Patent Application
20170328369
The present disclosure relates to motor-compressor units, comprising an electric motor and a compressor driven by the electric motor, housed in a pressure casing. Embodiments disclosed herein specifically relate to motor-compressor units for subsea applications. More specifically, the disclosure relates to improvements to motor-compressor units comprising one or more magnetic bearings supporting the driving shaft, which connects the motor and the compressor.
Motor-compressor units are usually comprised of an outer pressure casing which houses an electric motor and a compressor, connected to one another by a driving shaft. The shaft is rotatingly supported in the pressure casing by a plurality of bearings. In some applications, specifically in subsea applications, the pressure casing comprises a motor compartment, which houses the electric motor, and a compressor compartment, which houses the compressor. Both compartments are sealingly closed to prevent penetration of sea water. Earlier subsea motor-compressor units usually employed oil-lubricated bearings for supporting the driving. Recently, magnetic bearings, or active magnetic bearings have been introduced in this kind of machinery, in order to avoid certain disadvantages derived from the presence of lubricating oil in the pressure casings.
Magnetic bearings are controlled by an electronic control system. The electronic control system must be connected to the magnetic bearings housed in the pressure casing. Specifically in subsea applications, a wire connection with subsea water-tight connectors electrically connect the control system with the interior of the pressure casing. The control system is placed externally of the pressure casing and at a distance therefrom. Usually the motor-compressor unit and the control system are mounted on a skid or baseplate. The housing wherein the control unit is arranged is in turn connected by means of data and power cables with electric and electronic devices place above the sea level.
These known arrangements are expensive and cumbersome. The use of a relatively large number of subsea wire connectors renders this known systems prone to failure due to water leakages inside the motor-compressor casing and/or the separate housing wherein the electronic components of the control system are arranged.
Improvements relating to the arrangement of the control system of the magnetic bearings in a motor-compressor unit would thus be desirable.
According to an embodiment, a motor-compressor unit for sub-sea applications, comprises a pressure casing, an electric motor housed in a motor compartment formed in the pressure casing and a compressor housed in a compressor compartment formed in the pressure casing. The motor-compressor unit can further comprise a shaft drivingly connecting the electric motor and the compressor. The shaft can be rotatingly supported by at least one magnetic bearing, e.g. an active magnetic bearing. According to some embodiments, two or more magnetic bearings are provided. One or more magnetic bearing can be radial bearings and/or one or more magnetic bearings can be axial bearings. According to embodiments of the subject matter disclosed herein a control system for controlling the magnetic bearing(s) is housed in a control system compartment structurally connected to and supported by the pressure casing.
According to some embodiments the control system compartment is integrated in or within the pressure casing of the motor-compressor unit.
According to some embodiments, the control system is electrically connected to the magnetic bearing(s) by means of wirings, which is one embodiment is entirely housed in the pressure casing.
Embodiments of the subject matter disclosed herein provide for a pressure casing comprised of a main casing portion and at least an auxiliary casing portion sealingly connected to one another to form at least a part of the pressure casing. The control system compartment can be arranged in the auxiliary casing portion. The main casing portion can house at least one of the motor compartment and the compressor compartment and in one embodiment both the motor compartment and the compressor compartment.
In some embodiments, a partition wall can be arranged between the auxiliary casing portion and the main casing portion. Electric couplings extend through the partition wall. A control system compartment can be formed in the auxiliary casing portion and can be separated by the motor compartment and/or the compressor compartment by the partition wall. The partition wall can be sealingly coupled to the auxiliary casing portion. The control system compartment is thus fluidly isolated from the remaining compartments of the motor-compressor unit. Potentially dangerous or polluting agents, such as particulate or droplets in the process or cooling gas of the motor-compressor unit are thus prevented from contacting the electronic components and instrumentalities of the magnetic bearing control system.
According to a further aspect, disclosed herein is a method of connecting a control system to magnetic bearings in a motor-compressor unit, comprising the following steps:
providing a pressure casing having at least a main casing portion and an auxiliary casing portion; mounting at least one magnetic bearing in the main casing portion; arranging the control system in the auxiliary casing portion; electrically connecting the control system and the magnetic bearing to one another; sealingly connecting the auxiliary casing portion and the main casing portion to one another.
Features and embodiments are disclosed here below and are further set forth in the appended claims, which form an integral part of the present description. The above brief description sets forth features of the various embodiments of the present invention in order that the detailed description that follows may be better understood and in order that the present contributions to the art may be better appreciated. There are, of course, other features of the invention that will be described hereinafter and which will be set forth in the appended claims. In this respect, before explaining several embodiments of the invention in details, it is understood that the various embodiments of the invention are not limited in their application to the details of the construction and to the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein are for the purpose of description and should not be regarded as limiting.
As such, those skilled in the art will appreciate that the conception, upon which the disclosure is based, may readily be utilized as a basis for designing other structures, methods, and/or systems for carrying out the several purposes of the present invention. It is important, therefore, that the claims be regarded as including such equivalent constructions insofar as they do not depart from the spirit and scope of the present invention.
A more complete appreciation of the disclosed embodiments of the invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:
Fig.7 illustrates a yet further embodiment of a motor-compressor unit.
The following detailed description of the exemplary embodiments refers to the accompanying drawings. The same reference numbers in different drawings identify the same or similar elements. Additionally, the drawings are not necessarily drawn to scale. Also, the following detailed description does not limit the invention. Instead, the scope of the invention is defined by the appended claims.
Reference throughout the specification to “one embodiment” or “an embodiment” or “some embodiments” means that the particular feature, structure or characteristic described in connection with an embodiment is included in at least one embodiment of the subject matter disclosed. Thus, the appearance of the phrase “in one embodiment” or “in an embodiment” or “in some embodiments” in various places throughout the specification is not necessarily referring to the same embodiment(s). Further, the particular features, structures or characteristics may be combined in any suitable manner in one or more embodiments.
In embodiments disclosed herein a rotor of the motor-compressor unit is supported by a plurality of radial bearings and by an axial bearing. Both the axial as well as the radial bearings are magnetic bearings, in particular active magnetic bearings. In other embodiments, not shown, mixed configurations can be used. For instance, radial magnetic bearings can be combined with at least one axial hydrodynamic bearing. Or else, an active magnetic axial bearing can be combined with radial hydrodynamic bearings.
Referring now to
The motor compartment 9 and the compressor compartment 11 can be separated from one another by a separation wall 13. A shaft 15 drivingly connects the electric motor 5 and the compressor 7. In the schematic of
The shaft 15 extends through the separation wall 13. In some embodiments sealing arrangements 17 can be provided around the shaft 15 at the separation wall 13, to prevent or reduce gas leakages from one compartment to the other. Thus, processed gas processed by the compressor 7 is prevented from penetrating into the motor compartment 9.
The shaft 15 is rotatingly supported in the pressure casing 3 by means of a plurality of bearings. In some embodiments a first radial bearing 21 can be arranged at a first end of shaft 15. A second radial bearing 23 can be provided at a second end of the shaft 15. A third, intermediate radial bearing 25 can be provided in an intermediate position between the motor 5 and the compressor 7. In some embodiments one or more axial bearings can further be provided. In the exemplary embodiment of
The bearings 21, 23, 25 and 27 are represented only schematically in
Magnetic bearings require an electronic control system, which provides power and control signals to the magnetic bearings. According to embodiments disclosed herein the control system is housed in a control system compartment 31 which can be structurally connected to pressure casing 3, i.e. supported by pressure casing 3.
In some embodiments, as exemplarily shown in
According to some embodiments, the main casing portion 3B can be provided with a first mounting flange 33. The auxiliary casing portion 3A can be provided with a second mounting flange 35. The main casing portion 3B and the auxiliary casing portion 3A can be sealingly coupled to one another at flanges 33 and 35, for example by means of nut-bolt arrangements 38.
The control system compartment 31 can house one or more electric and electronic components. Four such components are schematically shown at 37A, 37B, 37C and 37D in
Since the electric and electronic components can be affected by the processed gas, the control system compartment 31 is more particularly filled with an inert gas, for instance nitrogen. In the context of the present description and attached claims, the term inert gas also encompasses noble gases, such as helium, for instance, as well as gas mixtures, for instances mixtures mainly composed of nitrogen or helium.
Moreover, in order to avoid damages to the electric and electronic components, the inert gas pressure inside the control system compartment 31 can be maintained below the pressure inside the pressure casing 3. In one embodiment the inert gas pressure is around 1 bar.
In the embodiment of
In some embodiments, the control system compartment 31 is sealingly isolated from the interior of the motor compartment 9 and/or the compressor compartment 11. In some embodiments, a partition wall 41 is provided between the motor compartment 9 and the control system compartment 31. If the latter is mounted on the opposite side, i.e. adjacent the compressor compartment 11, the partition wall 41 would then be located between the control system compartment 31 and the compressor compartment 11.
In some embodiments, the partition wall 41 can be mounted on the auxiliary casing portion 3A, for instance at the second mounting flange 35 and can be surrounded thereby. The partition wall 41 can be sealingly connected to the auxiliary casing portion 3A, so that the control system compartment 41 is protected against penetration of pollutants, moisture or other elements which might damage the electronic circuitry arranged in the control system compartment 31.
In some embodiments a connector flange 43 can be provided on the auxiliary casing portion 3A for the passage of power and/or signal cables 45 which connect the motor-compressor unit 1 to an external source of electric power and possibly to external control devices.
Electric connection between each electronic component 37A-37D and the respective magnetic bearings 21-27 can be obtained by means of pairs of electric connectors 47, 49 arranged on a first surface and on a second surface of the partition wall 41. In
As schematically illustrated in
With the arrangement described so far, the connectors between the electric components 37A-37D and the magnetic bearings 21-27 are entirely housed in inside the pressure casing 3. If the motor-compressor unit is used for subsea applications, the connectors are thus housed in a protected environment, instead of being immersed in sea water.
In some embodiments, for instance in subsea applications, the motor-compressor unit 1 can be provided with a cooling system, aimed at cooling the electric motor 5 during operation of the motor-compressor unit 1. In some embodiments a cooling circuit 51 can be provided, comprising a heat exchanger 53, as well as inlet duct 55 and outlet duct 57 fluidly connecting the heat exchanger 53 with the interior of the motor compartment 9. The ducts 55, 57, the heat exchanger 53 and the motor compartment 9 form a closed circuit wherein a cooling medium, such as a cooling gas circulates. In some embodiments, a cooling medium fan 59 can be provided for circulating the cooling gas in the cooling circuit 51. In some embodiments the fan 59 can be mounted on shaft 15, so that the same electric motor 5 rotates both the compressor 7 and the fan 59.
In some embodiments the cooling medium can be the same gas which is processed by the compressor 7. In a known manner, processed gas can be derived from the compressor 7, cleaned and filtered, if necessary, to remove particulate, or other contaminants, such as droplets of liquid hydrocarbons or the like from the gas. The thus cleaned gas is introduced into the cooling circuit, filling also the motor compartment 9. The partition wall 13 and the sealing arrangements 17 reduce or prevent cooling gas leakages from the motor compartment 9 towards the compressor compartment 7 and/or vice versa. Usually, the pressure in the motor compartment 9 is higher than the pressure in the first stage of the compressor 7, such that in case of leakage, clean gas will leak from the motor compartment 9 towards the compressor compartment 11, but contaminated gas will be prevented from leaking towards the motor compartment 9.
According to some embodiments, the inlet duct 55 can be fluidly coupled to a cooling medium duct 61, which extends through the control system compartment 31, ending at or near the fan 59. The opposite end of the cooling medium duct 61 ends near or at a cooling medium inlet flange arranged on the pressure casing 3. In this way, cooling gas circulates through the control system compartment 31, without contaminating the compartment, but contributing to removal of heat which can be generated by the electronic components 37A-37D housed in the control system compartment 31. The heat removed by the cooling gas circulating in the cooling medium duct 61 is discharged in the environment through the heat exchanger 53, together with heat removed by cooling gas from the electric motor 5. The cooling medium duct 61 can be finned to increase heat exchange. Mounting of the electronic and electronic components 37A-37B and wiring of the components and the magnetic bearings is facilitated by the above described configuration.
In
In a separate step, wirings W2 of the magnetic bearings 21-27 are installed inside the main casing portion 3B. In
Once the wirings W2 have been connected to the second electric connectors 49, the two casing portions 3A and 3B can be assembled and sealingly connected to one another as shown in
In
As best shown in
The electric connectors 65 can be electrically coupled to the second electric connectors 49 arranged on the second surface of the partition wall 41. The first electric connectors 47 placed on the first surface of the partition wall 41 are electrically coupled with the electric components 37A -37D through wirings W1 as described above.
In
In
In
In the embodiment of
In the exemplary embodiment of
In
In an embodiment of
This written description uses examples to disclose the invention, including the preferred embodiments, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| FI2014A000267 | Dec 2014 | IT | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2015/077759 | 11/26/2015 | WO | 00 |
