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Registered Member #8120
Joined: Thu Nov 15 2012, 06:06PM
Location: Moscow, Russia
Posts: 94
Fiddy wrote ... Im getting there. you havent been forgotten! Im a single bloke who works 12 hour shift work so sometimes its hard to find the time.
Sorry, didn't meant to sound like hurrying you up!
I just wondered if i missed something back then - no comments from anyone for a week and a half after you promised to start sending, then packages started arriving at the closest locations.
Registered Member #8120
Joined: Thu Nov 15 2012, 06:06PM
Location: Moscow, Russia
Posts: 94
Dr. Dark Current wrote ... n the data sheet you say: "If you exceed 3V per turn on the primary coil by putting too few turns on the primary coil, the secondary voltage may exceed the secondary insulation breakdown voltage and damage the transformer."
The secondary has 3000 turns, so if I put 3V/turn to the primary, I get 9kV on the secondary, assuming sine wave driving and no resonance.
With a square wave, the peak output will be higher because of the ringing, but still if you don't run it at resonance, it can be nowhere near 83kV.
Hm. I've been running some simulations of a typical ZVS driver with data from this transformer.
24V input, no load (500MOhm), 3V/turn primary. When the thing starts, the voltage goes up to 53kV peak, before stabilising at 27kV 10ms later. From ratio alone, you'd expect 24*(3000/8)=9kV, but you get several times that in ZVS. Next notch up, 4V/turn, you get 68kVpk start-up and 37kV stable. Which is close to the limit already. So, the warning appears to be valid.
No idea how correct the simulation is, but it matches up in the stable voltage part with another ZVS-driven AC flyback i have.
Registered Member #42796
Joined: Mon Jan 13 2014, 06:34PM
Location:
Posts: 195
a ZVS works at resonance, the output is a sine wave... the volt per turn is higher by PI due to resonant rise so your calculated 9kV gets multiplied by PI and that why you get 27-28kV
Registered Member #2431
Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639
Artlav wrote ...
24V input, no load (500MOhm), 3V/turn primary. When the thing starts, the voltage goes up to 53kV peak, before stabilising at 27kV 10ms later.
If its rated for absolute 83kV, I would'nt let it get to 53kV for even for a few mS. Id put 100 to 50 Mohms on it, or at least something. (at 53kV your at 64% of breakdown.) 35 to 40 kV is more survivable.
High frequency seems to reduce insulation life as much as heat, but Ive looked for years to find something more than the typical 60Hz and 1kHz de-rating.
Registered Member #8817
Joined: Mon Dec 17 2012, 05:16AM
Location: Australia
Posts: 110
I was running mine today trying to figure out a suitable capacitor to impedance match the secondary, with a 24VDC on my ZVS with 10 turns on the primary of the flyback i was getting a peak of 74V across it.
Registered Member #3414
Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245
I've been trying to pay using PayPal, but keep getting messages that you don't accept this type of payment. Has anyone else had any problems like this?
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Modern AC Flyback Transformers
