Permanent magnet submersible motor with a one-piece rotor/yoke configuration and resin embedded magnets

Abstract

The invention provides a permanent magnet submersible motor for electric submersible pump systems and a method of making the rotor of such a motor. The unitary construction of the rotor shaft and theyoke provides improved protection of the damage-prone magnets, while the larger effective shaft diameter also improves shaft bending resistance. Shaped form closures on the yoke promote secure magnetretention, even under highly centrifugal loads, while an exterior cladding tube and a cast resin filler material are used to further secure the magnets around the yoke periphery while also providing hermetic sealing against a working fluid.

Description

[0001] Cross References to Related Applications [0002] This patent application claims priority to U.S. Provisional Application Serial No. 62 / 266,919, filed December 14, 2015, entitled "Permanent Magnet Submersible Motor With A One-Piece Rotor / Yoke Configuration And Resin Embedded Magnets," the entirety of which Incorporated herein by reference. technical field [0003] The present disclosure relates generally to synchronous motors for submersible pump systems that use rotor mounted permanent magnets and, more particularly, to a rotor configuration that provides improved magnet protection against submersible pump environmental conditions and shaft deflection resistance. Background technique [0004] Electric submersible pumps (ESPs), also known as deep well submersible (DWS) pumps, are especially useful for extracting valuable resources from deep well geological formations. In one example, an ESP can be used to retrieve crude oil or natural gas from extremely deep subterr...

AI Technical Summary

Problems solved by technology

Unfortunately, these motor configurations are more expensive to construct than conventional (asynchronous) induction motors, negating the benefits of inherent efficiency improvements

More importantly, the special environment associated with submersible motors can prevent the long-term robustness needed to compensate for the higher cost of PMSMs; such environmental issues include: (a) requiring the use of long, thin rotors mounted on limited-diameter drills; holes or pipes to maximize power output for a given external motor diameter; (b) protection from the corrosive effects of motor lubricant or working fluid on the magnets; and (c) long intervals between maintenance on the ESP

This deflection can undesirably cause the rotor to come into contact with the stator

Similarly, the second problem is not ameliorated by using coatings on magnets because prolonged exposure of magnets to fluids (which are usually at elevated temperatures) always results in material degradation

Regarding this third question, the long time between this exposure (and the associated magnet and motor damage) and the desired overhaul is not consistent with the time it takes for submersible pumps to be viable economically

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