Switched Reluctance Machine Short Flux Path Design
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Solution Overview
Problem
Conventional switched reluctance machines (SRMs) suffer from long flux paths, high torque ripple, and increased core losses due to their conventional concentrated windings, which affect their efficiency and performance.
Innovation Solution
The design of a switched reluctance machine with an axially extending shaft and rotor, and an axially extending stator, where the number of rotor poles is related to the number of stator poles, phases, and windings are configured to create short flux-paths by using the lowest common multiple (LCM) relationship and ensuring an even number of poles, with adjacent stator poles wound with opposite polarities to reduce flux paths and enhance torque capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional concentrated windings are used in SRM, then the machine structure is simple, but the flux path becomes long causing high core losses
Solution Approach 1:
The patent divides the stator into multiple salient poles with distributed windings instead of conventional concentrated windings. Each stator pole has its own winding, creating multiple independent magnetic flux paths that are shorter and more efficient, thereby reducing core losses while maintaining manufacturing feasibility through modular construction
Solution Approach 2:
The patent transitions from a two-pole conventional configuration to a multi-pole configuration with specific pole count relationships (Ns and Nr both even, Ns > Nr). This dimensional change in the magnetic circuit structure creates shorter flux paths by reducing the magnetic reluctance and optimizing the flux distribution across multiple poles, directly addressing the core loss issue
2Device complexity
If conventional SRM configuration is used, then the structure is straightforward, but torque ripple is high
Solution Approach 1:
The patent segments the magnetic circuit into multiple stator poles (Ns) and rotor poles (Nr) with even numbers, where Ns > Nr. This segmentation creates multiple overlapping torque pulses that smooth out the overall torque output, reducing torque ripple while maintaining a relatively simple overall structure through the use of standard salient pole configurations
Solution Approach 2:
The patent optimizes the pole counts (Ns and Nr) as specific parameters to achieve desirable torque characteristics. By selecting even numbers with Ns > Nr, the magnetic field distribution and inductance profiles are optimized to reduce torque ripple, demonstrating parameter optimization within a structurally simple framework
3Ease of operation
If number of rotor poles equals number of stator poles, then the configuration is symmetric, but flux path is long
Solution Approach 1:
The patent changes the parameter relationship between stator poles (Ns) and rotor poles (Nr) from equality to inequality (Ns > Nr, both even). This parameter change optimizes the magnetic flux path length by creating a more favorable pole density distribution, reducing the average flux path length while preserving operational symmetry through the even-number constraint
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 results in lower core losses and improved torque capabilities by generating short flux-paths, making the SRM more efficient and easier to manufacture with symmetric pole distributions.
Implementation Method 1
The stator includes windings on the stator teeth to generate electromagnetic field and the rotor in the electromagnetic field has the tendency to align with the stator to achieve maximum inductance
Implementation Method 2
torque is produced by the tendency of the movable part of the machine to move into a position where the inductance of an excited winding is maximized
Data Source
AI summary
Various embodiments are described herein for switched reluctance machine configurations. In at least one embodiment, a switched reluctance machine configured according to the teachings herein comprises an axially extending shaft, an axially extending rotor mounted to the shaft, the rotor having a plurality of salient rotor poles, an axially extending stator disposed coaxially and concentrically with the rotor, the stator having a plurality of salient stator poles protruding radially from the stator towards the rotor poles, and a plurality of electrical coils wound about the stator poles to define a plurality of phases of the switched reluctance machine, where a number of rotor poles can be determined according to the following equation and at least one constraint condition:Nr=LCM(Ns,Nr)2×Nph.