The Beginnings of a Fusor Electrical System

This forum is for specialized infomation important to the construction and safe operation of the high voltage electrical supplies and related circuitry needed for fusor operation.
Rex Allers
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Re: The Beginnings of a Fusor Electrical System

Post by Rex Allers » Thu Aug 03, 2017 12:39 am

Duncan,

Reread my post of Mar 7 in the middle of this thread. See the one picture where I redrew your node diagram with some extra labels? I highlighted where I think the coils are by coloring the lines red.

So yeah, two primaries, each with a center-tap.

I suggest, put your low voltage AC input across pins 5 and 7. Put your meter common wire on pin 8 and the other meter wire on pin 3 (top of coil).

Slowly ramp up the voltage. I would expect with about 1 Vrms in, you may see about 250 V on pin 3.

If I am right, turn it off and try moving the meter lead from 3 to 4. About the same result with 1 V in?

Now try input across 9 and 12. I would expect again about the same.

What if you jumper (directly connect) 5 with 9, and 7 with 12 and put input 5 to 7?

Extra points for feeding less of the primaries (say 5 to 6) or hooking the two primaries in series (jumper 7 to 9, and input 5 to 12).

Now how do you figure out the turns ratios of primary to secondary?
Rex Allers

Duncan Wilkie
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Re: The Beginnings of a Fusor Electrical System

Post by Duncan Wilkie » Sun Aug 27, 2017 8:40 pm

The output voltage measured between pins 3 and 8 and between pins 4 and 8 was a very stable 400V at 1V input. Similar results were observed with the other primary. However, when jumpering them in parallel, there was only a 100V increase in voltage from the original 400. Jumpering in series yielded a decrease in voltage to ~100V and feeding half of the primary lead to an increase to about 500V. The turns ratio (primary/secondary) is 1:400.
Some say the glass is half full. Others see it as half empty. I say it is twice as big as it needs to be.

Duncan Wilkie
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Re: The Beginnings of a Fusor Electrical System

Post by Duncan Wilkie » Mon Jan 08, 2018 2:49 am

I have a question regarding current metering. The schematic on the FAQ for a center-tapped transformer (here) shows grounding to a metal case. I don't have a metal case on my device. I assume I simply place it in the ground loop of my device, but can I do this with an ac transformer?
Some say the glass is half full. Others see it as half empty. I say it is twice as big as it needs to be.

John Myers
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Re: The Beginnings of a Fusor Electrical System

Post by John Myers » Mon Jan 08, 2018 3:34 am

The center tap of that transformer is grounded to its own metal case.

The meter and sense resistor is connected in between system ground and the metal case of the transformer.

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