Christmas Comes Early!

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.
Andrew Seltzman
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Re: Christmas Comes Early!

Post by Andrew Seltzman » Sat Jun 10, 2017 9:14 pm

In that design, it was in an insulating tube in air. For your fusor you could go either way
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Garrett Young
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Re: Christmas Comes Early!

Post by Garrett Young » Sat Jun 10, 2017 11:42 pm

Andrew,

The RL snubber is a good suggestion. I'm calculating something on the order of 100mH in parallel with a 100kohm (5us short, 50kV, and 10nF output capacitance) to limit the current pulse to 3A. Does this make sense to you?
Last edited by Garrett Young on Sun Jun 11, 2017 12:10 am, edited 1 time in total.
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Re: Christmas Comes Early!

Post by ian_krase » Sun Jun 11, 2017 12:07 am

That's a very large value resistor, for a big ceramic one.

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Re: Christmas Comes Early!

Post by ian_krase » Sun Jun 11, 2017 5:34 am

And also a pretty big inductor. Seems like this might need to be made with smaller components under oil or paraffin.

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Richard Hull
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Re: Christmas Comes Early!

Post by Richard Hull » Sun Jun 11, 2017 5:09 pm

VCU (Virginia Commonwealth University) had a major issue with there grossly under powered, yet very expensive, Spellman supply on their fusor. They had to carefully select a ballast resistor due to the current limit tripping out the system when the plasma struck. Ultimately, they hit the correct value.

They have a 0-30kv 10ma model $$$$. They are limited to running at about 25 kv due to the gobbling up of voltage in the ballast. Thus, their fusion is minmal to marginal. Their good detection system was appropriated for some unknown reason and they were givien a virtually useless battery powered neutron detector of a type useful only in a real neutron field near a reactor. A complex scenario to be sure. They never seem to ask for assistance until they are up against it and it is late in the senior year. The effort is a continuing senior only project.
Thus, each new team must start cold. Not good. U of W has it right....Bring in all classes as pure volunteers letting the freshman be step-and-fetchits, machinists and low level techs. Each ascending class is allowed to become more involved at higher levels of operation and finally research.

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Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
Retired now...Doing only what I want and not what I should...every day is a saturday.

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Garrett Young
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Re: Christmas Comes Early!

Post by Garrett Young » Tue Jun 13, 2017 2:29 pm

My power supply arrived and it appears to be brand new. This particular X-version of the supply was private labeled for Hurletron. The only modifications required for 350W were as follows:

C39 0.022u/100V (i.e. KEMET R82EC2220DQ50J)
R50 4.7k 5% 1/4W

I didn't add a fan because of the short operational duration and low duty cycle for my application.
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Re: Christmas Comes Early!

Post by ian_krase » Tue Jun 13, 2017 8:18 pm

Man, thanks for doing the homework. What type of capacitor is that, a film one? Would ceramic be expected to work?

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Garrett Young
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Re: Christmas Comes Early!

Post by Garrett Young » Tue Jun 13, 2017 8:25 pm

A ceramic capacitor has the drawback that the capacitance changes with applied voltage so I would use a film capacitor (as used in the original design)
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Dennis P Brown
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Re: Christmas Comes Early!

Post by Dennis P Brown » Wed Jun 14, 2017 10:53 am

Where did you get the info on how to up the rated current on your unit?

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Garrett Young
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Re: Christmas Comes Early!

Post by Garrett Young » Wed Jun 14, 2017 1:27 pm

Schematics included in this thread. viewtopic.php?f=11&t=4852
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