Split Common Pole SRM Torque Generation
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Solution Overview
Problem
Switched reluctance machines (SRMs) face limitations in torque generation due to negligible reluctance variation from common poles, which restricts their efficiency and power density, despite having high power-density capabilities compared to synchronous machines with permanent magnets.
Innovation Solution
Introducing air slots within common poles to create reluctance variation between rotor and common poles, thereby enhancing torque generation without increasing machine dimensions or winding turns, using a flux barrier that inhibits flux flow between parts of the common pole.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If common poles are used without excitation windings to prevent flux reversal, then core losses are minimized and efficiency is improved, but torque generation is limited due to negligible reluctance variation
Solution Approach 1:
The common pole is segmented by introducing air slots that divide it into multiple regions. This segmentation creates reluctance variation as rotor poles move across different air gap distances relative to various segments of the common pole, enabling torque generation while maintaining the flux reversal prevention function.
Solution Approach 2:
Different regions of the common pole are given different magnetic characteristics through the air slots. The areas between air slots provide flux paths with varying reluctance, creating local quality differences that enable torque generation without requiring excitation windings on the common pole.
2Power
If machine dimensions and winding turns are increased to enhance torque generation, then power density is improved, but weight and volume of steel laminations and copper windings increase
Solution Approach 1:
The invention changes the magnetic circuit parameters by introducing air slots with specific dimensions and configurations. This modifies the reluctance characteristics of the common pole to create torque-generating reluctance variation, achieving enhanced power output without changing the overall machine dimensions or increasing copper winding content.
3Reliability
If common poles provide a path for return flux with unidirectional flow, then flux reversal is prevented and core losses are reduced, but torque generation is negligible due to constant reluctance
Solution Approach 1:
The common pole is divided into segments by air slots, creating multiple flux paths with different reluctance characteristics. This segmentation allows the common pole to maintain its flux reversal prevention function while simultaneously providing reluctance variation for torque generation through the differential magnetic paths.
Solution Approach 2:
The air slots act as intermediaries that modulate the magnetic flux flow through the common pole. They create controlled reluctance variations that enable torque generation while the overall common pole structure continues to provide the return flux path that prevents flux reversal in the excitation poles.
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 approach significantly increases torque and output power by ensuring reluctance variation across all overlapping surfaces, resulting in improved efficiency and power density, with the torque produced by SRMs with split common poles being 1.6 to 2.4 times that of those without split common poles over a large range of overlap angles.
Implementation Method 1
A flux barrier, disposed within the common pole, inhibits the flow of flux from one part of the common pole across the flux barrier to another part of the common pole. The flux barrier is less conducive to the flow of flux than is the common pole. More simply, the flux barrier has greater reluctance than does the common pole.
Implementation Method 2
Each of the excitation poles has a coil wound around it for inducing a magnetic flux through the excitation pole.
Data Source
AI summary
An electromagnetic machine stator has a common pole and a plurality of excitation poles. Each excitation pole has a coil wound around it for inducing a magnetic flux through the excitation pole. The common pole that does not have a coil wound around it for inducing a magnetic flux. A flux barrier, disposed within the common pole, inhibits the flow of flux from one part of the common pole across the flux barrier to another part of the common pole. The flux barrier is less conducive to the flow of flux than is the common pole.