Skewed Rotor Lamination Stack for Torque Ripple Reduction
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Solution Overview
Problem
The finite slot number in electric motors generates magnetic field ripples, leading to torque pulsations and noise, vibration, and harshness (NVH) issues in vehicles powered by such motors.
Innovation Solution
Implementing a skewed rotor design with substacks of rotor laminations having different or common stamping patterns, oriented relative to each other to cancel out slotting harmonics, using asymmetrical magnet holes and symmetrical rivet holes, and keys to achieve a skew angle based on stator slot angles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a finite number of slots are used in the stator, then the motor structure is simplified and manufacturing is easier, but magnetic field ripples are generated causing torque pulsations and NVH issues
Solution Approach 1:
The rotor is divided into multiple substacks with different stamping patterns, where each substack contributes to canceling specific harmonic components of the magnetic field ripples. This segmentation allows the rotor to actively counteract the harmful effects of the finite slot number while maintaining structural simplicity.
Solution Approach 2:
The rotor substacks employ asymmetric stamping patterns with specific asymmetries in magnet hole positions and shapes. This asymmetry is deliberately designed to create magnetic field distributions that cancel out the slotting harmonics generated by the stator, thereby reducing torque pulsations and NVH issues.
2Object-generated harmful factors
If rotor laminations are oriented to provide a skew, then torque pulsations and NVH issues are reduced, but manufacturing complexity increases
Solution Approach 1:
The skewed rotor structure is achieved by segmenting the rotor into multiple substacks, each with a specific orientation. This segmentation transforms the complex skewing operation into manageable discrete units that can be manufactured separately and then assembled, reducing overall manufacturing complexity.
Solution Approach 2:
Multiple rotor substacks with different orientations are combined to form the complete rotor assembly. This merging of simpler components achieves the desired skew effect and harmonic cancellation without requiring complex manufacturing processes for individual parts.
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 skewed rotor design effectively reduces torque pulsations and NVH issues by minimizing magnetic field ripples, enhancing the performance and customer experience of electric vehicles.
Implementation Method 1
a stator having slots; and a rotor including a stack of rotor laminations... an orientation of the first substack and the second substack relative to each other provides the rotor with a skew
Data Source
AI summary
An electric motor comprises: a stator having slots; and a rotor including a stack of rotor laminations, the rotor comprising: a first substack of the rotor laminations, wherein the rotor laminations in the first substack include first rivet holes and first magnet holes with first permanent magnets; and a second substack of the rotor laminations, wherein the rotor laminations in the second substack include second rivet holes and second magnet holes with second permanent magnets, and wherein an orientation of the first sub stack and the second substack relative to each other provides the rotor with a skew.