Segmented Electrical Machine Balancing Compensator
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Solution Overview
Problem
Segmented electrical machines in gas turbine engines experience radial unbalanced magnetic forces (UMF) due to non-axisymmetric stator segment distribution, leading to increased shaft eccentricities, bearing friction, and potential rotor vibrations, which reduce bearing life and cause deformation.
Innovation Solution
An active compensator with balancing segments, featuring a core structure of magnetically permeable material and conductor windings, is used to counteract UMF. These segments have salient teeth or varying air gaps to maintain a constant reluctance path and can incorporate permanent magnets or U/E-core geometries to balance radial and axial forces effectively, with a control system for rapid force compensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If stator segments are non-axisymmetrically distributed to accommodate pipes and cables, then space utilization is improved, but radial unbalanced magnetic force increases causing shaft eccentricity and bearing wear
Solution Approach 1:
The stator is divided into multiple independently controllable segments that can be selectively activated. By controlling which segments are energized, the system can accommodate spatial constraints (non-axisymmetric distribution) while managing unbalanced magnetic forces through selective activation patterns.
Solution Approach 2:
The electrical machine transitions from a static configuration to a dynamic one where stator segments can be selectively energized and de-energized based on operational requirements. This dynamic control allows adaptation to space constraints while compensating for unbalanced forces through real-time adjustment of segment activation.
2Ease of manufacture
If stator segments are non-axisymmetrically distributed, then ease of installation is improved, but rotor vibrations increase due to unbalanced magnetic force excitation
Solution Approach 1:
Dividing the stator into segments allows flexible installation configurations while enabling independent control of each segment. This segmentation permits non-axisymmetric arrangements for ease of installation while providing the means to control vibrations through selective segment activation.
Solution Approach 2:
The system changes operational parameters by selectively energizing different stator segments. This parameter control allows the machine to adapt its magnetic field distribution to minimize vibrations while maintaining the beneficial non-axisymmetric installation configuration.
3Device complexity
If conventional annular stator is used, then structural simplicity is maintained, but weight and component count increase
Solution Approach 1:
The conventional annular stator is segmented into multiple independent units. This segmentation reduces the weight of individual components and allows selective installation, thereby reducing overall system weight and component count while maintaining functional simplicity through modular architecture.
Solution Approach 2:
The invention extracts the essential stator function from a complete annular structure and distributes it across separate segments. This extraction allows removal of unnecessary material and components, reducing weight while preserving the core electrical machine functionality through coordinated segment operation.
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
The compensator achieves high force densities with low power requirements and high operational reliability, reducing UMF effects and extending bearing life by providing balanced forces independent of stator segment operation.
Implementation Method 1
conductor windings mounted to the core structure, which conductor windings are electrically excitable to magnetically energize the balancing segment
Implementation Method 2
core structure (e.g. formed of magnetically permeable material) and a conductor winding mounted to the core structure, which conductor winding is electrically excitable to magnetically energize the balancing segment
Implementation Method 3
the compensator can compensate for a UMF with a rapid response time... achieve high force densities
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
An electrical machine has a variable reluctance rotor, and a stator formed as an annular array of stator segments. The reluctance of the rotor-to-stator magnetic flux path varies with rotor position whereby the stator segments are magnetically energizable to rotate the rotor. The stator segments are arranged in the array such that, when energized to rotate the rotor, they produce an unbalanced force on the rotor. The machine further has a compensator including one or more balancing segments which are configured to be magnetically energizable to produce a balancing force on the rotor which balances the unbalanced force. The reluctance of the rotor-to-compensator magnetic flux path is substantially invariant with rotor position.