Induction Heating Control Unit Frequency Adjustment
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Solution Overview
Problem
Conventional induction heating units experience non-uniform temperature distribution in conductive sheets due to variations in sheet conveyance speed, leading to inconsistent heating results.
Innovation Solution
A control unit for induction heating units that adjusts AC power output frequency and current based on the relative permeability, resistivity, and thickness of the conductive sheet, using a magnetic energy recovery switch and frequency setting unit to maintain consistent temperature distribution across the sheet width.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the heating coil and capacitor make up a parallel resonance circuit to supply power to the heating coil, then the induction heating unit can operate efficiently, but when the apparent inductance varies with sheet conveyance speed, the power frequency varies causing non-uniform temperature distribution in the conductive sheet
Solution Approach 1:
The patent applies dynamics by making the power supply frequency variable rather than fixed. The frequency is dynamically adjusted according to the sheet conveyance speed to maintain constant heating effectiveness. When the sheet moves faster, the frequency increases; when the sheet moves slower, the frequency decreases. This dynamic frequency adjustment compensates for changes in apparent inductance, ensuring uniform temperature distribution across the sheet width despite variations in conveyance speed.
Solution Approach 2:
The patent changes the frequency parameter of the power supply to adapt to varying operating conditions. By adjusting the frequency based on sheet conveyance speed and apparent inductance variations, the system maintains optimal heating performance. This parameter change allows the system to operate effectively across different conveyance speeds without requiring a fixed resonance circuit configuration.
2Productivity
If the sheet conveyance speed increases, then the productivity of the induction heating unit improves, but the apparent inductance decreases causing frequency increase and non-uniform temperature distribution
Solution Approach 1:
The patent implements feedback control by monitoring the sheet conveyance speed and using this information to adjust the power supply frequency. The system detects changes in conveyance speed and automatically modifies the frequency to compensate for the resulting changes in apparent inductance. This feedback mechanism ensures that even at higher conveyance speeds that improve productivity, the temperature distribution remains uniform across the sheet width.
Solution Approach 2:
The system dynamically adjusts the power supply frequency in response to changes in sheet conveyance speed. Rather than operating at a fixed frequency, the system adapts its operating parameters in real-time to maintain consistent heating performance across varying productivity levels.
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
The solution ensures a uniform temperature distribution across the conductive sheet even with varying conveyance speeds, enhancing heating efficiency and reliability by independently controlling the induction heating process.
Implementation Method 1
an alternating magnetic field (AC magnetic field) generated by the heating coil... the eddy current is caused to the conductive sheet by an alternating magnetic field
Implementation Method 2
Joule heat is generated in the conductive sheet due to the eddy current
Data Source
AI summary
A control unit of an induction heating unit controls AC power output to a heating coil of a transverse type induction heating unit that allows an alternating magnetic field to intersect a sheet surface of a conductive sheet that is being conveyed to inductively heat the conductive sheet. The control unit includes: a magnetic energy recovery switch that outputs AC power to the heating coil; a frequency setting unit that sets an output frequency in response to at least one of the relative permeability, resistivity, and sheet thickness of the conductive sheet; and a gate control unit that controls a switching operation of the magnetic energy recovery switch on the basis of the output frequency set by the frequency setting unit.