MODULAR CRYOGENIC PERMANENT MAGNET ELECTRICAL MOTORS AND GENERATORSFOR SUBMERGED MOTOR PUMPS AND TURBINES AND RELATED SYSTEMS AND METHODS

Abstract

Motors, pumps, generators, fluid-handling devices, and related systems or methods may include a motor assembly comprising a motor housing and a motor comprising a rotor and a stator contained in the motor housing. The motor further comprises an alternating current medium voltage synchronous motor.

Claims

1. A motor assembly for use with a fluid handling device, comprising: a motor housing; a motor comprising a rotor and a stator contained in the motor housing, the motor comprising an alternating current medium voltage synchronous motor; a first bearing assembly coupled to a first end of the motor housing; and a second bearing assembly coupled to a second end of the motor housing and positioned at least partially within the motor housing, wherein the second bearing assembly is contained within a portion of the motor housing that is integral with another portion of the motor housing that surrounds the rotor and stator, the portion and the another portion of the motor housing configured to be collectively decoupled and demounted from the fluid handling device.

2. The motor assembly of claim 1, wherein the second bearing assembly is contained within a second bearing housing that is coupled to the motor housing to position the second bearing assembly within the motor housing.

3. The motor assembly of claim 2, wherein the second bearing housing is positioned within a lower mounting flange of the motor housing.

4. The motor assembly of claim 3, wherein the second bearing housing is bolted to the lower mounting flange of the motor housing.

5. The motor assembly of claim 2, the second bearing housing is configured to suspend the second bearing assembly within the motor housing by axially and radially supporting the second bearing assembly.

6. The motor assembly of claim 1, wherein the first bearing assembly is contained within a first bearing housing that is coupled to the motor housing.

7. The motor assembly of claim 6, wherein the first bearing housing is configured to suspend the first bearing assembly within the motor housing by axially and radially supporting the first bearing assembly.

8. The motor assembly of claim 6, wherein the first bearing housing is secured by bolting to an upper mounting flange of the motor housing.

9. The motor assembly of claim 1, wherein the first bearing assembly comprises a radial guide bearing and the second bearing assembly comprises two or more bearings for supporting a shaft.

10. The motor assembly of claim 1, wherein the motor housing, the first bearing assembly, and the second bearing assembly are configured to be collectively installed in and/or removed from a submergible cryogenic pump as a modular unit.

11. A submergible cryogenic pump comprising: fluid handling stages comprising impellers mounted to a shaft at least partially encompassed by one or more diffusers; and a motor assembly for transferring force to and/or receiving force from the fluid handling stages via the shaft, the motor assembly comprising: a motor housing; a motor comprising a rotor and a stator contained in the motor housing; and a bearing assembly for supporting the shaft, wherein the bearing assembly, the motor housing, and the motor contained in the motor housing are configured to be collectively decoupled and demounted from the fluid handling stages.

12. The submergible cryogenic pump of claim 11, wherein the motor further comprises an alternating current medium voltage synchronous motor configured to be driven at 1,000 Volts to 15,000 Volts and at a rotational speed between 2,000 RPM and 10,000 RPM.

13. The submergible cryogenic pump of claim 11, wherein the bearing assembly is contained within a bearing housing that is coupled to the motor housing to position the bearing assembly within the motor housing within a lower mounting flange of the motor housing.

14. The submergible cryogenic pump of claim 11, wherein the shaft is configured to move axially within the motor housing.

15. A method of providing a modular motor assembly for a fluid handling device, the method comprising: coupling a motor assembly to a fluid handling device comprising fluid handling stages including impellers mounted to a shaft at least partially encompassed by one or more diffusers, the motor assembly for transferring force to and/or receiving force from the fluid handling stages via the shaft, the motor assembly comprising a motor housing and a motor comprising a rotor and a stator integrally contained in the motor housing; supporting the shaft with more than one bearing assemblies integrally contained in the motor housing; and collectively decoupling and demounting the motor assembly including the motor housing and integrally contained components of the rotor, the stator, and the more than one bearing assemblies from the fluid handling device.

16. The method of claim 15, further comprising, after servicing at least a portion of the motor assembly, recoupling and remounting the motor assembly including the integrally contained components of the rotor, the stator, and the more than one bearing assemblies to the fluid handling device.

17. The method of claim 15, further comprising, after replacing at least a portion of the motor assembly, installing the replacement motor assembly on the fluid handling device.

18. The method of claim 15, further comprising positioning the more than one bearing assemblies within at least one bearing housing that is coupled to the motor housing to position and support the more than one bearing assemblies within the motor housing.

19. The method of claim 18, further comprising independently removing the at least one bearing housing with the more than one bearing assemblies while other elements of the motor assembly are not disturbed.

20. The method of claim 18, further comprising suspending the more than one bearing assemblies within the motor housing by axially and radially supporting the more than one bearing assemblies with the at least one bearing housing.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0028] While the specification concludes with claims particularly pointing out and distinctly claiming what are regarded as embodiments of the present disclosure, various features and advantages of embodiments of the disclosure may be more readily ascertained from the following description of example embodiments of the disclosure when read in conjunction with the accompanying drawings, in which:

[0029] FIG. 1 is an elevational cross-sectional view of a modular submerged motor/generator in accordance with an embodiment of the disclosure.

[0030] FIG. 2 is an elevational cross-sectional view of the general arrangement of modular submerged motor/generator as assembled to a hydraulic module to complete the modular submerged motor pump or submerged generator cryogenic energy recovery turbine unit in accordance with an embodiment of the disclosure.

[0031] FIG. 3 is an elevational partial cross-sectional of a pressure vessel with a modular motor/generator as it will be installed in a system showing the motor/generator as incorporated within a modular submerged motor pump or a cold energy recovery turbine in accordance with an embodiment of the disclosure.

[0032] FIG. 4 is a flowchart showing interfaces between a modular submerged motor/generator and electrical power and control systems in accordance with an embodiment of the disclosure.

DETAILED DESCRIPTION

[0033] The illustrations presented herein are not meant to be actual views of any particular fluid exchanger or component thereof, but are merely idealized representations employed to describe illustrative embodiments. The drawings are not necessarily to scale. Elements common between figures may retain the same numerical designation.

[0034] As used herein, relational terms, such as first, second, top, bottom, etc., are generally used for clarity and convenience in understanding the disclosure and accompanying drawings and do not connote or depend on any specific preference, orientation, or order, except where the context clearly indicates otherwise.

[0035] As used herein, the term and/or means and includes any and all combinations of one or more of the associated listed items.

[0036] As used herein, the terms vertical and lateral refer to the orientations as depicted in the figures.

[0037] As used herein, the term substantially, approximately, or about in reference to a given parameter means and includes to a degree that one skilled in the art would understand that the given parameter, property, or condition is met with a small degree of variance, such as within acceptable manufacturing tolerances. For example, a parameter that is substantially met may be at least 90% met, at least 95% met, at least 99% met, or even 100% met.

[0038] As used herein, the term fluid may mean and include fluids of any type and composition. Fluids may take a liquid form, a gaseous form, or combinations thereof, and, in some instances, may include some solid material. In some embodiments, fluids may convert between a liquid form and a gaseous form during a cooling or heating process as described herein. In some embodiments, the term fluid includes gases, liquids, and/or pumpable mixtures of liquids and solids.

[0039] While embodiments of the disclosure may discuss LNG and/or related light hydrocarbon liquids, embodiments of the disclosure may also be used with other fluids, such as, for example, liquid hydrogen or liquid ammonia.

[0040] In some embodiments, embodiments of the disclosure may include a modular cryogenic motor/generator (e.g., a motor and/or generator). For example, a modular cryogenic medium voltage motor/generator may drive a pump or be driven by a turbine as part of a machine that is submerged in refrigerated light hydrocarbon such as methane, ethane propane, butane, or a mixture thereof, within a protective pressure vessel.

[0041] As discussed herein, such a motor and/or generator may be referenced as a motor where the motor may act as a generator when being powered or driven, for example, by the force of a fluid flow. Thus, it is understood that such a motor may not be externally powered and may be used primarily, or secondarily, as a generator.

[0042] The motors may be modular in the fact that the motor may be removed as a unit to be serviced and/or replaced. In conventional designs, the motor is generally integral with the pump with multiple components of the motor or drive system being separately installed and held within the housing of the pump. In embodiments of the disclosure, the motor unit may be integral to itself, for example, with self-contained bearing assemblies that are resident in the motor housing. Accordingly, the motor may be removed as a unit along with the bearings and/or along with other motor components, enabling relatively easier repair and/or replacement.

[0043] Furthermore, the modular arrangement of the machines, wherein the rotor bearings are suspended axially and radially in housings within a motor stator housing, permits the motor/generator to be modularly separated from its load. For example, each element of the motor may be mechanically coupled as to be independently maintainable from the other, while the other element is not unnecessarily disturbed. The effect is to reduce the time and cost to repair or replace a defective element.

[0044] In some embodiments, the shaft in the motor (e.g., the motor shaft) may be separate from a pump shaft connected to the impellers (e.g., via collets and interference fit). For example, the motor shaft may be selectively coupled to the pump shaft in order to remove and/or install the motor. In some embodiments, the motor shaft and pump shaft may be coupled using complementary spline fittings on adjoining portions of the motor and pump shafts. In additional embodiments, the shaft may be a single shaft (e.g., a monolithic shaft) extending through the motor and into the pump in order to support the impellers.

[0045] In some embodiments, the motor/generators in accordance with some embodiments of the disclosure are of the permanent magnet pole type that permit the power density of the units to be increased, enabling the units to be lighter and more conveniently maintained.

[0046] In some embodiments, the motors/generators may include runup/rundown bearings within the motor/generator that are designed to stabilize the dynamics of the rotating elements during startup and shutdown.

[0047] Embodiment of the present disclosure include a vertical-axis electric motor or generator that may be used to drive or be driven by fluid handling devices or machines, such as centrifugal pumps, turbines, mixers, blowers, etc. in a cryogenically cold, environment potentially electrically hazardous environments.

[0048] In such harsh environments, embodiments the motors/generators may be implemented in pressure vessels that are designed to provide containment of a potentially flammable or explosive hazardous fluid by isolating the pumped fluid from the oxygen in atmospheric air, thereby removing one of the three conditions needed for combustion or explosion.

[0049] Further, submerging the motor/generator including associated electrical components in the very cold pumped fluid may reduce electrical resistance losses and reduce the loss pumped fluid to boiloff.

[0050] In some embodiments of the disclosure, the motors/generators may require that all components are suitable for operation within a working temperature range of 75-200 K. In such an embodiment, the housing components are designed to maintain structural integrity and provide leak proof containment at specified working pressures from 1 bara (e.g., bar) to 160 bara. Further, the electrical insulation is designed to be suitable for operation at 1,000-15,000 VAC and 25-333 Hz.

[0051] In some embodiments, the bearings of the motor may be selected to be suitable for a life of 25,000 hours (e.g., mean time between outages (MTBO)). Further, the electrical machines are required to meet the requirements of all bodies having code jurisdiction over the application in the service area, as qualified by suitable design reviews, testing and shall be certified to be such, by the manufacturers and or qualified third-party inspection agencies.

[0052] In some embodiments, the electric motors may be used as generators by applying a level of torque to the shaft of a motor that causes the back electro-magnetic force, measured in volts, to exceed the electric and magnetic fields (EMF) of the power system to which the machine is connected. Similarly, a generator, when connected to such a power system, can be configured to serve as a motor when the back EMF is less than that of the system.

[0053] In non-cryogenic applications, induction motors and/or generators are generally constructed of large heavy steel or cast-iron frames supporting laminated steel magnetic stators, into which are inserted high starting-current windings (e.g., also referred to as stator coils).

[0054] These machines embody high-inertia rotors that, when the unit is energized, will operate at a rotative speed slightly less than the source-frequency speed. Accordingly, these machines are generally designated as asynchronous. When the shaft of such a machine is forced to rotate at a speed rotative speed that exceeds the source-frequency speed, the machine becomes an asynchronous generator.

[0055] Embodiments of the present disclosure may be referred to as a synchronous motor/generator because their construction is such that the rotational speed of the machines is synchronized (e.g., always synchronized) with the line frequency of the source power system to which the machine is connected.

[0056] Moreover, the strength of the magnetic forces which drive the machines in accordance with embodiments of the disclosure are significantly greater than those found in conventional prior art, enabling the mass of the machine frames to be significantly reduced. Additionally synchronous permanent magnet rotor poles may permit the mass of motor/generator poles to be reduced and current controlled windings driven by variable frequency drives are enabled to follow the demand of the load. Such configurations may assist in reducing the mass of those elements and eliminating losses of unneeded energy, in turn reducing operating costs.

[0057] An alternating current permanent magnet motor or generator type will generally rotate at a speed in revolutions per minute (RPM) that is synchronized with the frequency of its power supply system, which may be calculated by multiplying the supply frequency in cycles per second times one-hundred and twenty (120) divided by total number of magnetic poles of the machine rotor. For instance, in a system operating at 160 Hz cycles/second, a four-pole motor or generator will rotate at 160120/4=4800 RPM. In some embodiments, the motor may be configured to rotate relatively fast than convention motors, for example, 2,000 through 10,000 RPM, above 4000 RPM, above 5000 RPM, above 6000 RPM, or above 7000 RPM.

[0058] If the frequency of the power supply is controlled, the speed of the motor may be synchronously adjusted. The power system frequency controller may be a variable frequency drive and, accordingly, the machine being controlled may be referred to as a variable speed synchronous motor or generator in accordance with embodiments of the disclosure.

[0059] Similarly, if such a machine is designed to operate in a power system where the supply electro-motive force is the range between 1,000 Volts to 15,000 Volts (e.g., 3,300 Volts to 6,600 Volts), such a system is said to be a medium voltage system and the machine is said to be a medium voltage motor or generator in accordance with embodiments of the disclosure.

[0060] FIG. 1 is an elevational cross-sectional view of a modular submerged motor/generator. Referring to FIG. 1, in some embodiments of the disclosure, modular medium voltage synchronous submerged motor/generator module 1 comprises an outer structural cylindrical module housing 10 at the lower edge of which a concentrically and perpendicularly mounting flange 12 is affixed and to which, at its upper edge, is a similarly affixed an upper mounting flange 14. Within the cylindrical module housing 1 an electrical stator 16 is concentrically mounted. The electrical stator 16 may be comprised of a laminated cylindrical stack 18 of a special magnetic steel discs compressed to remove any gaps between laminations and secured according to any suitable method. Notches of the housing 10, when correctly aligned, form axial channels into which an array of formed or random wound electrical coils 20 are inserted as required to define the desired number of electromagnet poles of the stator 16. The coils 20 are connected and electrical leads 22 (FIG. 2) are applied as required by the design of the motor/generator.

[0061] A permanent magnet rotor 24 (e.g., having four magnetic poles) is coupled to a shaft 31 (e.g., drive shaft) and suspended between the lower thrust bearing 26 and the upper radial bearing 30 with the shaft 31 extending through and supported by the lower thrust bearing 26 and the upper radial bearing 30.

[0062] In some embodiments, the rotor 24 may be slidably coupled to the drive shaft 31 such that the drive shaft 31 will rotate with the rotor 24, but the drive shaft 31 may move in an axial direction relative to the rotor 24 during operation of the cryogenic pump/generator. Accordingly, the motor 1 may be utilized to power the rotation of the drive shaft 31 through the slidable connection with the rotor 24, but the drive shaft 31 may slide and move in and axial direction (e.g., a direction parallel to the axis of rotation of the drive shaft 31) relative to the rotor 24 so that the drive shaft 31 may move axially independently of the rotor 24. In some embodiments, the rotor 24 may be coupled to the drive shaft 31 with a splined coupling wherein the splines extend parallel to (e.g., along) the axis of rotation of the drive shaft 31 to facilitate the transfer or torque between the rotor 24 and the drive shaft 31 while allowing the drive shaft 31 to slide and move in an axial direction relative to the rotor 24.

[0063] The lower thrust bearing 26 may be located in a lower bearing housing 28 which is secured by bolting to the lower mounting flange 12. In some embodiments, the lower bearing housing 28 may be part of the motor housing 10. As depicted, the lower bearing housing 28 may be at least partially (e.g., a majority being received, entirely received) in the motor housing 10. The lower bearing housing 28 may be coupled to and received in the motor housing 10 to position the lower thrust bearing 26 within (e.g., a majority within, entirely within) the motor housing 10.

[0064] The upper radial bearing 30 may be mounted in the pump upper bearing housing 32 and secured by bolting to the upper mounting flange 14 in axial and radial alignment with the magnet centers of the stator 16. In some embodiments, the upper bearing housing 32 may be part of the motor housing 10. As depicted, the upper bearing housing 32 may be coupled to an end of the motor housing 10.

[0065] In some embodiments, one or both of the lower thrust bearing 26 and the upper radial bearing 30 may accommodate axial movement of the rotor 24 (and/or shaft 31 within the rotor 24). For example, by enabling the rotor 24 to slide through the lower thrust bearing 26 and/or the upper radial bearing 30 and/or by moving axially with the rotor 24 and/or shaft 31 in and relative to the pump upper bearing housing 32.

[0066] In operation, the interior cavity of module housing 10 is filled with the species of pumpage which generally flows through passages in and around thrust bearing 26. The fluid may then flow through an annular path upwards through magnetic gap 36 exiting module housing 10 to the annular space surrounding said module via a plurality of active or passive pressure regulators 38. This flow of pumpage through module 10 carries heat generated by the operation of the thrust bearing and the fluid friction in the magnetic gap away, thus cooling the lower portion of the module 1.

[0067] In some embodiments, the thrust bearing 26 may include an assembly of bearings for supporting the rotor 24 in multiple axes. For example, the thrust bearing 26 may include two angular contact or thrust bearings positioned in opposition to each other to support axial forces applied to the rotor in both axial directions along a rotational axis of the rotor 26.

[0068] FIG. 2 is an elevational cross-sectional view of the general arrangement of modular submerged motor/generator as assembled to a hydraulic module to complete the modular submerged motor pump or submerged generator cryogenic energy recovery turbine unit. Referring to FIG. 2, an embodiment of the module housing includes a plurality of flow bypass tubes 34, the number and diameter of which is determined based on the total volume of liquid natural gas (LNG) or other species of pumpage to be transported.

[0069] A complementary flow of pumpage enters the module, through an orifice 40 in discharge manifold/upper motor cover 32, thence downward through passages in and around radial bearing 30 cooling the upper portion of motor/generator module 1 and exiting housing 10 through pressure regulators 38 of FIG. 1 (e.g., four pressure regulators 38 on each axial side of the motor/generator module 1).

[0070] As should be appreciated, embodiments of the module housing 10 will be influenced by the configuration of the hydraulic module 3. In some instances, the flow bypass tubes 34 may be eliminated and the discharge flow will be directed into the annular space between the shell of pressure vessel 52 of FIG. 3 and the module outer housing 10. In such a case, mounting flange 12 and upper mounting flange 14 may be eliminated and the thickness of the housing would be increased to permit the attachment of the hydraulic module to the lower extremity of housing 10 and discharge manifold/upper motor cover 32 to the upper extremity of housing 10.

[0071] In some of the described embodiments, structural components may be fabricated and/or machined, for example, from wrought plate and/or forged billets (e.g., of type 6061-T6 aluminum alloy). Further, rotor shafts may be fashioned of a lightly magnetic martensitic stainless steel (e.g., type 15-5 in condition HH1150) and electrical laminations are stamped or cut from a suitable electrical lamination steel.

[0072] Permanent magnet poles are formed by hot isostatic pressing rare earth powder metal such as samarium-cobalt (SmCo), neodymium (NdFeB), or praseodymium-nickel and secured to or within the periphery of the rotor 24. Three phase, medium voltage, alternating current is applied to the modular submerged motor 1, or to the system by the generator 1 through three single-phase insulated power connector bushings 33 each configured to provide a secure, non-sparking connection of the winding leads to each incoming power cables 34.

[0073] Incoming power connector bushings 33 for supplying power to motors are conventionally male gendered and those for receiving power from generators are conventionally female gendered.

[0074] In some embodiments, the assembly may include an active thrust balance element (e.g., balance drum 37) configured to at least partially counteract one or more axial forces applied to the rotor. In some embodiments, the slidable coupling between the rotor 24 and the drive shaft 31 may enable axial movement of the balance drum 37, which is rigidly coupled to the drive shaft 31.

[0075] FIG. 3 is an elevational partial cross-sectional of a pressure vessel with a modular motor/generator as it will be installed in a system showing the motor/generator as incorporated within a modular submerged motor pump or a cold energy recovery turbine. Referring to FIG. 3, in some embodiments, a modular submerged motor pump 1 or submerged generator CERT 1, is suspended from pressure vessel headplate 50 being secured to the headplate 50, at its underside at the upper extremity of discharge spool 51 by a plurality of fasteners 53a of a suitable number and kind and similarly, by a plurality of fasteners, at the lower extremity of said discharge spool to discharge manifold 32 of FIG. 2. As depicted, the motor/generator 1 is connected to a fluid handling device, such as pump/turbine 3a (e.g., via an upper pump/turbine 3a housing 2 that includes a stack of impellers and diffusers 56 in a stacked configuration.

[0076] Pressure vessel headplate 50 is supported, secured and sealed to pressure vessel 52 by a plurality of fasteners 53c.

[0077] Pressure vessel 52 embodies several integral mounting struts 52a each being secured to foundation 55 by suitable anchor bolts 53e and thermally insulated therefrom, each by a thermal barrier 54.

[0078] In some embodiments of the disclosure, the modular SMP 1 pumpage enters pressure vessel 52 through suction nozzle 57 and is discharged into the process piping system at discharge nozzle 58 at suitable location.

[0079] In some embodiments, the motor pump or generator 1 may be powered by an electrical feedthrough 60 including a power junction box 66. The electrical feedthrough 60 may include one or more process seals 62 for at least partially isolating the cryogenic environment from the ambient environment.

[0080] FIG. 4 is a flowchart showing interfaces between a modular submerged motor/generator and electrical power and control systems. As shown in FIGS. 3 and 4, the electrical connection 60 between the permanent magnet motor 1 and the variable frequency drive with the intermediate seal 62 and junction box 66 may include connections for each phase (e.g., three motor phases (A, B, & C)) plus a ground (GND).

[0081] While the present disclosure has been described herein with respect to certain illustrated embodiments, those of ordinary skill in the art will recognize and appreciate that it is not so limited. Rather, many additions, deletions, and modifications to the illustrated embodiments may be made without departing from the scope of the disclosure as hereinafter claimed, including legal equivalents thereof. In addition, features from one embodiment may be combined with features of another embodiment while still being encompassed within the scope of the disclosure as contemplated by the inventors.