Induction cooker, and method for operating an induction cooker
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Solution Overview
Problem
Induction cookers face inefficiencies due to varying ferromagnetic permeability of cooking vessels, causing semiconductor switches to overheat when dealing with vessels of higher or lower permeability than average, leading to suboptimal power transfer.
Innovation Solution
An induction cooker design featuring a movable coil and fluid conduction arrangement that adjusts the distance between the coil and cooking surface based on the vessel's permeability, using a fluid to transfer heat and control the coil's position through volume changes, eliminating the need for temperature sensors or electromechanical elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the coil position is fixed at a standard distance from the cooking surface, then the device structure is simple, but the power transfer efficiency varies significantly with different ferromagnetic permeability vessels causing semiconductor switches to overheat
Solution Approach 1:
The system uses the heat generated by the power electronics themselves to drive the adjustment mechanism. The thermal energy that would otherwise be wasted is converted into useful work by expanding a fluid (liquid or gas) that mechanically adjusts the coil position, eliminating the need for external power or control systems.
Solution Approach 2:
The invention changes the physical state of a fluid (between liquid and gas phases) to create volume changes that drive the mechanical adjustment. By controlling the phase and volume of the fluid, the system dynamically adjusts the coil-to-cooking-surface distance to optimize power transfer for different vessel types.
2Power
If the coil is positioned closer to the cooking surface, then power transfer to low permeability vessels is improved, but the semiconductor switches generate excessive heat
Solution Approach 1:
The system creates a closed-loop feedback mechanism where the thermal state of the power electronics directly controls the coil position. The heat generated by the switches expands the fluid, which automatically adjusts the coil position to optimize coupling, forming a self-regulating system that responds to real-time thermal conditions.
3Temperature
If the coil is positioned farther from the cooking surface, then semiconductor switch temperature is reduced, but power transfer to high permeability vessels becomes insufficient
Solution Approach 1:
The invention transforms the static coil position into a dynamic parameter that automatically adjusts based on operating conditions. The coil-to-cooking-surface distance becomes a variable that changes in real-time with the thermal state of the power electronics and the type of cooking vessel being used, optimizing performance across different scenarios.
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 allows for adaptive power transfer to cooking vessels of varying ferromagnetic permeability, maintaining optimal operating temperatures for the semiconductor switches and improving overall efficiency by dynamically adjusting the coil position in response to thermal changes.
Implementation Method 1
a fluid conduction arrangement (107, 207) that is filled with a fluid (108, 208) and that is thermally coupled to the power electronics circuit (104, 204)
Implementation Method 2
The switched currents pass through the induction coil and change with time according to the switching frequency. As a consequence a magnetic field is generated by the coil. This magnetic field induces currents in a ferromagnetic cooking vessel that is placed on the induction cooker and therefore the cooking vessel heats up.
Data Source
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AI summary
The present invention provides an induction cooker (100, 200) comprising a cooking surface (101, 201), a coil (103, 203) that is arranged under the cooking surface (101, 201), a power electronics circuit (104, 204) that is electrically coupled to the coil (103, 203) for driving the coil (103, 203) with a high frequency electric current, a movement arrangement (106, 206) that is coupled to the coil (103, 203) and that is configured to controllably move the coil (103, 203) towards the cooking surface (101, 201) and away from the cooking surface (101, 201), and a fluid conduction arrangement (107, 207) that is filled with a fluid (108, 208) and that is thermally coupled to the power electronics circuit (104, 204) and that is mechanically coupled to the movement arrangement (106, 206) such that a volume of the fluid (108, 208) controls the movement of the movement arrangement (106, 206). Further, the present invention provides a method for operating an induction cooker (100, 200).