Defrosting apparatus and methods of operation thereof
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Solution Overview
Problem
Conventional capacitive food defrosting systems face inefficiencies due to dynamic changes in food load impedance during the defrosting process, leading to uneven heating and inaccuracies in determining the optimal cessation of the defrosting operation, which can result in premature or late termination.
Innovation Solution
The implementation of a solid-state defrosting apparatus with a variable impedance matching network that adjusts during the defrosting operation to maintain optimal RF power transfer, using a system controller to monitor impedance changes and adjust the matching network to ensure efficient and even heating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional capacitive defrosting systems use fixed electrodes and constant power supply, then the system structure is simple, but the impedance mismatch during defrosting leads to inefficient power transfer and uneven heating
Solution Approach 1:
The patent implements dynamic impedance matching by making the matching network components variable during operation. The controller adjusts the impedance matching network in real-time based on feedback from power transfer measurements, allowing the system to adapt to changing food load impedance during defrosting. This dynamic adjustment maintains optimal power transfer efficiency throughout the defrosting process while resolving the contradiction between simplicity and efficiency.
Solution Approach 2:
The system incorporates a feedback mechanism where the controller monitors power transfer efficiency and adjusts the impedance matching network accordingly. By measuring the actual power transfer and comparing it to expected values, the controller can dynamically reconfigure the matching network to maintain optimal conditions, thereby improving defrosting efficiency without requiring overly complex fixed infrastructure.
2Measurement precision
If the defrosting operation duration is determined by weight-based timing, then the control method is simple, but inaccuracies lead to premature cessation or late termination after the load begins to cook
Solution Approach 1:
The system uses real-time feedback from power transfer measurements to detect defrosting completion. Instead of relying on pre-programmed timers, the controller continuously monitors the power transfer efficiency and detects when the food load reaches the desired defrosted state based on actual electrical characteristics. This feedback-based detection provides precise termination timing while avoiding the need for complex multi-sensor systems.
Solution Approach 2:
The system allows the food load itself to indicate its defrosting status through its electrical impedance characteristics. As the food transitions from frozen to defrosted state, its impedance changes in a characteristic pattern that the controller can detect. This self-indicating approach eliminates the need for external temperature sensors or complex monitoring equipment, achieving high measurement precision with relatively simple control logic.
3Use of energy by moving object
If fixed impedance matching is used throughout the defrosting operation, then the matching network is simple, but the dynamic impedance changes of the food load cause inefficient power transfer
Solution Approach 1:
The patent implements dynamic impedance matching by making the matching network components variable during operation. The controller adjusts the impedance matching network in real-time based on feedback from power transfer measurements, allowing the system to adapt to changing food load impedance during defrosting. This dynamic adjustment maintains optimal power transfer efficiency throughout the defrosting process while resolving the contradiction between simplicity and efficiency.
Solution Approach 2:
The system changes the electrical parameters of the impedance matching network during operation to match the varying impedance of the food load. By adjusting component values in the matching network based on real-time measurements, the system maintains optimal power transfer conditions throughout the defrosting process, transforming a static matching approach into a dynamic one that adapts to changing load 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 ensures efficient and even defrosting by dynamically matching the impedance, preventing premature or late cessation of the defrosting process, thereby maintaining high system efficiency throughout the operation.
Implementation Method 1
An RF signal source 320 is configured to deliver RF power to a variable impedance matching network 370 that is configured to match an input impedance of a cavity 360 plus load 364
Data Source
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AI summary
A defrosting system includes an RF signal source, two electrodes proximate to a cavity within which a load to be defrosted is positioned, a transmission path between the RF signal source and the electrodes, and an impedance matching network electrically coupled along the transmission path between the output of the RF signal source and the electrodes. The system also includes power detection circuitry coupled to the transmission path and configured to detect reflected signal power along the transmission path. A system controller is configured to modify, based on the reflected signal power, values of variable capacitors of the impedance matching network to reduce the reflected signal power. The impedance matching network may be a single-ended network or a double-ended network.