Permanent Magnet Synchronous Motor Rotor Stator Length Ratio
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Solution Overview
Problem
There is a need for a more compact and lightweight permanent magnet synchronous motor for electric vehicles that maintains nominal performance while reducing size and mass, as existing motors are constrained by increasing compactness requirements and are sensitive to climatic conditions affecting vehicle range.
Innovation Solution
A synchronous electric motor with permanent magnets featuring a wound stator and a rotor with axially extending magnets in a flow concentration architecture, where the axial length of the rotor is greater than the stator teeth, and a ratio of these lengths is optimized to enhance magnetic flux and minimize mass and material usage, using ferrite magnets and a stack of sheet materials for the carcass and cylinder head.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If the motor size and mass are reduced to meet compactness constraints, then the motor can be more compact and lightweight, but the nominal performance (torque and efficiency) may deteriorate
Solution Approach 1:
The patent changes the geometric parameters of the motor, specifically setting the rotor axial length to be greater than the stator teeth axial length with a ratio between 1.2 and 1.3. This parameter optimization allows the motor to maintain nominal performance while reducing overall size and mass, directly resolving the contradiction between compactness and performance
Solution Approach 2:
The patent utilizes the axial dimension more effectively by extending the rotor length beyond the stator teeth length. This dimensional approach creates a three-dimensional magnetic flux path that enhances torque production in a compact radial space, allowing performance maintenance while reducing motor mass
2Power
If the rotor axial length is increased to improve magnetic flux and torque, then the motor performance is improved, but the motor length increases
Solution Approach 1:
The patent optimizes the rotor-to-stator-teeth length ratio to be between 1.2 and 1.3, which maximizes torque production while limiting the axial length increase. This precise parameter control ensures that the rotor extends just enough to create effective three-dimensional magnetic flux without excessive lengthening
Solution Approach 2:
The patent applies different functional qualities to different axial regions: the portion of the rotor extending beyond the stator teeth (approximately 20-30% of rotor length) is optimized for generating three-dimensional magnetic flux, while the remaining portion maintains traditional two-dimensional flux patterns. This localized functional differentiation achieves high torque in a compact length
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 solution achieves reduced size and mass while maintaining or exceeding nominal torque and efficiency, allowing for higher power density and compactness, and is suitable for electric compressors in air conditioning systems, addressing the constraints of size, mass, and performance.
Implementation Method 1
a wound stator comprising stator teeth extending axially, formed in a carcass and a rotor comprising a plurality of these magnets extending axially
Implementation Method 2
a first contribution of a three-dimensional magnetic flux between the stator teeth and the rotor
Implementation Method 3
a first contribution of a three-dimensional magnetic flux between the stator teeth and the rotor is substantially equal to or greater than a second contribution of a two-dimensional magnetic flux
Data Source
Figure 1a~1b
Figure 2~3
Figure 4
AI summary
The synchronous electric motor with permanent magnets comprising a wound stator (1) comprising stator teeth extending axially formed in a frame and a rotor (5) comprising a plurality of said magnets extending axially into a cylinder head (6), being embedded according to a flux concentration construction of said rotor (5) in which a first length (Ls1) of said rotor (5) is greater than a second length (Ls1) of said stator teeth and in which a ratio of said first length (Ls1) to said second length (Ls2) is lower than 1.3. The compressor is characterised in that it comprises such an electric motor.