Rotor Air-Gap Layout for Low Cogging and Torque Ripple
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Solution Overview
Problem
Existing motors with grooves on the outer periphery of magnets face a challenge where reducing torque fluctuations when power is applied increases cogging torque, and vice versa, making it difficult to improve motor performance effectively.
Innovation Solution
The proposed solution involves a rotor design for a rotating electric machine that incorporates magnetic air gaps in the assisted salient pole member, which are offset to cancel out torque fluctuations when power is applied, thereby reducing both cogging torque and torque fluctuations independently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If conventional skew is applied to reduce torque fluctuations, then torque fluctuations are reduced, but device complexity increases
Solution Approach 1:
Instead of applying conventional skew to the entire rotor structure, the invention segments the rotor core and applies groove features only to specific segments. This localized approach reduces torque fluctuations while maintaining simpler overall structural complexity compared to full rotor skewing.
Solution Approach 2:
The invention applies groove features locally to specific segments of the rotor core rather than uniformly across the entire rotor. This local quality approach enables torque fluctuation reduction in critical areas while avoiding unnecessary complexity in other regions.
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 fluctuations when power is applied without decreasing the torque, allowing for improved motor performance in terms of efficiency, reliability, cost, and productivity, while also reducing vibrations and noises in electric vehicles.
Implementation Method 1
a first magnetic air gap 258a and a second magnetic air gap 258b are arranged, respectively, at positions offset from a q-axis a and a q-axis b
Implementation Method 2
the magnetic air gaps... are arranged... so as to cancel out torque fluctuations when power is applied
Data Source
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AI summary
A rotating electric machine includes a stator having a stator coil and a rotor provided rotatably around a specific rotation axis with respect to the stator. The rotor includes a plurality of magnets, a plurality of magnetically-assisted salient pole members provided between poles of any adjacent two magnets from among the plurality of magnets, and a magnetoresistance variation unit provided in the magnetically-assisted salient pole member along an axial direction of the rotation axis at a position offset in a circumferential direction of the rotation axis from a q-axis passing through a salient pole center of the magnetically-assisted salient pole member. The amount of offset of the magnetoresistance variation unit from the q-axis varies depending on positions of the magnetically-assisted salient pole members so that torque fluctuations cancel each other when power is applied.