Re: [TCML] SISG coil

[bartb <bartb@xxxxxxxxxxxxxxxx>]

Hi Jay,

SISG's do use IGBT's yes. But there is really no reason to parallel the 
IGBT's as they already use large cap sizes. However, even if you did 
parallel say 2 strings of SISG's, both strings would need to turn on to 
share current and that's going to be a bit of a problem. I'm sure there 
might be some tricks to do that could make it happen, but I think it's 
rather unnecessary since SISG's use high voltages unlike say a DRSSTC 
that uses relatively low voltages and high current. The SISG was 
basically a solid state replacement for a spark gap. In essence, pull 
out only the spark gap and drop the SISG in it's place. In reality, you 
really do want a much larger cap size than you would normally use for a 
spark gap coil. I don't believe the SISG is as efficient as a spark gap 
can be (then again, some spark gaps really suck).

I think from a solid state view, the DRSSTC is the winner in most cases 
for what you can do with a coil, from playing midi songs to building 
coils that can put out some serious spark lengths if that is your goal. 
For example, Phil Slawinski built a DR that put a spark length 5.3 times 
longer than his secondary length. That is really impressive and is 
certainly a very nice top notch DRSSTC.

Regards,
Bart

jhowson4@xxxxxxxxxxx wrote:
> Is there a way to parallel the components that limit the current, so  you could handle more current and thus use a larger cap size? 
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> I would imagine so, but i worry about an unequal current distrubution due to slight variences in the component itself and then there is the problem with what happens if both parts dont fire at the same time.    
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> The part i am talking about here is an IGBT right?  cause i dont really know.  
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> Thanks, 
> John "Jay" Howson IV 
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> "Why thank you, I will be happy to take those electrons off you hands."  
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> Thanks, 
> John "Jay" Howson IV 
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> "Why thank you, I will be happy to take those electrons off you hands."  
>
>
> ----- Original Message ----- 
> From: "James" <mustang3@xxxxxxx> 
> To: Tesla@xxxxxxxxxx 
> Sent: Friday, August 20, 2010 12:25:09 AM 
> Subject: [TCML] SISG coil 
>
> Hi Bart, prolly 100nF in that vid. I normally run that coil on three MOT's, 
> sec's in series, pri's in parallel. A large choke is used to control the 
> current. Normally (using MOT PS) the SISG coil uses 144nF. Firing at 12KV. 
> The firing voltage is determined by the SIDAC string. Each module conducts 
> around 900 to 1000 volts. I am using 12 when running on the MOT's, 16 
> modules when using the pole xmfr. Thing about the SISG coil is how spooky it 
> is. When the coil is energized, but the variac is set lower than the firing 
> voltage, there is no noise. Back in the old days with the spark gap coils 
> you could hear the coil was energized (it would hiss) even if it wasn't 
> firing the spark gap.  Since the SISG runs on DC, extreme caution is 
> required. James 
>
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