Electric motor, compressor, and refrigerating cycle apparatus
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Solution Overview
Problem
High-Br magnets used in electric motors are prone to magnetic saturation and demagnetization, leading to reduced efficiency and increased torque pulsation, despite magnetic flux-weakening control methods.
Innovation Solution
The electric motor design incorporates a rotor with grain boundary diffusion type magnets and a stator with teeth windings, where the total area of stator core cross-sections is optimized to be between 0.56 and 0.93 times the area of magnet surfaces, reducing demagnetization and magnetic saturation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If high-Br magnets are used to increase power density, then motor power and compactness are improved, but magnetic saturation occurs more frequently leading to reduced efficiency
Solution Approach 1:
The patent changes the geometric parameters of the motor, specifically optimizing the ratio between the stator core cross-sectional area and magnet surface area, and adjusting the air gap length. These parameter changes allow the use of high-Br magnets while preventing magnetic saturation, thereby maintaining high efficiency and power density simultaneously
2Volume of moving object
If high-Br magnets are used to increase power density, then motor compactness is improved, but torque pulsation increases due to magnetic saturation
Solution Approach 1:
The patent optimizes geometric parameters including the stator core cross-sectional area to magnet surface area ratio and air gap length. These parameter changes suppress spatial and temporal harmonics in the magnetic flux density distribution, reducing torque pulsation while maintaining compact motor volume
3Loss of energy
If magnetic flux-weakening control is applied to reduce iron loss, then efficiency is improved in certain operating regions, but demagnetization risk increases
Solution Approach 1:
The patent preliminarily optimizes the motor's geometric parameters (stator core area to magnet surface area ratio and air gap length) during design to prevent magnetic saturation under normal operating conditions. This preliminary action reduces the need for aggressive magnetic flux-weakening control, thereby protecting the magnets from demagnetization while maintaining efficiency
4Loss of energy
If the stator core cross-sectional area is increased to prevent magnetic saturation, then magnetic saturation is reduced, but motor compactness deteriorates
Solution Approach 1:
The patent optimizes the ratio between stator core cross-sectional area and magnet surface area, and adjusts the air gap length to achieve the optimal balance. This allows sufficient stator core area to prevent magnetic saturation while maintaining compact motor volume through coordinated parameter optimization
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 enhances motor efficiency, reduces demagnetization risk, and minimizes motor loss, while maintaining high power density and compactness.
Implementation Method 1
a rotor having magnets of a grain boundary diffusion type and a rotor core in which insertion holes, into which the magnets are inserted, are formed circumferentially; and a stator having windings and a stator core in which teeth, around which the windings are wound, are formed circumferentially
Data Source
AI summary
A stator of an electric motor (40) has windings (44) and a stator core (43) in which eighteen teeth (71), around which the windings (44) are wound, are formed circumferentially. A rotor of the electric motor (40) has magnets (72) and a rotor core (46) in which six insertion holes (73), into which the magnets (72) are inserted, are formed circumferentially. The magnets (72) are rare-earth magnets of a grain boundary diffusion type having a residual magnetic flux density Br of from 1.36 to 1.42 T. The total area of magnet-parallel cross-sections (84) of the teeth (71) is from 0.56 times to 0.93 times the total area of tooth-facing surfaces (83) of the magnets (72).