Offset Rotor Sections Reduce Torque Ripple and Axial Thrust
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Solution Overview
Problem
Electric machines, such as interior permanent magnet (IPM) and Synchronous Reluctance motors, experience high torque oscillations and axial thrust, leading to potential damage and mechanical system resonance, with existing methods to reduce torque ripple either increasing manufacturing complexity and cost or introducing core losses.
Innovation Solution
The implementation of offset rotor sections with a step-skewed configuration, specifically a herringbone pattern, reduces torque ripple and axial thrust by angularly shifting rotor sections and using keybars with a helicoidal profile to facilitate assembly and reduce stress on mechanical components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If stator skewing is used to reduce torque ripple, then torque oscillations are reduced, but axial thrust is introduced to the stator assembly
Solution Approach 1:
The rotor is divided into multiple rotor sections that can be independently skewed. Each rotor section is skewed by a different angle relative to the stator, allowing the torque ripple reduction benefits of skewing to be achieved while distributing and balancing the axial thrust forces across multiple sections rather than concentrating them in a single skewed stator structure.
2Reliability
If odd number of stator slots per pole pair is used to reduce torque ripple, then torque oscillations are reduced, but core losses increase
Solution Approach 1:
The invention changes the geometric parameters of the rotor structure by introducing skew angles to rotor sections. This parameter change allows torque ripple reduction through geometric configuration rather than through slot number selection, thereby avoiding the increased core losses that would result from using an odd number of stator slots per pole pair.
3Reliability
If single helicoidal path skewing is used to reduce torque ripple, then torque oscillations are reduced, but manufacturing complexity and cost increase
Solution Approach 1:
The rotor is segmented into multiple discrete sections that can be manufactured separately and then assembled. Each section can be skewed by a standard angle that is easier to manufacture than continuous helicoidal skewing. This segmentation simplifies the manufacturing process while still achieving torque ripple reduction through the cumulative effect of multiple skewed sections.
Solution Approach 2:
Multiple rotor sections with individual skew angles are combined in an assembly to create the overall skewed rotor structure. This merging of multiple simpler components achieves the torque ripple reduction effect of complex skewing patterns while maintaining simpler individual component manufacturing.
Data Source
AI summary
A component that includes a longitudinal axle, having a multiple keybars that extend outward from a surface of the axle, such that each of the keybars are disposed axially along and circumferentially around the axle. Also the axis of the keybars is parallel to the axle, such that a profile of all midpoints of the keybars is helicoidal around the axle, also the helicoidal profile is such that they make up one or more helicoidal paths. The profile may be herringbone skewed. The component may be part of a rotor assembly that is part of an electric machine such as an interior permanent magnet (IPM) or Synchronous Reluctance motor.