First DRSSTC / Tesla Coils / Forums

Forums

4hv.org :: Forums :: Tesla Coils

« Previous topic | Next topic »

First DRSSTC

previous 1 2 3 4 next

Move Thread

LAN_403

Reaching

Thu Feb 23 2006, 07:18PM

Registered Member #76 Joined: Thu Feb 09 2006, 10:04AM
Location: Hemer, Germany
Posts: 458

yeah, and i have a micro drsstc at around 300khz, and it was a pain to get it to work finally. now it works without problems.

Marko

Thu Feb 23 2006, 07:26PM

Registered Member #89 Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145

What was the key (if its not 'top secret'

)
Did you use ultrafast IGBTs, just short ON time, limiting current or something else?
People are getting such coils work with 40N60s quickly so i wanted to do something similar, seemed not to be some huge problem...

Thanks for input anyway

Reaching

Thu Feb 23 2006, 08:41PM

Registered Member #76 Joined: Thu Feb 09 2006, 10:04AM
Location: Hemer, Germany
Posts: 458

mhh, nothing top secret here. just keep the mmc relatively small, just 40-70nF to hold the peak current down. use low on times >100yS thats it

Marko

Thu Feb 23 2006, 08:55PM

Registered Member #89 Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145

If that is that coil on the picture i would be inpressed by half of that spark... lol
Its longer than secondary and still doesnt strike the rail, spike obivously helps here

So I should make full bridge of 40N60s, keep ON low and thats it?

I dont understand exactly wha is (for that frequency) half bridge so bad, it would spare me IGBTs
but its not problemat all to make H bridge...

cheers..

Reaching

Thu Feb 23 2006, 11:58PM

Registered Member #76 Joined: Thu Feb 09 2006, 10:04AM
Location: Hemer, Germany
Posts: 458

no, that is my mini drsstc. secondary is only 6" high, 0,1mm wire. max output 14"

you wont spare igbts if you build a halfbridge. at these frequencies you will have lots of switching losses on the igbts. by building a H bridge you can reduce losses .and you can go to higher peak currents, this will give you a bit safety.

williamn

Fri Feb 24 2006, 02:10AM

Registered Member #55 Joined: Thu Feb 09 2006, 04:56AM
Location:
Posts: 149

My Small DRSSTC is close to 300Khz. I am using a "fast" IGBT and as reaching explained, I also had to keep the MMC to 75nf. My on times max out at 90usec. I have not lost a IGBT yet, after much flogging all week. I have over and hour run time on this coil and it works fine.
william

HV Enthusiast

Fri Feb 24 2006, 02:12AM

Registered Member #15 Joined: Thu Feb 02 2006, 01:11PM
Location:
Posts: 3068

wrote ...

So I should make full bridge of 40N60s, keep ON low and thats it?

For a small DRSSTC, a half-bridge is all that is needed. A full-bridge is generally overkill for low power DRSSTCs.

EEYORE

Fri Feb 24 2006, 02:13AM

Registered Member #99 Joined: Thu Feb 09 2006, 06:10PM
Location: florida, usa
Posts: 637

Perhaps im just lucky, but ive run my mini drsstc(old one) around 500khz...No problems whatsoever(i used an interruptor)...

It even ran with very high on times(but got hot quickly so i kept them low)...

I think that you will be perfectly okay with your coil for lower power use. Dont run without an interruptor and also put a heatsink on the voltage regulator and driver chips(if you can).Id go for secondary feedback as well so a crappy antenna isnt to blame for a "burp" that kills your stuff:-|
Oh yea, and put caps all over your board!(decoupling, tantalum's)
And oh yea, go for a half-bridge with those 40n60s...Make sure you have a solid driver before you go applying power to th bridge.

Matt

Marko

Fri Feb 24 2006, 12:28PM

Registered Member #89 Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145

Now you confused me

at these frequencies you will have lots of switching losses on the igbts. by building a H bridge you can reduce losses .and you can go to higher peak currents, this will give you a bit safety.

As I can figure out transition losses will be higher with full bridge at that frequency, explain it a bit. H is good for dumping more power but I dont see how it benefits in reducing transition losses.

For a small DRSSTC, a half-bridge is all that is needed. A full-bridge is generally overkill for low power DRSSTCs.

Now I really dont know what to..

As I can see there are lots of such coils, operating at even more than 300khz so in the end it doesnt seem to be some huge problem after all, I never built such thing before so my experience is limited, so now I really need to know to use or not to use half/full bridge???

HV Enthusiast

Fri Feb 24 2006, 01:08PM

Registered Member #15 Joined: Thu Feb 02 2006, 01:11PM
Location:
Posts: 3068

For a small coil, you probably aren't expecting 20 foot arcs. A half-bridge will work fine and be able to produce 20"+ arcs with not much problem.

Its not a matter of switching losses or whatever, its a matter of complexity. No reason to build a full-fledged full-bridge with 4 devices, drive circuits, two transformers, etc... when a simple half-bridge topology will work as well.

Dan

previous 1 2 3 4 next

Moderator(s): Chris Russell, Noelle, Alex, Tesladownunder, Dave Marshall, Dave Billington, Bjørn, Steve Conner, Wolfram, Kizmo, Mads Barnkob