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ZakWolf

Tue Nov 27 2012, 12:24AM

Registered Member #3114 Joined: Sat Aug 14 2010, 08:33AM
Location:
Posts: 608

I want to make a SSTC driven by a zvs flyback driver. I need a couple things such as secondary res. frequency and primary res. frequency.

I use the formula f=1/2pi*sqrt(LC) **L in Henrys and C in farads**

My questions is that if i find my desired frequency what will the primary do? Wont it change the frequency that is being fed from the driver, ie more turns would alter the frequency be generated by the zvs driver. Or am i completely wrong ?

lastly, how do i find the res. frequency of a secondary? any good calculators?

Sulaiman

Tue Nov 27 2012, 07:36AM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140

my favourite calculator is JavaTC

Physics Junkie

Tue Nov 27 2012, 07:46AM

Registered Member #7267 Joined: Tue Oct 16 2012, 12:16AM
Location: Detroit, Michigan
Posts: 407

JavaTC is good. use the same equation to find the frequency of the secondary. Your units will be different of course and you will probably have to do some conversions but its pretty simple. Just change C of secondary from pF to uF and L of secondary from uH to mH

zzz_julian_zzz

Tue Nov 27 2012, 10:33AM

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

JavaTC is one of known good TC calculators. But there are plenty out there. But JAVATC's interface is more user friendly.

Steve Conner

Tue Nov 27 2012, 11:38AM

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

IMO, JavaTC is the best because it uses Paul Nicholson's numerical method for calculating the secondary resonant frequency.

Here's how I would design a SSTC driven by a ZVS:

Design a largish stubby secondary wound with the smallest wire you can handle. Use JavaTC to calculate the resonant frequency, and design your ZVS primary circuit to resonate at a slightly lower frequency than this.

For some inspiration check out the "Skori Coil", a SSTC driven by a circuit very similar to the ZVS, running off 12 or 24V.

ZakWolf

Tue Nov 27 2012, 03:27PM

Registered Member #3114 Joined: Sat Aug 14 2010, 08:33AM
Location:
Posts: 608

thanks everyone, Steve that coil is pretty cool. So thats what im going to try to do, wind a stubby secondary find its res. frequency, then build a zvs circuit to the correct frequency.

Steve you mentioned that the output frequency should be slightly lower, with that said what is a good driving range that wont put a lot of stress on the driver. 20khz-200khz, and by slightly lower do you mean by 10hkz or by 50khz?

Thanks for the answers.

Steve Conner

Tue Nov 27 2012, 03:34PM

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

Even with 0.125mm wire, which is a pain to wind, I couldn't get the resonant frequency of a tabletop coil below about 160kHz. You won't get it down to 20kHz.

The primary should be tuned something like 10kHz lower. You might want to adjust it once the coil is built. To do this I recommend putting smaller capacitors across the ZVS primary capacitor, just experiment for optimum spark output.

ZakWolf

Tue Nov 27 2012, 06:24PM

Registered Member #3114 Joined: Sat Aug 14 2010, 08:33AM
Location:
Posts: 608

Steve Conner wrote ...

Even with 0.125mm wire, which is a pain to wind, I couldn't get the resonant frequency of a tabletop coil below about 160kHz. You won't get it down to 20kHz.

The primary should be tuned something like 10kHz lower. You might want to adjust it once the coil is built. To do this I recommend putting smaller capacitors across the ZVS primary capacitor, just experiment for optimum spark output.

So i should aim for the higher range like 140-170khz. How will the zvs driver act running at hat frequency?

ZakWolf

Tue Nov 27 2012, 06:56PM

Registered Member #3114 Joined: Sat Aug 14 2010, 08:33AM
Location:
Posts: 608

I used a program wintesla to find these numbers.

Are these ok? i am going to use 40awg! i will wind until i cant wind any more.

According to the data at 40awg the res frequency is at 121khz

Lastly, in the primary data pic it says needed capacitance is 0.1622uf is that taking the 3+3 turn primary windings (approximate) into consideration, because if I plug those numbers in this equation f=1/2pi*sqrt(LC) **L in Henrys and C in farads** I get ~41khz.

Is this all checking out?

Physics Junkie

Wed Nov 28 2012, 01:15AM

Registered Member #7267 Joined: Tue Oct 16 2012, 12:16AM
Location: Detroit, Michigan
Posts: 407

The 121 khz is the frequency without the top load, you will want to make note of the frequency with the top load for more accurate matching of primary and secondary frequency. and I cant tell from the pics but when you calculate the primary frequency, don't forget about the capacitance of your mmc (you may or may not be using one with ZVS driven sstc)

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