Linear electric motor and method of using and constructing same

• US 5,734,209 A
• Filed: 10/17/1994
• Issued: 03/31/1998
• Est. Priority Date: 01/10/1990
• Status: Expired due to Fees

• Current Assignee: Uniflo Oilcorp Limited
• Original Assignee: Uniflo Oilcorp Limited
• Inventors: Hallidy, William M.
• Primary Examiner(s): LaBalle, Clayton E.
• Application Number:
  US08/211,016
• Time in Patent Office: 1,261 Days
• Field of Search: 310/12, 310/13, 310/14, 417/415, 417/416, 417/417
• US Class Current: 310/12.22
• CPC Class Codes: E21B 43/128 Adaptation of pump systems with down-hole electric drives
• CPC Class Codes: F04B 17/046 the fluid flowing through the moving part of the motor
• CPC Class Codes: F04B 47/06 having motor-pump units situated at great depth

Abstract

A small diameter linear motor is relatively short in length, and includes a hollow elongated mover, and a stator having a plurality of annular spaced apart stator teeth. Individual electrical coils are wound from individual uninterrupted single wires extending from outside of the assembly in the spaces between the teeth to avoid the need for electrical connections between the coils. The stator assembly and mover are dimensioned to fit within the hollow interior of a ferromagnetic tube. In another form, the linear motor includes a mover and a stator, the stator including a set of coils for producing a series of electromagnetic fields extending at least partially in an axial direction when energized with an electric current and a stator core defining a plurality of spaced-apart transversely disposed coil receiving slots and an annular axially extending mover receiving bore. The mover includes an elongated member mounted telescopically and reciprocatively within the mover receiving bore and a plurality of permanent magnets interleaved with low reluctance spacers for helping to reduce core flux density in order to improve overall motor performance. The assembly further includes a cartridge unit with a linear motor attached threadably between a discharge housing assembly adapted to be secured removably to a cable for hoisting the cartridge unit through the production tubing of a well and a suction housing assembly for facilitating the pumping of well fluids from a downhole well. The linear motor includes a mover adapted to engage threadably a stop valve for permitting one-way flow of fluid through the mover and into the discharge housing for discharge into the production tubing. For increased pumping efficiency, the suction housing and check valve are replaceable with a lifting pump and piston respectively. Thus, the assembly is usable in both shallow and deep wells.

Claims

1. A tubular linear motor construction for use in an elongated hollow ferromagnetic well tubing having an annular transverse cross-sectional area A_T, comprising:

elongated stator core means adapted to be raised and lowered within the well tubing for helping to define a magnetic flux path including an outer flux path portion in the well tubing, said stator core means including tooth means of a stator tooth area A_S for defining intermediate flux path portions of said magnetic flux path and having coil means disposed thereon within slots between said tooth means for carrying multi-phased electrical current and means defining a large area air gap for facilitating the production of an axial force of a given magnitude;

said coil means being disposed adjacent to the well tubing when received therein to facilitate heat dissipation from said coil means and to enable said air gap means to define said large area air gap;

elongated mover core means adapted to be received within said air gap and having a transverse mover area A_M for defining an inner flux path portion of said magnetic flux path, said mover core means including flux means for producing magnetic flux in said magnetic flux path for interacting electromagnetically with the multi-phased current to facilitate the production of said axial force of a given magnitude;

wherein the ratio of the stator tooth area A_S to the transverse tube area A_T of the hollow well tubing is equal to between about 0.1 and about 1.25 for enabling the thickness of said tooth means to be reduced without restricting said magnetic flux; and

wherein the ratio of the stator tooth area A_S to the mover area A_M is equal to between about 0.1 and about 1.25, to provide sufficient magnetic flux linkage between the well tubing, said stator core means and said mover core means to develop high thrust for the motor for a relatively short motor size, with reduced heat loss.

2. A tubular linear motor construction according to claim 1, wherein said outer flux path portion has an annular cross-sectional area A_FT which is a portion of the area A_T.

3. A tubular linear motor according to claim 2 wherein said flux means is a plurality of spaced apart pairs of oppositely poled permanent magnets and wherein said elongated mover core means includes an elongated mover core for mounting said plurality of spaced apart pairs of oppositely poled permanent magnets thereon, said mover core having an annularly cross-sectional area defined by A_M ;

and

wherein said elongated stator core means includes an elongated stator core for mounting said plurality of spaced apart electrical coils thereon, said stator core having an annular cross-sectional area defined by A_S.

4. A tubular linear motor according to claim 2, wherein a more preferred value of the ratio of A_S to A_T ;

is between about 0.75 and 1.0.

5. A tubular linear motor according to claim 4, wherein the most preferred value of the ratio of A_S to A_T is about 1.0.

6. A tubular linear motor according to claim 1, wherein said ratio of A_S to A_M is between about 0.75 and about 1.0.

7. A tubular linear motor according to claim 6, wherein the preferred ratio of A_S to A_M about 1.00.

8. A tubular linear motor according to claim 1, wherein said flux means includes radial permanent magnets.

9. A tubular linear motor according to claim 1 wherein said flux means is axially magnetized permanent magnet means, including a plurality of pairs of oppositely poled, spaced apart, annularly-shaped, permanent magnets.

10. A tubular linear motor according to claim 1 wherein mover core means includes a plurality of spaced apart annularly-shaped bearings each having a smoothly rounded outer surface for engaging the inner surface of said stator means.

11. A tubular linear motor according to claim 10 wherein said coil means is three single electrical conductors including a first phase conductor for carrying a first phase electrical current, a second phase conductor for carrying second phase electrical current, and a third phase conductor for carrying third phase electrical current, and wherein said mover core means is hollow throughout its axial length for passing pumped fluids therethrough.

12. A tubular linear motor according to claim 10 wherein said stator includes a plurality of spaced apart annularly-shaped iron rings, each one of said plurality of annularly-shaped iron rings having a unitary construction and including an annular-shaped base member having an outside diameter and an inside diameter and a conical-shaped tooth member having an outside diameter and an inside diameter, said tooth member extending upwardly from said base member and terminating in a lip defining a common opening between said base member and said tooth member.

13. A tubular linear motor according to claim 12 wherein the outside diameter of said tooth member is substantially less than the outside diameter of said base member.

14. A tubular linear motor according to claim 13 wherein each individual one of said plurality of annularly-shaped iron rings include an open slot, said slot extending radially inwardly from the outside periphery of said base member and terminating at about the outside periphery of said tooth member.

15. A tubular linear motor according to claim 14 wherein individual ones of the tooth members are spaced apart from one another for defining the coil receiving slots, said slots including a set of first phase coil receiving slots, a set of second phase coil receiving slots, and a set of third phase coil receiving slots.

16. A tubular linear motor according to claim 15 wherein said first phase conductor is received within said first phase and receiving slots, said second phase conductor is received within said second phase coil receiving slots, and said third phase conductor is received within said third phase coil receiving slots.

17. A method of using a tubular linear motor construction according to claim 1, comprising:

disposing said stator means within the well tubing;

disposing said mover core means within said air gap;

electromagnetically coupling said elongated stator means and said mover core means;

moving said mover means relative to said elongated stator means, and

pumping fluids from the downhole well tubing.

18. A tubular linear motor construction for use with a hollow ferromagnetic well tube having a wall thickness T_T, comprising:

a hollow thick-walled mover for defining a fluid carrying passageway, said mover having a wall thickness T_M ;

a hollow stator having a sufficiently small diameter to be received within the well tube for cooperating with the well tube and said mover to define a flux path therethrough, said stator further having a sufficiently large longitudinal passageway to receive said mover therein for free relative movement;

means defining a large air gap between said mover and said stator when said mover is surrounded by said stator, said large air gap having a diameter D and an axial length L;

a plurality of pairs of annularly-shaped spaced apart oppositely poled flux means disposed within said air gap for passing a plurality of fields of magnetic flux through said flux path;

said stator having a plurality of teeth members defining a series of annularly-shaped coil receiving slots along the axial length L;

phase A coil winding means mounted continuously within selected axially spaced apart ones of said slots and being integrally connected together;

phase B coil winding means mounted continuously between other selected ones of said plurality of spaced apart stator teeth;

wherein said teeth members are adapted to position said phase A coil winding means and said phase B coil winding means adjacent to the well tube for facilitating heat dissipation, and are further adapted to enable said air gap means to define said large air gap;

means for connecting electrically one set of ends of said winding means to form a common node; and

means at the other ends of said winding means for coupling electrically to a multiple phase power source.

19. A method of constructing a tubular linear motor construction for downhole use with ferromagnetic well tubing, comprising:

using a plurality of annularly-shaped iron rings to help define a magnetic flux path in cooperation with the well tubing, each individual ring including an annular base member having a top and bottom surface to define intermediate flux path portions of said magnetic flux path, conically shaped tooth member integrally connected to the top surface of said base member and extending upwardly therefrom terminating in a centrally disposed lip defining a common opening extending axially throughout the entire length of said iron ring;

mounting a plurality of said iron rings removably onto an elongated hollow mandrel having a stop on one end thereof to help define a stator unit, said stop having a diameter substantially greater than said common opening, adjacent ones of said plurality of iron rings defining a plurality of coil receiving spaces, each space being defined as the distance from the top surface of said base member to the lip of the integrally connected tooth member;

said plurality of coil receiving spaces including a set of spaced apart first phase coil receiving slots, a set of spaced apart second phase coil receiving slots, and a set of spaced apart third phase coil receiving slots;

wrapping a single first phase conductor for carrying electrical current about every tooth disposed in said set of spaced apart first phase coil receiving slots to form a plurality of first phase electrical coils, said first phase coils being wrapped continuously from tooth member to tooth member alternately in clockwise and counter-clockwise directions;

wrapping a single second phase conductor for carrying electrical current about every tooth disposed in said set of spaced apart second phase coil receiving slots to form a plurality of second phase electrical coils, said second phase coils being wrapped continuously from tooth member to tooth member alternately in clockwise and counter-clockwise directions;

wrapping a single third phase conductor for carrying electrical current about every tooth disposed in said set of spaced apart third phase coil receiving slots to form a plurality of third phase electrical coils, said third phase coils being wrapped continuously from tooth member to tooth member alternately in clockwise and counter-clockwise directions;

adapting said base members to permit said stator unit to be received within the well tubing, wherein said first phase conductor, said second phase conductor and said third phase conductor will be substantially enclosed by the well tubing, adjacent base members of adjacent iron rings, and said tooth member;

said adjacent base members defining intermediate portions of said magnetic flux path for cooperating with the well tubing when received therein, said well tubing defining an outer portion of said magnetic path;

electrically connecting one end of each of the single first phase, second phase and third phase conductors together to form a common node therebetween, and exposing the opposite ends of each of the single first phase, second phase and third phase conductors for attachment to different phases of electrical current, and

mounting elongated hollow mover means within said stator unit for free relative movement to produce magnetic flux within said magnetic flux path, and said mover means defining an interior portion of said magnetic flux path.

20. A method according to claim 19 further comprising:

mounting said stator unit within the hollow interior of the ferromagnetic well tube.

21. A method of using a tubular linear motor construction in cooperation with a downhole ferromagnetic well tube to transport well fluid, comprising:

using a stator including a plurality of annular tooth members coupled to one another to define an axial opening therethrough and a plurality of annual coil slots between adjacent ones of said tooth members to receive current carrying coils therein, and a mover adapted to be received within said axial opening and including a plurality of magnets disposed on a mover core having a fluid passageway therethrough;

disposing said stator within the well tube to position said coils adjacent to the well tube, wherein said coils are surrounded by the well tube and adjacent ones of said tooth members;

disposing said mover within said axial opening to help define a magnetic flux path for flux produced by said magnets through the well tube, said adjacent ones of said tooth members and said mover core;

conducting electrical current through said coils for electromagnetically coupling said stator and said mover to produce an axial electromagnetic force for facilitating the transportation of the well fluid through the fluid passageway; and

dissipating excess heat generated by the electrical current through the well tube.

22. A method according to claim 21, further comprising conducting a three phase electrical current through said coils.

23. A method according to claim 22, further comprising coupling the motor construction to a pump for pumping well fluids.