The industrial application of power electronic converters and systems of converters are varied (Motorola, 1991, 1993). Power electronic converters of electrical energy for electrical engineering technologies have a wide spread in industry.
TopIndustrial Applications
The industrial application of power electronic converters and systems of converters are varied (Motorola, 1991, 1993).
Power electronic converters of electrical energy for electrical engineering technologies have a wide spread in industry.
Electrical engineering technology is a technology to perform a particular process using electrical energy. The following positive effects are obtained using electrical energy in electrical engineering technology compared to the usage of other energy sources:
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Reduce of the total expense and prime cost of used energy
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Decrease of the technology process time
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Decrease of the harmful emissions in the environment
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Improving of the conditions of work of the staff, etc.
Metal heating with a purpose of its melting is more often made into furnaces using coal or natural gas according to the heat exchange principle.
The high-frequency induction heating (HFIH) use is increasingly expanded with the development of the power electronic converters. Besides at the melting, the HFIH is also used at surface hardening, welding, forging, hot printing, etc.
In 1831, Michael Faraday (1791 – 1867) discovered electromagnetic induction. It is used in all induction heating (IH) applied system. Electromagnetic induction refers to the phenomenon by which electrical current is generated in a closed circuit by the fluctuation of current in another circuit placed next to it. AC current flowing through a circuit affects the magnetic movement of a secondary circuit located near it. This is the basic principle of the induction heating, which is an applied form of Faraday’s discovery. Heat loss, occurring in the process of electromagnetic induction, could be turned into productive heat energy in an electric heating system.
Absence of any physical contact to heating devices in IH excludes unpleasant electrical accidents. High energy density is achieved by generating sufficient heat energy within a relatively short period of time.
Furthermore, induction heating is a combination of electromagnetic induction, the skin effect, and the principle of heat transfer. Briefly, the IH refers to the generation of heat energy by the current and eddy current created on the surface of a conductive object when it is places in the magnetic field formed around a coil, where the AC current flows through.
The principle of the IH is illustrated in Figure 1. It shows inductor 1, where a high-frequency current flows through, and detail 2 put inside the inductor. The system might be studied as a transformer with a secondary winding where induction current I2 flows through. The current density decreases according to an exponential law into the inside of the detail shown in Figure 2, according the relationship:
, (11.1)
Figure 1. Illustration of IH principle
Figure 2. System of inductor – detail and its equivalent schematic
where
is the current density on the detail surface,
is the current at
x distance inside the detail,
- a constant dependent on the properties of the detail material and the current frequency (Fairchild Semiconductor, 2000):
,
(11.2) where
ρ is specific resistance of the material,
k - coefficient,
μ - magnetic permeability of the material,
ω- angular frequency.