Variable Magnetomotive Force Rotary Electric Machine Magnetic Circuit Design
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Solution Overview
Problem
Existing rotary electric machines require expensive high-coercivity magnets and suffer from inefficient magnetic-field control and demagnetization issues, especially in high-load zones, where reluctance torque opposes magnet torque, leading to reduced efficiency.
Innovation Solution
A variable magnetomotive force rotary electric machine design featuring a stator and rotor with permanent magnets and magnetic gaps, where the d-axis magnetic flux bypasses through areas other than the magnets, providing controlled magnetic resistance and allowing for complete magnetization with lower-coercivity magnets, maintaining magnetization even in high-load conditions without expensive materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high-coercivity magnets (adding Dy to Nd-Fe-B alloy) are used to achieve strong magnetic-field control, then weak magnetic-field control is improved, but cost increases significantly
Solution Approach 1:
The patent changes the magnetic circuit parameters by introducing a magnetic gap part in the q-axis magnetic path and a d-axis bypass, which modifies the magnetic resistance characteristics. This allows the use of lower-coercivity magnets while achieving the required magnetic-field control through parameter optimization rather than material substitution
Solution Approach 2:
The patent replaces expensive high-coercivity magnets with cheaper low-coercivity magnets by compensating for the reduced magnetic strength through magnetic circuit design modifications, specifically the magnetic gap part and d-axis bypass structure
2Ease of manufacture
If low-coercivity magnets are used to reduce cost, then manufacturing cost decreases, but magnets become irreversibly demagnetized in high-load states
Solution Approach 1:
The patent applies preliminary anti-action by designing the magnetic circuit with a magnetic gap part in the q-axis magnetic path that prevents demagnetization before it occurs. The magnetic gap creates a controlled magnetic resistance that protects the low-coercivity magnets from irreversible demagnetization under high-load conditions
Solution Approach 2:
The magnetic gap part acts as an intermediary element between the permanent magnets and the stator, mediating the magnetic flux distribution and protecting the magnets from excessive armature reaction that would cause demagnetization
3Ease of manufacture
If Ld < Lq in rotary electric machine design, then manufacturing is simplified, but reluctance torque occurs in opposite direction from magnet torque, deteriorating efficiency in high-load zones
Solution Approach 1:
The patent changes the inductance parameters by creating Ld > Lq characteristics through the d-axis bypass and magnetic gap part design, which reverses the traditional Ld < Lq configuration. This parameter change ensures that reluctance torque acts in the same direction as magnet torque, improving efficiency
4Reliability
If magnetic gap part is added to q-axis magnetic path, then magnetization is maintained in high-load states, but device complexity increases
Solution Approach 1:
The patent segments the magnetic circuit into distinct paths: a q-axis magnetic path with a magnetic gap part and a d-axis magnetic path with a bypass. This segmentation allows independent optimization of each magnetic path to achieve both magnetization maintenance and simplified control
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 achieves stable torque production without high-coercivity magnets, reduces costs, and enhances efficiency by aligning reluctance torque with magnet torque, maintaining magnetization and reducing energy losses.
Implementation Method 1
The d-axis bypass provides a magnetic resistance in a d-axis direction that is set below a magnetic resistance in a q-axis direction that is orthogonal to the d-axis resistance
Implementation Method 2
The permanent magnet has a coercivity providing for complete magnetization by a magnetic field equal to or less than an armature reaction that is produced by a power-supplying inverter
Data Source
Figure 1
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AI summary
A rotary electric machine includes a stator and a rotor. The rotor has at least one permanent magnet arranged in a d-axis magnetic path. The rotor includes a magnetic gap part located between the permanent magnet arranged in the d-axis magnetic path of one pole and an adjacent magnet with a different polarity, such that a d-axis magnetic flux forms a d-axis bypass passing through an area other than the permanent magnet. The d-axis bypass provides a magnetic resistance in a d-axis direction that is set below a magnetic resistance in a q-axis direction that is orthogonal to the d-axis resistance.