lab electromagnet from scratch

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Chris Bradley
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Re: lab electromagnet from scratch

Post by Chris Bradley »

The yoke pieces look a bit thin to my eye. It depends on the material as to whether they saturate. Your original diagrams look more like what I would expect to see.

(An aside; for my 'inverted yoke' I deliberately used thin mild steel so the plates did saturate near the magnets, which caused a more uniform field in the working space, rather than have a concentrated field around the magnets. (I tried some pieces of borrowed mu metal, and the field uniformity was very poor.) That won't apply in a conventional yoke like this.)

Your adjustable pole pieces will likely not need any significant mechanical fixing. Once the induction field is applied, they'll stay well in place and not jump off the yoke. So you could simply have removable coils and pole pieces of variable length, then just have a hole through the yoke and tap a thread into the back of the pole pieces to hold it in place with a small bolt.

Maybe fix the upper permanently, with a given pole piece length, and vary the lower one. You'd slide the coil and the pole piece out, together.

I'm still unclear what you want this for ... it might help with suggestions. Is it for a 'micro-tron' of some description?
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Rich Feldman
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Re: lab electromagnet from scratch

Post by Rich Feldman »

>> I'm still unclear what you want this for ... it might help with suggestions. Is it for a 'micro-tron' of some description?

What do people want fusors for? This magnet project is to:
* get my hands dirty
* test my purported knowledge of E & M, engineering, and practical scrounging
* explore the low-cost low-power corner of magnets producing 1 tesla in 1 inch air gap.

Have previously claimed that for fixed ampere-turns, average coil diameter, and material: the product of conductor mass and electrical power is invariant.
Just ordered my conductor: about 70 lbs of aluminum at a bit more than $1.50 per pound. Here's half of it: http://www.ebay.com/itm/321162065864
coil_small.JPG
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It's 1100 composition, about 5.25 inches wide, 0.007 thick,
with a separable layer of 0.0025 plastic film which -might- serve as inter-turn insulation as received !

Here are the preliminary design numbers.
Magnet will have 2 coils very close to the size of the spool in picture, wired in series.
22,000 ampere-turns
760 turns x 29 amperes
Then at 20 degrees C:
0.6 ohms
17 volts
496 watts
Given the large exposed area on annular surfaces of each coil, this might be able to run continuously with forced air cooling.
All models are wrong; some models are useful. -- George Box
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Richard Hull
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Re: lab electromagnet from scratch

Post by Richard Hull »

Nice shot at making your magnet! I can't wait to see this thing perform. Smart move on the thin Al conductor. You might watch out for inductive kick back faulting your insulation. The insulation should extend a bit beyond the foil's edges, ideally. A very slow bring up with a variac and an ultra slow wind down on the variac at shut down will save the insulation. A 100 amp 1kv reversing diode across the coil would also help.

All the best.

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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Rich Feldman
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Re: lab electromagnet from scratch

Post by Rich Feldman »

My aluminum conductors arrived last week in coil form, almost perfectly filling two USPS flat rate boxes.
One is bigger and heavier than the other, and in much better shape (literally). Maybe that one can be used as a 400 turn electromagnet coil without being rewound. A 3" diameter steel pole piece, not yet procured, might be persuaded to slide through that core with no layers of cardboard peeled off.
DSCN6759.JPG
I immediately cut off a sample from the larger coil, on which to measure the material's thickness, weight, and electrical resistance.

The aluminum has a clear anodized coating on both sides, which I scraped away in a few places for electrical connections.
Questions up front. Can anyone cite experience to complement my Internet research on:
How to strip anodized coatings without rapidly etching the aluminum?
What fluxes and filler metals can solder aluminum at temperatures below 600F or 300C?

Here the sample is conducting 5 amperes from a benchtop power supply. Voltage drop is measured with a fancy DMM that can resolve microvolts. Keeping one meter probe at a fixed location, I used the other (with sharp pointy tip) to penetrate the anodized coating and map the potential.
DSCN6766.JPG
These contours are 1/2 millivolt apart, so the resistance between lines is 0.1 milliohms. The sample is barely long enough to demonstrate a rule of thumb for current spreading: Current density is practically uniform at places more than about 1 strip width away from a point source.
The sheet resistance worked out to be 0.24 milliohms per square, an unexpectedly high value. (Another rule of thumb: 1 ounce copper foil is 1/2 milliohm per square.) If my Al were 7 mils thick then its resistivity would be 427e-8 ohm-cm, a plausible value for 3004 alloy. But this is supposed to be 1100, practically pure Al, at around 300e-8 ohm-cm.
unimet_comp.jpeg
unimet_comp.jpeg (30.51 KiB) Viewed 14174 times
By the way, it's easy to remember the value for 100% IACS, a popular and practical reference value for stating the conductivity of metals. The International Annealed Copper Standard, which is 100 years old in 2013, adopted a standard resistance at 20 degrees C of a copper wire 1 meter long and 1 mm^2 in area: 1/58 ohm. Today we'd say 58 megasiemens per meter. It works out to 172.4e-8 ohm-cm. Modern copper wire routinely exceeds 101% IACS.

The discrepancy was resolved by careful thickness measurements, and some investigation of the maker's label inside the cores. Overall thickness is about 9.5 mils (0.24 mm), including the 2.0 mil (0.05 mm) clear plastic film. Originally I, like the used metal vendor, had peeled back the film and measured 7.0 mils. But that includes an adhesive layer that takes up 2.5 mils (0.06 mm). When that's cleaned off, the metal thickness is only about 5.0 mils (0.13 mm), consistent with resistivity of 305e-8 ohm-cm.
The labels inside the core say Adhesive Research, which is still in business. There's a special part number, but I think what I got is closely related to ARclad 5795 "EMI shielding foil". http://www.adhesivesresearch.com/Docume ... 0Sheet.pdf

So I got only about 28 lbs of Al in a 38 lb coil. The magnet power estimate must be revised upward, unless I want to strip that adhesive and use a thinner insulating film. On the other hand, original power estimate based on 7 mils used a very conservative value for resistivity.

Let's close with the one indirect measurement that's probably accurate to within 1%.
As wound, the thickness per layer is 9.73 mils (0.247 mm). I measured the metal ID and OD, and counted the 401 layers like rings on a tree.
DSCN0291_count2.JPG
The same measurements tell us that the strip is 803 feet long (1676 squares, so about 0.40 ohms). The AR label says the coil originally held 1200 lineal feet.

Thank y'all for reading this far. Both of you! :-)
All models are wrong; some models are useful. -- George Box
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Richard Hull
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Re: lab electromagnet from scratch

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I'd leave the anodization on the foil. It is not electrically important. For contact, you can scrap a bit. There are fluoride based fluxes and low melting point solders made especially for aluminum, search around. You could always use thin Al or Cu strips bolted to the ends of your coil using 2-56 hardware if soldering doesn't work out.

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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
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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Rich Feldman
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Re: lab electromagnet from scratch

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OK, time for a one-month update.

On August 14, I made the first steel purchase for this project.
Some rusty old 3 inch diameter HRS, in two pieces 7 inches long.
That's to allow some working room on both ends of the 5.75-inch-long coils.
It fits through the core of the "good" coil, now that I have removed the innermost ply of cardboard (and the attached A.R. label).
DSCN6892.JPG
Saw cuts at the shop cost $5 each, and took about 1 minute each.
I was pleased that they produced surfaces within about 1/16" of being square (to the rod axis). Perpendicular would be a better word, because the cut surfaces are round.
The available tool for rough machining to flat-and-parallelness was a Bridgeport.
IMG_0738.JPG
Next step is to contrive a closed flux path and a temporary drive coil.
Will find out how many ampere-turns it takes to magnetically saturate these parts.
I think that will have to be done with slowly changing current (not 60 Hz) because of eddy currents in the steel.
On the bright side, those eddy currents might usefully reduce the flux ripple when coils are driven with rectified 60 Hz AC.
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Rich Feldman
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Re: lab electromagnet from scratch

Post by Rich Feldman »

Another 23rd day of month, another update.

This will be a tale of two new coils, but first: an updated drawing of the proposed 3 inch pilot project.
1 inch per grid square. Aspect ratio is unusually skinny because there's enough conductor for a 6 inch magnet
but much less steel. Whole system should weigh less than me, and not need much heavy machining.
big3inch2.JPG
Design evolution is explained in earlier posts. Starting point was steel end plates 0.75" thick.
That drove choice of pole diameter = 3". Coil length and diameters are driven by the dimensions of adhesive-coated aluminum strip that I found at a surplus dealer by email inquiry. These particular coils, it turns out, are about 40% insulation. That increases the average turn length and reduces the number of turns, for a double penalty in electrical power per ampere-turn squared. But it only cost about $2 per pound of Al, like getting Cu at $1/lb.

The "plain old steel" will be characterized in a closed path test, with the pole pieces side by side.
DSCN7079.JPG
We expect the endplates to saturate before the poles, because their cross-section now has to carry the entire flux instead of just half.
My temporary drive coil is a 100 foot 3-conductor extension cord, on a bobbin made from nominal 3" ABS pipe and some pressboard annuli.
DSCN7053.JPG
DSCN7068.JPG
Got 5 layers of 14 turns, as planned, plus 2 extra turns. That's 216 turns of AWG14 wire (packed even less densely than the aluminum strip). Expected total resistance is about 3/4 ohm. 12 volts should be much more than enough to drive the steel to saturation at the bottleneck.

More later. Do any readers care about this much detail? Want to know how much the steel rod is oversize and non-round, and what that meant for spoolmaking? Would it make sense to start a blog for this stuff, instead of having to write it up for 3 forums? Any hints about simple blogging for beginners? Thanks!
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Ross Moffett
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Re: lab electromagnet from scratch

Post by Ross Moffett »

Rich, I imagine you have enough content to make your own website. They're inexpensive and available with lots of free templates, even if you go ad-free. If you don't go ad-free, you might even have some financial assistance for your projects by posting them to sites like hackaday.com and makezine.com after they're finished. The traffic is substantial. Nearly four years ago in my final semester of college I hacked my Rigol oscilloscope to change its bandwidth from 50 MHz to 100 MHz (a software / hardware restriction used to sell the same hardware as two models). To this day I still run into total strangers and if oscilloscopes come up, they'll say something like, "You should get a Rigol, you can hack it." I posted it to the eevblog forum, may have missed out on some bank!

I find your thread interesting, and I'm sure a lot of others do as well.
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Re: lab electromagnet from scratch

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Very interesting. This could all be in the construction forum in a single thread. You are making something here.

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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
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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Re: lab electromagnet from scratch

Post by Ross Moffett »

The forum title is "Other Forms of Fusion - Theory, Construction, Discussion, URLs." So as to not derail Rich's thread, I started a new one here.
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Re: lab electromagnet from scratch

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This forum is fine, especially if it is to be part of a cyclotron or related to some planned fusion effort.

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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
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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Re: lab electromagnet from scratch

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First Pull. Seems like a milestone for any electromagnet.
I got there last night, quick and dirty, after weeks of not having time to do it scientifically enough. Measuring BH curves can wait.

In the meantime, I had measured the orange coil's DC resistance: a disappointing 0.99 ohms. While measuring that with no iron core, I got some tiny sparks and, later, made a neon lamp flash. Still want to compute (and measure) the air-core inductance.
DSCN7496.JPG
In the pictured setup, with a current of 1.28 amps and power input of 1.62 watts,
I was able (with care) to lift the whole rig while holding only the top plate.
So lifting force was at least 63 pounds, over 14.5 square inches, amounting to around 4.3 psi.
For that pull, the required B is about 1/4 tesla in the round parts (and slightly more in the end plates).
Figuring the magnetic path length to be about 0.7 meters, and knowing there are 216 turns of wire, the average relative permeability (including air gaps) is around 600. That's plausible.

Next step is to trace a BH curve well into saturation, with this flux path and this coil. For that, I want a bipolar adjustable supply that can do 12 V and 12 A. Am planning to build my first H-bridge inverter, unless someone has a better idea. Anyone want to talk about high-side gate drive methods, not involving GDT's?

[edit] Uh, it'll be simpler to try an adjustable unipolar benchtop supply, with V and I meters, that can do 10 amps. Just need to configure a reversing switch (and will wire in some clamp diodes).
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Richard Hull
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Re: lab electromagnet from scratch

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At 275 amp-turns that is hard to fathom! It is tough to believe you got a flux of 2500 gauss. Any flux meter on hand to check that? You have a lot of surface area though. That meant that you only put around 1 volt into the system! I would have thought it would have taken a few thousand amp-turns?!

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Fusion is the energy of the future....and it always will be
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Re: lab electromagnet from scratch

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Well let's see. 276 amp-turns along 0.7 meters (perimeter of 7" square) is 395 amps/meter = 5 oersteds.
Permeability of 500 would give us 2500 gauss.

Remember the pull strength, and the electric power, are proportional to the SQUARE of the flux density. And the only air gaps in this case are those from crudely finished mating surfaces. (Too bad nobody has invented a ferrofluid or ferroputty with Bsat much above 0.2 T.)

My announced target of 1 tesla through 1 inch of air WILL need more than 20,000 ampere turns. I hope to get that with 25 amps in 800 turns, using different coils whose total resistance is less than that of this orange one. The more metal, the less resistance.
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Re: lab electromagnet from scratch

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Yeah, I forgot this is a completely closed path with decent permeance and just a watt of two in the right coil will give a tremendous flux level within the core and mechanical separation of a core path element would be a bitch.

It's that nasty permeability in an air gap that cuts the flux to nothing in the gap, requiring a lot more amp turns.
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: lab electromagnet from scratch

Post by Rich Feldman »

For the first time in decades, I have purchased a stamp for philatelic purposes.
An Amp stamp.
amp_stamp.jpg
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History of Science is a fascinating and valuable subject, IMHO.
What was André-Marie Ampère up to in his lab 200 years ago?
Most images show his hair much more curly than the image in this stamp.
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Re: lab electromagnet from scratch

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You may have seen an image of Ampere in a wig! They were still in vogue into his early adulthood. By the time he died, they were a thing of the past. The stamp image may be of a bust of him in later life. The droopy eyes seem to indicate this.

I have been a stamp collector all my life. Stamps can and do honor science history. One of my favorites is shown below. I have many mint, post office fresh, sheets of 50 each of these and use 'em for "makeup" postage sometimes. Can you believe they ever managed to deliver mail, twice a day, in the city, on foot, to you door for this 3 cent price?! They delivered around 10AM and then a second delivery, about 3:00PM. (in large cities only -rural only once a day)

This stamp was issued after Ike's famous Atoms for Peace speech at the U.N. His words adorn the framed edge of the stamp. This launched the Atoms for Peace Program in the U.S. and made isotopes available to the general public, but mainly for kids in school to help them train for careers in nuclear physics. "Project Plow Share" was a major component of this effort to find peaceful uses for atomic energy. In "Plow Share" they used nuclear bombs for large area excavation and natural gas rock fracturing tests ("Gas Buggy" test series).

I bought a bunch o' isotopes under Atoms for Peace from Oak Ridge, Abbott Labs. I attach a nice little price list I used back when you could get the rad stuff loose in bottles. Mailed in small lead pigs and delivered by postman in his big brown leather mail bag. I mowed more than a few lawns to get the fabulous "9 pack" (click the image to enlarge and read......)

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A list of what you could order sent to you home in 1963.  I ordered many times  1960-1966
A list of what you could order sent to you home in 1963. I ordered many times 1960-1966
Issued in 1955 when I was 10 and already collecting A bomb fallout from my rain gutters and bird bath.
Issued in 1955 when I was 10 and already collecting A bomb fallout from my rain gutters and bird bath.
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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: lab electromagnet from scratch

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OK, back to the electromagnet. My scrounging of NST's from doomed movie theater is over, except for telling the story about six more 15kV-ers etc. :-)

Plan is to measure, more properly than by pull strength, the magnetic flux vs. magnetizing current in closed-path stackup. The main unknowns are the permeability and hysteresis of the plain old steel materials in these parts.

Flux will be measured by the fluxmeter method. We integrate the voltage induced in a sense coil, as the current is changed. We can measure the flux inside a solid piece of steel, analogous to measuring total current in a solid copper wire using clip-on ammeter. Calibration amounts to knowing the sense coil's number of turns and area per turn. The latter can often be taken to be the area of steel around which coil is placed. To use a fluxmeter on a permanent magnet circuit, we move the sense coil between the place under test and a place where B is negligible.

To get the magnetic properties of my 3" HRS rod material by itself, without airgaps or complicated geometries, the plan has been to fabricate toriod-shaped cores from a surplus section. Then wind force and sense coils on them. That's how specimens are prepared for hysteresisgraphs in real industrial labs. Originally low priority, it became high when my brother said he'll need his hole saws back soon.

So I did the first steps of ring preparation:
1. Face the bad end of the surplus rod stock, which had been cut obliquely with a torch. Had to machine 0.300" off of the high spot.
2. Trepan some annular grooves more than 3/4 inch deep, using bi-metal hole saws from hardware store. It actually worked! See picture. Spindle speed for the 2 5/8" saw was 120 RPM. Backed the blade out every 0.030" of progress, to clear the chips & squirt in more cutting oil. The whole workpiece quickly became hot, in a way reminiscent of Count Rumford, so I set up a fan for continuous cooling (even during breaks from cutting).
3. Not yet done: separate the rings by sawing or parting on a lathe (not my toy lathe).

Note: the work is sufficiently secure in vise. Its non-roundness turned out to be two low areas on opposite sides. The diameter across 90% of circumference is 3.04 inches, but in the short direction it's only 3.02 inches.
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Re: lab electromagnet from scratch

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Fabulous fields can be attained with toroidial strutures. Most often seen when tremendous lifting work is needed. Nice looking work there.

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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: lab electromagnet from scratch

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Yay! Rich has own work to report, after brushing 18 months of dust from sort-of-big magnet.

While looking into audio amps as coil drivers, I stumbled upon "servo amplifiers" made to drive brushed DC motors. Immediately procured a 30A8T on ebay for about $35. http://www.a-m-c.com/download/datasheet/30a8.pdf Two big terminals receive DC power at 20 to 80 volts. The other two big terminals supply motor with pulse-width modulated rail voltage in either direction. 15 A continuous current, 30 A peak. Four-quadrant operation, as much as the primary supply can sink current.

A motor from a scrapped printer was my first trial load, while measuring the transfer function in voltage mode. The command is for voltage, not duty cycle.
servo_amp_transfer.PNG
Running magnet coil up to 6 amps (a limit set by windshield-wiper-blade-stiffener current shunt) had few surprises. Average current from primary supply is much lower than in coil, because coil inductance makes a buck converter. At 6 A the upper yoke plate could not be pulled off by hand, in spite of corrugated cardboard between vertical bars and lower yoke plate.
DSCN9837.JPG
DSCN9835.JPG
Since then I made a +/- 15 A shunt out of coat hanger wire. First measured some galvanized straps from lawn furniture, and painted steel bands that secured heavy loads: 4 mΩ is impractically long. Stainless-steel bands from lawn furniture and a rotted wooden flowerpot: 4 mΩ is impractically short. Stainless-steel hose clamp including worm gear for continuous adjustment: nearly ideal resistance, but I'm not equipped to solder or spot-weld stainless, and didn't want to drill holes for screws.
DSCN9838.JPG
Next steps are to properly stack the magnetic circuit, apply the fluxmeter, and see how much current is needed for saturation. The coil circuit has no common ground, so I need to find an isolated current sensor before a BH curve can be displayed on oscilloscope. 60 Hz is of no use here because of eddy currents, otherwise the BH curve would have been presented 18 months ago.
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Rich Feldman
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Re: lab electromagnet from scratch

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For a few weeks I was afraid I'd blown something up. Indicated current got squirrely after hitting 7 A. While troubleshooting, soon even the little motor wouldn't go in either direction. Had too-rapid voltage reduction kicked magnet energy back into DC PS? Had to wait before there was time for fresh, systematic attention. Seems I had hit an unexpectedly low current limit setting in amplifier as received (it has fast and slow limits). Also I was using an intermittent control knob.

With a new self-powered and filtered control knob, I got power satisfaction on the 4th of July. For loads of around 1 ohm, the knob goes from -15 A to +15 A. Here's the new, simplified configuration in schematic form:
magnet_sch1.PNG
and for real:
DSCN9902cr.jpg
Forgot to show in schem. that amp switches are set for Voltage Mode. The servo amp is shown converting DC 24.2 V 2.5 A to 7.19 V 7.5 A. A wooden clothespin secures a temporary 15 amp connection without the hazard of a conductive clip lead (whose far end would be energized). Magnet top plate has been replaced with a stiffly-supported crescent wrench.

Electromagnets are naturally more power-efficient as they get bigger, and it's great to see that even with a 3 inch pole diameter. The wrench demo was able to keep it up at 1 ampere.
DSCN9904.JPG
As the drive was turned down little by little after that, we read 313 mA before the still-magnetized wrench fell off.

Next step (same as stated a month ago) is to start measuring magnetic flux. Can skip the DC current sensor with ground-referenced output, if I manually tabulate data read from the analog meter.
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Got me an electric tesla

Post by Rich Feldman »

Finally got to measure some magnetic properties of my "plain old steel".
First, restored the magnetic circuit to a simple gapless configuration. Here the top and bottom plates have much less cross-sectional area than the round pole pieces (27.8 vs 45.6 cm^2), so they will saturate first. My quick-and-dirty sense coil is four turns of wire, conservatively placed about as far as possible from the forcing coil (whose decoration is left over from Halloween 2013).
flux1.PNG
Fluxmeters depend on an electrical conductor going around the magnetic flux of interest. It's analogous to measuring electric current by putting a ferromagnetic core around the place of interest. Both are noninvasive, and can take readings on solid bars or empty space. Fluxmeters measure changes of flux; a change of 1 weber (at any speed) generates 1 volt-second per turn in a sense coil. This unit has an analog voltage integrator with a reset button, a very sensitive offset-adjustment knob, and a digital display.
flux2.PNG
To get flux change from a gapped magnet, one can reset the integrator while sense coil is at the place of interest, then rapidly move the sense coil away from the strong field. With my electromagnet, I could have run demagnetizing cycles and then set the fluxmeter zero. This time, started at 10 amperes and set fluxmeter output to half of known peak-to-peak value, using a slow motion control kluge. (6 volts through 10 kΩ, applied in parallel with sense coil.)
flux3.PNG
One effect stood out which I had never seen while fluxmetering transformers. After each current step that caused a large flux change, but not similar current steps with small flux change, I had to wait for the least significant digit to stop changing. This has got to be an eddy current / skin effect thing. Coil current lags voltage a little. Average flux (esp. the last percent) lags current a lot. It will be fun to see that in a quantitative way.
All models are wrong; some models are useful. -- George Box
John Fenley
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Re: lab electromagnet from scratch

Post by John Fenley »

All the work I see here is discouraging me from attempting to build the magnet I need for my proposed fusion reactor... I'm going to need an extremely uniform .5T field over an area of about 18", and the thicker the better.

Fortunately, I realized that MRI machines have fields that meet my requirements. I'm going to be trying to get a permanent magnet MRI machine to act as a basis for my reactor.
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Richard Hull
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Re: lab electromagnet from scratch

Post by Richard Hull »

Magnetics can be fun and exciting. I actually put out a two hour long VHS tape on an introduction to magnetism back in 1993 titled "Minimal Magnetics" as part of my Tesla coil educational series of VHS tapes. I think there were 7 or 8 of these 2 hour tapes back then and about 60 of my 2 hour Tesla Coil report tapes.

Magnetics can be frustrating and very limiting due to the limitations in the permiability of metals which can concentrate and focus large field flux. Air, of course, is infinitely permiable, but then there are those pesky amp-turn limitations leading to meltdown with no core only conquered by either pulsed operation or Liqiud nitrogen or both.

As noted many times way back, there is only charged mass and gravity that manufacture the secondary and tertiary forces of all magnetisim and all light. (note at the very far end of light it seems only collapsing nuclear forces can make extremely hard gammas, but again, these nuclear forces are only there to constrain and contain the electrostatic charge forces of charged mass within the nucleus. The intense charge field relaxation of the nuclear force braking down might be he source of those hard gammas.

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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Rich Feldman
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Re: lab electromagnet from scratch

Post by Rich Feldman »

Good luck, John, with getting a permanent magnet MRI setup. Fusor.net has some discussions of permanent magnet systems shaped for small cyclotrons.
My electromagnet project is just slow to be executed, not really complicated. Magnetic flux path model is 1-dimensional, with a few discrete segments. Each has a length and area, permeability, saturation, and hysteresis. Pole diameter is only 3 inches to keep the steel weight manageable and the machining requirements easily accessible.

In other news, I got a bit Andrew Robinsoney on my pole pieces. Removed the mill scale by pickling in dilute hydrochloric acid, then gave them a nice coat of paint. Drilled carefully centered holes for alignment pins, to be followed by threaded holes for machine screws.
DSCN0213.JPG
Here is the "carrying case" for a 29 pound set of pole pieces.
DSCN0216.JPG
All models are wrong; some models are useful. -- George Box
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