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/diy/ - Do It Yourself

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159247 No.159247 [Reply] [Original]

So I'm trying to build an induction heater from this pdf in the link below (with some alterations for my needs).

http://www.neon-john.net/Induction/Roy/Buck_Converter_Schematic.pdf

However, for some reason, I keep tripping my surge protector, which means I'm drawing 15A or more and I have not a clue why. The details of the link said it should only be drawing 10A.

What I have built is as follows in my picture (with M1 switching at 30kHz). All the components that I have are rated at least 600V DC. The M1 is rated 1.2kV @ 25A and even the inductor is made from wires that are rated at 600 V.

The only things bothering me is that C1's farad rating might be too low, or the combination of L1 and C2's impedance is way too low causing a possible short, but I really don't know. Any advice?

>> No.159257

A resonant tank means a capacitor in parallel with an inductor. Is there are reason why yours are in series?

C1 is too small to provide any smoothing.

Did you pull the 30khz switching out of the air; or do you understand how LC resonance is supposed to work and calculate the correct frequency?

>> No.159283

Your tank is more or less a short circuit at 30kHz. Maybe it and the associated phase shift fuck your current limiting circuit?

>> No.159382

>>159257

My mistake, M1 should have been at 50kHz. Don't know what the fuck I was smoking when I said 30kHz. For my purpose, the switching frequency needs to be higher then the resonant frequency, and assuming the resonant frequency works in series as well, then it should still be 31 kHz.

As for why it is in series, that is for if I need to adjust my switching frequency if I need something higher, or lower, that's something flexible for me until I can get a solid frequency I'm satisfied with.

>>159283

So if my switching frequency is 50kHz, or anything higher, would I avoid a short circuit?

>> No.159742

>>159257
LC resonant tanks also work in series, same ckt really

the tank's resonant frequency is 1/[2*pi*sqrt(L*C)], or 30.6 kHz. sounds right

what happens if you turn off the driver (so that M1 is always off)? still trips the breaker?