Attempting the Kaizer sstc II

[Mads Barnkob]

Okay, that is good, what just not possible to see in the pictures

You have to double check your circuit to the schematic then, also use some larger capacitors for the primary circuit.

[CCX191]

Yeah thanks, but I have one more set of the same caps left so I guess I will give it a go again and I have redesigned my whole bridge circuit so crossing my fingers that it will work this time. Anyways do these polypropylene capacitor have voltage ratings? That is what I was given in the component shop at least

[Mads Barnkob]

That explains pretty well why it exploded

.68 = 0.68 uF
K = 10% tolerance
63 = 63 VDC

You need capacitors rated for at least 400 VDC in the primary circuit.

[CCX191]

I see.. My capacitor replacement will be arriving in an hour or so and for now I will work on the audio modulator. I'm wondering about the audio input section.. In terms of (+) and (-) I will be using a 3.5 mm audio jack but in terms of polarity is (+) the left channel and (-) ground or  (+) left, (-) right?

Oh and talking about the safety of using the audio moudulator, I see that you have a metal mesh over it to protect it from interference etc but would it work if i connect it to my phone since i see that you've used only a keyboard? Should an optocoupler be implemented or can just be omitted?

Currently 3D printing parts for me coil and toroid 

[Mads Barnkob]

I see.. My capacitor replacement will be arriving in an hour or so and for now I will work on the audio modulator. I'm wondering about the audio input section.. In terms of (+) and (-) I will be using a 3.5 mm audio jack but in terms of polarity is (+) the left channel and (-) ground or  (+) left, (-) right?

Oh and talking about the safety of using the audio moudulator, I see that you have a metal mesh over it to protect it from interference etc but would it work if i connect it to my phone since i see that you've used only a keyboard? Should an optocoupler be implemented or can just be omitted?

Currently 3D printing parts for me coil and toroid 

It is not a stereo input, only mono, so its either right or left channel as + and then ground, but notice that the ground of the audio is not tied directly to ground of the circuit!

Never connect anything directly via cable to a Tesla coil that you can not be without, this is why I used a cheap kids toy, I would not cry if I destroyed it I once destroyed a ipod nano from connecting it directly to a plasma speaker, back EMF destroyed the USB interface in it.

Optical isolation is always a good idea!

What kind of 3D printer do you own/have access to?

[CCX191]

So my audio modulator doesn't seem to work probably I've wired it incorrectly so I will just check that up.

As of now I haven't got my toroid mounted since I've ran out of print filament. I've tested my coil and it has successfully lit a florescent light but it's rather dim. A spark is not produced even with a tweezer as a breakout point but I guess I will try again later once the toroid is installed.  A small spark can be drawn though about 3mm-1cm that I've tried max

The thing is I've already tripped my house twice from drawing too much power from the wall :/ maybe at about 150VAC-200VAC. Not sure if I can do anything about this.

The printer I have is an Anet A8 that I bought from gearbest for about 155USD. Pretty cheap and a very worthy investment in my opinion, though some upgrades must be done like a change of better belts as the stock ones are horrible and bearings if you can't bare with the noise. I use SketchUp​ to model my things

Here was a setup I have earlier this afternoon

[Mads Barnkob]

So my audio modulator doesn't seem to work probably I've wired it incorrectly so I will just check that up.

As of now I haven't got my toroid mounted since I've ran out of print filament. I've tested my coil and it has successfully lit a florescent light but it's rather dim. A spark is not produced even with a tweezer as a breakout point but I guess I will try again later once the toroid is installed.  A small spark can be drawn though about 3mm-1cm that I've tried max

The thing is I've already tripped my house twice from drawing too much power from the wall :/ maybe at about 150VAC-200VAC. Not sure if I can do anything about this.

The printer I have is an Anet A8 that I bought from gearbest for about 155USD. Pretty cheap and a very worthy investment in my opinion, though some upgrades must be done like a change of better belts as the stock ones are horrible and bearings if you can't bare with the noise. I use SketchUp​ to model my things

Congratulations! You got sparks, so something is working, now it is just to get it working properly

A SSTC will work fine without a topload, sparks will just be shorter, but not as short as those you describe.

Try to reverse the phase of the primary coil, this is done by switching around the two leads from your bridge to the coil, a SSTC can actually operate out of phase, this would fix the small sparks, if that is the problem.

You should not trip your breakers whe only producing such small sparks, maybe you have a defective part that will first fail with a short circuit at high input voltage? Else it is also related to the above phasing issue.

Interesting and cheap little machine, I might try to get one, learn the basics and play around with a cheap machine instead of just going for a expensive first and maybe damage it

[CCX191]

I tried changing the primary coil phase but it did not work. I suspected that there should be a defective part and changed the whole bridge since the parts sourced locally are very unreliable just like the 555 timers I got previously.. took me a while to figure out what went wrong.

As of now my driver is practically broken I accidentally put 240v straight into the bridge without the driver turned on. As a result I did some testing(edit: I think it shouldn't really matter)... That there is nothing coming out from my GDT so I assume my UCCs are dead once again (edit: tested again seems to be kinda fine)

Though for my scenario of putting 240v into the bridge without the driver turned on would it kill the IRFP460 too?

For now I just have some spare UCC37322 but not UCC37321( they are shipping from China now) so I guess I can resume to retry it next week

Edit: my UCCs seems fine though :/
Edit: After some inspection and blowing the fuse on my variac... I'm pretty convinced that my bridge is screwed up so I guess I will redo it when I'm free. Schools gonna start again 

Today's setup with a temporary topload fixture using MDF

[Mads Barnkob]

Generally you should never power up a bridge/power section of a circuit without the driving circuit being powered up first. With no power on the driving section, you have no idea which state the MOSFETs are in, if you are really unlucky they are maybe turned on slightly into the linear region from induced currents from the mains supply. Where you say that it should not be a problem, I agree, but you have no way of knowing what will really happen

Always driver on first, then power electronics.

Be sure to not just check the MOSFETs, but also check diodes, resistors and zeners.

Your topload looks good, that will do fine for testing!

Beware of metal objects like screws and long bolts like the one in the corner, they will affect the resonant frequency of secondary circuit and will absorb some power, worst case you can have a spark jump from topload to the long bolt and then arc into your driver/bridge underneath the plate.

The screws holding the secondary in place are also subject to be induction heated from the primary coil, use nylon screws if possible, or glue the white plastic ring on the wood instead.

I hope you get new parts and find some time between school days to finish your coil and make some good long sparks

[CCX191]

Thanks! Nylon screws seems to be a good idea. I was about to ask if that might be a problem.  The long threaded rod at the corner was meant to be a striking rod since it directly connects to the the ground and I wasn't getting any sparks. But yeah it's a good safety precaution to take in.


I just redid my bridge and blew the fuse on my variac twice... So I guess there is something faulty with some of the parts. How do I test the MOSFETS though?

Is there any possibility if I just turned on the bridge and it might kill the driver? Since it's just connected by the GDT it seems unlikely? I'm not quite sure what's going now with my whole driver and bridge.

My first bridge worked fine though only if I have used the right DC blocking caps. But I guess it's a learning curve.

[Mads Barnkob]

It is a steep learning curve to do power electronics head on, build explode, rebuild, explode, rebuild, test, run, sparks, yay!

Check this video on MOSFET testing with a DMM

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A GDT provides galvanic isolation between driver and bridge, and you will often see exploded bridges where no harm have been done to the driver section, because of the GDT. It is mostly transistors, gate resistors, zeners and diodes in the bridge that takes damage from a fault.

[futurist]

You're doing great so far, coil looks very nice!
And don't worry about burnt components - FET is commonly interpreted as "Flame Emitting Transistor"

[CCX191]

Hey guys, I'm alive!

 School was very taxing this week and I've managed to rebuild my driver for the fourth time two days ago and then consequently blow it up the next day. After some inspections one of the FETs was not switching properly and a resistor blew for the FET that blew up.


My first MOSFET that blew up
It sounds like a sort of milestone/ achievement now.

[futurist]

Did you power the bridge?

[CCX191]

I did, got some really small sparks and then it blew up later

[futurist]

Have you scoped output of your GDT? How did you conclude the MOSFET didn't switch correctly?
I would suggest asking someone who is familiar with the electronics to help you, it's hard to tell what went wrong without seeing the setup live

[CCX191]

I'm unable to scope out my GDT output as this DSO138 scope seems to show unreliable signals. Perhaps I can try the scope in my school though, if it's even working.(sucks to be in highschool)

 I concluded that the MOSFET weren't running as 3 MOSFET's heatsink were relatively warm except for one.
I'm still waiting for my DMM to arrive to test the MOSFETS as I use a cheap analogue one . Though I borrowed my friend's cheap DMM to test and shown that 5 MOSFETS from China were shorted but I have to return it shortly after.

I just went to the component shop today and bought 8 IRFP460 just in case there is more to blow. It's rather expensive here (2$ for one) and the shop is quite far and I can't drive yet.

My resources are scarce and help locally is impossible to find since I'm just in highschool or rather the electrical engineers I know seems to have no knowledge in this field. So asking here is my best bet.

The first try I did created a spark naturally but due to the wrong cap I used, it burned down. So I shall assume that my GDT is doing fine as of now. The current sparks I have been getting recently are like a Van De Graaff Generator. Only can be seen if drawn to a metal stick or sort, rather minute.

Just to reassure are these caps correct?

[Mads Barnkob]

Your cheap scope should be enough to atleast check if the phasing of the GDT is correct, unless you are 100% sure of the phasing of the GDT, do not run it again, you will just risk blowing up more MOSFETs from maybe shortcircuiting one leg of your full brigde.

The capacitors are great for DC blocking on the primary circuit. They will be able to work with the currents in this circuit, atleast for shorter run times in the minutes range, not like we do much more than that anyway.

It is great to hear that your are venturing into unknown fields to electrical engineers, just tells how little basic electronics they actually do You are on a great journey and I wish I started as young as you did!

[CCX191]

So I took out my GDT, unwind it and checked. Phasing seems to correct. Since it's already unwinded I had a read on the datastream's guide on winding GDTs.

 I understand that the wire should be physically close together and wound tightly to reduce leakage. And that screened circumferential type of winding seems to perform better.
 From what I understand, tri-filar is by twisting all the wires together and then winded in the core. So if it's screened, is it just basically a tri-filar that's been somewhat insulated with perhaps heatshrink? Is it even called a tri-filar.. there's like 5 wires..

I have some enamelled 0.5mm wire should I use that instead or stick with Ethernet wire.

I think I'm still a little lost on this whole GDT thing 
I'm currently using this core http://my.element14.com/epcos/b64290l0048x830/ferrite-core-cylindrical-34mm/dp/2355017?CMP=i-55c5-00001621

Regarding my scope, I think I will try it again and take some pictures. I'm not too familiar with this scope yet though, or rather use one. I guess I will just play around with it. Do I connect both of the probes at each end of the wire or how?

Edit: This is what I get in my scope connected one end to the negative terminal and one end to the GDT from the primary


And the other end of the primary and the negative terminal


And this is what I get connecting it to the gate and source

[CCX191]

Nothing seems to work now. I turned on the variac and nothing happens.. checked the MOSFETs they seem all good.. Everything else seems fine too.. or rather Everything seems to be in order(probably not).. checked every connection.. tried changing the phasing.. nothing seems to be working... Help!

My capacitor would still hold it's charge though so I assume it's not even switching or power is even consumed. The MOSFETs are new same goes to  the diodes and resistors which I have tested all except for the blocking capacitor. Perhaps the blocking capacitor has failed? I can only get hold of my DMM this Sunday to test  it. I I'm actually trying to get it to work by this weekend supposedly so I can present it in school but I guess that's not going to happen.

Or.. is there a way to make this to a half bridge with the irfp460?