Brushless Motor Conduction Angle Adjustment for Torque-Speed Trade-off
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Solution Overview
Problem
Electric power tools with three-phase brushless motors face a challenge in simultaneously achieving high speed and high torque, as these performance metrics are often conflicting requirements.
Innovation Solution
The conduction angle of the three-phase brushless motor is set between 130 degrees and 180 degrees, allowing the motor driver to adjust this angle based on load conditions, enabling the tool to operate at high speed or high torque depending on the application, while also optimizing electrical efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the conduction angle is set to 120 degrees (conventional setting), then the motor produces high output torque, but the rotational speed per unit time is reduced
Solution Approach 1:
The patent applies dynamics by making the conduction angle adjustable rather than fixed. The motor driver can dynamically change the conduction angle between 120 degrees and 180 degrees based on operational requirements, allowing the system to adapt between high torque and high speed modes as needed
Solution Approach 2:
The patent directly changes the electrical parameter (conduction angle) of the motor control system. By varying this parameter from the conventional 120 degrees up to 180 degrees, the system can shift the motor's characteristic curve to achieve either high torque or high rotational speed depending on the workload requirements
2Speed
If the conduction angle is increased to 180 degrees, then the rotational speed per unit time is maximized, but the output torque is reduced
Solution Approach 1:
The system uses dynamic adjustment of the conduction angle to respond to changing operational demands. When high speed is required, the angle is increased toward 180 degrees; when high torque is needed, it is reduced toward 120 degrees, providing adaptive performance
Solution Approach 2:
The patent utilizes parameter changes by adjusting the conduction angle within the range of 120-180 degrees. This continuous or discrete adjustment of the electrical control parameter enables the motor to operate across different performance characteristics, balancing speed and torque based on actual needs
3Device complexity
If a fixed conduction angle of 120 degrees is used, then the motor design is simple, but the tool cannot adapt to different work requirements (high speed vs. high torque)
Solution Approach 1:
The patent implements dynamics by introducing an adjustable conduction angle mechanism controlled by a motor driver. This allows the originally simple 120-degree fixed system to become dynamically adaptable, switching between different conduction angles to match varying workload requirements while maintaining reasonable control complexity
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 the electric power tool to effectively balance speed and torque requirements, improving operational efficiency and adaptability to different workloads, and preventing overheating by adjusting the conduction angle based on detected conditions.
Implementation Method 1
a three-phase brushless motor for driving a tool
Data Source
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AI summary
An electric power tool is provided with a three-phase brushless motor that drives a tool and a motor driver that drives the three-phase brushless motor with square voltage waves. The motor driver is able to set a conduction angle to a value that is equal to or more than 130 degrees but not more than 180 degrees, and especially to change the conduction angle among at least two values that are equal to or more than 130 degrees but not more than 180 degrees. In this configuration, it may be preferable that the conduction angle is set to a larger value as a load applied to the tool becomes smaller. On the other hand, it may be also preferable that the conduction angle is set to a larger value as a load applied to the tool becomes smaller.