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Critical ZVS Malfunction

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Juniortore1

Wed Aug 03 2011, 10:07PM

Registered Member #4014 Joined: Wed Jul 20 2011, 05:31PM
Location: SE Michigan
Posts: 25

LOL, that is in a sense, the least of my care. This desk has so many burns and scratches. The paint is pealing off on the sides of the desk in many areas now. Although, when I spend time to hook up the driver instead of rushing to make a video, I usually put piece of plastic under the flybacks or heatsink I usually arc to.
------------------------------------------------- -------------------------------------------------- ------------

And OOh, my first star! Yayyyyyy.

Forty

Thu Aug 04 2011, 12:02AM

Registered Member #3888 Joined: Sun May 15 2011, 09:50PM
Location: Erie, PA
Posts: 649

with your hand on the supply transformer (not to mention the computer right there,) arcing to the table is a very bad thing. I'd mount your setup on a big insulating slab (wood, plexi, a cutting board) or better yet, move to a plastic table. and build a power switch into that transformer already, would you? if you get a cut or something on your finger that voltage will jump right in and you won't be happy.

on a more constructive note, have you tried using thick litz cable for the core windings? I noticed a lot less heating, plus you can make the cable as thick as you want/will fit, which means more current to the core.

Juniortore1

Thu Aug 04 2011, 01:58AM

Registered Member #4014 Joined: Wed Jul 20 2011, 05:31PM
Location: SE Michigan
Posts: 25

Yes, I know. This is a rather temporary setup. Cuts and 20+ volts feels horrible. I have done it before with a really low current transformer by accident.

Before today, i did not have this much current draw on a flyback, which is good, I want the ZVS to pull more current at lower voltages. So, the thin wire just became a problem today. I will try to replace it with thicker wire which results in bigger arcs. But on that specific flyback, there is little room for winding, so I will do my best. At some point, I want to try the three extra windings in parallel with a 100 ohm resistor like one ZVS schematic suggested for 30% more power. Thanks

Newton Brawn

Fri Aug 05 2011, 01:22PM

Registered Member #3343 Joined: Thu Oct 21 2010, 04:06PM
Location: Toronto
Posts: 311

Juniortore1:

You wrote:

@Newton Brawn: Killa-X made this PCB for me, I have never designed a PCB as I do not have the materials to do so. Anyhow, I will make a video showing front and back of the PCB. It is really simple.

Yes, the PCB (Printed Circuit Board), is very simple, easy to do... But I am not interested to do the PCB.

What Im looking for is the electrical schematic and detail of the caps, as well as the transfomer(s) winding data.

The schematic will show the topology of the circuit and how the, IRFP260N, 1n4744a zener diodes, 10k 1/4W resistors, 470 Ohm 2W resistors, .60uF 400V capacitor bank, 1n4007 "fast" diodes are wired one each other.

Also the schematic will provide precise answer to Marko, myself and other readers.

Regards

Newton

Arcstarter

Fri Aug 05 2011, 07:23PM

Registered Member #1225 Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253

I agree with marko. 1n4007's are far too slow, they probably couldn't recover so they just stayed in a sort of linear region and heated until they failed and all that current in the tank emptied into them.

The seperate 12v supply is one of the best things i could have ever done to my ZVS drivers. I use a single 1/4 resistor for each gate and they stay well within their tolerance range, though they can get somewhat hot. I use 15v, and i think 330 ohms to ensure the gate charged fast enough. This makes the gate resistor need to drop *far* less voltage, thus reducing heating, and it also makes it far less likely for the gates to see too much voltage... I never used zeners after using the 15v supply (i don't suggest this, but it worked for me).

And yes, i indeed have the same transformer as you

.

Edit: You have already commented on that video about the transformer

Juniortore1

Sat Aug 06 2011, 07:04PM

Registered Member #4014 Joined: Wed Jul 20 2011, 05:31PM
Location: SE Michigan
Posts: 25

I always have no luck with attachment pictures (.jpg format), but I will give it a try again instead of using imageshack.

I dont really understand what everybody is asking about the schematic, its just the simple ZVS schematic with the values I listed.
I am using dual power supplies now.

1312657438 4014 FT121539 My Zvs Schematic

haxor5354

Sat Aug 06 2011, 08:09PM

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

why do you need a seperate power line going to the FBT?
I pumped 50 volts into the original Mazili ZVS driver without any problems at all

pro tip: aquire lead acid batteries for moar current and less voltage drop when drawing long arcs

Juniortore1

Sat Aug 06 2011, 11:32PM

Registered Member #4014 Joined: Wed Jul 20 2011, 05:31PM
Location: SE Michigan
Posts: 25

Exactly. I input 59v on idle with the standard circuit. But everybody is telling me to use dual power supplies.

I have a rewound MOT ready which can do about 40VDC at however many amps the driver wants.

Conundrum

Sun Aug 07 2011, 08:15AM

Registered Member #96 Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4062

1N4007's are known to be utter shite for anything higher than 10 kHz.

Apparently the way to tell is to measure the reverse capacitance under high voltage of around 100V.
To do this build a simple 100kHz sine oscillator with 1V p-p output, connect an HV capacitor of known value in series with the output then connect your diode backwards (i.e. cathode to capacitor, anode to ground) between this and Gnd.
Connect a Schottky diode with the cathode pointing towards the DUT cathode, and feed into this about 100V regulated.
Then connect a second high precision >200V rated capacitor between DUT cathode and AC voltmeter.

To calculate the DUT capacitance use the well known XC formula to derive the ratios with known frequency.
Then treat the circuit like a resistive divider using XC's to determine equivalent series resistance.
What helps here is to use a known tuning diode as a well defined test source and calibrate from that.

A "GOOD" diode will measure less than 1pF whereas a bad one will be anything up to 200pF depending on the junction size and vary all over the place as the bias voltage is varied.

(wish I'd discovered this earlier before my numerous failures resulted in me losing interest in ZVS's)

As for transformers, I have a spare MOT from an inverter microwave here which could be repairable- the ferrite is cracked and glued but apparently this doesen't matter as much as if the winding is damaged.

-A

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