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need to make a 15 volts dc filter curcuit for a zvs driver

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ubuntupokemoninc

Tue Oct 19 2010, 10:23PM

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My lust for more powerful arcs is kicken in, and modded a mot for roughly 15volts to power my zvs driver because i need more power!

I've never made a psu before not sure were to turn, I know I need 2 caps and a resister, but what I'm really asking what values should I use?

1n5ane

Tue Oct 19 2010, 10:42PM

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If you're trying to build a DC power supply, you would first need to rectifiy the AC coming from the rewound MOT; a 25A-35A bridge rectifier is probably good. A large value capacitor (4700-1000uf) is probably sufficient for filtering, screw terminal type capacitors are usually the best for this. Also, remember that the RMS voltage will be higher than the AC voltage coming off the transformer. AC volts x 1.414 = DC rectified voltage.

If your output voltage is too high, you can either unwind a few turns off the MOT or you can use a couple rectifier diodes in series to drop the voltage...

ubuntupokemoninc

Tue Oct 19 2010, 10:51PM

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so then do i need 2 caps to follow this circuit, and what about the resister value?

1n5ane

Tue Oct 19 2010, 11:08PM

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An RC filter circuit like the one you posted isn't recommended for high current applications; the resistor would need to dissipate a large amount of power.

The "better" alternative is an LC filter; you basically replace the resistor with a choke. You can also "stack" several LC circuits for additional filtering if you wanted...

ubuntupokemoninc

Tue Oct 19 2010, 11:11PM

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how big of a choke? Any one know were to find electrical calculations so i don't have to keep asking noobie questons?

like how many UH=ohms is basicly what i'm asking

1n5ane

Tue Oct 19 2010, 11:20PM

Registered Member #3283 Joined: Wed Oct 06 2010, 11:03PM
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Try reading this:

In an nutshell, X = 2(pi)(F)(L) will give you an equivalent resistor that you would use in the RC equivalent of the LC circuit. In your case, F = 60Hz and X = whatever resistor you where gonna use in the RC circuit.

ubuntupokemoninc

Wed Oct 20 2010, 12:29AM

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ok then 376.8 hernes should give me roughly 10 amps with 20.3 volts in right?

btw I have been taking notes on the calculations you give me.

1n5ane

Wed Oct 20 2010, 12:46AM

Registered Member #3283 Joined: Wed Oct 06 2010, 11:03PM
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Current is not involved, I think you may be confusing the units... L = Inductance, F = frequency, X = ohms. The only time current comes into play is when you wind the choke; you simply need to make sure that the wire/windings can handle the current you need to draw...

X = 2(pi)(F)(L) involves the resistance you originally wanted to use in the RC circuit (X) and 2(pi)(F) which works out to 120(Pi). L (the inductance of the choke in henries) = x/(120 x Pi).

For example, if you wanted to use a 1k resistor in the original RC circuit: 1000/(120 x Pi) = 2.65H ... That means that you would simply sub in a 2.65H choke in the place of the 1k resistor.

If you do not have a particular resistor value in mind, you can just build a choke with a 50-100 turns of 20-16awg wire around a large ferrite core.

ubuntupokemoninc

Wed Oct 20 2010, 01:51AM

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I need 2 ohms

ScotchTapeLord

Wed Oct 20 2010, 01:58AM

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Why not just use the ripply waveform? Does this application really require more smoothing than a single capacitor after the rectifier provides?

High voltage devices sound more menacing with a little mains line hum, in my opinion!

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