PMSM Rotor Magnet Recess Layout for Higher d-Axis Inductance
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Solution Overview
Problem
Conventional permanent magnet synchronous electric motors face challenges in effectively increasing the d-axis inductance (Ld) due to displacement issues in the d-axis position when a stage skew structure is applied, which hinders efficient flux-weakening control and torque output during high-speed rotation.
Innovation Solution
The design includes a rotor core with protruding portions and recessed portions in the permanent magnets, where the distances between specific ends of the magnets and recessed portions (L1 and L2) are unequal (L1≠L2), aligned in a circumferential direction with a skew angle, enhancing d-axis inductance and enabling efficient flux-weakening control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If protrusions are formed at the center of magnetic poles with mirror symmetrical shape, then the d-axis inductance is increased, but torque ripple increases when stage skew structure is applied
Solution Approach 1:
The patent applies asymmetry by positioning the protrusion at an offset position from the center of the magnetic pole along the circumferential direction, rather than at the center. This asymmetric positioning allows the protrusion to effectively increase the d-axis inductance while avoiding the torque ripple issues that arise from symmetric center positioning when stage skew structure is applied to the rotor.
2Object-generated harmful factors
If a stage skew structure is applied to reduce torque ripple, then torque ripple is reduced, but the d-axis position displacement prevents effective increase of d-axis inductance
Solution Approach 1:
The patent applies local quality by creating a localized protrusion structure on the rotor core at a specific offset position from the magnetic pole center. This local structural modification increases the d-axis inductance in the critical region without requiring global changes to the rotor structure, thereby maintaining compatibility with the stage skew structure while effectively increasing the d-axis inductance.
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 increases d-axis inductance, allowing for improved torque output and reduced torque ripple during high-speed rotation, thereby enhancing the motor's performance.
Implementation Method 1
a terminal voltage generated by the electric motor needs to be equal to or lower than an input voltage
Implementation Method 2
a torque T generated by a surface magnet type permanent magnet synchronous electric motor
Implementation Method 3
the d-axis inductance Ld is increased to effectively function the flux-weakening control
Data Source
AI summary
A permanent magnet synchronous electric motor includes a stator, a rotor, and a plurality of permanent magnets. Each of the plurality of permanent magnets has a first magnet end and a second magnet end in a circumferential direction. A recessed portion of each of the plurality of permanent magnets has a first recessed-portion end and a second recessed-portion end in the circumferential direction. L1≠L2 is satisfied provided that a distance between the first magnet end and the first recessed-portion end is L1 and a distance between the second magnet end and the second recessed-portion end is L2.