Electric Machine Toroidal Stator Segments Harmonic Reduction
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Solution Overview
Problem
Electric machines with annular stators and rotors face high ohmic losses due to high spatial harmonic content in the stator magnetic field, which is exacerbated by the need for compact designs that increase eddy currents, and existing distributed windings require significant space for end windings.
Innovation Solution
The electric machine features stator segments with inner grooves and toroidal windings, where the winding windows are partially surrounded by outer arms creating a radially directed outer gap, allowing for an additional magnetic circuit outside the stator that reduces the inductance coupled to the rotor, thereby minimizing the impact of harmonic amplitudes on the rotor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a concentrated winding is used to achieve compact design, then the device complexity is reduced, but the spatial harmonic content increases causing high ohmic losses in the rotor
Solution Approach 1:
The stator is divided into multiple stator segments with individual winding windows, allowing the stator winding to be configured as a distributed winding rather than a concentrated winding. This segmentation enables the magnetic field to have lower spatial harmonic content, reducing eddy current losses in the rotor while maintaining compact design through the modular stator segment structure.
2Loss of energy
If a distributed winding is used to reduce eddy currents, then the ohmic losses are reduced, but a large amount of space is required for end windings
Solution Approach 1:
The patent utilizes the radial dimension by creating an outer gap between the stator segment outer arms, allowing return conductors to form an additional magnetic circuit in the radial direction outside the stator. This dimensional approach enables the distributed winding to achieve lower eddy currents while containing the magnetic circuit within a compact radial space, eliminating the need for large end winding spaces.
3Object-affected harmful factors
If the stator winding is configured to reduce harmonic amplitudes, then the rotor exposure to harmonics is reduced, but the winding inductance increases
Solution Approach 1:
The patent extracts the return conductors from the traditional winding configuration and positions them to form an additional magnetic circuit outside the stator through the outer gap. This extraction allows the main magnetic circuit coupling to the rotor to have reduced harmonic amplitudes, while the extracted return path provides the necessary inductance independently, decoupling the trade-off between harmonic reduction and inductance maintenance.
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 keeps the winding inductance small, reducing the rotor's exposure to harmonic amplitudes and minimizing eddy current losses, while allowing for a compact design with reduced spatial requirements.
Implementation Method 1
the stator has a stator winding which runs in toroidal fashion around the stator yoke
Implementation Method 2
generates a stator magnetic field with a high spatial harmonic content. This in turn causes high ohmic losses in the rotor of the electric machine owing to eddy currents
Data Source
AI summary
An electric machine includes an annular stator and a rotor disposed within the stator. The stator has a multiplicity of stator segments in a circumferential direction. Each of the stator segments has one or more inner grooves, disposed in the region of the inner circumference of the stator segment, and a winding window which is disposed in the region of the outer circumference of the stator segment. A stator winding is wound in toroidal fashion around the stator segment. The winding window is partially surrounded at its radial outer side by stator segment outer arms in such a way that a radially directed outer gap extending from the winding window to the outer circumference of the stator segment is formed between the stator segment outer arms.