In the process of manufacturing a product, heat-treatment becomes integral part for heating and drying. Until now methods used generally for heating were are, hot air, flame, steam, electrical heated wire and so on by combustion of fuel. These methods perform heating from outside of the object and transmit heat to inside slowly by thermal conductivity, so the heating process is called "EXTERNAL HEATING".
On the other hand, object to be heated itself is used as the heating source in heating methods like High frequency heating or Microwave heating etc. which uses electromagnetic wave for heating and hence it is called "INTERNAL HEATING". Internal Heating is very efficient compared to External Heating and not only that, heating in shorter time also becomes possible. Both High frequency induction heating and Microwave heating collectively called as "Electromagnetic wave heating". Fundamental principles are barely enough to understand but, now it is actively applied in wide range of industrial fields which results in to improvement of efficiency and rationality of the heat-treatment process, improvement of Work environment, Labor savings and so on and hence Electromagnetic Wave Heating technology providing excellent contribution towards Industry.
We Yamamoto Vinita focus immense attention towards this Electromagnetic Wave heating technology. Before in advance world is looking towards this technology, a lot of application products have been developed from us. But our unknown fields still remain.
After going through this website and understanding the Electromagnetic Wave Heating, if you have any concerns, please feel free to contact with us.
All materials are majorly classified into Conductors those allow current to flow easily and Insulators [dielectric substance] those won't allow to flow current easily. Most of the molecule of insulators has the charge of the plus and minus at both ends. In a word, it will be able to say that the insulator is a set of an electric dipole. When this insulator is put between the parallel electrodes mutually opposite and the high-frequency voltage is given, an electric condition of equilibrium warps everywhere of the material gets distracted and separation of the electrical charge happens. This phenomenon is called dielectric phenomenon, and the material with such a character is called a dielectric substance.
Each molecule of dielectric substance causes intense movements like the rotation, the collision, the vibration, and friction, etc. as the input frequency rises. At this time, change in the polarity is so intense that change occurs from hundreds of million of times to tens of millions of times in a second and this energy converts in to "Heat"
The energy generates by the above movements(the rotation, the collision, the vibration and the friction) the heat of dielectric substance. This is the process of high frequency dielectric heating. The electric wave energy is absorbed to dielectric substance (heated object with a dielectric loss), and the dielectric substance heats up. The electric power (P) consumed by the dielectric substance per m3 (the unit volume) is obtained by the following calculating formula.
Where E: strength of the electric field (V/cm) f: Frequency (Hz) εr: dielectric constant tanδ: dielectric loss angle
Product of εr and tanδ is called coefficient of loss, and this value depends on material, it changes depending on the temperature and the frequency. In case that the loss coefficient is big, the materials are heated very well. Also in case that the frequency is high and the electric field strength is big, the heat generating energy grows big.
Loss factor of material
Higher the value of the coefficient of loss is, the more the heat generation.
Even though coefficient of loss depends on material it can be changed by temperature and the frequency.
Heating which uses the electric wave between 3 KMz and 3,000GHz is called Electric wave heating. As for the electric wave heating, the inside of the material and the outside are heated concurrently by self-generation of heat.
The feature :
1. Heating is so fast regardless of the dimension, the cubic volume and the thermal conductivity of the material.
2. It is so small difference in temperature between internal and external, and it is possible to do uniform heating.
3. High heating efficiency and saving energy.
Kinds of Electrric Waves
Frequency
Wavelength
Name of Frequency
Industrial Application
30～300KHz
104～103
300～3000KHz
103～102
MF( Midium Frequency )
Induction Heating
3～30MHz
102～101
HF( High Frequency )
High Frequency Dielectric Heating
13.56MHz
27.12MHz
40.68MHz
30～300MHz
10 ～10-1
VHF( Very High
Frequency )
30～3000MHz
1～10-1
UHF( Ultra High Frequency)
Micro Wave Heating
915MHz
2450MHz
3～30GHz
10-1～10-2
SHF(Super High
Frequency )
30～300GHz
10-2～10-3
EHF( Extremely High Frequency )
High Frequency Dielectric Heating
Micro Wave Heating
Numbers of Frequency
13.56MHz 27.12MHz 40.68MHz
2450MHz
915MHz
Penetration of Depth
Deepest
Surface
Deep
Uniformity of Heating
Uniform heating
The hot spot and the edge effect sometimes happen.
Unsuitable Material for High
Frequency Heating
The material concerning small dielectric loss coefficient
High conductive material
Bumpy material, or irregular shape material
Area of Heating
It is possible to do partial heating by electrode size & shape
The material is heated from all directions.
Application of Heating
The material between a pair of electrodes is heated.
The material is heated at sealed space or through waveguide.
Generator
Output Range
（～200kw）
（～6kw）
（30～100kw）
Countermeasures
for Electric wave
( Government
Law and human’s damage )
The radio Law : Approved frequency
The radio Law : Due to not approved
frequency, must to be sealed strictly more.
Protection against human’s body : By sealing to the device
Protection against human’s body : By strict sealing to the device
