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Stepping down 200kv to 1kv

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Andy

Tue Sept 03 2013, 07:28AM

Registered Member #4266 Joined: Fri Dec 16 2011, 03:15AM
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Hi Proud Mary

That was the idea, one cycle would make it easier for the inductor to charge up(lower resistance) they other cycle would make it imposable(higher resistance)

Proud Mary

Tue Sept 03 2013, 08:10PM

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Antonio

Wed Sept 04 2013, 01:11AM

Registered Member #834 Joined: Tue Jun 12 2007, 10:57PM
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The last schematic also practically short-circuits the DC power supply. Remember that for DC inductors are just wires. Look at the current coming from the power supply.
A magnetic amplifier uses core saturation to vary the inductance of a coil, and so its impedance for AC signals. The control is DC. Linear simulations would not show the effect.
About the question about stray capacitances: Any coil has an equivalent capacitance across it, and two from both ends to ground (approximating the distributed capacitances). These capacitances must cause resonances much above the operation frequency. Calculating the capacitance that resonates with 80 H at 100 kHz, the obtained value is 0.0316 picofarads.

A sphere with 1 mm of radius has about 0.1 pF of capacitance to the surroundings. The whole 80 H transformer must be microscopic to operate at 100 kHz...

Andy

Wed Sept 04 2013, 01:29AM

Registered Member #4266 Joined: Fri Dec 16 2011, 03:15AM
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Hi Antonio

The saturation, would it make the inductance drop and current rise?.

I got abit carried away with 100khz, I'm working on 10khz for the driver.

Antonio

Thu Sept 05 2013, 12:27AM

Registered Member #834 Joined: Tue Jun 12 2007, 10:57PM
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Saturation decreases the incremental inductance, lowering the impedance. Transformers shall be designed with the minimum possible inductance for the application, or soon problems with stray capacitances, and excessive size or cost appear.

Andy

Thu Sept 05 2013, 12:44AM

Registered Member #4266 Joined: Fri Dec 16 2011, 03:15AM
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Hi Antonio

If the core is small, that should make the main inductor impedance match the wire resistance when one of the driver circuits is on, but when one side of the driver circuit trys to make more resistance by flowing in the opposite direction would that also lower its resistance, or won't it matter?
Should the driver be at a high voltage or more current than the main one, so to stop the field expanding?

Thanks

To anyone, would iron powder and PVA or fibreglass work as a ferrite. If I surround the below pic in the stuff would the coupling be around 0.1-0.3 0.4-0.6, 0.7-0.9. Its got 5000 permeability with 1.2T/meter at 100A/meter

Andy

Fri Sept 06 2013, 04:10AM

Registered Member #4266 Joined: Fri Dec 16 2011, 03:15AM
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Done a little test with what I had on stock, The transformer was a MOT, the two inductors were just some hookup wire wrapped 20 times around a piece of steel, flicking the switch on and off made the cap have a voltage of 1.20v from 0.07v. When hooking up the ac supply the voltage didn't raise above 0.07v.

Any ideas?

Proud Mary

Fri Sept 06 2013, 05:42AM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

Well now, if we estimate the path R1, L1, L2, to have a DC resistance of 0.75Î©, then 16A will flow from your 12V battery if it is big enough (i.e. a car battery) and R1 is big enough not to burn out.

If the battery can't supply that much current, the voltage will fall, because the battery will think there is a short circuit across it.

What the effect might be of injecting a low AC voltage into this arrangement via T1 is anybody's guess, since it will act on the electrochemistry of the battery in a way that is probably best discovered by experiment. The battery might, in time, explode, for example. Who can say?

If you would explain, step by step, and component by component, what this circuit is intended to do, it would make life simpler for those who are prepared to comment on it.

The sort of questions you should be able to answer might include, for example only, 'what would be the effect on circuit operation of increasing the value of R1 to 100Î©? ' or "what would be the effect of increasing L1 to 10mH, while decreasing L2 to 0.5mH?' or 'what would be the effect on circuit operation of changing the transformer ratio to 20:1 while decreasing the battery voltage to 6V?

Andy

Fri Sept 06 2013, 06:19AM

Registered Member #4266 Joined: Fri Dec 16 2011, 03:15AM
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Posts: 874

Hi Proud Mary

L1 and L2 are inductor divider network, with dc the cap should have zero voltages across it(the dc supply has small ripple). The transformer does.... I think act as two inductors in parallel, pulsating dc applied to the other side of the transformer probable changes the inductance...or the pulsating dc makes the other side generate a voltage across it in antiparrellel to the battery(which is what I'm trying to do, to stop the cap discharging when a trigger is present).

But why does it work with L1 there but not when its not there.??????

Replace T1 and L1 with a transistor and that is the setup that I'm after.

R1 isn't meant to be there, it effects what I'm after, but forgot to remove it.
I keep going back to the same theory on all these posts, and they all wouldn't work without L1 there, changing L1 and L2 doesn't do anything measurable as there isn't much power from the driver, but it looks like this setup would be the way to go.

Ash Small

Fri Sept 06 2013, 11:44AM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

Andy wrote ...

To anyone, would iron powder and PVA or fibreglass work as a ferrite.

"Ferrites are ceramic compounds of the transition metals with oxygen, which are ferromagnetic but nonconductive. Ferrites that are used in transformer or electromagnetic cores contain nickel, zinc, and/or manganese compounds. They have a low coercivity and are called "soft ferrites" to distinguish them from "hard ferrites", which have a high coercivity and are used to make ferrite magnets. The low coercivity means the material's magnetization can easily reverse direction without dissipating much energy (hysteresis losses), while the material's high resistivity prevents eddy currents in the core, another source of energy loss. The most common soft ferrites are:
Manganese-zinc ferrite (MnZn, with the formula MnaZn(1-a)Fe2O4). MnZn have higher permeability and saturation levels than NiZn.
Nickel-zinc ferrite (NiZn, with the formula NiaZn(1-a)Fe2O4). NiZn ferrites exhibit higher resistivity than MnZn, and are therefore more suitable for frequencies above 1 MHz."

Powdered iron is not ferrite. Ferrites are oxides.

(there was a recent link to a video here somewhere which suggested that it might be possible to 'sinter' ferrites in a microwave oven)

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