LC Parallel resonance induction heater

Thread Starter

Stoyan.Nikolov.2Induction

Joined Nov 26, 2023
13
Consider parallel LC resonance induction circuit with solid iron workpiece, inserted in the inductor. Is it possible to obtain more heat power output from the heated solid iron workpiece in the inductor, compared to the electrical power consumed in an LC parallel resonance induction circuit?

Is it possible as a result, the electrical power input to LC circuit to be, for example, 100 watts, the heat power generated from the the heated solid iron workpiece to be higher, say 200 watts (680 BTU/h) or more, depending on the efficiency of the system and the characteristics of the load?

Lets say (Parallel LC resonance), First I prepare the inductor and the workpiece , then i switch capacitors in parallel until I reach resonance state, so that the input current become very low (Very high ratio of I_L/I_in ).
 

MrAl

Joined Jun 17, 2014
11,268
Consider parallel LC resonance induction circuit with solid iron workpiece, inserted in the inductor. Is it possible to obtain more heat power output from the heated solid iron workpiece in the inductor, compared to the electrical power consumed in an LC parallel resonance induction circuit?

Is it possible as a result, the electrical power input to LC circuit to be, for example, 100 watts, the heat power generated from the the heated solid iron workpiece to be higher, say 200 watts (680 BTU/h) or more, depending on the efficiency of the system and the characteristics of the load?

Lets say (Parallel LC resonance), First I prepare the inductor and the workpiece , then i switch capacitors in parallel until I reach resonance state, so that the input current become very low (Very high ratio of I_L/I_in ).
Hi,

When you consider ALL the input power and ALL the output power, the efficiency can never be higher than 100 percent. In fact, with most mechanisms of any kind it cannot even be 100 percent because then you could not take any energy out of it. There is one case of late where it may be 100 percent and still serve a useful function, but it can never be over 100 percent, which is what you are suggesting. The calculations are very simple.

If you input 100 watts and get 200 watts output, that would be an efficiency of 200 percent, which by today's physics is impossible. In fact, if you input 100 watts and get 100.001 watts out, that's still an efficiency of over 100 percent so that's also impossible by today's understanding of physics.
Many electronic converters are 80 percent, 85 percent, and 90 percent, maybe 92 percent, but it's hard to get higher than that.

I think it seems the question that you are alluding to is, does resonance somehow allow a higher than 100 percent efficiency.
The answer is no. Just because you could get a peak response or the transfer of energy back and forth between components does not mean you get higher than 100 percent efficiency.
You may get 100 percent efficiency in theory (and one possible practical application), but that's it. Two components that resonant, in theory, can resonate forever, but take even the smallest amount of energy to use for anything useful and the resonance will eventually decay.

So the answer is no, and resonance does not imply a greater than 100 percent efficiency. In fact, physical resonance is a sort of storage of energy, and that means that whatever energy you put in will stay in storage, but you can't get any more energy out than what you put in in the first place.

Renewable energy is interesting though because you can get as much energy as you need for free if you are willing to build or buy the apparatus to do that. I used a solar panel for a long time and was surprised that even a smaller panel maybe 18 inches by 18 inches gave me the power I needed for a particular automotive application. The ISS space station uses solar panels that span some 200 feet across and that powers a lot of stuff up there.
 
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