Systems and Methods for Electric Motor Construction

Systems and methods for the construction of electric motors, where multiple laminations within the stator core incorporate interlocking features such as dimples and corresponding depressions or recesses to prevent the laminations from rotating with respect to each other. The end laminations of the stack are welded to snap rings, and the snap rings are welded to the housing to prevent rotation of the laminations within the stator housing. The use of the interlocking features to prevent rotation of the laminations within the housing eliminates the need for compression of the laminations and the use of encapsulants to prevent rotation of the laminations.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

As described herein, various embodiments of the invention comprise systems and methods for construction of electric motors in which a stator core in which the multiple laminations within the core incorporate interlocking features such as dimples and corresponding depressions to prevent the laminations from rotating with respect to each other, and the end laminations of the stack are welded or otherwise affixed to the housing to prevent rotation of the laminations with respect to the stator housing. In one embodiment, the stator is used in a motor for a system such as an electric submersible pump (ESP).

Referring toFIG. 1, a stator core for a downhole motor in accordance with one embodiment is shown.FIG. 1is a partially cut-away view of stator core100. Stator core100includes a tubular stator housing110and a stack120of magnetic laminations (e.g.,121) that are positioned within the housing. The laminations may be identical, although this is not necessarily the case. The laminations may be made of the same material, or some of them may be made of different materials, particularly in rotating bearing areas. In the embodiment ofFIG. 1, a pair of snap rings130and131are positioned at the ends of stack120. Snap rings130and131are seated within corresponding grooves140and141in the inner surface111of housing110. In this embodiment, the laminations (122,123) at the ends of stack120are welded to snap rings130and131.

Referring toFIGS. 2 and 3, a lamination suitable for use in stator core100is shown. Each lamination is a thin disk of steel or other ferromagnetic material which has the shape of a cross-section of the stator core. The laminations normally have a thin layer of varnish or other non-conductive material which separates the laminations when they are stacked together.

Lamination200is generally annular, having a circular outer edge210and an inner aperture220. When multiple laminations are stacked together, the outer edges of the laminations form a cylindrical outer surface of substantially the diameter as the inner surface111of stator housing110. The inner apertures of the stacked laminations form the bore of the stator, within which the rotor of the motor will be positioned in the assembled motor.

Lamination200is configured to form a closed-slot stator core. This type of stator core has a set of passageways or “slots” which extend through the stator core. Magnet wire will later be threaded through these slots to form stator windings. Lamination200therefore includes a plurality of slot apertures (e.g.,230) that will form slots of the stator core.

Lamination200includes a set of “dimples”. Each dimple has a bump (e.g.,240) on one side of the lamination and a corresponding depression (e.g.,250) on the opposite side of the lamination. The pattern of the dimples on each lamination is the same, so that when the laminations are stacked together, the bumps of one lamination fit within the depressions of an adjacent lamination. In one embodiment, the dimples of the laminations are formed by partially punching these features in the laminations. When the laminations are stacked together, the dimples interlock to prevent each of the laminations from rotating with respect to the adjacent laminations. It should be noted that the dimples can be any suitable size and shape, and there may be any appropriate number of dimples on each lamination. Additionally, the dimples may be formed so that all of the bumps are on the same side of the lamination, or they may be on both sides of the lamination.

As noted above, a set of identical laminations are stacked and inserted into a stator housing to form the stator core. After the stacked laminations are inserted into the housing, snap rings are positioned in corresponding snap ring grooves on the inner surface of the housing to maintain the position of the lamination stack within the housing. In one embodiment, the lamination at each end of the stack is welded to the adjacent snap ring to prevent the lamination from rotating with respect to the snap ring, and the snap ring is welded to the housing. In an alternative embodiment, the end laminations may be welded to the housing itself. By welding the end laminations to the snap rings or housing, these laminations, and consequently the other, interlocked laminations, are prevented from rotating with respect to the housing.

The stator core described above is one of many embodiments of the present invention. Another exemplary embodiment may comprise a method for compressionless, encapsulant-free manufacture of a stator. Referring toFIG. 4, a flow diagram illustrating this method is shown. At step405, a set of stator core laminations are formed. Each of the laminations is identical, and each has a set of one or more dimples formed thereon. The laminations may, for instance, be punched from a sheet of metal or other conductive material, and the dimples may be partially punched in the laminations. The laminations are then stacked and aligned so that the dimples of adjacent laminations are interlocked (step410). The stack of laminations is then inserted into a stator housing (step415). The laminations are preferably sized to fit snugly within the housing, but this is not necessary to prevent rotation of the laminations within the housing. After the laminations are inserted into the stator housing, snap rings are inserted in the interior of the housing (step420) to maintain the position of the stack of laminations within the housing. Finally, the lamination at each end of the stack is welded to the adjacent snap ring, and the snap ring is welded to the stator housing (step425).

In one embodiment, the method may also include the step of removing the snap rings from the housing so that the stator core laminations can be removed from the housing. Because the interlocking dimples and recesses prevent the relative rotation of the laminations, no encapsulant was required, and the individual laminations can be easily separated from each other and reused.

These and other embodiments of the invention may provide a number of advantages over the prior art. For instance, as noted above, the laminations of a stator are conventionally compressed against each other so that friction between the laminations will prevent them from rotating with respect to each other. Because the dimples of the laminations in the present systems and methods are interlocked, the laminations are prevented from rotating with respect to each other without the need to compress the stack of laminations. By eliminating the compression, the resulting bending of the stator is eliminated, which in turn eliminates the need for costly and time consuming straightening operations.

Another advantage of the present systems and methods is the elimination of the need to use encapsulants in the stator. Conventionally, the slots of the stator are filled with an encapsulant such as epoxy or varnish to help prevent the laminations from rotating with respect to each other. The use of an encapsulant such as epoxy in a stator not only prevents adjacent laminations from rotating, but also prevents the impregnated laminations from being disassembled and repaired or reused. Because the interlocking dimples eliminate the need for an encapsulant to prevent relative rotation of the laminations, the laminations can be separated for repair, remanufacture or reuse in the event that the stator fails. This can save substantial time and money over simply discarding the stator in the event of a failure. Consequently, additional embodiments of the present invention may comprise methods for disassembly and/or remanufacture of stator cores of the type described herein.

While the present invention has been described with reference to particular embodiments, it should be understood that the embodiments are illustrative and that the scope of the invention is not limited to these embodiments. Many variations, modifications, additions and improvements to the embodiments described above are possible. For instance, In one embodiment, the stator core laminations may have simple dimples and recesses which interlock between the laminations, but alternative embodiments may have interlocking structures and recesses that have varying shapes, sizes and numbers. Each laminations may have all of the dimples (or all of the recesses) on the same side, they may be on both sides of each lamination.