ITCO20100009A1 - ELASTIC CONE FOR SEALING AND METHOD - Google Patents

Description

ELASTIC CONE FOR SEALING AND METHOD

KNOWN ART FIELD OF THE INVENTION

The embodiments of the object disclosed in this document refer in general to methods and systems and, more specifically, to mechanisms and techniques for sealing a containment structure while maintaining the integrity of said structure when it is exposed to thermal stress.

SUMMARY OF KNOWN ART

Over the past few years, with the increase in the price of fossil fuels, interest in many aspects related to the processing of fossil fuels has increased. In addition, there is a greater interest in the production of engines, machinery, turbines, compressors, etc. more efficient and reliable to facilitate better production and distribution of oil and natural gas based products.

One of these fields is generically related to fluid transport systems and, more specifically, to an electrical machinery that moves fluids along a pipeline. For example, fluids are transported from onshore or offshore locations to processing plants for later use. There are different types of fluids that need to be transported between different locations. One such fluid can be a highly corrosive gas. In other applications, fluid transportation is used in the chemical and petrochemical industries and to facilitate distribution to end users. At least some of the fluid transport stations use machinery, such as compressors, fans and / or pumps, driven by gas turbines. Some of such turbines drive the associated fluid conveying apparatus by a differential which increases or decreases the speed of the output drive shaft of the gas turbine at the predetermined speed of the drive shaft of the apparatus. Electrical machinery (i.e. electrically operated conductive motors or conductive electric motors) can be advantageous over mechanical machinery (i.e. gas turbines) in terms of operational flexibility (e.g. variable speed), ease of maintenance, lower capital cost and operating, greater efficiency and greater environmental compatibility.

Furthermore, electric motors are normally simpler in structure than mechanical ones, require a generally smaller support base, can be easier to integrate with the fluid transport apparatus, can eliminate the need for a differential and / or can be more reliable than mechanical motors. However, systems using electric motors generate heat through motor components, such as stators, and may need additional systems to help dissipate the heat. For example, some electric motors use the transported fluid as the primary heat exchange medium and channel the fluid through and around the stator. However, in some cases, the transported fluid may consist of aggressive materials or contain impurities that can have adverse effects on the efficiency of the stator components. For example, a transported acidic fluid has a negative effect on the copper components of the stator.

For these reasons, traditional electrical machinery can place the machine stator within a containment structure that isolates the stator from the rotor as disclosed by Kaminski et al. (U.S. Patent No. 7,508,101, the entire content of which is incorporated herein by reference) and Kaminski et al. (US Patent No. 7,579,724, the entire content of which is incorporated herein by reference). There may be oil inside the containment structure to keep the stator in an oil bath environment that does not damage copper or other components and at the same time dissipates heat from the stator while the transported fluid enters in contact only with the rotor. The containment structure has part of the walls made of metal and a wall, between the stator and rotor, made of non-metallic material, as known in the art.

A problem with traditional electrical machinery is the thermal stress / stress applied to the non-metallic wall during operation of the machinery. If the thermal stress / stress between the metal walls and the non-metal wall is significant, the non-metal component can break, which would lead to an oil spill from the containment structure which would damage the machine. Thermal stress / stress is generated when the machine is operational and its temperature increases from ambient temperature (which can be approximately 20 ° C) to operating temperature (which can be between 80 and 150 ° C) . Another factor that contributes to the thermal stress is the difference between the thermal expansion coefficients of the metal wall and the non-metallic wall, it being known that a metal, in general, has a thermal expansion coefficient three times greater than a component. not metallic. Therefore, under operating conditions, the metal walls expand more than the non-metal wall, which can result in failure of the non-metal wall due to the strain / stress applied by the metal walls.

Consequently, it is desirable to provide systems and methods that prevent stress on the non-metallic wall of the containment structure.

SUMMARY DESCRIPTION

According to an exemplary embodiment, there is a motor comprising a frame provided with a cavity; a stator configured to be fixed within the cavity; an elastic cone configured to be fixed to a first end of the frame; a rigid cone configured to be attached to a second end of the frame opposite the first end; a non-metallic component configured to be fixed to the elastic cone and to the rigid cone; and a rotor present within the cavity and configured to rotate within the stator. The frame, spring cone, rigid cone and non-metallic component form an airtight containment structure in which the entire stator is enclosed and the airtight containment structure is configured to contain a cooling fluid which cools the stator as well as to prevent that the cooling fluid reaches the rotor.

According to another exemplary embodiment, there is an elastic cone fixed to a frame of an engine. The spring cone comprises a curved body extending from a wide end to a narrow end; one or more holes in the wide end configured to accommodate a bolt for securing the spring cone to the engine frame; and a receiving portion present at the narrow end and configured to accommodate one end of a non-metallic component which isolates a motor stator from a motor rotor. The receiving part has a groove configured to accommodate a metal seal which seals an interface between the resilient cone and the non-metal wall.

According to a further illustrated exemplary embodiment, a method exists for providing a hermetically sealed containment structure within an engine. The method comprises attaching a stator to an engine frame; fixing a rigid cone to a first end of the frame; fixing an elastic cone to a second end of the frame, said second end opposite the first end, so that the stator is surrounded by the frame, the rigid cone and the elastic cone; connecting a non-metallic wall to the rigid cone and the elastic cone to form a hermetically sealed containment structure such that the stator is within the containment structure; and inserting a rotor into a stator and facing the stator through the non-metallic wall.

According to a subsequent further exemplary embodiment, there is a system for transporting a fluid. The system includes a compressor configured to increase a fluid pressure and a motor connected to the compressor and configured to drive the compressor. The motor comprises a frame provided with a cavity, a stator configured to be fixed inside the cavity, a spring cone configured to be fixed to a first end of the frame, a rigid cone configured to be fixed to a second end of the opposite frame at the first end, a non-metallic component configured to be fixed to the elastic cone and to the rigid cone and a rotor present inside the cavity and configured to rotate inside the stator. The frame, spring cone, rigid cone and non-metallic component form an airtight containment structure in which the entire stator is enclosed and the airtight containment structure is configured to contain a cooling fluid which cools the stator as well as to prevent that the cooling fluid reaches the rotor.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in the detailed description of which they form a part, represent one or more embodiments and, together with the description, illustrate such embodiments. In the drawings:

Figure 1 is a schematic diagram of an engine with two rigid cones;

Figure 2 is a schematic diagram of a rigid cone used in an engine for forming a containment structure;

Figure 3 is a schematic diagram of an engine having a rigid cone and a spring cone according to an exemplary embodiment;

Figure 4 is a schematic diagram of an elastic cone according to an exemplary embodiment;

Figure 5 is a schematic diagram of an elastic cone and a non-metallic wall according to an exemplary embodiment;

Figure 6 is a schematic diagram of a connection between an elastic cone and a non-metallic wall according to an exemplary embodiment;

Figure 7 is a schematic diagram of an elastic cone according to an exemplary embodiment;

Figure 8 is a schematic diagram of a detail of the elastic cone in Figure 7 according to an exemplary embodiment;

Figure 9 is a flow chart illustrating the method of assembling an engine with a spring cone according to an exemplary embodiment; And

Figure 10 is a schematic diagram of a fluid transport system according to an exemplary embodiment.

DETAILED DESCRIPTION

The following description of the exemplary embodiments refers to the accompanying drawings. The same reference numerals in different drawings identify the same or similar elements. The following detailed description does not limit the invention. The field of application of the invention is instead defined by the attached claims. The following embodiments are treated, for reasons of simplicity, in relation to the terminology and structure of an electric motor provided with a stator and a rotor. However, the embodiments to be dealt with below are not limited to such systems, but can be applied to other systems that use a containment structure with walls made of different materials.

Throughout the detailed description the reference to "an embodiment" means that a particular feature, structure or property described in connection with a realization is included in at least one embodiment of the disclosed object. Therefore, the use of the expressions "in an embodiment "at various points of the detailed description will not necessarily refer to the same embodiment. Furthermore, the particular features, structures or properties may be combined in any suitable manner in one or more embodiments.

According to an exemplary embodiment, a stator of an electric motor is present in a containment structure provided with a metal wall and a non-metal wall. The non-metallic wall is fixed at one end to an elastic wall which does not apply as much tension to the non-metallic wall as would a rigid wall, thus applying less strain / stress on the non-metallic wall as the metal wall expands for the temperature rise.

As in Figure 1, an electric motor 10 comprises a frame 12. The frame 12 is equipped with a cavity 14 in which there is a stator 16. The stator 16 is fixed with respect to the frame 12, that is, the stator 16 does not rotate with respect to the frame 12. There is a rotor 18 inside the frame 12, but the rotor 18 is configured to rotate around a longitudinal axis X. Two rigid cones 20 and 22 are fixed to the frame 12 facing the ends of the stator 16. Between the two cones 20 and 22 there is a non-metallic wall 24. The non-metallic wall 24 is fixed to the cones 20 and 22 and is configured so as not to touch the stator 16.

Figure 2 shows in more detail the connection between the non-metallic wall 24 and the cone 22. A brazing layer 26 is disposed between the cone 22 and the non-metallic wall 24 and the containment structure 28 is defined by the frame 12 and the wall metal 24. The containment structure 28 is hermetically sealed thanks to the brazing layer 26. The narrow brazing layer is applied between the other end of the metal wall 24 and the cone 20.

However, since the frame 12 and the cones 20 and 22 are made of metal while the non-metallic wall 24 is formed of a non-metallic material, when the temperature of the electrical machinery 10 increases, for example, from the ambient temperature (about 20 ° C) at the operating temperature of the machinery (approximately between 150 and 250 ° C), the expansion of the frame and cones is higher than the expansion of the non-metallic wall, which applies a thermal stress / stress to the non-metallic wall. metallic. In one application, a direction of the stress / stress applied to the non-metallic wall is illustrated by S in Figure 2. This stress / stress can, in certain situations, break the non-metallic wall 24. In that case, a possible harmful fluid circulating between the stator 16 and the rotor 18 can enter the cavity 14 and damage the stator 16. Furthermore, if a cooling fluid is used inside the cavity 14 to cool the stator 16, the cooling fluid can infiltrate as far as rotor 18, creating unwanted problems.

According to an exemplary embodiment illustrated in Figure 3, an electric motor 40 is equipped with a frame 42 and two sides 44 and 46 facing towards a stator 48. The stator 48 is rigidly fixed to the frame 42. The side 46 (also called support of the body of the bearing) of the frame 42 is connected to a bearing body 50, which includes a bearing system for the rotational support of the motor 52. A non-metallic wall 56 is connected between a rigid cone 60 and an elastic cone 62. The rigid cone 60 is analogous to the rigid cone 20 illustrated in Figure 1. The rigid cone 60 is fixed to a side 44 of the frame 42. In one application, the rigid cone 60 is compressed against the non-metallic wall 56 with a seal 64 interposed between the rigid cone 60 and the non-metallic wall 56.

However, the other end of the non-metallic wall 56 is not attached to a rigid cone as illustrated in Figure 1; on the contrary, it is fixed to an elastic cone 62 which reduces a stress / strain applied to a non-metallic wall 56 as the temperature of the frame increases. Figure 4 shows the elastic cone 62 present between the two sides 44 and 46 of the frame 42. Furthermore, a cavity 66 in which the stator is hermetically sealed is formed by the frame 42, by the side 44, by the rigid cone 60, by the non metal 56 and the elastic cone 62. In one application, the rigid cone 46 does not form the boundary of the cavity 66. A cooling fluid to cool the stator is present inside the cavity 66. In one application, the cooling fluid can be oil.

The non-metallic wall 56 is connected to the elastic cone 62 in such a way that the cooling fluid of the cavity 66 does not infiltrate reaching the rotor 52. For this reason, a seal 68 may be present at the interface between the elastic cone 62 and the wall. non-metallic 56. In one application, seal 68 may be a metallic seal. In one application, seal 68 is identical to seal 64.

According to an exemplary embodiment illustrated in Figure 4, the elastic cone 62 can be fixed to the frame 42 by a plurality of bolts 70. Corresponding holes 72 can be drilled in the frame 42 and in the elastic cone 62 to allow the bolts 70 to enter the frame 42 In an exemplary embodiment, the same bolt 70 is also used to secure the side 46 to the frame 42 as illustrated, for example, in Figure 4.

We will now discuss an advantage of one or more of the above exemplary embodiments, with reference to Figures 5 and 6. Figure 5 shows in greater detail that the elastic cone 62 is mounted on an intermediate portion 78 of the frame 42 with a gap 76 In other words, when the end 62a of the elastic cone 62 comes into contact with the non-metallic wall 56, the end 62b creates a gap 76 with the intermediate portion 78. Therefore a voltage T (see Figure 6) is applied to the non-metallic wall 56 by the resilient cone 62 when the resilient cone 62 is attached to the frame 42 at the end 62b. This preload of the elastic cone 62 is proportional to the interspace 76. It should be noted that no voltage is applied to the non-metallic part in traditional motors at room temperature, during the assembly of the motor. In one application, the gap 76 is between 1 and 5 mm. In another application, the gap is calculated to be greater than the thermal expansion of the frame. In a further application, the gap is calculated to be at least five times greater than the thermal expansion of the frame.

Therefore, consider the running engine; the temperature of the frame 42, of the rigid cone 60, of the elastic cone 62 and of the non-metallic wall 56 is increased from the ambient temperature to the operating temperature. Given the expansion of the frame 42 greater than that of the non-metallic wall 56, it is expected that a stress / thermal stress / S will appear in the non-metallic wall 56 as shown in Figure 6. However, given the preload applied to the elastic cone 62 , the thermal stress / stress S ends up reducing and / or canceling the tension T, thus reducing the force that could damage the non-metallic wall 56. According to the dimensions of the gap 76 and the materials of the frame 42 and of the elastic cone 62, the preload force T can be calculated to reduce the force S due to thermal expansion to zero. In one application, the T force reduces the effect of the S force, but does not reduce the S force to zero.

According to an exemplary embodiment, the elastic cone 62 can be considered as a spring acting on the non-metallic wall 56, thus staggering the non-metallic wall towards the rigid cone 60 (see Figure 3). According to the resilient properties of the resilient cone 62 and the dimensions of the gap 76, the force T applied to the preload by the resilient cone 62 can be adjusted as desired. As an example of the material that can be used for the spring cone 62, note that a super alloy, an ICONEL alloy (600, 625, 718, etc.) or a steel alloy may be used for the spring cone. The elasticity of the elastic cone 62 may be due to its specific shape and size and not to the specific composition of the material. In this way, the elastic cone is about 10 times more elastic than the rigid cone. In an application, the spring cone has high tension response properties and is shaped such that it has a higher elasticity constant than the rigid cone.

In one application, the frame can expand approximately 1 mm when an operating temperature between 80 and 150 ° C is reached and the spring cone is configured to reduce, in the non-metallic wall, a thermal stress associated with the expansion of the chassis. In an exemplary embodiment, the non-metallic wall 56 is brazed to the resilient cone 62 at a contact interface 80. Alternatively, the non-metallic wall 56 can be bolted to the resilient cone 62 or secured by other means known in the art. However, there is a case where the interface 80 is free of fasteners except seal 68. In this case, the offset applied by the resilient cone 62 to the non-metallic wall 56 is the only means that holds the two elements together.

In another exemplary embodiment, the motor 10 may comprise the first and second bearing devices 50 (see Figure 3) present at the corresponding ends of the rotor 52 and the first and second bearing body support devices (51 and 46) present at the corresponding ends of the stator so that the elastic cone is present between the second bearing body and the stator.

According to an exemplary embodiment illustrated in Figure 7, the elastic cone comprises a curved body 100 extending from a wide end 102 to a narrow end 104, one or more holes 106 in the wide end 102 and configured to accommodate a bolt for securing the spring cone to the motor frame, and a receiving part 108 (see Figure 8) present at the narrow end 104 and configured to accommodate one end of a non-metallic component which isolates a motor stator from a rotor of the motor. The receiving part 108 has a groove 110 configured to accommodate a metal seal which seals an interface between the resilient cone and the non-metal component. The resilient cone has a three-dimensional shape similar to a curved cone, as illustrated in Figure 7. According to an exemplary embodiment illustrated in Figure 9, there is a method for providing a hermetically sealed containment structure within an engine. The method comprises a step 900 of fixing a stator to an engine frame; a step 902 for fixing a rigid cone to a first end of the frame; a step 904 of fixing an elastic cone to a second end of the frame, said second end opposite the first end, so that the stator is surrounded by the frame, the rigid cone and the elastic cone; a step 906 for connecting a non-metallic wall to the rigid cone and to the elastic cone so as to form a hermetically sealed containment structure so that the stator is inside the containment structure; and a step 908 of inserting a rotor inside a stator and facing the stator through the non-metallic wall.

According to an exemplary embodiment illustrated in Figure 10, there is a system 120 to facilitate the transport of petroleum products and natural gas. For example, the system 120 may be a motor 122 and a compressor 124. In one application, the compressor 124 is replaced by a pump. The engine 122 may be the engine 40 shown in FIG. 3 or another engine known in the art. A motor shaft 122 may be directly coupled by a coupling 126 to a compressor shaft 124. Alternatively, coupling 126 may be a differential. The motor 122 can be connected to the electrical network (not in the figure) and configured to drive the compressor 124. The compressor 124 can have an input 128 in which the product to be transported is supplied. Part of the product can be diverted through the motor 122, for example to the inlet 130. The product can cool the motor 122 as described in connection with Figures 1 and 4; the used product can then be returned to the inlet 128 of the compressor 124. The high pressure product is delivered from an outlet 132, for example, into a transport pipeline. As illustrated in Figure 10, the motors 122 and 124 can be within the same frame. Alternatively, the two units can be in different frames.

The exemplary embodiments discussed herein provide a system and method for preventing cracks or failures in a non-metallic wall forming part of a containment structure within an engine. It must be clear that this description is not intended to limit the invention. On the contrary, the exemplary embodiments are intended to apply to alternatives, modifications and equivalent solutions, which fall within the spirit and scope of the invention as defined by the attached claims. Furthermore, in the detailed description of the exemplary embodiments, numerous specific details are set out in order to allow a comprehensive understanding of the claimed invention. However, the art expert would understand that various realizations can be implemented without such specific details.

Although the features and elements of the present exemplary embodiments are described in the embodiments in particular combinations, each feature or each element can be used individually without the other features and elements of the embodiments or in various combinations with or without other features and other disclosed elements. from this document.

This written description uses examples of the subject matter of the present to allow any expert in the field to implement the invention, including the realization and use of any device or system and the execution of any incorporated method. The patentable scope of the subject matter herein is defined by the claims and may include other examples known to experts in the field. Said other examples fall within the scope of the claims.

Claims (10)

CLAIMS / CLAIMS 1. An engine comprising: a frame provided with a cavity; a stator configured to be fixed inside the cavity; an elastic cone configured to be fixed to a first end of the frame; a rigid cone configured to be attached to a second end of the frame opposite the first end; a non-metallic component configured to be fixed to the elastic cone and to the rigid cone; And a rotor present inside the cavity and configured to rotate inside the stator, in which the frame, spring cone, rigid cone and non-metallic component form a hermetic containment structure in which the entire stator is enclosed and the hermetic containment structure is configured to contain a cooling fluid which cools the stator as well as to prevent that the cooling fluid reaches the rotor. 2. The motor of Claim 1, wherein the elastic cone is made of a metallic material with high tension response properties and has a shape such as to have a higher elastic constant than the rigid cone. 3. The engine of Claim 1, wherein the spring cone is attached to the frame with one or more bolts. 4. The motor of Claim 1, wherein the resilient cone is configured to offset the non-metallic wall and press said non-metallic wall against the rigid cone. 5. The engine of Claim 1, further comprising: a metallic seal disposed between, and in contact with, the non-metallic wall and the elastic cone as well as the non-metallic wall and the rigid cone in such a way that liquid leaks are prevented at the interface between the non-metallic wall and the rigid and elastic cones . 6. The engine of Claim 1, wherein the resilient cone is mounted together with the frame and the non-metallic wall so as to be subjected to preload stress at room temperature. 7. The engine of Claim 1, wherein the hermetic containment structure is filled with oil and the hermetic containment structure protects the stator from a corrosive gas circulating between the non-metallic component and the rotor. 8. An elastic cone to be fixed to the frame of an engine, called an elastic cone comprising: a curved body extending from a wide end to a narrow end; one or more holes at the wide end, configured to accommodate a bolt for securing the spring cone to the engine frame; And a receiving part disposed at the narrow end and configured to accommodate the end of a non-metallic wall which isolates a motor stator from a motor rotor, wherein the receiving part has a groove configured to accommodate a metal seal which seals an interface between the resilient cone and the non-metal wall. 9. A method of providing a hermetically sealed containment structure within an engine, said method comprising: attaching a stator to an engine frame; fixing a rigid cone to a first end of the frame; fixing an elastic cone to a second end of the frame, said second end opposite the first, so that the stator is surrounded by the frame, the rigid cone and the elastic cone; connecting a non-metallic wall to the rigid cone and resilient cone from the hermetically sealed containment structure such that the stator is within the containment structure; And supplying a rotor inside the stator and facing the stator through the non-metallic wall. 10. A system for transporting a fluid, said system comprising: a compressor configured to increase a fluid pressure; and a motor connected to the compressor and configured to drive the compressor, wherein the motor comprises, a frame equipped with a cavity, a stator configured to be fixed inside the cavity, an elastic cone configured to be fixed to a first end of the frame, a rigid cone configured to be attached to a second end of the frame opposite the first end, a non-metallic component configured to be fixed to the elastic cone and the rigid cone, e a rotor present inside the cavity and configured to rotate inside the stator, in which the frame, spring cone, rigid cone and non-metallic component form a hermetic containment structure in which the entire stator is enclosed and the hermetic containment structure is configured to contain a cooling fluid which cools the stator as well as to prevent that the cooling fluid reaches the rotor. CLAIMS / CLAIMS: 1. A motor, comprising: a casing having a cavity; a stator configured to be attached to an inside of the cavity; an elastic cone configured to be attached to a first end of the casing; a rigid cone configured to be attached to a second end of the casing that is opposite to the first end; a non-metallic part configured to be attached to the elastic cone and the rigid cone; and a rotor provided inside the cavity and configured to rotate inside the stator, wherein the casing, the elastic cone, the rigid cone, and the non-metallic part form a hermetic enclosure in which the entire stator is enclosed and the hermetic enclosure is configured to hold a cooling fluid that cools the stator and also to prevent the cooling fluid to reach the rotor. 2. The motor of Claim 1, wherein the elastic cone is made of a metallic material that has a high tensile properties and it is shaped to have higher elasticity constant than the rigid cone. 3. The motor of Claim 1, wherein the elastic cone is attached to the casing by one or more bolts. 4. The motor of Claim 1, wherein the elastic cone is configured to bias the nonmetallic wall and press the non-metallic wall against the rigid cone. 5. The motor of Claim 1, further comprising: a metallic seal disposed between and contacting the non-metallic wall and the elastic cone and also between non-metallic wall and the rigid cone such that the cooling fluid is prevented from leaking at the interface between the nonmetallic wall and the elastic and rigid cones. 6. The motor of Claim 1, wherein the elastic cone is assembled with the casing and the non-metallic wall to be under a preload strain at room temperature. 7. The motor of Claim 1, wherein the hermetic enclosure is filled with oil and the hermetic enclosure protects the stator from a corrosive gas that circulates between the non-metallic part and the rotor. 8. An elastic cone to be attached to a casing of a motor, the elastic cone comprising: a curved body extending from a wide end to a narrow end; one or more holes in the wide end configured to receive a bolt for attaching the elastic cone to the casing of the motor; and a receiving portion provided in the narrow end and configured to receive an end of a non-metallic wall that isolates a stator of the motor from a rotor of the motor, wherein the receiving portion has a trench configured to receive a metallic seal that seals an interface between the elastic cone and the non-metallic wall. 9. A method for providing a hermetically sealed enclosure inside a motor, the method including: attaching a stator to a casing of the motor; attaching a rigid cone to a first end of the casing; attaching an elastic cone to a second end of the casing, the second end being opposite to the first end, such that the stator is surrounded by the casing, the rigid cone and the elastic cone; connecting a non-metallic wall to the rigid cone and the elastic cone to form the hermetically sealed enclosure such that the stator is inside the enclosure; and providing a rotor inside the stator and facing the stator through the nonmetallic wall. 10. A system for transporting a fluid, the system comprising: a compressor configured to increase a pressure of the fluid; and a motor connected to the compressor and configured to drive the compressor, wherein the motor includes, a casing having a cavity, a stator configured to be attached to an inside of the cavity, an elastic cone configured to be attached to a first end of the casing, a rigid cone configured to be attached to a second end of the casing that is opposite to the first end, a non-metallic part configured to be attached to the elastic cone and the rigid cone, and a rotor provided inside the cavity and configured to rotate inside the stator, wherein the casing, the elastic cone, the rigid cone, and the non-metallic part form a hermetic enclosure in which the entire stator is enclosed and the hermetic enclosure is configured to hold a cooling fluid that cools the stator and also to prevent the cooling fluid to reach the rotor.