Looking for RF dielectric heating consulting

Thread Starter

Longschool

Joined Oct 8, 2022
1
Hi, first time posting and first time on the forum please remove if not allowed

I was wondering if I can connect with anyone here on whatsapp that could offer some RF consulting for a design I am working on?

I am currently trying to set up dielectric heating with a parallel capacitor utilizing an rf generator and an impedance match box at 13.56mHz.

Thanks,
 

Janis59

Joined Aug 21, 2017
1,537
Heheheeee. For me it took about century quarter to teeth it through. But, understanding Your motivation I can offer to send You for a while unpublished article about this problem with some math and well proven technical offers if You swear never to noone give it out of hands (understand please, with that I may loss the publication rights if some find out I had "published" that earlier to You). Thus, let send me Your mail - mine is Janis_59 at inbox dot LV. Dont wait too impatiently, when You have a day, We here have a night :) :)
 
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Janis59

Joined Aug 21, 2017
1,537
By the way, 13 MHz is not any good for heating up. Nearer to GHz range it would be far more effective. But even at 27 MHz what I am familiar, the PCB heats up until the explosion in seconds at so minor power as few hundred Watts at serial tank producing in voltage resonative multiplication about 3...5 kV and small tens of Amperes. So, feed the oldie goodie Clapp circuit with 24 Volts and glass textolyte will want to blow up. I have explored that heating by means of thermal cam, the skin-effect here makes the absolute mninority impact, but clearly dominates the volume-born heat outcome.And, as more threads inside, more multiple reflections between them, thus more heat buildup.
 

DickCappels

Joined Aug 21, 2008
9,513
I suspect he is trying to keep the frequency to one of the Industrial, Scientific, Medical (ISM) bands, which included a region around 27 MHz.
 

Janis59

Joined Aug 21, 2017
1,537
OK, may Copy&Paste one compact theory brick be helpful to mind over. Sometimes. ....--->

The model of lossy capacitor uses the term of dissipation factor (DF), where DF=ESR/Xc=tanδ; δ is the loss angle.
Thus the equivalent serial resistance ESR=DF*Xc= =DF/(2*π*f*C)
and thermal power outcoming flux is P(therm)=i^2*ESR

Sometimes the capacitor quality factor Q is handier in use, where Q=1/DF
For the resonance tank then Q(of tank)=1/(1/Q{of C}+1/Q{of L})
so the effort to alter the capacitor Q over the coil`s in resonant tank is aimless.

Yet for electrotechnical applications more often are used the PF (power factor) where PF=cosφ; φ is the phase angle and φ=90º-δ, therefore for small angle of δ<10º may be written an approximation tanδ=sinδ=cosφ creating the bold approximation: DF=PF.
Due to heat-flux outcome at given circulating reactive power P(therm)=P(circ)*PF
for capacitor case it looks P(therm)=P(circ)*DF

The DF is mostly given at one fixed frequency, thus for any other effective work frequency of choice this pre-given DF(0) in that region where DF is diminishing by frequency, can be recalculated to DF(eff)=DF(0)*sqrt[f(eff)/f(0)].
The exception is far below the frequency of any molecular or atomic resonances, where the frequency response curve is typically flat.


P.S. Sometimes may be beneficial to look into Murata`s calculator: https://article.murata.com/en-eu/article/heat-generation-characteristics-capacitors-measurement
 
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