Electric Working Machine Motor Stop Control
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Solution Overview
Problem
In electric power tools, regenerative currents generated by motor magnetic energy can increase power-supply voltage, causing adverse effects in other circuits, and existing methods fail to effectively inhibit these currents when stopping the motor.
Innovation Solution
An electric working machine with a motor, switching elements, a rectifier element, and a controller that maintains the first current path while interrupting the second current path, allowing a loop current to circulate and consume magnetic energy, thereby inhibiting regenerative currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If all switching elements in the drive circuit are turned OFF to stop the motor, then the motor stops, but a regenerative current flows from the motor to the power source causing power-supply voltage increase
Solution Approach 1:
A diode is introduced as an intermediary component in parallel with the motor to provide a dedicated path for regenerative current. This mediator allows the regenerative current to circulate through the diode and motor winding without flowing back to the power source, thus preventing power-supply voltage increase while enabling complete motor stop.
Solution Approach 2:
The current paths are segmented into two separate routes: one for normal motor operation and another for regenerative current dissipation. By dividing the current flow paths, the patent enables independent control of motor stopping and regenerative energy management, preventing the regenerative current from affecting the power source.
2Use of energy by stationary object
If both first and second current paths are interrupted to stop power supply, then the motor stops, but the magnetic energy generates regenerative current
Solution Approach 1:
The patent converts the harmful regenerative current into a beneficial loop current that circulates through the motor winding and diode. By maintaining the first current path while interrupting the second, the magnetic energy is dissipated as heat in the winding resistance rather than being fed back to the power source, transforming a harmful effect into a controlled energy dissipation mechanism.
3Object-affected harmful factors
If the first current path is maintained while interrupting the second current path, then regenerative current is inhibited, but the first switching element remains conductive
Solution Approach 1:
The system uses the motor's own magnetic energy and winding resistance to dissipate the regenerative current internally. By maintaining the first current path with the first switching element conductive, the motor winding serves its dual function of both generating the magnetic field and dissipating the regenerative energy through its inherent resistance, eliminating the need for additional active components.
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
Effectively stops motor energization and prevents regenerative current generation, ensuring stable power supply and reducing potential malfunctions by consuming magnetic energy during motor stop conditions.
Implementation Method 1
The rectifier element is configured to allow a loop current to circulate through the winding via the rectifier element and the first switching element in response to interruption of the second current path. The loop current flows due to a magnetic energy accumulated in the winding.
Data Source
AI summary
An electric working machine in one aspect of the present disclosure includes a motor, a first switching element, a second switching element, a rectifier element, and a controller. The controller is configured to perform a stop control, in which completion of a first current path is maintained via the first switching element for a specified period and a second current path is interrupted via the second switching element, in response to satisfaction of a stop condition for stopping power supply from a power source to the motor during rotation of the motor.