Permanent Magnet Motor Air Pockets Reduce Torque Ripple
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Solution Overview
Problem
Conventional permanent magnet electric motors for vehicles face challenges with high noise/vibration/harshness (NVH), torque ripple, and total harmonic distortion (THD), which compromise their ability to generate high drive torque continuously, often requiring costly design modifications that increase size and weight.
Innovation Solution
A permanent magnet electric motor design featuring a stator with alternating full and partial-width slots and a rotor with strategically placed air pockets, optimizing magnetic flux and reducing harmonic distortion, allowing for improved torque output and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If permanent magnet electric motors are designed to generate high drive torque continuously, then drive torque capability is improved, but voltage total harmonic distortion increases
Solution Approach 1:
The rotor is segmented into multiple poles (M poles) with permanent magnet assemblies distributed around the circumference, creating a multi-pole magnetic field configuration that reduces harmonic distortion while maintaining high torque output capability
Solution Approach 2:
Different regions of the motor are given different properties: the stator uses specific slot configurations (N slots with N/2 apertures) and the rotor uses V-shaped permanent magnet assemblies with specific air gap distances, optimizing local magnetic field distribution to reduce THD while maintaining high drive torque
2Object-generated harmful factors
If design modifications are made to mitigate voltage total harmonic distortion, then THD is reduced, but maximum drive torque is reduced
Solution Approach 1:
The motor uses specific parameter combinations: N slots in the stator, M poles in the rotor, V-shaped permanent magnet assemblies with specific angles, and controlled air gap distances, which together optimize the magnetic field to reduce THD while preserving high drive torque capability
3Power
If motor size is increased to compensate for reduced drive torque, then drive torque capability is maintained, but cost and weight increase
Solution Approach 1:
The motor combines permanent magnets with V-shaped configurations arranged in multi-pole assemblies, creating a composite magnetic field structure that achieves high drive torque density without increasing motor size, thereby avoiding additional weight and cost
4Reliability
If conventional permanent magnet electric motors are used, then they work well for their intended purpose, but noise/vibration/harshness characteristics are poor
Solution Approach 1:
The motor design actively addresses vibration through its magnetic field configuration: the V-shaped permanent magnet assemblies and multi-pole arrangement create a more uniform magnetic field that reduces magnetic pulsations and associated mechanical vibrations, improving NVH characteristics while maintaining reliability
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 motor achieves reduced torque ripple and THD, maintaining high drive torque levels while minimizing noise and vibration, with approximately 133 Nm at base speed and 51 Nm at maximum speed, along with low harmonic distortion, enhancing overall performance and efficiency.
Implementation Method 1
A permanent magnet electric motor is a type of electric motor that uses permanent magnets rather than electromagnetic coils
Implementation Method 2
the motor comprises: a stator comprising a round wire defining N portions and a stator lamination defining an inner surface, N slots, and N/2 apertures
Implementation Method 3
at least three sets of air pockets disposed proximate to the respective permanent magnet assembly
Implementation Method 4
the second and third air pockets act as a flux barrier and an optimizing flux path
Data Source
AI summary
A permanent magnet electric motor for a vehicle comprises a stator comprising a round wire defining N portions and a stator lamination defining an inner surface, N slots, and N/2 alternating, full-slot-width apertures in the inner surface, wherein the N portions of the round wire are disposed in the N slots, respectively, and a rotor comprising M permanent magnet assemblies defining M respective poles, each of the M permanent magnet assemblies comprising a pair or bar magnets arranged in a V-shaped configuration with respect to each other, wherein N equals 6 and M equals 4 or N and M equal respective double multiples thereof, and a rotor lamination having the M permanent magnet assembles disposed therein and defining, for each of the M permanent magnet assemblies, at least three sets of air pockets disposed proximate to the respective permanent magnet assembly.