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Registered Member #152
Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384
This won't be practical if you wanted to run it in the parallel resonant mode producing a sine wave output, because you'd need an air gap in the transformer core, the primary current would have to be many times higher than maximum secondary current divided by turns ratio (this means a huge transformer with ridiculously thick primary winding), this current would flow even at no load! and the frequency would rise as you load the output.
Registered Member #2893
Joined: Tue Jun 01 2010, 09:25PM
Location: Cali-forn. i. a.
Posts: 2242
Massive derp.
Turns out my ZVS is running in sine mode. When I took pix of the oscilloscope I mixed them up when I was naming the files. I named "gate" "output" and "output" "gate." The thing puts out a perfect 32khz sine. Man do I feel stupid.
Also haxor, the frequency changes with load. With a short circuited secondary the frequency on min jumps to 50kHz, which is a massive increase. That wouldn't bode well for anything you plug into your xformer.
If you want a perfect 60hz, you could try using a micro controller and an 8 bit A/D converter to make a pseudo sine, and use a couple caps or an inductor to smooth it out. Then feed that into a high powered MOSFET or an IGBT. I have no idea if it'll work, but it sounds good in theory. Well everything sounds good in theory in electronland, then it blows up in your face. I have a good feeling about this idea though.
The cool thing about the MC is that ATMEGAS programmed with the arduino boot loader are only 5 bucks. You could also make the sine wave any frequency you please just by changing a line of code, or even using a pot as an input.
How will you power this? Assuming 100% efficiency, drawing 3 amps from this transformer would draw 30@12v on the primary. You're going to need one hell of a battery to make that thing last a while.
Registered Member #1225
Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253
Steve McConner wrote ...
haxor5354 wrote ...
is it possible to make a ZVS driver to produce 60Hz output? I want to make a 120v AC inverter, i just finished making the transformer today. its a modified microwave transformer that outputs 12 + 12 volts. if its not possible to make a 60Hz ZVS, what other options do i have?
This works, I've done it. But be aware of the following:
1. You don't use the DC link choke or resonant capacitor, and it operates as a ferroresonant inverter with a square wave output.
2. You need a transformer with a center tap, and the higher the coupling between the two windings, the better. I used a 6.3-0-6.3 filament transformer from an old piece of tube equipment.
3. A toroidal transformer would be really good because they have high coupling between primaries, and saturate nice and hard, making the ferroresonant mode of operation more efficient.
4. The frequency is determined by the input voltage, and it probably won't be too near 60Hz unless you're really lucky.
Nevertheless, mine worked well enough to let me run one of my old tube amps off a 12V battery.
"For dc (rectified output) applications, ferros supply a quasi-square wave output which can reduce or even eliminate the need for filtering. For ac load applications, ferros can be designed to supply a high quality, low distortion sine wave output."
Sounds good to me
Some UPSs even use ferroresonance, and for good reason too. See more here:
Registered Member #30
Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706
Grenadier wrote ...
If you want a perfect 60hz, you could try using a micro controller and an 8 bit A/D converter to make a pseudo sine, and use a couple caps or an inductor to smooth it out. Then feed that into a high powered MOSFET or an IGBT. I have no idea if it'll work, but it sounds good in theory.
Mine ran off 24V from two deep cycle batteries in series, and drew about 30A.
The only thing is, you do the smoothing out of the waveform AFTER it goes through the high powered MOSFETs.
Registered Member #2893
Joined: Tue Jun 01 2010, 09:25PM
Location: Cali-forn. i. a.
Posts: 2242
I have a question, does it really need to be 60Hz? Many electronic devices use switch mode supplies now, and they rectify and smooth the electricity anyway. I've run a computer off of 120V dc before just to see if I could, and it worked just fine. It had no mains isolation transformer in the PSU though, that's the catch.
Obviously things with transformers and motors won't work, but things like light bulbs, CFL lamps, and computers should work OK.
Actually, I'm going to try this now. I'm going to wind an xformer on a FBT core, 6+6 turns on the primary and 120 on the secondary. I'll let you know how things work.
Registered Member #2893
Joined: Tue Jun 01 2010, 09:25PM
Location: Cali-forn. i. a.
Posts: 2242
Well would'ya look at that. It worked perfectly.
I spent the last two hours winding a transformer on a projection TV flyback core. 120 turns on the secondary, 12 on the primary [10:1]. When I pumped 12 volts into it with my ZVS, it lights up a 40 watt bulb just as bright as the wall socket does. I can't measure the volts though because my voltmeter won't do it for some reason. Maybe it's too fast, IDK.
Current leaves a lot to be desired. At short circuit I get a total of 333mA out, and at 120V that's 40 watts. Since the 40 watt lightbulb lit up at 100% brightness the volts are likely 120. 3.9 amps are going into the thing, and with .333mA@120V coming out .57 amps are lost. (3.9 - [10 * .333]). So this circuit is 85.38% efficient. That's a lot better then I expected.
Now here's something worth noting. Without an air gap in the x-former the ZVS went into the craziest oscillations my oscilloscope had ever seen. The oscillations were in harmonics, one really high pitched, one medium pitched, and one low pitched. Low defined as around 3khz and high around 15khz. The higher the squeal the brighter the lamp got. The lamp was nearly 50% brighter with the highest oscillation. With a .25mm air gap that all went away.
For some reason this won't power a CFL lamp like the one I made a while ago did. Odd. As for practical uses, the only ones I can think of are charging capacitors and powering incandescent lamps.
Registered Member #2063
Joined: Sat Apr 04 2009, 03:16PM
Location: Toronto
Posts: 352
i just wound a transformer from a ferrite inductor core, 12V ZVS input and the rectricfied + smoothed output is 33 volts but it drops to 24 volts under a load of a 12v dc brush motor
Registered Member #162
Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140
Grenadier, when you have a near short-circuit on the secondary the primary (resonant) inductance will be mainly leakage inductance, very low - so high frequency oscillation. when you have an airgap the initial operating frequency will be higher than without but with a load the frequency changes less.
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60Hz ZVS
