Dielectric Heating | Principle | Advantages | Disadvantages

Here we learn some information about Dielectric Heating, Principle of Dielectric Heating
There are some questions
1. Describe the following electric heating methods with their working pfindiple
A. Resistance heating. B. Di-eleotrio heating

2. Write the principle and draw an electical
equivalent ciagram of dielectrio heating
3. state and explain the principle of dielectric
heating. List any to applications.
4. Explain the dielectric heating with neat sketch and write its applications.


5. Explain dielectric heating with suitable diagram.
6. State the principie of dielectric heating. State its any four applications.

Dielectric Heating

Dielectric heating is another type of RF heating. It makes use of the dielectric loss in imperfect dielectric materials and is therefore, suitable for heating non-metals.

Principle of Dielectric Heating:

~ In dielectric heating, a high frequency, high voltage ac voltage is applied across a dielectric material.

~ The dielectric workpiece is held between two metal electrodes as shown in Fig. 11.6.1 (a). The dielectric material can be plastic, wood etc.
~ Due to the high voltage RF excitation, some current flows through the dielectric material and due to this current flow some loss takes place in the dielectric which is called as "dielectric loss"
~ This power loss takes place in the form of heat and the dielectric material gets heated up due to it. This is the principle of dielectric heating.
~ The power loss taking place in a dielectric material is given by the following equation :
0.55 × 10-1f [V/b cm]
Where, f = Frequency of operation.
v = Applied voltage.
b = Thickness of the dielectric workpiece.

The power loss per unit volume (P.) in a dielectric slab depends upon following factors :
1. It increases with increase in frequency of operation.
2. It increases with the square of voltage gradient, (V/b cm)" and
3. It depends upon the constants of the dielectric material through the loss factor, (E, tan d).

Advantages of Dielectric Heating :

1. The heating is uniform.
2. It is possible to control the heat automatically.
3. There are no byproducts of the heating process.
4. Heating process is neat and clean.
5. The process of heating is free from gases and ash.
6. It is possible to achieve high rate of heating.
7. The heat delivered to work piece can be precisely controlled.

Disadvantages of Dielectric Heating:

1. It is not possible to increase the supply voltage beyond the breakdown of the dielectric material.
2. It is not possible to increase the frequency of ac source beyond the resonant frequency of the electrodes and the capacitor formed by the electrodes and job.
3. For better quality, it is necessary to apply a uniform field.