Induction Cooker Coil Frequency Control for Composite Heating

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Solution Overview

Problem

Induction heating cooking apparatuses struggle to uniformly heat composite heating targets with magnetic and nonmagnetic materials due to inadequate power distribution, leading to uneven temperature profiles.

Innovation Solution

The apparatus includes multiple heating coils with a controller that determines the material type of each heating target and adjusts the frequency of the high-frequency current supplied to each coil, setting a higher frequency for nonmagnetic materials and a lower frequency for magnetic materials to optimize heating uniformity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If a single frequency of high-frequency current is supplied to all heating coils, then the control system is simple, but uneven heating occurs in composite heating targets with magnetic and nonmagnetic materials

Engineering Contradiction:
Improvecontrol system complexityVSAvoidheating uniformity
Core Design Contradiction:
Device complexityVSTemperature

Solution Approach 1:

The patent applies local quality by assigning different frequencies to different heating coils based on the material type detected in each region. Heating coils are divided into first and second groups, with the first group operating at a first frequency and the second group at a second frequency, allowing each region to be optimized for its specific material (magnetic or nonmagnetic).

Inventive Principle:
Principle #3Local quality

Solution Approach 2:

The control system dynamically adjusts the frequency of high-frequency current supplied to each heating coil group based on real-time material detection. The controller switches between different frequency settings depending on whether magnetic or nonmagnetic materials are detected, enabling adaptive heating optimization.

Inventive Principle:
Principle #15Dynamics

2Area of stationary object

If power distribution is adjusted based on outer diameter of heating target, then heating coverage is optimized, but material-specific heating characteristics cannot be achieved

Engineering Contradiction:
Improveheating coverageVSAvoidmaterial adaptability
Core Design Contradiction:
Area of stationary objectVSAdaptability or versatility

Solution Approach 1:

The patent changes the frequency parameter of the high-frequency current based on material type detection. When magnetic materials are detected, a first frequency is used, while nonmagnetic materials trigger a second frequency. This parameter change enables the system to adapt to different material properties while maintaining appropriate heating coverage through multi-coil configuration.

Inventive Principle:
Principle #35Parameter changes

3Ease of operation

If all heating coils are supplied with the same high-frequency current, then the system operation is simple, but interference sounds are generated due to frequency differences in adjacent coils

Engineering Contradiction:
Improvesystem operation simplicityVSAvoidinterference sound
Core Design Contradiction:
Ease of operationVSObject-generated harmful factors

Solution Approach 1:

The system divides heating coils into distinct groups with different frequency assignments based on the material regions they serve. By localizing different frequency operations to specific coil groups corresponding to magnetic or nonmagnetic material regions, the patent eliminates interference sounds while maintaining operational simplicity through automated material detection and control.

Inventive Principle:
Principle #3Local quality

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 reduces temperature unevenness and allows for efficient heating of composite targets by matching the frequency of the high-frequency current to the material type, enhancing heating uniformity and efficiency.

Implementation Method 1

a plurality of heating coils aligned in at least one row on a flat surface, a plurality of inverter circuits each configured to supply a high-frequency current to the corresponding one of the plurality of heating coils

Methodology Applied
Scientific EffectElectromagnetic induction: Electromagnetic Induction

Implementation Method 2

supply a high-frequency current to the corresponding one of the plurality of heating coils

Methodology Applied
Scientific EffectEddy current: Eddy Currents

Implementation Method 3

inhibits interfering sound caused by a difference in frequencies of high-frequency magnetic fields generated by heating coils arranged adjacent to each other

Methodology Applied
Scientific EffectJoule heating: Joule Heating

Data Source

PatentEP3758442B1Induction heating cooker
Publication Date: 2024.01.24 MITSUBISHI ELECTRIC CORP
  • EP3758442B1 patent drawingFigure 1
  • EP3758442B1 patent drawingFigure 2~3
  • EP3758442B1 patent drawingFigure 4~5

AI summary

An induction heating cooking apparatus includes a plurality of heating coils aligned in at least one row on a flat surface, a plurality of inverter circuits each configured to supply a high-frequency current to the corresponding one of the plurality of heating coils, and a controller configured to control driving of the plurality of inverter circuits. The plurality of heating coils include a first heating coil and a second heating coil that are adjacent to each other. The controller is configured to, when a material forming a heating target loaded on an upper part of the first heating coil is a magnetic material, and a material forming the heating target loaded on an upper part of the second heating coil at least includes a nonmagnetic material, set a frequency of the high-frequency current supplied to the second heating coil higher than a frequency of the high-frequency current supplied to the first heating coil.