Modular stator for downhole electric motors
Motors for use in downhole systems such as electric submersible pumps. In one embodiment, an ESP system includes a pump and a motor which drives the pump. The motor has an elongated cylindrical stator and a rotor which is concentrically positioned within a bore through the stator. The rotor is driven by the stator to rotate within the bore. The stator comprises a plurality of separable, interconnected modular stator sections which may be identical. Between each pair of adjacent stator sections, a corresponding interconnect electrically connects coils of magnet wire in the stator sections to a power source. In some cases, the interconnect between stator sections electrically connects the coils of magnet wire serially in the adjacent stator sections. In other embodiments, the coils in adjacent stator sections are connected in parallel the power source.
1 . An electric submersible pump (ESP) system comprising:
a pump;
a motor configured to drive the pump, the motor having an elongated cylindrical stator and a rotor which is concentrically positioned within a bore through the stator, wherein the stator is configured to generate magnetic fields directed radially inward to drive the rotor to rotate within the bore;
wherein the stator comprises a plurality of separable interconnected modular stator sections, wherein each of the modular stator sections comprises a corresponding stator housing defining a longitudinal length that is greater than an outer diameter of the modular stator section; and
for each pair of adjacent stator sections, a corresponding interconnect that electrically connects coils of magnet wire in the stator sections to a power source, wherein each corresponding interconnect comprises a set of connectors which are engaged by securing the pair of adjacent stator sections to each other, wherein the stator housing of each stator section having, at each end, a corresponding flange configured to secure the stator housing to the stator housing of the adjacent stator section, and wherein each flange has a subset of the connectors mounted thereon, such that when facing flanges of adjacent stator sections are secured to each other, the connectors mounted on the facing flanges are engaged with each other and are isolated from an external wellbore environment.
2 . The ESP system of claim 1 , wherein the interconnect electrically connects coils of magnet wire in a first one of the pair of adjacent stator sections to coils of magnet wire in a second one of the pair of adjacent stator sections in a serial configuration.
3 . The ESP system of claim 1 , for each pair of adjacent stator sections, the corresponding interconnect comprises a first end portion of a first one of the pair of adjacent stator sections and a second end portion of a second one of the pair of adjacent stator sections.
4 . The ESP system of claim 3 , wherein each of the stator sections has a corresponding stator core; wherein for each of the stator sections, the corresponding stator core does not extend axially into the corresponding end portion.
5 . The ESP system of claim 4 , further comprising, for each pair of adjacent stator sections, a corresponding bearing positioned within the end portions of the pair of adjacent stator sections, the bearing supporting a shaft of the rotor coaxially within the stator.
6 . The ESP system of claim 1 , wherein the coils of magnet wire in successive ones of the stator sections are connected by the interconnects to a power source in parallel to each other.
7 . The ESP system of claim 1 , wherein each of the modular stator sections is identical.
8 . The ESP system of claim 1 , wherein the stator comprises a plurality of gaps between stator cores of the stator sections, wherein the rotor comprises a plurality of rotor core sections separated by bearings that support a shaft of the rotor coaxially within the stator, wherein the bearings are positioned at axial locations which are coincident with the gaps between stator cores of the stator sections.
9 . The ESP system of claim 8 , wherein the rotor core sections are coextensive with the stator cores of the stator sections.
10 . A downhole motor comprising:
an elongated cylindrical stator configured to generate magnetic fields directed radially inward; and
a rotor which is concentrically positioned within a bore through the stator and is driven by magnetic fields generated by the stator to rotate within the bore;
wherein the stator comprises a plurality of separable interconnected modular stator sections, wherein each of the modular stator sections comprises a corresponding stator housing having, at each end, a corresponding flange configured to secure the stator housing to the stator housing of the adjacent stator section, and wherein each corresponding stator housing defines a longitudinal length that is greater than an outer diameter of the corresponding stator housing;
wherein each stator section has a set of connectors that engage a corresponding set of connectors of an adjacent one of the stator sections to electrically connect coils of magnet wire in the stator section to coils of magnet wire in the adjacent stator section, wherein each flange has a subset of the connectors mounted thereon such that the connectors engage simultaneously with the securing of the flanges and are isolated from an external wellbore environment; and
wherein the stator comprises a gap between stator cores of each pair of adjacent stator sections, the stator further comprising a plurality of bearings that support a shaft of the rotor, wherein the bearings are positioned at axial locations which are coincident with the gaps between the stator cores of the adjacent stator sections.
11 . The downhole motor of claim 10 , wherein the sets of connectors electrically connect coils of magnet wire in a first one of the pair of adjacent stator sections to coils of magnet wire in a second one of the pair of adjacent stator sections in a serial configuration.
12 . The downhole motor of claim 10 , wherein the coils of magnet wire in successive ones of the stator sections are connected by the corresponding sets of connectors to a power source in parallel to each other.