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60Hz ZVS

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haxor5354

Sun Oct 31 2010, 01:29AM

Registered Member #2063 Joined: Sat Apr 04 2009, 03:16PM
Location: Toronto
Posts: 352

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?

1n5ane

Sun Oct 31 2010, 02:19AM

Registered Member #3283 Joined: Wed Oct 06 2010, 11:03PM
Location: Toronto, Canada
Posts: 29

The frequency depends on the inductor and the capacitor you use in the ZVS circuit, varying either will alter your frequency. However, you can't get it as low as 60Hz

You're better off using a simple mosfet and 555 timer style driver.

Adam Munich

Sun Oct 31 2010, 02:32AM

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

You'll want something that outputs a sine wave. A zvs outputs a sawtooth from my measurements, and a simple 555 driven FET will give you a square.

^WRONG

haxor5354

Sun Oct 31 2010, 02:51AM

Registered Member #2063 Joined: Sat Apr 04 2009, 03:16PM
Location: Toronto
Posts: 352

ok maybe im better off by making a DC-DC converter with a ZVS driver

Sulaiman

Sun Oct 31 2010, 10:09AM

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

From my experience;
- if a zvs is producing triangle waves it's not a zvs!
(it may be a zvs circuit diagram but it's not operating in zvs mode)

- it certainly is possible to operate a zvs at 60 Hz
the secondary can be used as the resonant inductance
the end result would be extremely expensive, large transformer/capacitor.
Don't forget, you also have to build the battery charger.

- the 'standard' way to make such an inverter is a two-stage one
1, a squarewave dc/dc converter , e.g. 48 Vdc to 180 Vdc
2, a high frequency full-bridge dc/ac converter with output inductance

Frankly,
the development effort to make a reliable converter is not worth it,
a comercial PC ups is probably cheaper than your cost of parts alone.
Also, you can learn a lot from studying a commercial ups
and you get a dc battery supply with charger
and an isolated 120 Vac supply.

Myke

Sun Oct 31 2010, 04:00PM

Registered Member #540 Joined: Mon Feb 19 2007, 07:49PM
Location: MIT
Posts: 969

I agree with Sulaiman. I'm not sure how you could get anything but a sine wave with the ZVS because it's a resonant tank circuit. I guess you could somehow try to force it to look triangular but that would mean you are wasting lots of energy doing so.

Quick question Sulaiman. Can't you use the primary as the resonant inductance? The secondary has a fairly high resistance for a 12V input so the tank wave would look damped and the MOSFETs would have to deal with switching across the difference. Does the core saturation have to do with the current though the coil -- because that directly affects the magnetic field -- or the voltage across it? If it were the voltage across the coil at any time, the core should be quite far from saturation (roughly 36V peak) but if it were dependent on the current, it may saturate because of the large circulating currents in the parallel LC tank.

Adam Munich

Sun Oct 31 2010, 04:40PM

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

I'm actually getting more of a sawtooth sine type thing. Whatever, it seems to work fine because It pushes 1280 watts out of a computer FBT (@36v).

haxor5354

Sun Oct 31 2010, 05:30PM

Registered Member #2063 Joined: Sat Apr 04 2009, 03:16PM
Location: Toronto
Posts: 352

does a 'standard' 60Hz transformer work on high frequency switching from a ZVS driver?

Antonio

Mon Nov 01 2010, 01:04PM

Registered Member #834 Joined: Tue Jun 12 2007, 10:57PM
Location: Brazil
Posts: 644

Grenadier wrote ...

I'm actually getting more of a sawtooth sine type thing. Whatever, it seems to work fine because It pushes 1280 watts out of a computer FBT (@36v).

The "zvs" driver has a "wrong" mode of operation that produces pulsed output and drains a huge current from the power supply. Heavy load or too small series inductance puts the system in it, usually causing destruction. The picture shows a simulation of the currents in the normal mode and in the other mode:

Steve Conner

Mon Nov 01 2010, 01:25PM

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

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.

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