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 either premature or late termination.
Innovation Solution
The implementation of a solid-state defrosting apparatus with a variable impedance matching network that dynamically adjusts to match the changing impedance of the food load, using RF energy to ensure efficient and even defrosting by continuously monitoring and adjusting the RF power absorption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional capacitive defrosting systems use fixed electrodes and constant power supply, then the system structure is simple, but the defrosting efficiency decreases due to dynamic impedance changes in the food load
Solution Approach 1:
The patent applies dynamics by transitioning from fixed electrodes to variable impedance matching networks that dynamically adjust their electrical characteristics during the defrosting process. The matching network components (inductors, capacitors, switches) are configured to change impedance values in real-time based on food load impedance variations, maintaining optimal power transfer efficiency throughout the defrosting operation.
Solution Approach 2:
The patent implements parameter changes by modifying electrical parameters (impedance, inductance, capacitance) of the matching network during operation. The controller adjusts these parameters in response to detected food load impedance changes, ensuring continuous optimization of RF power absorption by the food load without requiring complex structural modifications.
2Ease of operation
If the defrosting operation duration is determined based on food load weight, then the control method is simple, but the temperature control precision decreases resulting in premature or late cessation
Solution Approach 1:
The patent implements feedback by using a sensor (such as an RFID tag or impedance sensor) to continuously monitor the actual impedance of the food load during defrosting. The controller receives this feedback information and compares it against expected impedance values at different defrosting stages, enabling precise determination of when the food load has reached the desired temperature state, thereby avoiding premature or late cessation.
Solution Approach 2:
The patent replaces the mechanical/time-based control method (timer based on weight) with an electromagnetic field-based detection system. Instead of relying on temporal estimation, the system uses RF impedance sensing to directly measure the thermal state of the food load, substituting mechanical timing mechanisms with electromagnetic measurement and control.
3Temperature
If low power electromagnetic energy is supplied continuously, then the food load is gently warmed, but the defrosting process takes longer time and may result in uneven heating
Solution Approach 1:
The patent applies periodic action by implementing pulsed or cyclical power delivery patterns through the variable impedance matching network. The system can alternate between higher power pulses for rapid thawing and lower power intervals for gentle warming, creating a periodic heating pattern that accelerates the overall defrosting process while maintaining temperature uniformity through controlled thermal cycles.
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 enables efficient and uniform defrosting by maintaining optimal RF power transfer throughout the process, ensuring the defrosting operation is completed at the desired temperature, thereby improving the accuracy and efficiency of the defrosting operation.
Implementation Method 1
solid-state defrosting apparatus that uses radio frequency (RF) energy to defrost a load
Implementation Method 2
a variable impedance matching network that dynamically adjusts to match the changing impedance of the food load
Data Source
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, a value of a variable passive component 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.