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Longest time you can run a ZVS for?

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Alex M

Sun Oct 23 2011, 08:55PM

Registered Member #3943 Joined: Sun Jun 12 2011, 05:24PM
Location: The Shire, UK
Posts: 552

Hello, after lots of playing around with my ZVS driver I am now looking to put it to good use this Halloween.

I am just wondering how long have you guys ever had your ZVS flyback driver running continuously for?

This is for a Halloween display (at home). I will be supervising at all times with my finger on the kill switch and the arc will be taking place inside of a pumpkin (lol, really!) between some carefully spaced aluminium "sparkler" electrodes. I will be running it on 24v input rather than 36v to reduce heating of the flyback. I only really plan on running it continuously for about 3 minutes max then letting it cool down for a while.

Basically my question is: What is the longest amount of time you have ever had your ZVS flyback driver running for?

Adam Munich

Sun Oct 23 2011, 09:30PM

Registered Member #2893 Joined: Tue Jun 01 2010, 09:25PM
Location: Cali-forn. i. a.
Posts: 2242

All depends on the components, mostly the capacitor. Choose a sturdy cap and there is no reason it can't run forever.

Pieznice29

Mon Oct 24 2011, 01:36AM

Registered Member #3918 Joined: Sun May 29 2011, 08:42PM
Location:
Posts: 34

I use a ZVS driven flyback to power a carbon dioxide laser, i've run it for anything up to half an hour at a time with no noticeable damage, drop in output, or large amounts of heat. I see no reason you can't run it continously other than cheap components exploding...
Like Grenadier said, the cap is probably the most important thing. I brought some expensive audio-grade caps for mine and i've never noticed any heat coming out of it at all with 24V input driving a 350Wish load.
Point a small fan in the drivers direction and it should run happily all day long.

...

Mon Oct 24 2011, 05:04AM

Registered Member #56 Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445

Like others of have said, the driver should run forever. If you use a poor quality resonant cap you might run into issues with it, but as long as the cap doesn't get warm you will be fine.

I would be more worried about the flyback, since they are usually not designed for the huge amounts of power that you can push with these drivers. I would do a test run and look for signs of heating, keeping in mind that flybacks have pretty poor thermal conductivity between the windings and the outer plastic shell, so it may take a while for the outside of the transformer to get hot, and blowing a fan on it will only mask the effects and not do much to prevent the secondary from melting internally.

Dr. Dark Current

Mon Oct 24 2011, 09:50AM

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

I often had problems with the core getting too hot. After it gets above the Curie temperature, the inductance drops and driver goes pop.

Alex M

Mon Oct 24 2011, 10:27AM

Registered Member #3943 Joined: Sun Jun 12 2011, 05:24PM
Location: The Shire, UK
Posts: 552

Thanks for the replies guys!

Yes the capacitor is what I was concerned about the most, as the caps I am using are two filter caps in parallel from an old power supply and they do get quite warm after about 2 minutes. Everything else on the driver stays nice and cool (minus the flyback lol, although I am not too bothered about the flyback as I have a whole box of them).

Would this sort of thing be a decent replacement for the ZVS capacitor

I was thinking of buying a 0.47uF and a 0.22uF then putting them in parallel.

I also found some audio grade caps but they are only rated for DC current

, although I am not sure if they are actually polarised.

Let me know what you guys think as I can pick them up from the store in the week ready for the weekend.

Thanks.

@Dr. Kilovolt What input voltage were you running your ZVS @ in order for the core to get very hot?

Dr. Dark Current

Mon Oct 24 2011, 01:50PM

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

Alex, the heating is mostly dependent on volts per turn and frequency, however the core also tends to heat up from the primary.
I often had the problem of "screaming" arcs, which is usually cured by adding air gap in the core, but this also increases primary current and frequency and the core gets hot.

Pieznice29

Mon Oct 24 2011, 02:30PM

Registered Member #3918 Joined: Sun May 29 2011, 08:42PM
Location:
Posts: 34

Alex1M6, the first caps you linked are the ones I used. Specifically the 0.47uF 500v one. I was going to use 2 of them in parallel, but they only had one in stock at the time. So I pulled some of those x2 class filter caps out of a PC power supply, and put a 0.33uF one of those in parallel with the audio cap I brought. Had no issues with that setup so far.

Dr. Dark Current

Mon Oct 24 2011, 06:03PM

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

Yes, X2 MKP caps usually run cool in this application and are very cheap (or free if you take apart a few PC PSUs).

coil.marc

Tue Oct 25 2011, 07:49PM

Registered Member #4164 Joined: Tue Oct 25 2011, 07:28PM
Location:
Posts: 2

I passed the ZVS with IRF Mosfets 740 it works well, after he dropped

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