Induction Heating systems
The induction heating power supply converts AC line power to a higher frequency alternating current, delivers it to a work coil and creates an electromagnetic field within the coil.
Your work piece is placed in that field which induces eddy currents in the workpiece. The friction from these currents generates precise, clean, non-contact heat. A water cooling system is generally required to cool the work coil and induction system.
Operating Frequency
The size of the work piece and the heating application dictate the operating frequency of the induction heating equipment. Generally, the larger the work piece the lower the frequency, and the smaller the work piece, the higher the frequency.
The operating frequency is determined by the capacitance of the tank circuit, the inductance of the induction coil and the material properties of the work piece.
Magnetic Materials
If your work piece material is magnetic, such as carbon steel, it will be heated easily by induction’s two heating methods, eddy current and hysteretic heating. Hysteretic heating is very efficient up to the Curie temperature (for steel 600°C (1100°F)) when the magnetic permeability reduces to 1 and the eddy current is left to do the heating.
Depth of Penetration
Induced current in the work piece will flow at the surface where 80% of the heat produced in the part is generated in the outer layer (skin effect). Higher operating frequencies have a shallow skin depth, while lower operating frequencies have a thicker skin depth and greater depth of penetration.
Coupling Efficiency
The relationship of the current flow in the work piece and the distance between the work piece and the induction coil is key; the closer the coil, the more current in the work piece.
But the distance between the coil and the work piece must first be optimized for the heating required and for practical work piece handling. Many factors in the induction system can be adjusted to match to the coil and optimize the coupling efficiency.
Coil Design
Induction heating efficiency is maximized if your work piece can be placed inside the induction coil. If your process won’t allow your work piece to be placed inside the coil, the coil can be placed inside the work piece.
The size and shape of the water-cooled copper induction coil will follow the shape of your work piece and be designed to apply the heat to the correct place on the work piece.
Heat losses and uneven, inconsistent application of heat result in increased scrap and diminished product quality, driving up per-unit costs and consuming profits. Best manufacturing economies are seen when the application of energy is controlled.
To bring a batch oven up to temperature and to hold the entire chamber at the required temperature for the process time demands much more energy than is required to process the parts. Flame-driven processes are inherently inefficient, losing heat to the surroundings. Electrical resistance heating can also result in the wasteful heating of surrounding materials. Applying only the energy needed to process your parts is ideal.
Induction selectively focuses energy only on the area of the part that you want to heat. Each part in a process enjoys the same efficient application of energy. Since the energy is transferred directly from the coil to a part, there is no intervening media like flame or air to skew the process.
The precision and repeatability of induction heating help to reduce process scrap rate and to improve throughput. The selective application of heat to the targeted area of a part enables very tight control of the heating process, also cutting the heating time and limiting energy requirements.
Delivering the highest quality parts for the least expense in the least time is accomplished with an efficient process, in which the input elements of materials and energy are tightly and precisely controlled. Induction heating’s targeted application of heat to the part or an area of the part, as well as repeatability, provides the most uniform results for the least cost. Repeatability and throughput are two things that can be greatly improved with induction compared to resistance or flame heating.
Induction heating delivers savings primarily from significant reductions in process scrap rates, improved throughput and from the thrifty use of energy. There is no need for process ramp-up; heat is applied and stopped instantly. In comparison, batch heating in an oven requires an investment of time and energy that serves only the process, not the product. Throughput and efficiency are increased by induction heating with the careful application of energy (heat) in amounts no more than required by the product.
Any heating process carries a risk of operator contact with the heated materials. A technology like induction heating that limits the extent of operator-contacted surfaces does reduce the overall risk. If heating can be limited to only the part and further limited to a zone of the part, safety is improved even more.
Compared to a flame or hand-held heating operation, each induction heat process cycle is identical, and the process requires no running adjustment. Therefore once established and proven, an induction heating process does not require highly-trained personnel to operate.
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AMBRELL Ltd.
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