Axial Rotor Core Layout for Compact Motor Rotation Stability

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Solution Overview

Problem

In compact motors, the reduced size and inertia of the rotor core lead to unstable rotation, causing vibration and noise due to load pulsation, especially in compressors where efficient size reduction is desired without increasing the motor's overall size.

Innovation Solution

The motor design features a rotor core with a longer axial length than the stator core, incorporating regions with and without magnets, and steel laminations with varying slit and hole configurations to increase inertia while minimizing iron loss and noise, by optimizing the weight distribution and magnetic flux.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Volume of moving object

If the motor size is reduced, then the motor becomes more compact, but the rotor inertia decreases causing unstable rotation

Engineering Contradiction:

Improvemotor sizeVSAvoidrotation stability

Core Design Contradiction:

Volume of moving objectVSStability of the object's composition

Solution Approach 1:

The rotor core is divided into different regions (first region with magnets and second region without magnets) with different steel lamination configurations. The second region has reduced opening areas to increase local weight and inertia, while the first region maintains normal openings for magnetic flux. This local differentiation allows the rotor to have increased inertia for stability without significantly increasing the overall motor volume.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The rotor core uses composite construction with steel laminations of different configurations combined in one structure. The stack includes both laminations with normal opening areas (first region) and laminations with reduced opening areas (second region), creating a composite rotor structure that optimizes both inertia and magnetic performance within compact dimensions.

Inventive Principle:

Principle #40Composite materials

2Stability of the object's composition

If the rotor core length is increased to increase inertia, then the rotation stability improves, but the motor size increases

Engineering Contradiction:

Improverotation stabilityVSAvoidmotor size

Core Design Contradiction:

Stability of the object's compositionVSVolume of moving object

Solution Approach 1:

Instead of uniformly increasing the entire rotor core length, the invention applies weight optimization locally only to the second region where magnets are not inserted. This allows selective increase of inertia in specific areas without proportionally increasing the overall motor size, as the first region with magnets maintains its original lamination configuration.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The rotor core is segmented into multiple steel laminations stacked in the axial direction, with different regions having different opening area configurations. This segmentation allows independent optimization of each region's contribution to inertia while maintaining the overall compact motor structure.

Inventive Principle:

Principle #1Segmentation

3Power

If steel laminations with slits and holes are used, then the magnetic flux is optimized, but the iron loss increases

Engineering Contradiction:

Improvemagnetic flux efficiencyVSAvoidiron loss

Core Design Contradiction:

PowerVSLoss of energy

Solution Approach 1:

The invention applies different slit and hole configurations to different regions of the rotor core. The first region (with magnets) has laminations containing slits and holes for optimal magnetic flux, while the second region (without magnets) has laminations with reduced or no openings to minimize iron loss. This local differentiation optimizes magnetic performance where needed while reducing energy loss in regions where magnets are absent.

Inventive Principle:

Principle #3Local quality

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 configuration stabilizes the motor's rotation, reduces vibration and noise, and enhances efficiency by increasing the rotor's inertia without increasing the motor's size, thus addressing the challenge of load pulsation in compressors.

Implementation Method 1

increase the inertia of the rotor and thereby stabilize the rotation of the rotor

Methodology Applied

Scientific EffectInertia: Inertia

Implementation Method 2

a magnet inserted in the magnet insertion hole

Methodology Applied

Scientific EffectMagnetic field: Magnetic Field

Data Source

PatentUS11949291B2Motor having rotor with different core regions, compressor, and air conditioner having the motor

Publication Date: 2024.04.02 MITSUBISHI ELECTRIC CORP

AI summary

A motor includes a stator core having an annular shape about an axis, a coil wound on the stator core, and a rotor core disposed on an inner side of the stator core in a radial direction about the axis. The rotor core has a stacked body in which a plurality of steel laminations are stacked in a direction of the axis, and a magnet insertion hole famed in the stacked body. The rotor core has a length in the direction of the axis longer than that of the stator core. A magnet is inserted in the magnet insertion hole. The rotor core has a first region where the magnet is inserted in the magnet insertion hole and a second region where the magnet is not inserted in the magnet insertion hole, in the direction of the axis. At least one steel lamination in the second region of the rotor core has an opening area smaller than an opening area of each steel lamination in the first region of the rotor core.