Multi-Inverter Current Balancing for Plasma Torch IGBT Thermal Trips
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Solution Overview
Problem
Temperature differences among insulated gate bipolar transistors (IGBTs) in different inverters can lead to thermal trips during plasma torch operation, as the junction temperature of IGBTs varies, causing some to reach a thermal trip condition before others.
Innovation Solution
The system regulates current flow through multiple inverters by measuring the temperature of IGBTs in each inverter and adjusting the current flow based on temperature differences and current request signals, ensuring that all IGBTs approach or reach a threshold trip temperature simultaneously.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If multiple inverters are used to deliver current to the plasma torch electrode, then the power delivery capability is improved, but temperature differences among IGBTs in different inverters cause premature thermal trips
Solution Approach 1:
The system continuously monitors the temperature of IGBTs in each inverter and uses this feedback information to dynamically adjust current distribution. Temperature sensors provide real-time data to the control system, which then modulates the PWM signals to balance thermal loads across all IGBTs, preventing premature thermal trips while maintaining high power delivery capability
Solution Approach 2:
The current distribution among inverters is made dynamic rather than static. The system continuously adapts the current flow through each inverter based on real-time temperature conditions, allowing the operational state to change in response to thermal variations. This dynamic adjustment ensures optimal power delivery while preventing thermal overload
2Productivity
If current flow is increased to meet power demand, then the productivity is improved, but temperature differences cause some IGBTs to reach thermal trip condition before others
Solution Approach 1:
Each inverter receives a customized current allocation based on its specific thermal state. Instead of uniform current distribution, the system applies local quality control by adjusting PWM duty cycles individually for each inverter, ensuring that IGBTs with lower thermal headroom receive reduced current while those with higher headroom can handle more load, thereby maximizing overall productivity without triggering thermal trips
Solution Approach 2:
The system changes the operational parameters (current magnitude, PWM duty cycle) of each inverter based on temperature measurements. By dynamically adjusting these parameters in response to thermal conditions, the system maintains high productivity while preventing any single inverter from reaching thermal trip conditions
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 approach minimizes the occurrence of thermal trips by reducing temperature differences among IGBTs, ensuring that all inverters are either operating within safe temperature ranges or are shut down collectively, thus preventing premature thermal trips.
Implementation Method 1
The IGBT or IGBTs of each inverter may be thermally coupled to a cooling plate that is cooled by a fluid flowing therethrough
Data Source
AI summary
Systems and methods for lessening temperature differences between first and second IGBTs respectively residing in first and second inverters, the first and second inverters being configured to collectively deliver current to an electrode of a torch for the purpose of producing a plasma arc. According to one method, the temperature of each of the first and second IGBTs is measured and the flow of current through one or more of the first and second inverters is altered based on the measured temperatures. The regulating of current flow through the first and second inverters is also based on a current request signal that is indicative of an amount of current requested to be delivered to the electrode. The lessening of temperature differences between the first and second IGBTs can additionally be based on current signals indicative of the current measured at the output of each of the first and second inverters.