The present invention relates to electric motors and more particularly, the present invention relates to electric motors especially suited for use in the borehole pumping and drilling art.
Motors for oil and gas wells are often long electric motors, and the stators for these rotors are correspondingly long. Motors of this type must be such as to meet the special space requirements of a borehole, so that the outside diameter is generally very limited, whereas such motors may be very long. The precise length depends on the desired power of the motor. Further to the special space requirements during operations in a downhole environment, this type of environment also represents challenging conditions such as high pressure, high temperature and an aggressive chemical environment.
The dielectric oil is also used to lubricate the rotor bearings, and provide a means to transmit the heat from the motor windings to the outside of the motor and in additional, provide electrical insulation for the motor windings.
However, the rotor cavity fluid can become contaminated with wellbore fluid, and once this occurs, the motor windings can be quickly degraded causing the eventual catastrophic destruction of the motor.
According to the present invention, there is provided canned modular stator elements equal in length to a bearing span for the rotor and bearing supports for the modular stator elements to seal into to enable the rotor cavity to be sealed from the motor winding cavity.
According to the present invention, there is provided a means for making modular stator elements.
According to further aspect of the invention, stator modules are the length of a bearing span.
According to a further aspect of the invention, the bearings are supported in an insulated, ridged bearing support.
According to further aspect of the invention, the injection moulding material is an electrical insulation for the bearing support.
According to a further aspect of the invention the stator laminations are mounted on a monel alloy tube, which hermetically seals the stator module rotor bore from the winding cavity.
According to a further aspect of the invention extruded tubes of an electrical insulation material hermetically seal the stator motor winding slots from end to end.
According to a further aspect of the invention the stator modules can be stacked together and sealed by an o ring, to seal the rotor cavity from the motor winding cavity.
According to a further aspect of the invention the stators are aligned using the stator slot insulator.
According to a further aspect of the invention the bearing supports could be ceramic.
According to a further aspect of the invention the bearing supports are a hybrid construction using an inner and outer steel tube and an electrical insulated injection moulded material to hold together and provide winding slots for the motor windings.
According to a further aspect of the invention internal woodruff key ways are incorporated into the bearing supports to provide an anti-rotation feature for the outer bearing race of the rotor.
According to a further aspect of the invention, the bore of the rotor cavity is smooth.
According to a further aspect of the invention, the liner tube isolating the rotor cavity from the stator cavity is made from more than one monel tube so creates minimum impedance losses associated with a single steel canned tube.
According to a further aspect of the invention the motor housing provides a containment for potting the stator.
According to a further aspect of the invention, the stator is pressure compensated with its own dielectric fluid.
According to a further aspect of the invention the motor windings have a second independent electrical insulation barrier separate to the wire insulation enamel which isolates all phase to phase and phase to ground.
The advantage using injection moulding the manner described means the volumes in stot windings and elsewhere don't have to be pressure compensated. Also, the encapsulated modular structure makes it easier to handle.
The provision of the ceramic end wafers allows a convenient and precise guide for the winding end turning connections, ensuring that they are precisely and correctly located, insulated and tightly packed against vibration.
Referring to
A set of stator laminations 1 are arranged in a row and mounted onto a thin wall (0.5 mm) monel tube 2, the set laminations making a total length L (this length is typically dictated by the bearing span). A TIG or laser weld on the OD at 3 and at 4 on the OD of the monel tube and the lamination at each end of the stack of laminations holds the individual components together as a rigid assembly. The monel tube 2 extends 5, 6 beyond the set of laminations. These extending portions 5, 6 seals with the bearing support derived below.
Referring to
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The winding turns occur at different spacings from the end of the stator lamination stack, and each cover interlocks with the previous, early fitted one. Some of the cover plates have been removed in
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External and internal features described here as provided by machining could equally be provided by injection molding to that shape, and equally, features described here as being provided by the injection molding could instead be machined.
Number | Date | Country | Kind |
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1507258.0 | Apr 2015 | GB | national |
Filing Document | Filing Date | Country | Kind |
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PCT/GB2016/051222 | 4/28/2016 | WO | 00 |