To the everyday engineer, induction is a captivating methodology of heating. Watching a bit of metal in a coil turn cherry red in a matter of seconds could be shocking to those unfamiliar with induction heating. Induction heating equipment requires an understanding of physics, electromagnetism, power electronics and process control, but the primary concepts behind induction heating are simple to understand.
Discovered by Michael Faraday, Induction starts with a coil of conductive materials (for instance, copper). As current flows by the coil, a magnetic subject in and around the coil is produced. The ability of the of the magnetic discipline to do work depends upon the coil design as well as the amount of present flowing by way of the coil.
The direction of the magnetic subject depends on the direction of current circulate, so an alternating present by way of the coil will end in a magnetic subject altering in direction on the similar rate as the frequency of the alternating current. 60Hz AC current will cause the magnetic area to switch directions 60 times a second. four hundredkHz AC present will cause the magnetic area to switch four hundred,000 occasions a second.
When a conductive materials, a work piece, is placed in a changing magnetic field (for example, a subject generated with AC), voltage can be induced in the work piece (Faraday’s Law). The induced voltage will outcome in the circulate of electrons: present! The present flowing by way of the work piece will go in the opposite direction as the current within the coil. This signifies that we will management the frequency of the current in the work piece by controlling the frequency of the present within the coil.
As present flows through a medium, there can be some resistance to the movement of the electrons. This resistance shows up as heat (The Joule Heating Impact). Supplies which might be more proof against the circulate of electrons will give off more heat as present flows through them, but it is certainly potential to heat highly conductive supplies (for instance, copper) using an induced current. This phenomenon is critical for inductive heating.
What do we need for Induction Heating?
All of this tells us that we need fundamental things for induction heating to occur:
A altering magnetic field
An electrically conductive material placed into the magnetic discipline
How does Induction Heating examine to other heating strategies?
Diagram to signify traditional heating stream
There are a number of methods to heat an object without induction. Among the more widespread industrial practices embody gas furnaces, electric furnaces, and salt baths. These methods all rely on heat transfer to the product from the heat supply (burner, heating factor, liquid salt) by way of convection and radiation. As soon as the surface of the product is heated, the heat transfers via the product with thermal conduction.
Diagram to symbolize induction heating stream
Induction heated products are not counting on convection and radiation for the delivery of heat to the product surface. Instead, heat is generated in the surface of the product by the move of current. The heat from the product surface is then switchred by the product with thermal conduction. The depth to which heat is generated directly utilizing the induced present is determined by something called the electrical reference depth.
The electrical reference depth depends tremendously on the frequency of the alternating present flowing by way of the work piece. Higher frequency current will lead to a shallower electrical reference depth and a lower frequency present will lead to a deeper electrical reference depth. This depth additionally relies on the electrical and magnetic properties of the work piece.
For many processes melting is the first step in producing a helpful product; induction melting is fast and efficient. By changing the geometry of the induction coil, induction melting furnaces can hold costs that range in size from the quantity of a coffee mug to hundreds of tons of molten metal. Additional, by adjusting frequency and power, companies can process virtually all metals and materials together with however not limited to: iron, steel and stainless metal alloys, copper and copper-based mostly alloys, aluminum and silicon. Induction equipment is customized-designed for each application to make sure it is as efficient as possible.
A major advantage that’s inherent with induction melting is inductive stirring. In an induction furnace, the metal charge material is melted or heated by current generated by an electromagnetic field. When the metal becomes molten, this field also causes the bathtub to move. This is called inductive stirring. This constant motion naturally mixes the tub producing a more homogeneous mix and assists with alloying. The quantity of stirring is determined by the dimensions of the furnace, the facility put into the metal, the frequency of the electromagnetic subject and the type/amount of metal in the furnace. The amount of inductive stirring in any given furnace could be manipulated for special applications if required.
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