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Registered Member #540
Joined: Mon Feb 19 2007, 07:49PM
Location: MIT
Posts: 969
A cheap way to make a high current transformer is the rewind an MOT (microwave oven transformer). They can be picked up from the curb in your area for free or bought cheaply from something similar to a flea market depending on where you live. You would either remove the high voltage secondary windings with a hacksaw and pound them out with a hammer or cut the welds and clamp it back together. I would leave the welds intact even though you have to feed a lot of wire through the core because it's difficult to stop the MOT from humming after the welds have been cut (also you would need to make some sort of clamp to hold it together tightly). You need a high current bridge rectifier to handle the currents you would be drawing. It would be a good idea to put in a fast blow fuse on the secondary to try to protect the bridge in case the MOSFETs fail or you accidentally short the leads. You also need a fairly large capacitor to smooth out the voltage from the bridge. Make sure the capacitor's max voltage rating isn't exceeded by having it be at least sqrt2*Vrms with a little head room (so maybe around 130% of the peak output voltage? It doesn't hurt to have more headroom).
Registered Member #56
Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445
I have had good luck with the 10A variac but a nice filter capacitor, it will give you more or less unlimited power as far as most flybacks are concerned.
If you don't have a variac, stacks of ATX power supplies work well, or a rewound MOT if you don't have ready access to old supplies.
Registered Member #3114
Joined: Sat Aug 14 2010, 08:33AM
Location:
Posts: 608
im using a 19v .8 amp power supply and i get arcs that over an inch but when i put a 12v 2.5 amp in series with it, i can draw a long white arc then it shuts off am i drawing to much current?
Registered Member #2416
Joined: Sun Oct 04 2009, 04:23AM
Location: Oceanside, CA
Posts: 91
Probably. At 19v the circuit will draw much more current than 800mA. So if you're stressing your supply too much it will either shut down or the voltage will drop under the heavy load. At 30v you should be able to get 4-5in white arcs. Here is a video of mine running of 40v form my 10amp variac.
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Cheap power supply for my ZVS driver
thanks
