Rotor Slit Orientation for PMSM Torque Ripple Reduction
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Solution Overview
Problem
Existing permanent magnet synchronous motors with embedded magnets suffer from high vibration and noise due to large harmonic components in electromotive force, and inefficiencies such as increased iron loss and ineffective magnetic flux utilization, while complex slit designs in other motors increase process costs and reduce efficiency.
Innovation Solution
A permanent magnet synchronous motor design featuring a stator and rotor with magnetic steel plate cores, concentrated windings, and strategically oriented slits that optimize magnetic flux usage, reducing harmonic components and enhancing efficiency, vibration, and noise control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If permanent magnets are embedded in a cylindrical rotor core with slits elongated from the outer circumferential side, then torque ripple is reduced, but harmonic components in electromotive force increase causing vibration and noise
Solution Approach 1:
The patent applies local quality by differentiating the slit orientations in different regions of the rotor core. Slits in the pole center region are oriented differently from slits in the pole border region, allowing each region to optimize its magnetic flux distribution locally. This regional differentiation reduces harmonic components in the electromotive force while maintaining torque stability.
Solution Approach 2:
The patent introduces asymmetry by orienting slits at different angles in different regions. Specifically, slits in the pole center region have one orientation while slits in the pole border region have a different orientation, creating an asymmetric slit configuration that balances magnetic flux distribution and reduces harmonic distortion.
2Object-generated harmful factors
If complicated slit shapes are used to reduce harmonic components, then vibration and noise decrease, but process costs increase
Solution Approach 1:
The patent segments the rotor core into distinct regions (pole center region and pole border region) with different slit configurations. This segmentation allows each region to be optimized independently for reducing harmonic components while maintaining manufacturing simplicity through standardized slit formation processes in each zone.
Solution Approach 2:
By applying different slit orientations to different regions rather than using a complex uniform pattern throughout, the patent achieves harmonic reduction through localized structural variations that are simpler to manufacture than a completely complex unified design.
3Ease of manufacture
If uniform slit pitches are used in end portions, then manufacturing is simplified, but magnetic flux of permanent magnets in end portions is not effectively utilized
Solution Approach 1:
The patent applies different slit pitch characteristics to different regions: uniform pitches in end portions for manufacturing simplicity, and varied pitches in inner portions for optimal magnetic flux utilization. This local differentiation allows each region to optimize its properties for its specific functional requirements.
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
The design achieves a highly efficient motor with reduced vibration and noise by effectively utilizing magnetic flux, minimizing copper loss, and approximating the electromotive force waveform to a sine wave, thereby improving motor efficiency and reducing costs.
Implementation Method 1
the permanent magnets; and a plurality of slits formed in the rotor core on an outer circumferential side of the magnet retaining holes
Implementation Method 2
The stator windings are provided in the slots of the stator core
Implementation Method 3
slits in a vicinity of a magnetic pole center of the rotor core are oriented in a direction toward a point in a line of the magnetic pole center by a permanent magnet converges outside the rotor core
Data Source
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AI summary
It is an objective to provide a permanent magnet synchronous motor that is highly efficient with low vibration and low noise. A stator 30 includes a stator core 1 that includes magnetic pole teeth 2 each formed between adjacent slots 3, and stator windings 4 that are provided in the slots 3 of the stator core 1. A rotor 40 includes a rotor core 5, a plurality of magnet retaining holes 8, permanent magnets 7 inserted in the magnet retaining holes 8, and a plurality of slits 6 in the rotor core 5 on an outer circumferential side of the magnet retaining holes 8. Among the slits 6, slits 6 in a vicinity of a magnetic pole center of the rotor core 1 are oriented in a direction where a magnetic flux generated by a permanent magnet 7 converges outside the rotor core 1, whereas slits 6 in a vicinity of a pole border portion of the rotor core 5 are oriented in another direction that is different from the direction of the plurality of slits 6 in the vicinity of the magnetic pole center of the rotor core 5.