Brushless Motor Skew Angle Optimization for Torque Ripple
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Solution Overview
Problem
Brushless motors face challenges in achieving low torque ripple and high output simultaneously while maintaining easy control, as increasing skew angle to reduce torque ripple decreases motor torque and increases control complexity due to the need for short control cycles with high-order harmonic components.
Innovation Solution
A brushless motor with a 2P3S×n structure, featuring a stator with 2n slots and a rotor with 3n magnetic poles, where the fifth harmonic component in the induced voltage is set between 4.5% to 6.5% of the fundamental wave, and the skew angle is between 36° to 57° electrical, along with a magnet ratio of 0.76<W=Wm/Wp<0.86, to optimize torque and rotation speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If the skew angle is increased to reduce torque ripple, then the torque ripple is reduced, but the motor torque is reduced
Solution Approach 1:
The patent optimizes the skew angle parameter to a specific range (36° to 57° electrical) and sets the fifth harmonic component content ratio to 4.5%-6.5% to simultaneously achieve low torque ripple and maintain high motor torque, resolving the contradiction between torque ripple reduction and torque maintenance through precise parameter control
2Object-generated harmful factors
If high-order harmonic components are contained in the control current to reduce torque ripple, then the torque ripple is reduced, but the control cycle must be set extremely short increasing control complexity
Solution Approach 1:
The patent extracts and focuses only on the fifth harmonic component rather than using multiple high-order harmonic components, setting its content ratio to 4.5%-6.5%. This selective approach reduces torque ripple while avoiding the need for extremely short control cycles, thereby simplifying the control system
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 allows for increased torque and rotation speed while reducing torque ripple and facilitating control, enabling longer control cycles and reducing the load and cost of the control system.
Implementation Method 1
a rotor having 3n magnetic poles, the brushless motor being rotatingly driven by a three-phase driving current
Data Source
AI summary
A brushless motor has a 2P3S×n structure, in which a ratio (W) of a circumferential width (Wm) of each of magnets to a length (Wp) of a chord formed between endpoints of an arc with a center angle θp=360°/pole-number 3n, the arc being included in an inner-diameter circle C2 of each of the magnets, is in a range of 0.76<W=Wm/Wp<0.86. Therefore, in the brushless motor of the 2P3S×n structure, a skew angle may be set in a range of 36°≦θskew≦57° in terms of electrical angle, while a content ratio of a fifth harmonic component contained in an induced voltage of the brushless motor may be set in a range of 4.5% to 6.5% with respect to a fundamental wave.