Induction Heating Principle and its Applications
Induction heating principle has been used in manufacturing processes since the 1920s. As it’s said that – necessity is the mother of invention, during world war-2, the need for a fast process to harden the parts of the metal engine, has developed induction heating technology rapidly. Today we see the application of this technology in our day to day requirements. Recently, the need for improved quality control and safe manufacturing techniques has brought this technology into the limelight once again. With today’s high-end technologies, new and reliable methods for implementation of induction heating are being introduced.
What is Induction Heating?
The working principle of the induction heating process is a combined recipe of Electromagnetic induction and Joule heating. Induction heating process is the non-contact process of heating an electrically conductive metal by generating eddy currents within the metal, using electromagnetic induction principle. As the generated eddy current flows against the resistivity of the metal, by the principle of Joule heating, heat is generated in the metal.
How Induction Heating Works?
Knowing the Faraday’s law is very useful for understanding the working of induction heating. According to Faraday’s law of electromagnetic induction, changing the electric field in the conductor gives rise to an alternating magnetic field around it, whose strength depends on the magnitude of the applied electric field. This principle also works vice-versa when the magnetic field is changed in the conductor.
So, the above principle is used in the inductive heating process. Here a solid state RF frequency power supply is applied to an inductor coil and the material to be heated is placed inside the coil. When Alternating current is passed through the coil, an alternating magnetic field is generated around it as per Faraday’s law. When the material placed inside the inductor comes in the range of this alternating magnetic field, eddy current is generated within the material.
Factors to be Considered While Designing Induction Heating System
There are some factors that should be considered while designing an induction heating system for any type of applications.
- Normally, the induction heating process is used for metals and conductive materials. The non –conductive material can be heated directly.
- While applied on magnetic materials, heat is generated both by eddy current and hysteresis effect of magnetic materials.
- Small and Thin materials are heated quickly compared to large and thick materials.
- Higher the frequency of the alternating current, lower the heating depth of penetration.
- Materials of higher resistivity are heated quickly.
- The inductor in which the heating material is to be placed should allow easy insertion and removal of the material.
- While calculating power supply capacity, the specific heat of the material to be heated, the mass of the material and the temperature rise required are to be considered.
- The heat loss due to conduction, convection, and radiation should also be taken into account for deciding the power supply capacity.
Applications of Inductive Heating
- Targeted heating for surface heating, melting, soldering is possible with the inductive heating process.
- Besides metals, heating of liquid conductors and gaseous conductors is possible by inductive heating.
- For heating of silicon in semiconductor industries, the inductive heating principle is used.
- This process is used in inductive furnaces for to heat metal to its melting point.
- As this is a contactless heating process, vacuum furnaces make use of this process for making specialized steel and alloys that would get oxidized when heated in the presence of oxygen.
- Induction heating process is used for welding of metals and sometimes plastics when they are doped with ferromagnetic ceramics.
- Induction stoves used in the kitchen works on the inductive heating principle.
- For brazing carbide to shaft induction heating process is used.
- For tamper resistant cap sealing on bottles and pharmaceuticals, the induction heating process is used.
- Plastic injection modeling machine uses induction heating to improve energy efficiency for injection.
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