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My first working DRSSTC had some problem

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hsieh

Fri Jan 27 2012, 03:14AM

Registered Member #1412 Joined: Thu Mar 27 2008, 04:07PM
Location: Taipei Taiwan
Posts: 278

This is my first working DRSSTC.The driver is based on Steve's DRSSTC-1(I choose this driver because I found many hobbyists in China have good result with it)The halfbridge is consists of two 40N60B3 IGBT.Resonant capacitors are three 8KV 0.1uF capacitor connected in series.Resonant frequency is around 277Khz~288Khz.

I only get 10cm sparks at 110VAC input even if the on time is set at maximum.OCD is set at 100A but it is not triggered.What might be the problem?

Daniel Kramnik

Fri Jan 27 2012, 06:42PM

Registered Member #3885 Joined: Sun May 15 2011, 12:47AM
Location: Newton, Massachusetts, United States
Posts: 94

You need a topload (I'm surprised it's even working without one!), and you'll probably want less coupling.

Also, you might want a bit more capacitance so you can push a little more primary current, but that's something you should only worry about once you see how it performs with a topload and proper primary. I'd still take it down from 3 series to 2 series CDE caps though.

Did you tune it for resonance with an oscilloscope?

E.TexasTesla

Fri Jan 27 2012, 11:17PM

Registered Member #4362 Joined: Sat Jan 21 2012, 03:44AM
Location: Texas
Posts: 98

I only see one set of gate drivers. Steves schematic "drsstc 1" shows 2 drivers each for the gate transformers. I only see one transformer or am I missing something?

X2 on the toroid.

Dr. Dark Current

Fri Jan 27 2012, 11:35PM

Registered Member #152 Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384

Also, your primary position/coupling seems kind of weird and your primary looks untunable.

hsieh

Sat Jan 28 2012, 02:10AM

Registered Member #1412 Joined: Thu Mar 27 2008, 04:07PM
Location: Taipei Taiwan
Posts: 278

Daniel Kramnik wrote ...

You need a topload (I'm surprised it's even working without one!), and you'll probably want less coupling.

Also, you might want a bit more capacitance so you can push a little more primary current, but that's something you should only worry about once you see how it performs with a topload and proper primary. I'd still take it down from 3 series to 2 series CDE caps though.

Did you tune it for resonance with an oscilloscope?

Yes,I tune it using an oscilloscope.

zzz_julian_zzz

Sat Jan 28 2012, 02:12AM

Registered Member #3964 Joined: Thu Jun 23 2011, 03:23AM
Location: Valenzuela City
Posts: 332

Phasing is the problem.. It will work w/o toroid, coupling should be fixed properly, Your coil looks an SSTC and not a drsstc, fres sec must be greater than the primary fres.

hsieh

Sat Jan 28 2012, 03:31PM

Registered Member #1412 Joined: Thu Mar 27 2008, 04:07PM
Location: Taipei Taiwan
Posts: 278

I add the topload,use slightly larger capacitor(now:total 0.047 previous:total0.33).My capacitor is now WIMA FKP1.I build a new primary and also check my resonant frequency with oscilloscope.My secondary is 235KHz and primary is 230KHz.

I tried to reverse my primary phasing but if I do so my coil won't work at all.

It's too difficult for me to make a flat and adjustable primary.I don't have necessary tools and stores here don't open during Chinese new year vacation.

But it's performance is about the same.

teravolt

Sat Jan 28 2012, 05:36PM

Registered Member #195 Joined: Fri Feb 17 2006, 08:27PM
Location: Berkeley, ca.
Posts: 1111

have you tried using those other caps in parallel instead of in series since they are 8Kv each? use the oscilloscope and a signal generator to determine whether your primary is resonant with your secondary. you may have a tuning problem. your signal generator can be as simple as a 555 and one-shot to peduce a variable frequency and pulse width. another thing I see is a lack of power. you can also increase your primary wire diameter to something like 10 awg. the things that make a spark larger in a Tesla system is tuning and power delivery to the secondary. So try using a primary that gets closer to your secondary with out flashing it to increase coupling. coupling will increase your power delivery but one of the trade offs is flashing or arcing to the primary. if you have the energy you could rewind your secondary with a finer wire say 28 or 30 awg and that will give your coil more inductance, higher Q, lower Fres. the trade off is higher voltage and lower current out. just remember that power=spark length but the trade off is you have to protect your silicon.

Steve Conner

Sat Jan 28 2012, 07:00PM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

I think you did great getting a DRSSTC to work at all, congrats!

You just need to use a bigger topload and reduce the number of primary turns, until you get the spark length you want, or it explodes.

Uspring

Sat Jan 28 2012, 08:44PM

Registered Member #3988 Joined: Thu Jul 07 2011, 03:25PM
Location:
Posts: 711

hsieh wrote:

I only get 10cm sparks at 110VAC input even if the on time is set at maximum.OCD is set at 100A but it is not triggered.What might be the problem?

110V AC input should amount to about 150V DC bus voltage. That you can't get 100A into your primary tank seems to indicate a lot of primary resistance, i.e. >1.5 ohms. With thick wires or copper tubing resistance of about 0.3 ohms should be feasible. Do you know how high your primary current is?

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