Rotor Core Bridge Geometry for Wide-Range Torque Pulsation Reduction
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Solution Overview
Problem
Conventional rotating electric machines experience torque pulsations due to magnetic saturation in the d-axis core portion, which varies with load states, making it difficult to reduce torque pulsations across a wide operating range.
Innovation Solution
The rotor core is designed with magnet insertion holes and d-axis cores on either side, featuring different distances and cross-sectional shapes to maintain consistent magnetic flux distribution, reducing magnetic saturation and torque pulsations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a conventional rotor core design is used, then the structure is simple, but magnetic saturation occurs in the d-axis core portion causing torque pulsation that varies with load state
Solution Approach 1:
The patent applies local quality by making the d-axis core portions have different cross-sectional shapes at different locations. Specifically, the d-axis core portions are designed with different circumferential widths, and the bridge portions connecting them have different thicknesses, creating localized magnetic path variations that prevent uniform magnetic saturation across the rotor core.
Solution Approach 2:
The patent employs asymmetry by intentionally designing the rotor core with non-uniform d-axis core portions and bridge portions. The asymmetric configuration ensures that magnetic flux distribution is non-uniform, preventing the d-axis core portions from entering magnetic saturation simultaneously, thereby reducing torque pulsation across different load states.
2Reliability
If the d-axis core portion is made larger to reduce magnetic saturation, then magnetic flux capacity increases, but the rotor core becomes more complex and manufacturing difficulty increases
Solution Approach 1:
The patent applies segmentation by dividing the rotor core into distinct components: d-axis core portions and bridge portions. This segmentation allows for optimized magnetic flux paths while maintaining manufacturability, as each segment can be designed and manufactured independently with standard processes.
Solution Approach 2:
The patent uses parameter changes by varying the geometric parameters of the d-axis core portions and bridge portions. Specifically, the circumferential widths and thicknesses are adjusted to optimize magnetic flux distribution, achieving reliable performance without excessive complexity in manufacturing.
3Reliability
If torque pulsation is reduced at one load state, then performance is optimized for that condition, but torque pulsation increases at other load states
Solution Approach 1:
The patent applies local quality by creating different magnetic path characteristics at different locations in the rotor core. The varied cross-sectional shapes of d-axis core portions and bridge portions ensure that magnetic saturation occurs at different levels across the rotor, providing consistent torque pulsation reduction across multiple load states and expanding the effective operating range.
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 effectively reduces torque pulsations across a wide operating range, minimizing noise and vibration in electric vehicles.
Implementation Method 1
a leakage magnetic flux of a permanent magnet passes through a d-axis core portion close to an end of the permanent magnet
Implementation Method 2
the d-axis core portion is magnetically saturated
Implementation Method 3
a q-axis magnetic flux caused by a q-axis current of a motor passes through a d-axis core portion of the permanent magnet
Data Source
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AI summary
To provide a rotating electric machine that can reduce torque pulsation in a wide operating range. A rotating electric machine includes a stator and a rotor having a rotor core. The rotor core includes a d-axis core (41) and an inner circumferential side core disposed on an outer circumferential side and an inner circumferential side of the magnet insertion hole, respectively, and a q-axis core (46) adjacent to the d-axis core. The d-axis core is coupled to the inner circumferential side core by a first bridge portion (61) and a second bridge portion (62) adjacent to both ends of the magnet insertion hole. A distance L1 between an end of the d-axis core on the first bridge portion side and a magnetic pole center (C) is larger than a distance L2 between a connection portion between the first bridge portion and the d-axis core and the magnetic pole center. A distance L3 between an end of the d-axis core on the second bridge portion side and the magnetic pole center is larger than a distance L4 between a connection portion between the second bridge portion and the d-axis core and the magnetic pole center. The rotor core has multiple types of cross-sectional shapes for a one-pole pitch angle τp.