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Andre

Mon Jan 14 2013, 02:50PM

Registered Member #6921 Joined: Wed Sept 26 2012, 07:47PM
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Posts: 109

Electra wrote ...

The higher peek voltage you were reading could possibly be down to switching spikes during the off time.

That's very interesting, could you please let me know where I can read more about it? I mean where it explains about the peak during off time, and the peak voltage for a transformer with 1:100 turn ratio, please dont say google :)

Andre

Mon Jan 14 2013, 03:00PM

Registered Member #6921 Joined: Wed Sept 26 2012, 07:47PM
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Posts: 109

Ash Small

Mon Jan 14 2013, 03:52PM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

Andre wrote ...

Electra wrote ...

The higher peek voltage you were reading could possibly be down to switching spikes during the off time.

Can you please post details of your driver circuit, as this will enable us to give you the correct advice?

Thanks.

Patrick

Mon Jan 14 2013, 04:56PM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

yes we need details as Ash says.

But as per your request, kickback is generally the explanation for large coils developing high V swing at the switch-off moment. as the coil tries to keep the coil current going, it developes cemf, though there a complicating factors too.

so this is the brief explanation as to how iggies work, they take in 12-15 volts at a a few amps. then the primary current is interupted, which generate 300-600 V CEMF across the primary turns. This primary spike is then what the secondary sees. so we get 20kv from 12 v without absurd turn ratios (and a fast rise time across the spark plug).

there are some other contributing factors (like a sign change) to oil-can and HEI coils, but its all a blur to me at the moment.

so you may have some of these factors working secretly inside your transformer, which makes it all difficult to seperate and figure out.

Andre

Mon Jan 14 2013, 07:21PM

Registered Member #6921 Joined: Wed Sept 26 2012, 07:47PM
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Posts: 109

Thanks Patrick that makes a lot sense, do you happen to know the formula for it?

Ash I have the pull -push driver circuit running at 25khz

Patrick

Mon Jan 14 2013, 07:58PM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

here;

and this is the basic derivation:

Ash Small

Mon Jan 14 2013, 08:27PM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

Andre wrote ...

Thanks Patrick that makes a lot sense, do you happen to know the formula for it?

Ash I have the pull -push driver circuit running at 25khz

I was hoping for more detailed information, eg a circuit diagram (schematic).

I assume from what you've posted it's a full 'H' bridge, rather than a half bridge or Mazilli ZVS Royer circuit (or whatever you want to call it).

At least now we know you are not driving it in 'flyback mode', for example.

Is it a circuit you built yourself, or did you aquire it 'ready built' from somewhere?

A full circuit diagram would give us a lot more information, along with details like how much current is being drawn, what the 24V supply is, etc.

Patrick

Mon Jan 14 2013, 09:23PM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

we do need more detail to give him a useful explanation of possibilities, even though hes not in flyback mode, he may still be getting some contributions from high H coils.

Tony Matt

Tue Jan 15 2013, 02:12AM

Registered Member #3700 Joined: Sat Feb 19 2011, 12:59PM
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Posts: 107

Andre:

Provide us more information, so you will receive a better advice...

Disclose the cross section of the core.
What is switching frequency ?
The total number of turns in each coil?
How many turns in each layer?
How many layers on each coil?
What material and thichness of insulation between layers ?
HOW IS THE INSULATION BETWEEN THE COIL AND CORE ?(thichness and material)
Pictures taken at dark room show corona ??
Regards

Andre

Tue Jan 15 2013, 02:54PM

Registered Member #6921 Joined: Wed Sept 26 2012, 07:47PM
Location:
Posts: 109

Thanks for the interest guys, but as Electra already explain is the offtime peak voltage, you can see the same results if you build a coil with 10 turns on the primary and 20 on the secondary, if you put 24V in and you should get 48V out but you would get about 200VDC with a rectifier, and 48VAC with out, and if you put a resistor load the voltage will drop, I was just looking for the formula to that concept,
Patrick thanks but what you posted didn't make much sense to me, I was looking to understand the peak voltage for example something as simple, that I put 24V on a 1:2 transformer and I get 200VDC, you can plug your own values,

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