Important Factors to Consider
There are several factors that will determine the efficiency of an induction heating system for a specific application: the factors of the workpiece itself, the design of the induction coil, the capacity of the power supply, and the amount of temperature change that required for the application.
The Factors of the Workpiece
METAL OR PLASTIC
First, induction heating will only work with conductive materials, generally metals. By first heating a conductive metal which produces and transfers heat to the non-conductive material, in this way, other non-conductive materials, such as plastics can also be heated indirectly.
MAGNETIC OR NON-MAGNETIC
It’s easier to heat magnetic materials. In additionally, the heat is induced by eddy currents, magnetic materials also produce heat through what is called the hysteresis effect.
THICK OR THIN
Regarding conductive materials, nearly 85% of the heating effect occurs on the surface of the workpiece; the distance from the surface increases while the heating intensity diminishes. So to heat small or thin workpiece normally is much faster than to heat large or thick workpiece. Especially when heating with the larger workpiece all the way through.
Researchers have found a relationship between the frequency of the AC current and the heating depth: the higher the frequency, the shallower the heating in the workpiece. Frequency range 100 – 400 kHz produce relatively high-energy heat, which is ideal for quickly heating smaller workpiece or the surface of larger workpiece. It’s more effective to use lower frequency range 5-30 to deep, penetrating heat.
The result will be very different when you use the exactly same induction process to heat two same size pieces of steel and copper, why? Steel, carbon, tin and tungsten have high electrical resistivity. As these kinds of metals strongly resist the current flow, heat builds up quickly. Copper, brass and aluminum take longer to heat because of low resistivity. With temperature increases, resistivity increases.
Induction Coil Design
Inductor design is one of the most important aspects of the overall system. A well-designed induction coil not only provides the proper heating pattern for your workpiece, but also maximizes the efficiency of the induction heating power supply.
Power Supply Capacity
It can be easily calculated the required induction power supply for heating a particular workpiece. First, how much energy needs to be transferred to the work-piece must be determined. This depends on three parts: the quality of the material being heated, the specific heat of the material and the required heating temperature. We should also consider about the heat losses from conduction, convection and radiation.
Degree of Temperature Change Required
At final, the efficiency of induction heating for specific application depends on the amount of temperature change required. A wide range of temperature changes can be accommodated; generally, more induction heating power is utilized to increase the degree of temperature change.