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Re: The Beginnings of a Fusor Electrical System

Posted: Sat Jul 22, 2017 9:46 am
by Rex Allers

I hesitate to post because you never acknowledged anything I posted in this thread earlier, but, oh well.

The point of feeding the primary with the combination of the variac and the step-down to 12V transformer is so you can very gradually bring up the primary input from nothing to just a volt or two while measuring the secondary voltage. The secondary voltage should never get above a few hundred volts rms while you are figuring this out. That's the point of the very low primary voltage.

So, you don't need oil and you don't need or want those big diodes while you are figuring out the coils. As long as you are careful, you shouldn't need those high ohm resistors either. All that (oil, diodes, resistive divider) are for later when you have verified enough about the transformer coils to venture into giving it more input AC voltage.

For your first tests, turn the variac up very slowly and watch the AC output on what you expect to be the secondaries with your meter on the highest AC scale. (That looks to be 600V from your pictures.) You should probably use clip leads so you don't have to get your hands close to any dangerous voltages -- clip on the meter, then start to slowly turn up the input voltage from zero.

The goal is to figure out the turns ratio and try to determine the best primary hook-up configuration for feeding it with full 120 or 220 V later.

Much more could be said about the process you might use but I won't waste more time now. I hope this reality check helps a bit. Good luck. Be careful.

Maybe others will have more to say. I think your last diagram posting indicates you don't have a very clear understanding of a practical circuit for the supply you want to make.

Re: The Beginnings of a Fusor Electrical System

Posted: Sat Jul 22, 2017 6:31 pm
by Richard Hull
Rex is right. I worry about these "quick rinse" assists we are giving to folks who have not the slightest idea or clue related to the electrical/electronic end of things. So many landing here, have found this site on their smart phones or in a link on line and have become enthralled with the fusion quest. Most arrive with, if not zero skill sets, perhaps only one of the many skill sets needed to super this effort. Most, who ultimately succeed, will knuckle down and study, via reading well before they attempt any hands-on work in the more dangerous areas.

The high voltage supply is certainly the most dangerous and immediate effort in the fusion quest. The dangers here far outweight any other of the other fusion cautions and dangers including radiation, gas handling, implosion, etc. While nothing in the average linear HV supply being assembled in this thread goes beyond simple basic electrical skills, having little or no skills in this area is a great danger.

Yet, as Rex, myself and others have constantly noted, it is so very easy to test a suspect transformer and noodle out every single aspect of it. First with an ohm meter to get the lay of the land and then with a variac hooked to a step down xfmr, at least an AC volt meter and to have a number of clip leads on hand. Notes must be taken throughout the process with wire color codes, ohmic readings and finally output voltages.

It would be nice to start with an old Stereo/ Hi Fi transformer or ancient TV transformer that bristled with wires. Noodle out something relatively safe first to get a set of sea legs under you.

Richard Hull

Re: The Beginnings of a Fusor Electrical System

Posted: Sun Jul 23, 2017 4:30 am
by Duncan Wilkie
I feel that I first have to apologize for any perception of my ability as inadequate or lacking, as most of the time it seems to be my incoherency or unclear explanations that lead to these situations. This is my attempt to clarify my goals and what I know and don't know.

I'll first explain how I approach the problem of the fusor electrical system. I understand the general principles behind a transformer, as well as general electricity, but I recognize I have no practical and detailed knowledge of the interactions and circuits inside transformers. I have thus far treated the transformer as a sort of "black box" that takes an input and steps it up to a higher voltage output. I've been reading Faraday and Maxwell in an attempt to understand the foundational principles of electricity, but it takes time to develop the deep understanding I want. I still, however, have very little of the practical knowledge of the internal organization and the specific wiring of these specific types of transformers, or any idea how to gain a proper picture of that (I now understand the concept of discerning the windings from resistance measurements). The apparent gaps in my knowledge are simply a lack of specific practical ability relating to methods which can only be built through experience. My last post was intended as a sort of catch-all depiction of the parts I've acquired in the past couple of months in which I've been off the forums as well as my general plan forward (hence the talk about oil and resistors and diodes). I wasn't sure how much input range I would need to gain an accurate picture of the transformer's power due to the fact that my variac is analog metered, and if that input range would lead to an output of over 600V, I would need to rectify the output and step it down with a resistor chain to measure it with a DC metering DPM. I also wasn't sure if mixing up the inputs would lead to irrevocable damage to my transformer, even at these low voltages. That leads me to how I've been using this thread. I've used it as a place to submit all my thought process to an audience of people who clearly know more than me to ensure I'm not about to either kill myself or give myself a major headache over an expensive broken piece of equipment (and, yes, also as a request for guidance). Maybe the questions I ask, withholding all my assumptions to ensure safety, have lead to the perception of a lack of knowledge. I just want to let you all know I'm not a complete idiot with respect to electricity, and that the best help you can give is specific, practical responses to my questions or a request for clarification. Thanks to all who have helped me for your assistance, patience, and concern for my safety.

Now, my next step will be to take Rex's advice for acquiring information about the turn ratio and the capabilities of my unit. If I assume my transformer to be the standard 40kv, then I can set up a simple equation to find that if I want an output of 600v then I can input 18 volts, assuming the voltage the transformer outputs is linearly related to the input. This assumption just gives me a testable estimate for the transformer step-up to give me a framework to interpret my findings and an expectation for where I can set my input. Going by Richard Hull's interpretation of my resistances, I will record the voltages when power is introduced to combinations of pins 5,6,7 and 9,10,12 which were theorized to both possibly be primary coils with differing inputs for 120 and 220.

Re: The Beginnings of a Fusor Electrical System

Posted: Sun Jul 23, 2017 8:26 am
by Finn Hammer
Duncan, all,

Powering an unknown high voltage transformer up, by energizing the primary windings, is probably not the safest thing to do. Even with a 10:1 step down transformer in between, you can be over and out of the DVM range, and what then?.
A safer alternative would be to power the transformer up "in reverse", with the high voltage windings attached to the mains via the variac, and then measure the output at the low end. This method eliminates the risk of generating the high voltages that either kill or damage the dry transformer.

Cheers, Finn Hammer

Re: The Beginnings of a Fusor Electrical System

Posted: Sun Jul 23, 2017 7:13 pm
by Richard Hull
The key point was to use a variac (0-120vac) before the low potential step-down transformer to feed the primary of the HV xfrmr.
The reverse 120v on the secondary might work as well. I would be worried some error could creep in as the primary is nearest to the core and the secondary is on the outside creating a possible coupling error, but it should not heavily impact the result at 60hz .

Richard Hull

Re: The Beginnings of a Fusor Electrical System

Posted: Tue Aug 01, 2017 1:32 am
by Duncan Wilkie
So, after ordering some more alligator leads, I ran a test on my fusor. I had imperceptible voltages across all points with backwards wiring. I switched my measuring lead to be on 3 and 4, and turned my variac down to under 5 volts, put my inputs on pins 5 and 6, and turned the input on. The output voltage was jumping all over the place (2-10V), and when I removed my leads they were warm to the touch. When I switched the leads to 5 and 7, again keeping the input under 5V, my alligator lead wires began to smoke. I immediately turned off the supply without looking at the voltmeter. I assume the transformer was drawing massive amounts of power on the second test, more than my about 20 gauge cables could handle. The transformer was humming, so I know it was working.

I shall perform a more informing test after fusing the input.

Re: The Beginnings of a Fusor Electrical System

Posted: Tue Aug 01, 2017 6:57 am
by John Futter
first check your new alligator leads
I just got some @ work and the leads themselves stick to a magnet ( not the alligator clip the wire itself)
Further check very very lightly copper plated iron wire each lead 2.74 ohms
Seems the Chinese have found a new way to cheat us out of we expect

Re: The Beginnings of a Fusor Electrical System

Posted: Tue Aug 01, 2017 4:22 pm
by Rich Feldman
>> wires began to smoke.

Welcome to the club, Duncan!

>> I shall perform a more informing test after fusing the input.

Fusion of transformer windings is _not_ what this forum is about.

Did you omit the low voltage transformer between variac and XRT, after at least three of us told you not to? That would be stupid, for more reasons than one. Wallplug transformers generally have fuses built in. I guess so do enclosed variacs. Get some 1 and 2 amp fuses to fit the variac. Get more than a couple of each. They won't protect against high voltage damage/injury from putting high single digit voltage on a XRT primary!

[edit] Hey, you can save fuses by putting a low voltage lamp in series in the primary circuit. How about a small incandescent from your parents' least favorite Christmas tree lights?

Re: The Beginnings of a Fusor Electrical System

Posted: Tue Aug 01, 2017 10:43 pm
by Duncan Wilkie
Bit of a diagnosis on my problem yesterday: I did some digging into my step-down's wiring and it was designed for use with a dimmer circuit. The state of the transformer without a dimmer circuit is full 120v through the output. So, yeah I ran a calculation and that was approximately 1.6 kV running through connections that were very casual for that voltage. Pretty scary. I ordered a new step-down without the whole dimmer bit, and will return with conclusive results in about a week.

Lesson learned: pay more attention to purchases, and always test before use.

Re: The Beginnings of a Fusor Electrical System

Posted: Wed Aug 02, 2017 11:18 pm
by Duncan Wilkie
The new step-down yielded strange results as well; all voltages I could find on with inputs on pins 5-12 had highly variable values.
All inputs were at 10V. The highest values for the "highest" portions I show were approximately 100v.
The connections that were under and around a volt actually seemed to be exactly what my input voltage was (input 1V with the step-down, output 1V for the lowest voltage connections).
These findings seem to indicate two primary coils with a 120 and a 240 input.

*EDIT* The "flickering" values were a result of a bad multimeter. I tested it against straight input from my variac, and still the flickering values. I think trying to measure 1.6KV fried it.