Induction Heating Boiling Detection via Frequency Sweeping
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Solution Overview
Problem
Induction heating systems face challenges in accurately determining the relationship between actuation frequency and electric power delivered to the load, leading to inefficiencies in temperature control and boiling detection due to unpredictable coupling factors between the induction coil and load.
Innovation Solution
A method involving a sequence of actuation frequency variations within a single half-wave of the AC current envelope to calculate current peak values and determine boiling conditions by analyzing current peak/actuation frequency relations, allowing for reliable boiling detection with minimal interference in power delivery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the actuation frequency is varied to assess the frequency/power relationship, then the temperature control accuracy and boiling detection reliability are improved, but the power delivery is interrupted causing heating inefficiency
Solution Approach 1:
The patent performs frequency/power relationship assessment during the initial phase when the load is first placed on the cooking surface, before the main heating process begins. This preliminary measurement establishes the coupling characteristics without significantly delaying the overall heating process, as the assessment is completed while the system is still in the setup phase.
Solution Approach 2:
The patent implements periodic reassessment of the frequency/power relationship at specific intervals during the heating process, particularly when significant changes in coupling are detected (such as when the load position changes or when boiling is detected). This periodic approach balances measurement accuracy with minimal disruption to continuous heating.
2Measurement precision
If dynamic measurements are performed to assess actuation frequency and electric power relationship, then the control accuracy is improved, but the response time and measurement speed are reduced
Solution Approach 1:
The system performs comprehensive frequency/power relationship assessment during the initial setup phase when the load is first placed on the cooking surface. This preliminary measurement establishes the coupling characteristics and creates a lookup table or calibration data that can be used for rapid control decisions during the actual heating process, avoiding repeated time-consuming measurements.
Solution Approach 2:
The patent performs full dynamic measurements only when necessary (such as when coupling conditions change significantly), rather than continuously. Between these partial reassessments, the system uses the previously established frequency/power relationship data for control, reducing overall measurement time while maintaining adequate control accuracy.
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
Enables rapid and accurate assessment of the actuation frequency and electric power relationship, improving temperature control and boiling detection efficiency while minimizing disruption to the heating process.
Implementation Method 1
heating an electrically conducting load by inducing eddy currents in the load through a time-varying magnetic field generated by an alternating current (hereinafter, simply AC current) flowing in an induction heating coil
Implementation Method 2
inducing eddy currents in the load through a time-varying magnetic field
Implementation Method 3
The internal resistance of the load causes the induced eddy currents to generate heat in the load itself
Data Source
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Figure 2B
AI summary
A method for boiling detection in an induction heating system is disclosed, in which the induction heating system comprises an electrically conducting load and an inverter circuit comprising a switching section and a resonant section, the switching section comprising switching devices adapted to generate an AC current from an AC input voltage comprising a plurality of half-waves, and the resonant section comprising an induction heating coil adapted to receive the AC current for generating a corresponding time-varying magnetic field in order to generate heat in the electrically conducting load by inductive coupling, wherein the AC current oscillates at an actuation frequency of the switching devices and has an envelope comprising a plurality of half-waves corresponding to the half-waves of the AC input voltage, and wherein the amount of heat generated in the load depends on the frequency of the AC current. The method comprises performing at least once the following sequence of steps: (a) varying, within a same half-wave of the envelope, the actuation frequency according to a sequence of actuation frequency values, each actuation frequency value of the sequence being set for a corresponding time interval corresponding to a fraction of the duration of the half-wave of the envelope; (b) for each actuation frequency value of the sequence, calculating a corresponding current peak value based on a corresponding set of at least one absolute value peak assumed by the AC current during the corresponding time interval, so as to generate a corresponding current peak/actuation frequency relation; and (c) based on evaluating variations in the current peak/actuation frequency relations generated for plural actuation frequencies, determining a boiling condition.