Asymmetric Rotor Lamination Layout for Lower Motor Torque Ripple
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Solution Overview
Problem
Existing electric machines in electric vehicles experience torque ripple oscillations due to the interaction between harmonic magnetic flux and stator winding current, leading to inefficiencies and oscillations in motor torque output.
Innovation Solution
The electric machine incorporates a rotor core with rotor laminations that have asymmetrically arranged arcuate grooves or scallops on their outer edges, and a portion of the rotor laminations are rotated or flipped by 180 degrees relative to the others, optimizing the magnetic flux distribution and reducing torque ripple.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If symmetric rotor laminations are used, then the structure is simple and easy to manufacture, but torque ripple oscillations occur due to harmonic magnetic flux interaction
Solution Approach 1:
The patent applies asymmetry by configuring rotor laminations with different patterns in different regions. Specifically, first rotor laminations have grooves at specific positions while second rotor laminations have grooves at different positions, creating an asymmetric magnetic flux distribution that reduces torque ripple oscillations caused by harmonic magnetic flux interaction with stator winding current.
2Object-generated harmful factors
If rotor laminations are rotated or flipped by 180 degrees, then torque ripple is reduced, but the manufacturing process becomes more complex
Solution Approach 1:
The patent segments the rotor core into multiple groups of rotor laminations, where each group has a specific rotational or flipped configuration. The rotor includes first rotor laminations in a first configuration and second rotor laminations rotated or flipped by 180 degrees, creating distinct segments that work together to reduce torque ripple while maintaining manageable manufacturing complexity through modular assembly.
3Object-generated harmful factors
If asymmetric groove patterns are used on rotor laminations, then magnetic flux distribution is optimized, but manufacturing precision requirements increase
Solution Approach 1:
The patent applies local quality by configuring different rotor laminations with different groove patterns suited to their specific positions and functions. First rotor laminations have grooves positioned at specific locations to address local magnetic flux characteristics, while second rotor laminations have grooves positioned differently to address other local characteristics, optimizing overall magnetic flux distribution while managing manufacturing precision requirements through localized design.
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 significantly reduces torque pulsation, improving the electric machine's efficiency and maintaining performance during both forward and reverse rotations, as demonstrated by reduced torque ripple percentages at various mechanical frequencies.
Implementation Method 1
optimizing the magnetic flux distribution and reducing torque ripple
Implementation Method 2
torque ripple oscillations due to the interaction between harmonic magnetic flux and stator winding current
Data Source
AI summary
An electric machine includes a stator rotatably supporting a rotor, the rotor includes a stacked rotor laminations forming a rotor core with cavities having magnets arranged in the cavities through at least two adjacent rotor laminations and parallel to a rotor central axis, each lamination including an outer edge having grooves or scallops arranged asymmetrically about the circumference to reduce torque ripple. At least one groove or scallop may be arranged along a q-axis and at least one groove or scallop may be arranged between a q-axis and a d-axis of the rotor core. The laminations may be substantially identical with a first group of laminations flipped or rotated about a diametric axis relative to a second group of laminations. An electrified vehicle includes an electric machine powered by a traction battery, the electric machine having a rotor core with stacked rotor laminations having a scalloped outer edge.