Electric Machine Rotor Top Bridge Segments for Torque Ripple Reduction
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Solution Overview
Problem
Torque ripple in electric machines caused by harmonic magnetic fluxes leads to undesirable vibrations and noise, particularly in hybrid electric vehicle powertrains, where lower frequency oscillations are difficult to filter and result in mechanical issues.
Innovation Solution
The rotor design features a cavity with a top bridge having segments that monotonically increase in width from the Q-axis to the D-axis, reducing the rate of change of rotor airgap flux density and magnetomotive force, thereby minimizing torque ripple and iron loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a conventional rotor with uniform top bridge width is used, then the structure is simple and easy to manufacture, but torque ripple and vibrations increase due to harmonic magnetic fluxes
Solution Approach 1:
The top bridge is divided into multiple segments with different width characteristics. Each segment has a specific width profile that varies monotonically, creating different rates of change of flux density in different regions. This segmentation allows the rotor to reduce torque ripple while maintaining manufacturability through modular design.
Solution Approach 2:
Different segments of the top bridge are designed with locally optimized width characteristics. The width varies monotonically across segments, with each segment having minimum width closest to the Q-axis and maximum width closest to the D-axis. This local quality variation smooths the flux distribution and reduces harmonic magnetic fluxes, thereby reducing torque ripple and vibrations.
2Object-generated harmful factors
If the top bridge width is varied to reduce torque ripple, then torque ripple and vibrations decrease, but the device complexity increases
Solution Approach 1:
The top bridge is segmented into multiple sections, each with controlled width variations. This segmentation enables the complex flux distribution pattern to be achieved through manageable geometric modifications rather than a completely complex structure, balancing performance improvement with制造 feasibility.
Solution Approach 2:
The top bridge segments feature curved or rounded transitions rather than sharp corners, with widths that monotonically increase from Q-axis to D-axis. This curvature smooths the magnetic flux distribution and reduces harmonic content, effectively reducing torque ripple while maintaining a relatively simple overall rotor geometry.
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 design effectively reduces torque ripple and iron loss by smoothing the flux distribution and reluctance, leading to improved motor performance and reduced vibrations and noise.
Implementation Method 1
a rate of change of rotor airgap flux density associated with each segment differs
Implementation Method 2
a rate of change of rotor magnetomotive force associated with each segment differs
Data Source
AI summary
An electric machine may include a rotor defining a cavity containing a magnet, an outer periphery and a top bridge therebetween. The top bridge defines at least two segments. Each of the segments has a width that is minimum closest to a Q-axis, is maximum closest to a D-axis, and monotonically increases from the minimum to the maximum such that during operation a rate of change of rotor magnetomotive force associated with each segment differs.