Current Limiting Device for Plasma Power Supply Arc Control
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Solution Overview
Problem
In plasma surface treatment, the current flowing between a plasma chamber and a power supply varies rapidly due to changes in plasma and substrate properties, making it challenging to maintain a controlled voltage source independent of load current, especially with high power impulse magnetrons.
Innovation Solution
A current change limiting device is introduced in the current path between the power supply and the plasma chamber, comprising a non-linear device and an inductor pre-charged with DC current, which limits current changes by adjusting the additional current applied to the inductor, thereby controlling the current flow and allowing for arc detection and switch-off.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a capacitor is used to maintain voltage independence from load current, then voltage stability is improved, but response time to current changes deteriorates due to the finite charging/discharging time of the capacitor
Solution Approach 1:
The inductor is pre-charged with a DC current before normal operation. This preliminary action ensures that when an arc occurs or current spikes, the inductor already has stored energy and current flow ready to immediately counteract the current change, eliminating the response delay that would otherwise occur during arc detection and switch-off operations.
2Object-affected harmful factors
If the current path is interrupted quickly to prevent arcs, then arc prevention is improved, but voltage stability deteriorates due to abrupt current changes
Solution Approach 1:
The pre-charged inductor provides preliminary anti-action by having its current flow ready to counteract arc-induced current spikes before the arc can fully develop. The inductor's stored energy creates an opposing electromagnetic force that prevents harmful arcs from establishing, while simultaneously maintaining voltage stability through controlled current limitation.
Solution Approach 2:
The inductor acts as a cushioning element by being pre-charged with current that can absorb and smooth out abrupt current changes during arc events. This beforehand cushioning prevents both harmful arcs and voltage instability by providing a buffer that manages current transitions gracefully.
3Object-affected harmful factors
If the inductor current is increased to limit current changes, then arc prevention is improved, but energy consumption increases due to continuous DC current application
Solution Approach 1:
Instead of applying excessive continuous current to the inductor, the system uses partial action by maintaining a controlled DC pre-charge current that is sufficient for arc prevention but minimized to reduce energy consumption. The inductor current is precisely managed to provide just enough protective action without wasteful over-energyization.
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 ensures fast and effective limitation of current changes, maintaining voltage stability and preventing arcs by slowing down current rise, allowing sufficient time for detection and switch-off, even during high load variations and high power impulse magnetron operations.
Implementation Method 1
an inductor that is pre-charged by application of a DC current to the inductor
Data Source
AI summary
The current (Iout) flowing between a plasma chamber and a power supply is limited by limiting the current change di/dt if the current exceeds a predetermined current. A current change limiting device is provided in the current path between the power supply and the plasma chamber and is configured to determine if the current exceeds the predetermined current and limits the current change.