracing any leaking substances or medias

20. End shield

21. O-ring sealing including at least one tightening element and O-ring

Claims

1. A canned electrical machine (1) comprising at least one rotor (4) as a rotating part, at least one stator (5) as a stationary part with electrical windings (6) and structures such as iron laminates and/or similar flux conducting structures (7, 8) enabling the flux to be established and conducted wherein said rotor and stator interact by magnetic flux and hence forces via at least one airgap (12), and a can (9) segregating said electrical machine (1) in two separate compartments (10, 11), characterized in that said can (9) is placed away from said airgap (12) that separates said at least one rotor (4) from said at least one stator (5).

2. A canned electrical machine (1) according to claim 1, wherein said can (9) is placed in said at least one stator (5).

3. A canned electrical machine (1) according to claim 1 or 2, wherein said can (9) is placed in-between segments (7, 8) of said stator (5) laminates and/or similar flux conducting structures.

4. A canned electrical machine (1) according to claim 3, wherein said stator segments comprise one side (7) - iron laminates and/or similar flux conducting structures - segment non-airgap side (7) - including the electrical live parts (3) and another side (8) - iron laminates and/or similar flux conducting structures - segment airgap side (8) - including stator tops (17) facing the airgap (12).

5. A canned electrical machine (1) according to any of the preceding claims, wherein said can (9) is placed substantially concentrical to said airgap (12).

6. A canned electrical machine (1) according to any of the preceding claims, wherein said compartment (10) on said stator side is filled with a substantially non- compressible fluid (13) compatible with said live electrical parts (3) such as transformer oil.

7. A canned electrical machine (1) according to any of the preceding claims, wherein said stator (5) structure delineation/pressure carrying structure (14) to ambient (15) can withstand the pressure and pressure variations, the machinery is exposed to.

8. A canned electrical machine (1) according to any of the preceding claims, wherein said at least one can (9) is made of flexible material such as very thin sheets of un- magnetic metal or polymer foils.

9. A canned electrical machine (1) according to claim 8, wherein said can (9) is made of flexible material, such as polymer or metal materials e.g. material of Polyoxymethylene (POM) or silicone rubber for example in fiber reinforced configurations or stainless steel material e.g. a highly corrosion-resistant high- performance alloy enabling said can (9) to adapt to variation in motor dimensions due to deflection of the mechanical structure (14) and volume change of said fluid (13) due to temperature, pressure and force impacts.

10. A canned electrical machine (1) according to claim 8, wherein said can (9) is made of flexible material, such as polymer material, coated with thin layer(s) of non- permeable materials such as glass, metals, ceramics etc. for example using physical vapor deposition (PVD) or chemical vapor deposition (CVD) in the coating process.

11. A canned electrical machine (1) according to any of the preceding claims, wherein said machine is to drive or to be driven (2) by machinery handling substances and medias desired not to be inflicted by or inflicting the electrical live parts (3) of said electrical machine e.g. ammonia, water or water vapor, corrosive, aggressive and/or toxic substances and medias, substances and medias not to be contaminated as well as vacuum.

12. A canned electrical machine (1) according to any of claims 8 to 11, wherein the thickness of said flexible material is in a range of 50-1000 μιη.

13. A canned electrical machine (1) according to any of the preceding claims, wherein said can (9) is axially sealed to adjacent housing by means of squeezing the said can between at least one tightening element and O-ring (21) grooved in adjacent housing and/or said O-ring sealing is made in tandem having a tracing track (19) connected to ambient in-between.

14. A canned electrical machine (1) according to any of the preceding claims, wherein said machine is an electrical machine with salient poles e.g. in stator and/or rotor of a switched reluctance motor.

15. Use of a canned electrical machine according to any of claims 1 to 14 as driving or driven member for compressors, turbines, pumps, decanters, expanders or similar machinery such as a driving member for an ammonia compressor.