Power Tool Motor Commutation Control at Expanded Conduction Angles
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Solution Overview
Problem
Existing electric motor control systems face issues with inaccurate commutation point detection, leading to commutation lag and system failures, particularly when the conduction angle is expanded beyond 120°, causing the floating phase to be submerged during commutation.
Innovation Solution
A power tool with a controller that accurately detects the commutation point by monitoring phase voltage and current, adjusting the conduction angle of the stator windings, and adapting the conduction manner based on load conditions to prevent commutation lag and system failures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the conduction angle of the electric motor windings is expanded beyond 120° to increase rotational speed, then the rotational speed is improved, but the commutation point detection accuracy deteriorates, causing commutation lag and system failures
Solution Approach 1:
The controller predicts the ideal commutation point in advance based on the electrical angle and rotational speed of the motor. By calculating the expected commutation timing before it occurs, the system compensates for detection delays and ensures accurate commutation control even when the conduction angle is expanded beyond 120°.
Solution Approach 2:
The system continuously monitors the actual commutation point detection status and compares it with the predicted ideal commutation point. Based on this feedback, the controller adjusts the commutation timing to eliminate lag and maintain precise control under expanded conduction angle conditions.
2Speed
If the conduction angle is increased to more than 150° to improve field weakening and rotational speed, then the rotational speed is improved, but the floating phase may be submerged during commutation, causing system failure
Solution Approach 1:
The controller calculates and determines the ideal commutation point in advance based on the expanded conduction angle and motor operating conditions. By preparing the commutation timing beforehand, the system ensures that the floating phase does not get submerged during commutation, maintaining system reliability even at conduction angles exceeding 150°.
Solution Approach 2:
The system takes preliminary measures to prevent floating phase submersion by predicting potential commutation issues and adjusting the commutation timing in advance. This proactive approach counteracts the harmful effect of floating phase submersion before it can occur, ensuring stable operation at high conduction angles.
Data Source
Figure 1A~1C
Figure 2
Figure 3~4
AI summary
Provided is a power tool and a control method thereof. The power tool includes an electric motor including a rotor and three-phase stator windings, where the stator windings have a certain electrical conduction angle when the electric motor operates; a driver circuit having multiple semiconductor switching elements; a parameter detection module configured to detect a working parameter of the operating electric motor; and a controller electrically connected to at least the driver circuit and the electric motor. The controller is configured to acquire the working parameter; and according to the working parameter, correct the electrical conduction angle of the stator windings of the operating electric motor.