Capacitor Inrush Current Control in AC Power Tools
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Solution Overview
Problem
Existing electric power tools face challenges in efficiently driving motors due to voltage fluctuations, which can lead to large inrush currents when the AC power is inputted, potentially damaging components if not managed properly.
Innovation Solution
An electric working machine comprising a rectifier circuit, a capacitor, a series switching element, a resistive element, a drive circuit, a peak voltage value acquirer, and a controller, where the series switching element is brought into conduction based on a specified conducting condition related to the peak voltage value to inhibit large currents from flowing through the capacitor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the capacitance of the smoothing capacitor is increased to reduce voltage fluctuations, then the smoothing effect is improved, but the inrush current becomes larger and flows for a longer period
Solution Approach 1:
The patent applies preliminary action by detecting the peak voltage value of the AC power supply before the smoothing capacitor is fully charged, and using this information to control the timing of when to connect the capacitor to the circuit. This prevents the capacitor from drawing excessive inrush current when first connected, while still achieving effective voltage smoothing during operation.
2Productivity
If the switching element is turned ON immediately to allow charging current to flow through the smoothing capacitor, then charging efficiency is improved, but large current may flow through the capacitor causing damage to components
Solution Approach 1:
The patent uses feedback by continuously monitoring the peak voltage value of the AC power supply and using this information to control the switching element. The controller adjusts the timing of the switching element based on the detected peak voltage, ensuring that the capacitor is charged efficiently while preventing excessive current that could damage components.
3Device complexity
If the switching element is turned ON at improper timing, then the control simplicity is maintained, but large current flows through the capacitor potentially damaging various elements
Solution Approach 1:
The patent applies preliminary action by detecting the peak voltage value before actuating the switching element. This preliminary detection allows the system to determine the appropriate timing for turning on the switching element, ensuring safe operation without requiring complex real-time control mechanisms.
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 solution effectively suppresses inrush currents and ensures appropriate charging of the capacitor, preventing damage to components and ensuring efficient motor operation by controlling the conduction timing of the switching element.
Implementation Method 1
a rectifier circuit configured to rectify an AC power inputted from an AC power supply and to output a rectified power
Implementation Method 2
a capacitor configured to be charged by the rectified power outputted from the rectifier circuit and to smooth the rectified power
Data Source
AI summary
An electric working machine according to one aspect of the present disclosure comprises a motor, a rectifier circuit, a capacitor, a series switching element, a resistive element, a drive circuit, a peak voltage value acquirer, and a controller. The capacitor smooths power rectified by the rectifier circuit. The series switching element is coupled in series with the capacitor. The resistive element is coupled in parallel with the series switching element. The controller brings the series switching element into conduction in a case where AC power is inputted to the rectifier circuit and where a specified conducting condition based on a peak voltage value acquired by the peak voltage value acquirer is satisfied.