Induction Heating Inverter Frequency Control for Power Delivery
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Solution Overview
Problem
Induction heating systems face challenges in dynamically adjusting electric power delivery to loads due to unpredictable coupling between induction heating coils and loads, leading to inefficiencies and potential damage to power switching elements, especially when trying to maintain specific temperature settings in applications like induction cooking and ironing.
Innovation Solution
A method is introduced that rapidly assesses the relationship between actuation frequency and electric power delivery by varying the actuation frequency within a half-wave of the AC voltage envelope, calculating current peak values, and setting the actuation frequency to achieve the target electric power, using a control unit to dynamically adjust the frequency based on measured current peak values and power delivery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the actuation frequency is adjusted to match resonance frequency for maximum power delivery, then the electric power delivered to the load is maximized, but the power switching elements may be irreparably damaged due to heat dissipation and control instability
Solution Approach 1:
The patent implements dynamic frequency adjustment by continuously varying the actuation frequency around the resonance frequency based on real-time coupling conditions. The control unit adjusts the frequency dynamically rather than fixing it at resonance, allowing the system to adapt to changing load conditions while avoiding sustained operation at dangerous frequency points that cause overheating
Solution Approach 2:
The patent employs feedback control by monitoring the actual coupling between the induction heating coil and the load, then using this information to adjust the actuation frequency. The control unit receives feedback about coupling conditions and modifies the frequency accordingly, preventing the system from operating at frequencies that would cause power switching element damage while maintaining optimal power transfer
2Measurement precision
If dynamic measurements are carried out to assess the actuation frequency/electric power relation, then the control accuracy is improved, but the time required to deliver the requested power increases
Solution Approach 1:
The patent performs preliminary characterization of the induction heating system by pre-establishing the relationship between actuation frequency and electric power delivery for different coupling conditions. This pre-assessed data is stored and used during operation, eliminating the need for time-consuming real-time measurements while maintaining control accuracy
Solution Approach 2:
The patent uses a simplified measurement approach by assessing the actuation frequency/power relation at selected operating points rather than continuously across the entire range. The control unit determines frequency adjustments based on partial assessments at key frequencies, reducing measurement time while maintaining sufficient precision for effective control
3Power
If the actuation frequency is lowered to increase the amplitude of the AC current envelope, then the electric power delivered to the load increases, but the coupling between the induction heating coil and the load becomes more unpredictable
Solution Approach 1:
The patent dynamically adjusts the actuation frequency based on real-time coupling conditions rather than operating at a fixed low frequency. By continuously adapting the frequency to match the actual coupling between the induction heating coil and the load, the system maintains predictable power delivery even when operating at frequencies that produce high current amplitudes
Solution Approach 2:
The patent changes the actuation frequency parameter in response to varying coupling conditions. When coupling deteriorates or becomes unpredictable, the control unit adjusts the frequency to compensate, maintaining optimal power transfer despite changes in load position, type, or geometry
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 allows for efficient and rapid adjustment of electric power delivery to match user requests, improving power delivery speed and reliability, especially in dynamic applications like induction ironing, by reducing the time required to set the actuation frequency and minimizing the risk of power switching element damage.
Implementation Method 1
induction heating coils are located under a cooking hob surface for heating cooking pans made (or including portions) of electrically ferromagnetic material placed on the cooking hob surface
Implementation Method 2
The internal resistance of the load causes the induced eddy currents to generate heat in the load itself
Implementation Method 3
The internal resistance of the load causes the induced eddy currents to generate heat in the load itself
Implementation Method 4
the electric power provided to the load is at its maximum when the current flowing through the induction heating coil oscillates at the resonance frequency of the resonant section
Data Source
AI summary
An induction heating system is disclosed. The system has an electrically conducting load and an inverter circuit with a switching section and a resonant section, wherein the switching section can generate an AC current from an AC input voltage incorporating a plurality of half-waves. The resonant section has 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. The amount of heat generated in the load depends on the electric power delivered to the load through the induction heating coil, which depends on the frequency of the AC current. A method for managing an induction heating system also is disclosed.