BLDC Machine Eight-Switch Controller Torque Ripple Reduction
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Solution Overview
Problem
Conventional BLDC machines with six power electronic switches suffer from torque ripples due to six stable positions of the magnetic field, resulting in reduced average torque, which is inadequate for small vehicles, necessitating a larger machine size.
Innovation Solution
A BLDC machine with eight power electronic switches, where two switches are connected in series between the power supply and four configurations are repeated, with the middle portion of the fourth configuration connected to the neutral point of the star winding, allowing for finer steps of the rotating magnetic field, increasing average torque without altering peak torque.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a conventional BLDC machine with six power electronic switches is used, then the machine structure is simple, but the average torque is reduced due to six torque ripples in one mechanical revolution
Solution Approach 1:
The patent segments the switching sequence into finer intervals by introducing an additional switch configuration. Instead of switching at six stable positions per mechanical revolution, the system now switches at eight positions, creating more granular control segments that reduce torque ripple magnitude and increase average torque output.
Solution Approach 2:
The patent changes the switching frequency parameter by adding two more switching events per mechanical revolution (from six to eight positions). This parameter change modifies the torque waveform characteristics, reducing ripple amplitude and increasing the area under the torque curve, thereby increasing average torque without fundamentally changing the machine structure.
2Power
If the machine size is increased to meet load-torque requirements, then the average torque can be increased, but the machine cannot be placed in small sized vehicles
Solution Approach 1:
The patent changes the control parameter of switching positions from six to eight per mechanical revolution. This parameter modification increases the duty cycle of torque-producing intervals and reduces the depth of torque ripples, thereby increasing average torque output from the same machine size, eliminating the need to scale up machine dimensions.
3Device complexity
If six switching positions are used per mechanical revolution, then the control system is simple, but the torque waveform has six ripples that reduce average torque
Solution Approach 1:
The control system segments the switching cycle into eight positions instead of six, creating finer control intervals. This segmentation allows for more precise control of current commutation timing, reducing the overlap and gap periods that cause torque ripples, thereby increasing average torque with only moderate increase in control complexity.
Solution Approach 2:
The patent introduces dynamic switching position adjustment by adding intermediate switching positions between the traditional six stable positions. This dynamic approach allows the controller to optimize switching timing for maximum torque production throughout the entire mechanical revolution, reducing ripple effects and increasing average torque output.
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 enables a compact BLDC machine to achieve higher average torque, meeting higher load torque requirements and enabling smaller machine sizes suitable for small vehicles while maintaining peak torque performance.
Implementation Method 1
An electric machine is usually composed of stator and rotor... for a BLDC machine having a star winding configuration, and the controller used for such machines are also equipped with six power electronic switches that control the current through three phases of the machine
Implementation Method 2
An electric machine is usually composed of stator and rotor... This results in six stable positions for the magnetic field causing six ripples in a torque waveform
Data Source
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AI summary
The present invention relates an electric machine of a vehicle (100), and more particularly, the present invention relates to a controller equipped with switches for the electric machine of a vehicle (100). The rotating magnetic field is created in steps of 60⁰ electrical angles, which results in rotor torque selected as a combination of 60⁰ of the torque versus angle waveform, which has a peak torque resulting in six repeated torque waveforms. By the present configuration, it is possible to increase the lowest torque of the output torque waveform, which in turn increases the average torque of the rotor and still keeping the peak torque same.