Wednesday, October 22, 2014

The Quad Flyback Driver --200KV from color TV flybacks!

Ok, Here it is, I will post still pics later.  This is a 200kv DC generator that uses 4 color TV flyback transformers in series.  There are NO voltage multiplication circuits here.  It is powered by my homemade CD-707 lab supply using a 1200W mosfet, IFXB100N50.   It uses a lot of power and I am pushing the limits of flyback design here.  I used to think 2 flybacks were a problem!  Four of them was more then a challenge. Put in oil, and with enough insulation and testing, this circuit runs incredibly well.  It is important that the driver can be tuned, and all primary windings are done in the same direction.  Also, very large wire must be used--HV TV wire--even in oil, 200kv will arc through almost anything.  I burned out a lot of wire before I found one that can handle it.  It runs on about 22volts at 7.8amps (about 170W).  Care must be taken not to overdrive the flybacks. A long in-oil capacitor bank prevents punching too much power through the integral flyback diodes and helps collect peak voltages.   The voltage can arc over 7 inches!  It might be possible to do more, but after a certain point the voltage on one side will probably blow through the flyback's insulation even in oil.  So using more flybacks in this way may not work long, even in oil.  To my knowledge I am the first person/lab to ever put 4 flybacks directly in series secondary connection on YouTube.

The diodes on each end must be protected since the newer color TV flybacks typically have 4 fast HV diodes in them, some more some less.  They are arranged between separated windings to prevent arcing inside the flyback itself.  Not just one diode as is often assumed. The early TV sets only had one thermionic diode tube for CRT HV system. Since the use of solid state diodes, most flybacks have at least 4 and as many as 8 or more in them.  However, on the ground and hot sides, the last diodes have to handle a lot of power when in a chain like this.  Keeping this circuit from overloading or damaging those diodes is possible but you don't want to overdrive them with too much current. Flyback failure can happen very quickly and without warning.  Once a flyback fails--there is no fixing it.  This can be from internal arcing, melted windings or diode failure.  Under some conditions a DC flyback can even change to AC--usually if it's over powered without a load.  This is rare however, I have only seen it happen once.  Many people want to remove the diodes to get an AC output, this is practically impossible since these modern DC flybacks are made of very tough materials and cannot simply be melted away or cut apart. Even very strong acids are ineffective.  Best if you want an AC flyback, buy one or wind one yourself.  There is a video on my YouTube channel "mostlymacros" describing this.  I wound up to 20kv high current AC flybacks myself. There are some companies still making them as well for various devices and they are easy to order last I checked.. Also a good resonant frequency must be found to get peak voltages out of this kind of system.  This can be done with a PWM, a 555 timer will also work fine. I have many more pics will post later (a lot of disks to burn!).   I also have other projects not yet posted, including an ion drive working model. Be sure to see my latest project below, the VTTC1000.

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