Electromagnetic induction heating is a heating technique for any electrical conductive materials (for example metal, graphite, getters, carburized metals etc . Induction heating is frequently applied in several thermal processes such as melting of metals for casting, skin heating for case hardening, core heating for forging and through hardening, heating for expansion, heating for coating with polymers like metal seals/ gaskets, pre-heating for welding or post heating for stress relieveing etc.
Induction Heating Operating Principle
Induction heating results from the direct application of two physical laws, the LENZ law and the JOULE effect: any electrically conductive material placed in a variable magnetic field (generated by an exciting winding called inductor) is the site of induced electric currents, called Eddy currents. Due to the Joule effect (P =R x I² ), these currents dissipate heat in the material in which they appeared. In order to transfer a maximum amount of energy to the part to be treated, The heat generated in the material implies a quick response and a high efficiency.
Several parameters must be taken into consideration :
The respective positions of the inductors and the parts to be treated (coupling, respective lengths).
The supply frequency and the skin effect which characterize the dispersion of the induced current throughout the part: the higher the frequency, the closer to the surface the induced currents will concentrate. This fundamental notion is determined by the penetration depth, also referred to as skin thickness. - simpfied formulae do = 503.3 (ρ/μr f)1/2.
The magnetic (relative permeability μr ), electrical (resistivity ρ) and thermal (conductivity) properties of the parts to be heated, most of which vary in accordance with the temperature. The type of inductor (geometry, type of conductor, technology).
Induction Heating Equipments
An induction heating plant generally comprises :
One or several heating inductors,
- A medium or high-frequency power source combining a frequency converter (generator or inverter) and an impedance matching and compensating unit composed of a capacitors bank and an impedance matching transformer if required. These systems are classified into two categories which are Current Fed (Parallel Tank Circuit) and Voltage Fed (Series Tank Circuit)
- A water cooling system for the power source the matching unit and off-course the inductor.
- A positioning and handling system for the parts to be heated,
- A plant control panel
The Advantages of Induction Heating
Whatever the intended industrial application, induction heating offers several inherent advantages which explain its constant market development :
- Heating speed linked to the possibility of obtaining very high power density,
- Exact location of the heating effect thanks to the inductor design and an operating frequency perfectly adapted to the part to be heated,
- The possibility to heat at very high temperatures with an efficiency practically independent of the temperature,
- A process perfectly adapted to industrial medium-sized and mass production requirements
- Easy automation of equipment,
- Absence of thermal inertia (rapid start-up),
- Repeatability of operations carried out,
- Often extremely high heating efficiency,
- Absence of pollution from the source of heating (cold source),
- Good working conditions.
These machines are used extensively in industry for forging, melting, brazing and case hardening applications. We are presently manufacturing these machines from a mere 25 KW to 250 KW capacity. In models above 100 KW capacity we are putting in equipment for energy management and power saving.
All these machines are manufactured on the basis of application and hence are priced accordingly.
