The Beginnings of a Fusor Electrical System

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Rich Feldman
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Re: The Beginnings of a Fusor Electrical System

Post by Rich Feldman »

OK, Duncan. It wasn't clear where you had measured the 8.04 volts, which looks like the full voltage of a nominal 9V battery that's seen some use or is rechargeable.

I am guessing that your transformer, as pictured, has a resistive path all the way from 1 to 4. It might or might not include the filament winding. Then a hidden bias resistor, then the left side secondary, then node 8 and the core, the visible 10K resistor before or after node 8, and finally the right side secondary winding. Total resistance on the order of 100 kΩ. You could see what happens if you measure 1 to 4 with an ohmeter.

Suppose that guess is right. In normal service, the white wire and the pair of yellow wires have high voltage AC of similar magnitude and opposite phase, with respect to the core and the equipment ground. In fusor service, you would have high voltage rectifiers on the white and one yellow, with their anodes connected together and to the HV ballast resistor. Point 8 and the core would be connected to _your_ equipment ground. With that full-wave rectification, each secondary winding would carry about half of the DC plasma current, in directions that cancel each other instead of adding (which could create a magnetic saturation issue).

If the only energy source is your 9 volt battery, I wouldn't worry about damage to battery or transformer or yourself. As explained above, I would expect point 8 voltage to be about in the middle of the battery voltage. Measured with respect to point 8, the battery terminals would be around +4 and -4 volts, and the other terminals at intermediate voltages according to the resistance ratios. Terminals in isolated circuits would read zero, no matter which point in the HV loop (battery circuit) is your reference.
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Re: The Beginnings of a Fusor Electrical System

Post by Duncan Wilkie »

So, I've measured 0 on everything but point 2 at the battery voltage in respect to point 4, and 0 on everything except for a 7.5V reading on point 2 in respect to 8. In respect to point 1, there are -6.6V on point 4 and -7.6V on either 8 and 10.
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Re: The Beginnings of a Fusor Electrical System

Post by Rich Feldman »

Maybe it's time for us to take this off line, Duncan. I will send you a PM.

Thanks for taking the time to try it my way. Even allowing for some ambiguities in your report, I see no way to reconcile the numbers with the model of voltage as potential, if the battery stayed connected between p1 and p4 for the whole experiment. How can p4 and p8 be 1.0 volt different when reference is p1, but not different when ref is p4 or p8? How can p8 be more negative than p4 (measured W.R.T. p1) when p4 is tied to negative battery terminal?

What's your voltmeter's input impedance?

On ohms range, is there any continuity between p3 and any other point? Is there very low resistance between p1 and p2?

The set of pins on which you found any nonzero voltage is 1, 2, 4, 8, 10. You could check that they are isolated from everything else, then we can nail down that 5-terminal network.
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Re: The Beginnings of a Fusor Electrical System

Post by Richard Hull »

It has been wisely suggested to make an x-y table of all the pins/wires/terminals and work your way through measuring resistances. This will speak volumes and identify all windings.

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Re: The Beginnings of a Fusor Electrical System

Post by Duncan Wilkie »

I've worked to identify the wires on the transformer. The x-y table of the resistances is listed below, and I've laid out the separate networks in a drawing labeled with the resistances.


image001.png


Resistor Diagram XRT.jpg
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Re: The Beginnings of a Fusor Electrical System

Post by Richard Hull »

3 and 4 are your HV outputs with 8 being the center tap of the HV winding. Wire number 11 may be a high voltage metering tap relative to the center tap, (wire 8). NOTE: does wire 8 measure 0 ohms to the metal core?..It should. If not, it must be grounded by you.


1 and 2 might be the filament winding

5, 6 and 7 might be the primary with 5 and 6 being 220 volts and 6 and 7 120 volts. I would try the `120volts across 5 and 7 first. USE A VARIAC!! see what the output voltage is.
10, 12 and 9 are an identical winding to 5,6,7 and may be a companion or related primary.

All the above assumes this is a 60 hz transformer.

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Fusion is the energy of the future....and it always will be
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Re: The Beginnings of a Fusor Electrical System

Post by Rex Allers »

Duncan,

Your table of resistances is good, but I don't think what you have presented is sufficient.

You have assigned the terminals or connections the numbers 1 through 12. I think first you need a simple table that describes what each of these numbers (1-12) means. I couldn't easily figure that association out and in your table you have a color on each of these numbers that didn't make sense to me on a quick look.

Your transformer is made up of two coil sections. For working things out and labeling your terminal definitions, I'd call one coil Left and the other Right. With the transformer in front of you you can decide which one makes most sense to call Left. For the sake of this discussion, let's say the Left coil is the one that has the 3 HV output wires with colors Red, Yel and Yel. So then the Right coil would be the the one with one corresponding white wire.

Then let's call the side of the L coil with the Red, Yel, Yel wires the coil "Top". Each coil also has wires going to 4 consecutive terminals on the plastic terminal strip. Let's say each of these wires comes from the coil "End". The 4 wires from the coil "Ends" to the terminal strips each have color codes that (I think) are the same for each of the coils (L and R). I would also put these wire codes in the definition table.

So the first definition table entry might be for over-all terminal 1, and this might also be terminal strip connector 1 and be the black wire from the L coil End. Some other over-all terminal definition (Lets say #9) might say it is not on the plastic terminal strip, but is the red wire on the Top of the L coil.

In your resistance table, you have assigned terminals 1 through 12. I assume this is terminal strip terminals 1 through 8, plus the 4 wires on the Top of the two coils (3 on L and one on R). I don't think this is enough.

Using the coil Top definition for where the (probably) HV wires are, the the opposite "Bottom" side of each coil has two Black wires that appear to have been cut. I think you need to get access to these wires, strip their ends and add them to your definition and resistance tables. My guess is the two black Bottom wires from one of the coils are probably connected together and can be treated as one connection. If you get two these wires and find the two black wires from one coil have zero resistance between them, you can treat the two wires as one terminal, so you would only need two more terminals in your tables rather than four more. 14 terminals total vs. 16.

I hope this makes sense to you. You might want to go back to the early post I made in this thread, trying to guess what the connections might be. Until proven wrong, I'll stand by the big picture of what I think the connections were.

Oh, I almost forgot. You also have the blue thermal switch and the power resistor to contend with. Their connections and resistance need to be factored into the analysis. I think the thermal switch should be like a closed switch, so if that measures true, can be though of as an extension of the wire that connects to it (Black End wire, I think).
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Re: The Beginnings of a Fusor Electrical System

Post by Rich Feldman »

To all: Duncan's pin numbers were pictorially assigned by me in a preceding post: viewtopic.php?f=11&t=11223&start=10#p74002 We decided to save the black wires for later.

Duncan, it's good to see you back. You didn't give me credit for off-forum help with your DC resistance table, long ago. I filled in the upper triangle (by symmetry) and color coded the isolated groups (by inspection). Richard Hull was first to call for the plain resistance-table attack, etc.

For the network consisting of pins 3, 4, 8, and 11, your diagram has six paths. If you connect six resistors as drawn, the node-to-node measurements will all be lower than what you observed.
We want a simple circuit model that matches all six of your measurements and would work in an x-ray generator.
Three elements are sufficient, in a series string (as opposed to a wye configuration). Looks like what you have is:

Pin 3: HV end of secondary winding for cathode (close to filament winding pins 1 and 2).
*R1* 160 K ohm coil resistance
Pin 8: LV end of cathode winding, core connection in picture, and (implicit) external ground.
*R2* 10 K ohm current sense resistor
Pin 11: LV end of anode winding, and (implicit) external current indicating meter
*R3* 160 K ohm coil resistance
Pin 4: HV end of secondary winding for anode.

Verstehen Sie?

Now go figure the voltage drop and power dissipation in one HV winding, from a DC current of 20 mA.
One shudders to think of fusor kids who don't learn enough about electricity to answer those questions.
In full-wave-rectified operation (two diodes), each winding sees all the voltage and half the power.
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Re: The Beginnings of a Fusor Electrical System

Post by Rex Allers »

OK, I follow the numbering now, and agree with most of what Richard and Rich have said.

To make it clearer to me about the physical meanings, I interpreted things as I mentioned in my last post. Here are two pictures showing that.
Top view
Top view
Terminal End view
Terminal End view
So in my labels TL=Top Left, TR=Top Right, EL=End Left, and ER=End Right. I also added the transformer wire colors to my labels. The resistance node map provided was very helpful in visualizing the connections. To help my understanding, I edited the image to add my physical labels. After looking at it, I also added red lines on the map to show the actual transformer windings and one orange line to show the power resistor. Here's the result.
Node map of connections
Node map of connections
On the primary side there are two matching sets of two series coils on the Left and Right. I would expect that the left and right sides would be connected in parallel for 110V or in series for 220V (ish). Not sure about using all or part of each side series coils. I'd start with the maximum coils or across 5-7 (left) and 9-12 (right). So for (eventual) 110VAC input I have one AC wire to 5 & 9 and the other AC wire to 7 & 12. Other opinions welcomed. As others suggest, I'd start feeding it with a very low voltage and measure outputs for sanity check.

Maybe others have a good approach for figuring out how much of each side's primary to use. I've suggested starting with AC across 5 & 7 (both coils in series). It could also be 5 & 6 for just one coil. The second would make higher output voltage but too little primary would saturate and do bad things. I'm not sure how to work out the proper connections for an input voltage.

There's also that thermal switch to eventually get correct. I think it is between terminal 5 and the black wire of the left transformer coil. If my parallel connection suggestion is correct, the Thermal opening would only cut out one coil. Something needs to be changed to have this thermal switch opening, switch off all primary.

Assuming the 10K resistor is to measure current in the original operation with load between HV outputs of 3 and 4, this wont be right for fusor operation with the two HV outputs feeding push/pull into two diodes for a full wave rectifier. Shouldn't 8 & 11 be connected together with some sense resistor between this node and ground?

If It was me, I'd also fish out at least one (for starters) of the cut black wires on the bottom of the coils and see how it relates to the other nodes. They must be there for something.
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Re: The Beginnings of a Fusor Electrical System

Post by Richard Hull »

Sad,sad,sad. I am fortunate to own metering and systems up the wazzoo. AC or DC metering high and low voltage for each....Variacs that are fully metered in currnt and volts, etc. I would have had this puppy noodled out and turned on in minutes. Bottom line....If you don't have the gear needed, you are looking somewhere between time tortured guess work and and a possible early death in the family as you play "guess the windings". Some are obvious using an ohmeter. Many good and perhaps correct answers abound here, but when the rubber has to meet the road, only good instrumentation, in hand, will figure out what you really do have.

Fire it up and tune for minimum smoke......

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Fusion is the energy of the future....and it always will be
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Re: The Beginnings of a Fusor Electrical System

Post by Duncan Wilkie »

Rich-
Please correct me if I'm wrong, but this is the calculation I did to get the values.
For the coil with a resistance of 160K ohms at .02A, voltage drop is derived from V=IR, so V=. 02*160000,so V=3200V. Power Dissipation is P=IV, so P=.02*3200, so P= 64A.
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Re: The Beginnings of a Fusor Electrical System

Post by Richard Hull »

This is a DC reisitance of a coil and relates to the secondary's "source impedance"' and is a complex issue based on the load type and value. DC figures can't be used accurately on a coil of wire supplying AC in a transformer system. Much also depends on the core and how it is made. To noodle out the complex issues, good instruments and a bit of investigation is needed.

DC Coil resistances only give a clue as to what "might" be their function, and little to do with there actual in-circuit performance, which is based on many other factors.

DC circuits and networks can be taught and learned in a one semester college course. All the ramifications of AC, reactive and HF power circuitry can consume 2 years of upper level college study.

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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
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Re: The Beginnings of a Fusor Electrical System

Post by Rich Feldman »

Duncan, your answer to my latest numerical question is correct, except for a petty typographical error.

Drawing 20 mA from an XRT secondary winding that has 160 kΩ of DC resistance will cause the voltage to drop by 3,200 V, and will generate 64 watts of heat in the winding. Those numbers hold for DC or RMS AC. The resistance and copper loss will increase as the winding heats up.

As mentioned before: if you configure a full-wave rectifier, using one HV diode on each secondary winding, each winding would provide half of the average current and get half (not 1/4) of the heating calculated above. Each diode needs to withstand at least twice the fusor voltage. (Same applies to full wave rectifier circuit on a NST in demo fusor FAQ).
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Re: The Beginnings of a Fusor Electrical System

Post by Duncan Wilkie »

Would the next step be to variac the primary way down and see what the ratio of power increase is? Or is there more still to learn before I plug it in?
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Re: The Beginnings of a Fusor Electrical System

Post by Rich Feldman »

>> ... next step be to variac the primary way down and see what the ratio of power increase is?
>> Or is there more still to learn before I plug it in?

I'm still concerned about your very junior level of knowledge about electricity. Transformers do not increase power, in fact they invariably lose some. What's the name (or even just the initials) of your adult mentor who has experience with electrical connections and measurements at voltages over 100 V? Over 300 V?

You could do what I did when I had an unfamiliar x-ray transformer. It's slightly different, in some important ways, from your proposal copied above.

Step 1. Set up instrumentation that can measure AC voltages up to a few thousand. This can be tested, and sensitivity verified, with regular house power. Could be an analog or digital multimeter on an AC volts range, with simple external attenuation as described in FAQs.
Alternative: Set up to measure DC voltages up to a few thousand, and connect it to the _rectifed_ output of your XRT under test. You'll need that anyway for your demo or real fusor.

Step 2. Get your Variac, but don't use it to directly feed any XRT primary, with or without ballast.
Put a step-down transformer in between, that normally reduces house voltage to 12 volts or less. These are common for low-voltage outdoor lighting, and indoor lights that use low-voltage halogen bulbs. Generally have their own fuses on low voltage side. I'd find one rated for at least 50 VA, as opposed to (say) a doorbell transformer, or something out of an inexpensive cordless tool charger. The filament winding of a MOT (2 or 3 volts) might serve, with suitable precautions.

Then you can use most of your variac range, for much better resolution and repeatability, without having to put your XRT properly under oil. You could still die from touching an XRT secondary connection, even with primary voltage much less than 10% of nominal. But it won't jump through (much) air to get you.
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Re: The Beginnings of a Fusor Electrical System

Post by Duncan Wilkie »

Thanks for your response, Rich. I did mean the voltage increase when I said power. Sorry for that careless mistake. I do have a guy, Matt D. who works at the local coal power plant who has helped me in the past and will likely help me with the overall system (i.e. grounding, other things specific to my setup).
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Re: The Beginnings of a Fusor Electrical System

Post by Duncan Wilkie »

Quick question: I would use the full-wave rectification circuits for single-phase 120V 60hz input (standard mains electricity), grounding the positive load-end and using the negative rectified polarity with the instructional circuit seen in the schematic included? Not 100% sure, and I don't want to move on this until I have a plan.
03444.png
Also, are there any specific diodes or diode types I need to deal with fusor-level voltage flow?
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Re: The Beginnings of a Fusor Electrical System

Post by Rich Feldman »

RTFF.
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Re: The Beginnings of a Fusor Electrical System

Post by Dennis P Brown »

As for specific diodes, you just need to be certain they can handle the surge currents (which can be much greater than the normal continuous current.) Of course, the voltage limit of the diode should be around twice the fusor max voltage (remember RMS?)

Aside: I fuse the input voltage of my x-former so that if the primary exceeds an "acceptable" level of input current, the fuse then blows preventing my primary or secondary from exceeding a safe current level that could damage those wire.

I bought 1 amp 20 kV diodes (under $3 each - so I got 20 total for various projects) and used two in series for each of my current paths. These diodes in series should withstand a max voltage of 40 kV. My x-former can easily handle 100 ma for a few minutes so my surge currents can be very high ...since I do not know how high, I error'ed on the cautious side and got those diodes (also, couldn't resist that great price.)

I placed my diodes under oil to improve their cooling but also because I could then use normal wiring and connectors with the diodes to save $$$ and avoid corona problems.

Aside: DO NOT add diodes to a system if you have not, as yet, determined proper wiring of the x-former; that can lead to a bad day for the didoes and it achieves nothing in determining wiring configuration. What people here have told you is outstanding advice - use a very, very low AC input if in doubt about the wiring configuration. AC voltages can start to become deadly very fast. Air grounding occurs quickly and then makes these voltages deadly. Follow HV safety procedures (i.e. one rule is: always assume any source is hot and deadly until proven otherwise!)
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Re: The Beginnings of a Fusor Electrical System

Post by Duncan Wilkie »

So, I finally acquired all of the components necessary to test my supply. I've spent the last few months working, and I've bought the components I believe will enable me to reach the demo phase. So, what I'll do in this post is verify my plan and pose a few questions I have.

The main question I hold is a general uncertainty about connections under oil. Can I use screw terminals? Can I use normal solder joints? My plan for encasing all connections in oil is to use a 5-gallon fish tank I had laying around and just submerging all my components in a configuration kind of like this:
This is the configuration for my supply. The rectifier of 4 20kv 3A diodes is on top of the Plexiglas sheet and below it is my resistor chain of 8 50M resistors. All components will be totally immersed in oil.
This is the configuration for my supply. The rectifier of 4 20kv 3A diodes is on top of the Plexiglas sheet and below it is my resistor chain of 8 50M resistors. All components will be totally immersed in oil.
To test the transformer, I have a variac and a 120vac-12vac step-down which I will connect to pins 5 and 7 (per Richard Hull's post). Then I'll connect 3 and 4 to my diodes and connect pin 8 to the positive reference of my meter. I'll connect the output of the pin 4 diode to the output of the pin 3 diode. The combined outputs of the diodes are the negative potential I'll run into my fusor or in this test the negative input of my metering circuit. I'll put two of my 50M resistors to step the voltage down to something measurable by my DPM.
My variac/step-down setup
My variac/step-down setup
Close image of my diodes and resistors
Close image of my diodes and resistors
My last big question: Will my meter and resistors be sufficient as a load to the voltage?
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Re: The Beginnings of a Fusor Electrical System

Post by Rex Allers »

Duncan,

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.
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Re: The Beginnings of a Fusor Electrical System

Post 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
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
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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Re: The Beginnings of a Fusor Electrical System

Post 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.
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.
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Finn Hammer
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Re: The Beginnings of a Fusor Electrical System

Post 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
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Richard Hull
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Re: The Beginnings of a Fusor Electrical System

Post 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
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
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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