Stator Tooth Recesses for Harmonic Reduction in Electric Machines
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Solution Overview
Problem
Brushless electric machines with concentrated windings suffer from numerous harmonic components of the magnetomotive force, leading to iron losses, acoustic impairments, and vibrations, which reduce efficiency and cause unwanted vibrations during operation.
Innovation Solution
The electric machine incorporates recesses in the stator teeth to reduce undesired harmonic components, specifically by creating a mechanical barrier that attenuates the fundamental wave and enhances the operating wave, thereby increasing nominal torque and efficiency without significant additional manufacturing effort.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If concentrated windings are used in brushless electric machines, then compact design and high winding factors are achieved, but numerous harmonic components of the magnetomotive force are generated causing iron losses and vibrations
Solution Approach 1:
The stator teeth are segmented by introducing recesses that divide the continuous tooth structure into separate regions. This segmentation creates magnetic barriers that interrupt the flux paths, effectively reducing the harmonic components generated by concentrated windings while preserving the compact design benefits.
Solution Approach 2:
The recesses are strategically positioned in specific regions of the stator teeth where harmonic reduction is most needed. By creating local variations in the magnetic path properties (differentiating between regions with and without recesses), the solution selectively attenuates harmful harmonics while maintaining the overall compact structure and high winding factors of concentrated windings.
2Loss of energy
If recesses are added to stator teeth to reduce harmonic components, then iron losses and vibrations are reduced, but manufacturing complexity increases
Solution Approach 1:
The recesses modify the geometric parameters of the stator teeth by creating controlled voids or reductions in tooth material. This parameter change alters the magnetic circuit properties, reducing iron losses by minimizing flux density variations and harmonic content, while the relatively simple geometric modification keeps manufacturing complexity manageable.
3Object-generated harmful factors
If recesses are introduced in stator teeth, then fundamental wave of magnetic flux is attenuated, but operating wave can be enhanced through proper recess design
Solution Approach 1:
The recesses, which initially appear to harmfully attenuate the fundamental wave, are designed to convert this attenuation into a benefit by selectively reducing harmful harmonics while preserving or even enhancing the operating wave through constructive interference patterns and optimized flux distribution in the modified tooth structure.
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 solution significantly reduces undesired harmonic waves, enhancing machine efficiency, reducing acoustic impairments and vibrations, and increasing the operating wave, resulting in improved torque performance.
Implementation Method 1
the recess forms a mechanical barrier for reducing the fundamental wave of the magnetic flux in the tooth area
Data Source
AI summary
The invention relates to an electric machine comprising a stator and a rotor moveable relative to the stator. The stator has slots for accommodating electrical windings, wherein teeth of the stator are formed between adjacent slots. During operation of the machine, an operating wave of the magnetomotive force is different from a fundamental wave of the magnetic flux. The stator comprises at least one recess which is arranged in the tooth region and extends substantially in the radial direction.