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I will modify it to have 20 turns and try it at full 120 tonight. I am keeping the IGBTs cool at 30V and letting a 3" arc stay for over 10 min. but ill try to increase the turns because I was indeed in deep saturation. I have 240 ohm resistors on the gate is that ok or should I go lower?
edit
I tried 20 turns on each so total of 40 and it started to squeal I turned up the voltage and while drawing an arc to 4" at 70V the wire on the primary melted (18awg magnet) and the IGBTs both failed. .
ok so I am having a continuing problem with this I have been able to get very long arcs with it but the windings on the transformer melt and the heat sinks on the IGBTs get so hot I fan cooled them I cain't seem to find the problem.
my two suspects are:
1) the resistor is too low or too high of a value on the gate of the IGBT
2) I have too few turns and I am saturating the core at higher voltages even though I calculated it and I should be able to run it up to 80V it fails at 40-50V. as I have 15 turns on each so a total of 30 turns on the flyback.
any help here it would be nice to fide the problem so I can package it up.
Registered Member #89
Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145
Please, have you read the article?
What you must understand that *frequency* is the factor that will lead to core saturation.
Leaving a 0,68uF capacitor and increasing number of turns will not accomplish anything. (You need to reduce it gradually to keep no-load frequency constant.
You need to calculate your frequency by 1/2pi*sqrtLC. Then use the equation from thedatastream's site.
Don't go over 100kHz to keep switching losses down.
1) the resistor is too low or too high of a value on the gate of the IGBT
Resistors can't be too small - they can only be too hot but that is OK if you don't mind.
Registered Member #540
Joined: Mon Feb 19 2007, 07:49PM
Location: MIT
Posts: 969
You could tune it. It helped with the heating but tuning it makes it draw a ton of current. I tuned my ZVS flyback driver and I'm drawing 8.5A at 12V. Make sure that your wires can handle the current. You find the resonant frequency with a signal generator on the primary and an o-scope on the secondary. Start at a low frequency and increase it until the output voltage peaks and starts to go down. Then you measure the frequency at the peak. It should be around 40KHz for a monitor flyback and 15-16KHz for a TV flyback.
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ZVS Fly back driver PCB and updated schematics
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