Induction Heater MK4 - A technical description
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- čas přidán 5. 09. 2024
- MK4 is the more civilized version of my induction heater MK3. This video shows a bit more technical detail of the circuit and its construction layout.
The power supply ripple voltage is discussed, and is shown on an oscilloscope, and how it varies with load current and the size of the power supply filter capacitors.
It also shows the output waveform in the induction coil tank circuit, and how that varies with load for two coil examples.
Finally, the heater is shown trying to melt some silver, and a beer can.
Brasileiro assistindo. Parabéns pelo vídeo!
Que bom que gostou!
Hello, can you please share the project of the over current protection circuit?
It's not really a protection circuit, as it's operated manually. Just a switch and a large resistor.
The circuit is powered via the resistor at startup, and seeing a normal current draw on the meter (meaning it's oscillating, and not just one FET stuck on), I flick the switch to provide full power without the resistor.
@@bertoid thanks
Filter capacitor after rectifier is not needed for heating application, as heating is proportional to RMS value of current. Infact, connecting the capacitor reduced the power factor of the entire application and hence, the recitifier drawn spike current at the peak of AC input. If we do not use the capacitor, the heating generated by induction coil will pulsate at 100Hz or 120Hz (depends on where you are located) and that also keep PF good. This is why most commercial design of induction heater or cooker do not use the filter capacitor after rectifier.
Interesting comments! I haven't touched this thing for a long time, but want to play with again soon. I'll try to investigate operation in both modes. (not that power factor is of much importance for what I'm doing)
Some of my commentary on voltages read from the oscilloscope are incorrect. Sorry, new to making narrated videos...
hey fella, we are treading a similar path! which mosfets are you using and whats your capacitor setup on the tank? I have implemented a crude but effective under voltage( by way of over current) cut out with an lm311 voltage comparator that looks at the gate voltage and if it drops below 24 it turns the mains off. this has saved about 100 mosfets so far. check out my heater if you fancy. it has done ali, copper, glass and very nearly iron all to pour ing temp (but not quite the iron - aaarrrrgghh). would love to share tech and design. cool work
Thanks. I'm using the same MOSFETs as you, IRFP260. (But I'll have to use some higher voltage devices when I try a higher supply voltage, since they have a VDS of 200V, and the tank peaks at 150V now)
The tank caps are 16x 220nF/630V, so total is 3.5uF (and the coil dimensions calculate to 2.8uH, so resonance should be at 50KHz, close to the 53KHz observed)
Your protection circuit is interesting (gate voltage? Isn't it watching the supply voltage?), detecting overcurrent by a sag in the (supply?) voltage. I would have thought that a relay would be too slow to help the MOSFETs, but apparently not.
You seem to have minimal supply capacitance, so the ripple must be high. It would be interesting to see the supply and tank waveforms on a scope. If you did add more supply capacitance, your protection circuit might stop working though, as there may be enough stored energy to blow the MOSFETs.
I have some other comments, I'll put them in your MK3 video...
Could u send me scemeatic
There is no overall schematic for this thing,. But if you mean just the actual oscillator board, it's the standard ZVS/Royer oscillator that can be found all over the net. As I said in the video.
Poor design this design won’t provide stable power and good gate driving and current control use halfbridge design you will get cooler working of igbt and and the coil is not connected directly to the two fet drain its resonating connection between large capacitor bank and drain that will melt any steel at 360 volt
Are you saying that this circuit can work with 360 volts?