Axial Split-Phase Bearingless Flywheel Motor Decoupling
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Solution Overview
Problem
Current bearingless switched reluctance motors (BSRMs) face challenges with strong electromagnetic coupling, limiting their application in flywheel energy storage systems due to complexity in analysis and high-speed control, and existing three-phase structures lack self-starting properties and result in low torque output and high torque ripple.
Innovation Solution
An axial split-phase bearingless flywheel motor with three phases and four degrees of freedom is designed, featuring a stator and rotor divided into phases A, B, and C with staggered rotor poles, torque and suspension poles, and a magnetic isolation component, enabling self-starting and improved torque output while decoupling suspension and torque control magnetic circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If magnetic bearings are used to reduce suspension support loss, then system efficiency is improved, but the flywheel rotor axial length increases, reducing critical speed and complicating structure
Solution Approach 1:
The patent combines the suspension support function and drive motor function into a single integrated bearingless switched reluctance motor structure. The stator includes both suspension windings and torque windings, eliminating the need for separate magnetic bearings and reducing the axial length of the flywheel rotor while maintaining the energy efficiency benefits of magnetic suspension.
Solution Approach 2:
The stator structure performs multiple functions simultaneously: it provides magnetic suspension support through suspension windings and generates torque through torque windings. This multi-functional design eliminates the need for separate components, reducing overall axial length while achieving both suspension and drive functions.
2Loss of energy
If bearingless switched reluctance motor is used to eliminate mechanical bearings, then friction loss is reduced and service life is extended, but electromagnetic coupling becomes complicated, increasing control difficulty
Solution Approach 1:
The stator is segmented into distinct suspension poles and torque poles with separate winding systems. The suspension windings and torque windings are independently controlled, allowing the electromagnetic coupling to be decoupled into separate suspension control and torque control channels. This segmentation simplifies the control strategy while maintaining the benefits of eliminating mechanical bearings.
Solution Approach 2:
The patent introduces a decoupling control strategy that acts as an intermediary between the complex electromagnetic coupling and the control system. By transforming the coupled electromagnetic equations into decoupled control equations, the system can independently control suspension and torque, significantly reducing control difficulty while maintaining frictionless operation.
3Ease of operation
If two-phase axial split-phase structure is used to achieve suspension at four degrees of freedom, then self-starting capability is lost and torque output is reduced with high torque ripple
Solution Approach 1:
The patent applies different pole configurations to different phases: phases A and C have both suspension poles and torque poles with specific geometric characteristics, while phase B has only torque poles. This local differentiation allows the motor to achieve four-degree-of-freedom suspension control while generating sufficient torque output with reduced ripple through the combined action of all three phases.
Solution Approach 2:
The patent merges the suspension function and torque generation function into a unified three-phase structure where all phases work together. The suspension windings in phases A and C provide four-degree-of-freedom suspension control, while the torque windings in all three phases cooperate to generate smooth, high-density torque output, overcoming the limitations of two-phase designs.
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 design achieves self-starting, reduces torque ripple, enhances torque output and power density, and simplifies control, facilitating reliable high-speed operation and extended service life in flywheel energy storage systems.
Implementation Method 1
uses a permanent magnet to produce a biased magnetic flux, reducing the loss in suspension support and improving system efficiency and power density
Implementation Method 2
strong and complicated electromagnetic coupling exists between windings, magnetic circuits, and the electromagnetic force inside the motor
Implementation Method 3
The control coils on two opposite suspension poles in the phase A and the phase C are connected in series to form two sets of suspension windings in orthogonal directions
Data Source
AI summary
An axial split-phase bearingless flywheel motor includes a stator, a stator sleeve, a rotor, a rotor sleeve, and a flywheel. The stator and the rotor are axially divided into phases A, B and C. An axially magnetized permanent magnet is provided between every adjacent phases. Twelve rotor poles are provided at equal intervals on an inner side of the rotor core in each of the phases A, B, and C. The rotor poles in the phases A, B and C are staggered in sequence along a circumference by ⅓ of a rotor pole pitch. Eight torque poles in a shape of narrow teeth and four suspension poles in a shape of wide teeth are provided on the stator core in both the phases A and C, and twelve torque poles of a uniform width are provided on the stator core in the phase B.