Magnetically Permeable End Rings for Permanent Magnet Motor Torque

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Solution Overview

Problem

Conventional permanent magnet electric motors used in ESP systems face challenges in torque production due to non-magnetically permeable end rings, which limit power density and efficiency, especially in constrained spaces where securing these rings is difficult.

Innovation Solution

The use of magnetically permeable end rings made of soft magnetic composite materials that actively contribute to torque production, allowing the rotor laminations and end rings to be secured effectively within the motor, enhancing power density and efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If non-magnetically permeable end rings (aluminum bronze) are used to secure rotor laminations, then the rotor structure is mechanically stable and easy to manufacture, but torque production is limited because the end rings do not contribute to magnetic flux

Engineering Contradiction:

Improvetorque productionVSAvoidend ring securing difficulty

Core Design Contradiction:

PowerVSEase of manufacture

Solution Approach 1:

The patent applies composite materials by combining magnetically permeable material (for torque production) with high resistivity material (for eddy current reduction) within the end ring structure. This allows the end rings to actively participate in torque production while minimizing harmful eddy currents, resolving the contradiction between power output and manufacturing ease.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent changes the magnetic permeability parameter of the end ring material from non-magnetically permeable (aluminum bronze) to magnetically permeable material. This parameter change enables the end rings to contribute to torque production, directly addressing the limitation of conventional designs where end rings were merely structural components.

Inventive Principle:

Principle #35Parameter changes

2Volume of moving object

If the outer diameter of the ESP motor is constrained to less than 5.62 inches (commonly 4.5 inches or less), then the motor can be deployed in standard wellbores, but the space available for stator and rotor laminations is severely limited

Engineering Contradiction:

Improvepower densityVSAvoidshaft diameter

Core Design Contradiction:

Volume of moving objectVSLength of moving object

Solution Approach 1:

The patent extends the active magnetic material continuously from the rotor laminations through the end rings, creating a continuous path for magnetic flux. This eliminates the discontinuity created by conventional non-magnetic end rings, allowing the entire rotor length including end rings to contribute to torque production, thereby increasing power density within the constrained volume.

Inventive Principle:

Principle #20Continuity of useful action

3Loss of energy

If high resistivity magnetically permeable material (soft magnetic composite) is used for end rings, then eddy current losses are reduced, but the material selection and manufacturing process become more complex

Engineering Contradiction:

Improveeddy current lossesVSAvoidmaterial selection flexibility

Core Design Contradiction:

Loss of energyVSAdaptability or versatility

Solution Approach 1:

The patent changes the electrical resistivity parameter of the end ring material by selecting soft magnetic composite material with inherently high resistivity. This parameter change reduces eddy current losses while maintaining magnetic permeability, directly addressing the energy loss issue despite increased material selection complexity.

Inventive Principle:

Principle #35Parameter changes

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This configuration increases torque production by 10-12% and improves efficiency by 1% compared to conventional designs, while reducing eddy current losses through high resistivity materials.

Implementation Method 1

In the presence of rotating magnetic fields generated by a stator, both the lamination stack and the end rings are active in the production of torque

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Implementation Method 2

reducing eddy current losses through high resistivity materials

Methodology Applied

Scientific EffectEddy currents: Eddy Currents

Data Source

PatentUS10680476B2Systems and methods for constructing permanent magnet motors having increased power density

Publication Date: 2020.06.09 BAKER HUGHES CO

AI summary

Systems and methods for constructing permanent magnet electric motors in which rotors have magnetically permeable end rings that are active for torque production. In one embodiment, a rotor section has a set of flat, generally annular laminations stacked on an inner rotor sleeve, with a pair of end rings positioned at opposing ends of the lamination stack to secure the stack. One or both of the end rings is made of a magnetically permeable and highly resistive material such as a soft magnetic composite, so that the end ring(s) actively produce torque during operation of the motor without significant increase in core loss at end rings. A set of permanent magnets are installed in or on the rotor core formed by the laminations. These magnets or other magnets may be positioned to axially overlap with the end rings and aid active torque production by the end rings.