Induction heating technology is of choice in many industrials such as domestic and medical applications due to its advantages such as less heating time, localized heating, direct heating and good efficient energy consumption. The operating principle of induction heating is based on the law of the Electromagnetic Induction Discovered by scientist Michael Faraday in 1831.
There are two major components of an induction heating system that generates heat.
- A coil of wire (often a copper coil) producing a time-varying magnetic field upon receiving a high-frequency alternating current.
- Electrically conducting material
The magnetic field also changes its direction as the direction of the alternating current changes.
When a conduction material is exposed to such a time-varying magnetic field, current loops called eddy currents are induced in the conducting material.
As the magnetic field changes its direction rapidly the eddy currents also change their directions rapidly. The eddy currents always form closed loops inside conducting materials in planes perpendicular to the varying magnetic field. Eddy currents, generate Joule heat(I2R) due to the existence of resistance of the material.
Eddy currents are developed become larger when following are higher.
- Magnetic field created is stronger or
- Electrical conductivity is higher or
- The rate of change of magnetic field is larger
The eddy currents which are generated by the high-frequency alternating current in the coil will exist only within a limited thickness near the surface of the material due to what is called skin effect.
The skin effect is the tendency of any high-frequency electric current to distribute itself in a conductor with the current density being largest near the surface of the conductor and decreasing very rapidly with the depth of the conductor. The thickness across which eddy currents are distributed becomes even smaller due to the mutual attraction between the alternating current in the coil and the eddy current loops. This is called the proximity effect. In addition to the Joule heating, an additional heat is also produced within the material due to a phenomenon called hysteresis effect. It occurs only in ferromagnetic materials such as some stainless steel, cast iron, nickel, etc. In response to the varying magnetic field produced by the alternating current, the magnetic domains in these materials repeatedly change their orientations. The energy required to turn them around finally is converted to heat. The rate at which the heat is generated due to hysteresis effect increases with the frequency of the varying magnetic field. Click more
Commercially available induction heating systems operate at frequencies approximately from 60 Hz to about 1 MHz and deliver power in the range from a few watts several Megawatts.
The cookers that are available in the market as induction cookers operate on this principle. In an induction cooker, a coil of copper wire is mounted just under the surface of the cooker top where the cooking pot is placed, without touching it, and an alternating electric current is sent through the coil. The entire bottom of the cooking pot itself acts as the conducting material that generates the heat. The varying magnetic field produced by the coil enters the bottom of the cooking pot creating eddy currents and hysteresis losses, generating heat. In order to make use of both effects for heat generation, the cooking pots or the bottoms of the cooking pots are made of ferromagnetic materials such as some stainless steel or cast iron. There is no current waste because heat depends on high-frequency of alternating current and minimum usage of current. No energy waste.
The following are some examples. And also right upper side and header of this site you can see many examples.
- Induction Cooktop Countertop Burner, Induction Heating System Rice Cooker & Warmer.
- Induction Heating Board Module
It is really wonderful because fire is generated by the high-frequency alternating current. It is powerful. you can use this for any heat treatment, Also can be used with a graphite crucible melting gold, silver, copper, aluminum and other metals, uniform heating fast, very convenient.
- Low Voltage Induction Heating Board Module Tesla coil.