Does magnetic field present between the capacitor when there is current? If yes, is it significant for dielectric heating?
I understand that changing electric field produces magnetic field and vice versa.
Yes there is a magnetic field in the capacitor when an AC current passes in it . This magnetic field increases from the center of the capacitor up a maximum value at the edges of the capacitor then it begins to decrease again as we go away from the capacitor. This is the consequence of Ampere Law, Integral H. dl on a a closed path circulating the displacement current of the capacitor is equal to the current enclosed in the circular path.
So, any capacitor has self inductance and self resonance.The self inductance is really small and its effect can be neglected at relatively low frequency.
As for the dielectric heating it occurs because of the electric polarization of the dielectric dipole materials with the effect of the electric field. It is an electric field field effect. The electric dipoles of the material will try to follow the variation of the electric field with time. Because of its inertia it can not follow the electric field and it gets lagging which causes heating of the material.
In simple words, the current in the capacitor will be no longer at 90 degrees phase with the voltage on the capacitor. This means an effective dissipation of the electric energy in the capacitor as Peffective= VI cos phi,
phi will be smaller than 90 degrees, and peffective will be no longer zero.
As phi decreases the losses increases. This appears as if the capacitor behaves partly capacitive and partly resistive.
As we see the dielectric heating is predominantly due electric field
Best wishes
Yes there is a magnetic field in the capacitor when an AC current passes in it . This magnetic field increases from the center of the capacitor up a maximum value at the edges of the capacitor then it begins to decrease again as we go away from the capacitor. This is the consequence of Ampere Law, Integral H. dl on a a closed path circulating the displacement current of the capacitor is equal to the current enclosed in the circular path.
So, any capacitor has self inductance and self resonance.The self inductance is really small and its effect can be neglected at relatively low frequency.
As for the dielectric heating it occurs because of the electric polarization of the dielectric dipole materials with the effect of the electric field. It is an electric field field effect. The electric dipoles of the material will try to follow the variation of the electric field with time. Because of its inertia it can not follow the electric field and it gets lagging which causes heating of the material.
In simple words, the current in the capacitor will be no longer at 90 degrees phase with the voltage on the capacitor. This means an effective dissipation of the electric energy in the capacitor as Peffective= VI cos phi,
phi will be smaller than 90 degrees, and peffective will be no longer zero.
As phi decreases the losses increases. This appears as if the capacitor behaves partly capacitive and partly resistive.
As we see the dielectric heating is predominantly due electric field
Best wishes
what is the frequency of operation? are you planning to heat any material inside the capacitor?
It won't be significant for dielectric heating (by definition, it is a magnetic field, not an electric field), but it might be for magnetic heating, but no more so than if there were magnetic materials next to or around the wires going into the capacitor.
Hi Katrib,
I am planning to heat grains using radio frequency at 27.12 MHz.
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