Electric motors for powering downhole tools
An electric-motor assembly for installation in a borehole to power a downhole tools such as a pump has a first impermeable tube defining an axis and a stator fixed in the tube and having a series of coiled windings and laminations and electrically insulating potting in which the laminations and windings are imbedded. The windings have a connection to an electronically controlled power supply. An annular rotor in the tube radially surrounding the stator includes a permanent magnet coaxial with the windings. The tube seals the stator and rotor from the environment.
1. An electric-motor assembly for installation in a borehole to power a downhole tool, the assembly comprising
a first impermeable tube defining an axis;
a stator fixed in the tube and having a series of coiled windings and laminations and electrically insulating potting in which the laminations and windings are imbedded, the windings having a connection to an electronically controlled power supply, the stator forming a flowpath that extends through the stator; and
an annular rotor in the tube radially surrounding the stator and including a permanent magnet coaxial with the windings, the tube sealing the stator and rotor from the environment.
2. The electric-motor assembly defined in claim 1 wherein the potting material is impervious to wellbore fluids.
3. The electric-motor assembly defined in claim 1 wherein the potting material is introduced under a vacuum.
4. The electric-motor assembly comprising a second such assembly as defined in claim 1 with the two assemblies connected in series.
5. The electric-motor assembly defined in claim 4 wherein the electric-motor assemblies are secured together and both imbedded in the potting material.
6. An electric-motor assembly for installation in a borehole to power a downhole tool the assembly comprising:
a first impermeable tube defining an axis;
a stator fixed in the tube and having a series of coiled windings and laminations and electrically insulating potting in which the laminations and windings are imbedded, the windings having a connection to an electronically controlled power supply;
an annular rotor in the tube radially surrounding the stator and including a permanent magnet coaxial with the windings, the tube sealing the stator and rotor from the environment;
a second tube coaxial with the first tube; and
annular end members that substantially seal an annular space between the first and second tubes.
7. The electric-motor assembly defined in claim 6 wherein the annular end members are attached to the first and second tubes by swaging.
8. An electric-motor assembly for installation in a borehole to power a downhole tool, the assembly comprising:
a first impermeable tube defining an axis;
a stator fixed in the tube and having a series of coiled windings and laminations and electrically insulating potting in which the laminations and windings are imbedded, the windings having a connection to an electronically controlled power supply;
an annular rotor in the tube radially surrounding the stator and including a permanent magnet coaxial with the windings, the tube sealing the stator and rotor from the environment;
a metal tube set the potting;
an O-ring in the metal tube; and
wiring exiting from the potted material through the O-ring and metal tube.