Asymmetric Permanent Magnet Rotor for Compressor Motor

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Solution Overview

Problem

Interior permanent magnet type motors experience high cogging torque and noise due to symmetrical permanent magnet shapes, leading to increased manufacturing costs and complexity when skewed magnets are used to prevent vibration.

Innovation Solution

The use of asymmetrically shaped permanent magnets with vertical and inclined surfaces that adhere closely to the slot sides, eliminating the need for additional sub-magnets and simplifying the manufacturing process, while reducing cogging torque and total harmonic distortion.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If symmetrical permanent magnets are used in the rotor, then the manufacturing process is simple, but cogging torque and noise increase significantly

Engineering Contradiction:

Improvemanufacturing process simplicityVSAvoidcogging torque and noise

Core Design Contradiction:

Ease of manufactureVSObject-generated harmful factors

Solution Approach 1:

The patent applies asymmetry by designing permanent magnets with different shapes at different positions within the same slot. Specifically, the magnet shape varies along the axial direction, creating an asymmetric magnetic distribution that reduces cogging torque and noise while maintaining manufacturing feasibility through a controlled variation rather than complete complexity

Inventive Principle:

Principle #4Asymmetry

2Object-generated harmful factors

If skewed magnets are used to reduce cogging torque, then noise decreases, but manufacturing cost increases and process complexity increases

Engineering Contradiction:

Improvecogging torque and noiseVSAvoidmanufacturing process complexity

Core Design Contradiction:

Object-generated harmful factorsVSDevice complexity

Solution Approach 1:

The patent applies local quality by implementing different magnet shapes only in specific local regions (different axial positions) rather than skewing the entire magnet structure. This localized variation achieves noise reduction while keeping the overall manufacturing process simpler, as each local region can be manufactured independently with standard processes

Inventive Principle:

Principle #3Local quality

3Reliability

If sub-magnets are added to fill gaps and prevent vibration, then magnet stability improves, but manufacturing cost and process complexity increase

Engineering Contradiction:

Improvemagnet stability in slotVSAvoidnumber of magnet parts

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent applies segmentation by dividing a single magnet into multiple segments along the axial direction, with each segment having a different shape. This segmentation achieves vibration prevention and stability without requiring additional sub-magnets, as the segmented structure itself provides the necessary support and fit within the slot

Inventive Principle:

Principle #1Segmentation

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 decreases cogging torque by 80% and total harmonic distortion by 44%, reduces manufacturing costs, and allows for varied magnet shapes without altering the rotor core slots, enhancing motor performance and reducing vibration-related issues.

Implementation Method 1

each of the plurality of permanent magnets includes: a top surface part; a bottom surface part formed opposite to the top surface part; and first and second side surface parts connecting the top surface part and the bottom surface part, wherein a first vertical part and a second vertical part, which are in contact with side surface parts of the slot, are formed in the first and second side surface parts, respectively

Methodology Applied

Scientific EffectGeometric constraint:

Data Source

PatentUS10615651B2Interior permanent magnet type rotor, permanent magnet type motor having the interior permanent magnet type rotor, and compressor having the permanent magnet type motor

Publication Date: 2020.04.07 LG ELECTRONICS INC

AI summary

An interior permanent magnet type rotor includes: a rotor core having a plurality of slots formed therein, the plurality of slots having a symmetric longitudinal sectional shape; and a plurality of permanent magnets respectively inserted into the plurality of slots, the plurality of permanent magnets having an asymmetric longitudinal sectional shape, wherein each of the plurality of permanent magnets includes: a top surface part; a bottom surface part formed opposite to the top surface part; and first and second side surface parts connecting the top surface part and the bottom surface part, wherein a first vertical part and a second vertical part, which are in contact with side surface parts of the slot, are formed in the first and second side surface parts, respectively.