Permanent Magnet Tandem Motor Coupling for Pole Alignment
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Solution Overview
Problem
Permanent magnet ESP motors have not been operated in tandem due to the challenge of rotationally aligning the pole magnets of the lower and upper tandem motors, which is necessary for proper operation.
Innovation Solution
The use of alignment means such as coupling irregularities, shaft irregularities, coupling keyways, indicia on the coupling and shafts, and orientation slots with guide members to ensure rotational alignment of the magnetic poles of the first and second drive shafts before securing the motor housings together.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If permanent magnet ESP motors are operated in tandem to increase horsepower, then the power output is improved, but the rotational alignment of pole magnets between upper and lower motors becomes difficult to achieve
Solution Approach 1:
A coupling device with internal splines serves as an intermediary between the upper and lower drive shafts. This coupling includes alignment features such as a keyway or irregularity that engages with corresponding features on the shafts to automatically establish proper rotational alignment when the shafts are connected, eliminating the need for manual alignment procedures
Solution Approach 2:
Alignment features are pre-configured into the coupling and shaft assemblies during manufacturing. The coupling includes pre-positioned keyways, irregularities, or indexing features that automatically guide the shafts into correct rotational alignment when connected, performing the alignment action automatically before the motors are operated together
2Reliability
If the rotor sections are enclosed in a housing for protection, then the reliability is improved, but the ability to visually align pole magnets during connection is lost
Solution Approach 1:
The coupling acts as an external intermediary alignment device that does not require opening the motor housings. It provides visible alignment features on its exterior that can be seen and used during connection, while the rotor sections remain enclosed and protected within their respective housings
Solution Approach 2:
The alignment function is transferred from a visual inspection of the rotors themselves to a mechanical coupling system with external alignment features. The coupling's keyways, irregularities, or indexing marks provide the necessary alignment information mechanically and visually without requiring exposure of the enclosed rotor sections
3Ease of operation
If alignment features are added to the coupling and shafts to enable rotational alignment, then the ease of operation is improved, but the device complexity increases
Solution Approach 1:
The coupling and shafts incorporate asymmetric features such as keyways, irregularities, or indexing marks at specific positions. These asymmetric elements provide unique alignment references that guide the shafts into the correct rotational position relative to each other, enabling easy alignment without complex adjustment mechanisms
Solution Approach 2:
The alignment function is merged into the existing coupling and shaft structure. Rather than adding separate alignment devices, the alignment features are integrated directly into the coupling's spline interface and the shafts, combining the connection and alignment functions into a single unified system
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 solution allows for the successful tandem operation of permanent magnet ESP motors by ensuring that the magnetic poles of the upper and lower motors are properly aligned, enhancing the operational efficiency and reliability of the ESP system.
Implementation Method 1
A coupling connected with the first drive shaft for rotation in unison has internal splines that engage the external splines for causing the first and second drive shafts to rotate in unison
Implementation Method 2
Another type of ESP motor has permanent magnets in the rotor sections rather than copper rods. Each permanent magnet provides one pole of the motor
Implementation Method 3
Each permanent magnet provides one pole of the motor, which may have four or a different number of poles
Implementation Method 4
Each of the rotor sections has a plurality of circumferentially spaced permanent magnets. The rotor keyway is between each of the rotor sections and the shaft of each of the motors, defining magnetic poles
Data Source
Figure 1~2
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Figure 4
AI summary
An electrical submersible well pump assembly (15) has first and second permanent magnet motors (18, 20). The first motor drive shaft (50) is connected to a coupling (77) that has internal splines (79) for receiving an externally splined end (83) of the second motor drive shaft (69). Alignment devices (82, 87) rotationally align magnetic poles (55) of the first drive shaft (50) with the magnetic poles of the second drive shaft prior to securing the housings (39, 67) of the first and second motors together. The alignment devices may be a coupling irregularity (82) in the internal splines that is at a controlled orientation relative to the magnetic poles of the first shaft and a shaft irregularity (87) in the external splines (85) that prevents the second drive shaft from fully engaging the coupling unless the shaft irregularity is in a specified rotational position relative to the coupling irregularity.