Two-Layer Rotor Permanent Magnet Angles Torque Ripple
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Solution Overview
Problem
Interior permanent magnet motors experience torque ripple and noise issues at high speeds, particularly due to frequency components corresponding to 6 times the pole number, which contribute to noise, vibration, and harshness in green vehicles, and reducing torque ripple can worsen total harmonic distortion and increase maximum current.
Innovation Solution
A rotor with a two-layered structure formed by inserting at least two permanent magnets into the rotor core, where the polar arc angles of the upper and lower permanent magnet groups are set to be different, specifically with first and second polar arc angles of 14° and 2° for the upper group and 19.6° and 1.85° for the lower group, respectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If torque ripple is reduced by adjusting permanent magnet configuration, then noise and vibration are reduced, but total harmonic distortion increases and maximum current increases
Solution Approach 1:
The rotor is divided into two distinct layers: an upper permanent magnet layer and a lower permanent magnet layer. Each layer has its own polar arc angle configuration, allowing independent optimization of torque ripple reduction while maintaining acceptable harmonic distortion and current characteristics.
Solution Approach 2:
Different polar arc angles are assigned to different regions (upper and lower layers) of the rotor. The upper permanent magnet layer has a first polar arc angle, while the lower permanent magnet layer has a second polar arc angle, creating local quality variations that reduce torque ripple without excessively increasing harmonic distortion.
2Device complexity
If a single-layer permanent magnet structure is used, then the structure is simple, but torque ripple and noise at high speeds cannot be effectively reduced
Solution Approach 1:
The rotor structure transitions from a single-layer configuration to a two-layer configuration, adding a vertical dimension to the permanent magnet arrangement. This dimensional change enables independent control of magnetic field distribution in different zones, effectively reducing torque ripple and high-speed noise.
Solution Approach 2:
The permanent magnet structure is segmented into two separate layers with distinct polar arc angles. This segmentation allows each layer to contribute differently to the overall magnetic field, creating a composite effect that reduces torque ripple while maintaining manageable structural complexity.
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
Significantly reduces torque ripple components corresponding to the 6th-order frequency while maintaining motor performance, minimizing noise and vibration at high speeds without significantly affecting total harmonic distortion or increasing maximum current.
Implementation Method 1
An upper permanent magnet group is configured to be inserted into the rotor core to form a magnetic pole. A lower permanent magnet group is configured to be inserted into the rotor core below the upper permanent magnet group to form a two-layered structure with the upper permanent magnet group.
Data Source
AI summary
A rotor of an interior permanent magnet motor includes a rotor core configured to form a body of the rotor. An upper permanent magnet group is configured to be inserted into the rotor core to form a magnetic pole. A lower permanent magnet group is configured to be inserted into the rotor core below the upper permanent magnet group to form a two-layered structure with the upper permanent magnet group. Each of the upper and lower permanent magnet groups may include two V-shaped permanent magnets. A polar arc angle formed by the two permanent magnets of the upper permanent magnet group may be different from a polar arc angle formed by the permanent magnets of the lower permanent magnet group.