Induction heating device and method of controlling induction heating device
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Solution Overview
Problem
Existing induction heating devices face challenges in accurately measuring input current values for each working coil to determine eccentricity between the coil and container, leading to potential circuit overload, burnout, and noise due to frequent on-off cycles.
Innovation Solution
Incorporating a shunt resistor between the smoothing circuit and inverter, with a controller that calculates output power values using current measurements from the shunt resistor, allowing for simple and noise-free determination of eccentricity without stopping the other working coil's operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single CT sensor is used to sense input currents of multiple inverters, then device complexity is reduced, but measurement precision deteriorates because accurate current measurement requires stopping other working coils
Solution Approach 1:
The patent introduces a shunt resistor as an intermediary component to measure the total input current from the power supply. This shunt resistor is placed in series with the DC link, allowing the controller to sense the combined current without requiring individual CT sensors on each inverter or working coil. The shunt provides a voltage drop proportional to the total current, which can be measured by the controller to determine individual coil currents through calculation, thus avoiding the need to stop other coils for measurement.
2Measurement precision
If input current measurement is performed by stopping other working coils, then measurement precision is improved, but productivity deteriorates due to frequent on-off cycles causing noise and operational interruptions
Solution Approach 1:
The patent enables continuous operation of all working coils during current measurement by using the shunt resistor to measure the total input current. The controller calculates individual coil currents based on the total current measurement and the known switching states of each inverter, eliminating the need to stop any working coil for measurement purposes. This maintains continuous heating operation without interruptions or noise from frequent on-off cycles.
3Ease of operation
If current measurement is performed without proper isolation, then ease of operation is improved, but reliability deteriorates due to circuit overload and burnout risks
Solution Approach 1:
The shunt resistor serves as an isolated measurement point in the DC link, providing electrical isolation between the high-voltage inverter circuits and the low-voltage controller. The controller measures the voltage drop across the shunt to determine current, which is a safe and isolated method that prevents direct electrical connection between the controller and high-power circuits. This isolation protects the controller and prevents circuit overload or burnout while maintaining ease of operation.
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 easy measurement of input current values for each working coil, preventing eccentricity-related issues and reducing noise by allowing continuous operation of all coils, thus enhancing the reliability and efficiency of the induction heating device.
Implementation Method 1
a shunt resistor RS1 coupled between the smoothing circuit 203 and the inverter 212... measuring an input current value of each of the plurality of inverters 212 and 214
Implementation Method 2
alternating current (AC) currents are supplied to the working coil. As the AC currents are supplied to the working coil, an induced magnetic field is created around the working coil
Implementation Method 3
eddy currents are generated in the container. As the eddy currents flow in the container, the container is heated by Joule heat that is generated by the resistance of the container
Data Source
AI summary
An induction heating device according to an embodiment includes a rectifying circuit configured to rectify an AC voltage supplied from a power supply, a smoothing circuit configured to smooth a voltage output from the rectifying circuit, an inverter comprising a plurality of switches and configured to supply current to a working coil, a shunt resistor coupled between the smoothing circuit and the inverter, a drive circuit configured to supply switching signals to the plurality of switches provided in the inverter, respectively, and a controller configured to determine a driving frequency of the inverter and drive the working coil by supplying a control signal based on the driving frequency to the driving circuit.