It is long gone. I have nothing similar. I have two HP supplies for my
personal use, but 0-40 volt and lower amps. I also have one Lambda
power supply 0-10v that we use for the kids' HO scale railroad.
(finally something that does not fail all the time)
On a second thought I have a PP-1104C/G, you can google it. Up to
100a. However, I am not really in the mood to sell it, it is my last
one of very many and it is usable sometimes.
The bottom line is, unfortunately I cannot help, I can only recommend
owning a few power supplies that cover a range of uses.
Just curious why you need one, for electrolysis of something?
Oh well. I assumed it was long gone but just in case I figured buy from
someone I know :-). There are several on ebay at a range of prices, I'll
keep shopping and pick one up in the next few weeks. I told my old adviser
I'd charge a 3 tesla supercon magnet for him when he gets an experiment
ready to go, after I heard that he got a quote of $28k from the
manufacturer. That's a bit extreme considering that they used to charge $5k
20 years ago and that included a day spent shimming the field with an nmr
probe that they supplied - no shimming needed on this one. I actually
charged this magnet once back when I was a student, after repairing a vacuum
leak and pumping the cryostat back down, but we borrowed a supply back then.
For this I need low ripple so I want the HP, the Lambda's I looked at were
way noisier (5 mVpp vs 75 or 100 mV), and while for this I only need 38 amps
or so, I figured I might as well get the 6260B at 100 A instead of a 6259B
at 50 A since the prices are pretty similar (but 110 V is more convenient
than 220, hmm, decisions, decisions :-)). Voltage will peak at maybe 4 V
early on up to 15 or 20 A, then it gets tapered off as the current comes up
and the permissible rate of change of field goes down. It'll be a fun
outing if it works out. Thanks, anyway.
I do not see any on ebay in the range of prices. The one for $133.12
Mine sold for $56.00 in March 2005. (and it was good) I did not mind
Reviewing my emails... On the same day, I sold two brand new diesel
engine heads for an Onan military genset. I bought both for $100 and
sold for $910. The person who bought it, purchased it for EXPRESS
PURPOSE of selling it back to the military, as part of a repair
project, for a much greater price than what he paid me.
Note that sometimes "bad" means that the vendor does not know
how it is supposed to work.
I got a pair of "bad" Power Designs 2005 power supplies (20 V,
5 A) which were set by multiple concentric switches in steps of 1,
0.100, 0.010, and 0.001 V, plus a toggle switch which adds 10 V to the
total. There is also a pot for tweaking the output from 0.000 to 0.001
Anyway -- what was "wrong" with the supplies, and what I
suspected was the problem was that the "sense" terminals on the back
were not connected to the V+ and V- terminals. Normally, they are
connected, and the front panel terminals are used -- but for use in
rack-mounted test setups (and these two were in a dual rack mount frame)
it is common to run the power and the sense wires from the back of the
supply, to leave the front panel uncluttered by cables. Running the
sense wires to where the load is assures that the regulation produces
the set voltage *where the sense and power leads join*, instead of at
the panel, allowing the loss of several milivolts or more depending on
how long the cables are. The sense leads should be run back in a
shielded pair cable to keep noise pickup from affecting the output
Anyway -- once I got them home and replaced the missing sense
jumpers, both worked just as designed. And I got them for what I
considered to be a particularly good hamfest price for the period. (It
helped that I used to use these at work, and knew what they would do so
I wanted them. :-)
Not any good on eBay -- unless the vendor includes photos of the
back panel and you can see that there are no jumpers between the power
terminals and the sense terminals there. On something capable of 100 A,
the sense terminals will probably be normal sized Jones barrier strips,
and the power terminals on the back will be on an extra heavy duty
barrier strip -- or even on stud terminals on the back.
Of course -- if you can see the sense wires are connected in the
photo -- don't bother bidding. :-)
Email: < firstname.lastname@example.org> | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
I guess I'm constitutionally incapable of a true cliff-notes length answer,
but this is my short version:
It's a 6" horizontal room temperature bore 3 tesla persistent mode
superconducting magnet with a homogenous cylindrical volume of about 2"
diameter by 4" long with a uniformity of 10 ppm (parts per million). There
are actually 10 superconducting shims that can improve this to 1 ppm but for
this experiment that's not needed. It's the magnet for a Fourier transform
mass spectrometer. That's the what for, the what is that it has about nine
miles of superconducting wire on the order of 0.1 mm diameter wound into a
solenoidal coil about 30" long, ID about 8", and a complete guess on the OD
is12". This is in a dewar so it can be submerged in liquid helium at 4.2
kelvin, surrounded by a radiation shield thermally connected to the top of
the He dewar boiloff tubes so it stays at about 20 K, which is then
surrounded by a liquid nitrogen dewar at 77 K which is wrapped loosely with
20-50 layers of superinsulation (very thin aluminized mylar for thermal
radiation shielding) which is then surrounded by the outer cryostat housing
at room temperature. Down the bore there are three tubes within tubes - the
smallest is at room temperature, the next is mounted at the ends to the
nitrogen dewar, and the next is mounted at the ends to that 20 K radiation
shield. The gaps between tubes and between the 20 K tube and the helium
dewar are about 1/4" (on the radius) so the thermal gradient there is pretty
steep and that's mostly what drives the helium boiloff rate. Takes about 30
liters of liquid He to keep the coil submerged, and the dewar holds another
30-40 L above that for a hold time of about 2 months. I forget the nitrogen
capacity but a 160 L dewar provides a refill every 3-4 days and lasts 2
weeks. Go look at ebay item 310164162456 for a vertical bore version from
the same company, Oxford Instruments (this magnet has higher field, smaller
bore, and about the same homogeneity after shimming the superconducting
shims). Outer cryostat diameter is about 36-40". New back in the early
1980's this was a $50,000 or so magnet.
For whatever reason Oxford favored small diameter wire and lots of turns,
which has the effect of making the inductance of the coil very large. I
think this magnet is about 30 henries and it reaches full field at 36 amps
or so. This inductance limits the rate of change of current because you
want to keep the voltage as low as possible. The superconducting wire in
this case is single filament niobium titanium embedded in copper. Start
with a tube of niobium, put a titanium rod down the middle, and draw it down
to some mm diameter (I could have the metals reversed). Put that in a
copper tube and draw that down to under 1 mm diameter and maybe 1-5 miles
per spool. Put that in a furnace for days and form a cylindrical shell of
the superconducting niobium-titanium alloy, which is used because it works
and is flexible :-). Okay, it can be used up to maybe 5 tesla in this form
at current densities of 10^5 amp/cm^2. To go higher do all this but make
multiple filaments which gets you to 7-11 tesla depending on bore size. To
go higher make a smaller coil wound with similar wire but niobium-tin and
fire that coil after winding because that alloy can't be bent without
breaking and put that coil inside a larger coil made from the first wire (to
minimize the amount of expensive wire) to get to 15-18 tesla and $2-4
million per magnet at the upper end for a room temperature bore of 6".
Okay, back to the single filament wire - wind that on an aluminum bobbin,
bringing the ends out each time a spool runs out. After winding, splice the
ends by crimping and maybe soldering with pure lead and support these on
stalks so they stick up like a porcupine. This gets them to a low enough
magnetic field that they stay superconducting - the critical current density
and magnetic field of the joints is markedly inferior to the wire.
Somewhere along the way vacuum impregnate the coil with epoxy so the wire
cannot move under the hoop stress induced by the magnetic field. Take the
very ends of the solenoid and connect a special piece of superconducting
wire which has a heater wrapped around it and support this somewhere towards
the top of helium dewar so when you heat up the heater you don't boil off
all the liquid. Wire some power resistors in parallel with the switch, put
the coil in the dewar, weld everything together, pull a vacuum on the dewar,
cool everything down, and connect a power supply across the coil. Other
manufacturers chose bigger wire and fewer turns, like ebay item 120465624954
made by Magnex that runs at 296 amps and can be charged in 5 minutes but now
all the wires from power supply to coil have to be that much bigger and will
carry that much more heat into the dewar, boiling off that much more helium
during charging. In the end I think they all work and none is obviously
Okay, back to charging our magnet. First connect everything and set the
power supply to zero volts and zero amps. Then set the voltage to maybe 2-3
volts and slowly raise the current limit so that over maybe 10-30 seconds
you get to full current of 36 amps. At this point the current flows from
power supply to the junction at one end of the coil, through the
superconducting switch which is still cold at this point and takes the
current because the coil inductance makes that current rise very, very slow
at this point, through the switch, and back to the power supply. Lock the
current limit knob if possible and turn the voltage back to zero. This sets
the supply so you don't try to run the current up too high and tests all the
connections. Now warm up the switch by applying about 5 V and 20 mA to the
switch heater and waiting 10-30 seconds for it to go non-superconducting.
Now slowly turn the output voltage up to 3.5-4 V (I'm working from old
memories so could be off a volt or an amp here or there). Now the current
will flow from supply through the coil and back to supply, with a tiny bit
going through the switch since it's resistance is now tens of ohms, and the
current will rise at a rate set by the inductance and the applied voltage.
The copper matrix that the superconducting alloy is embedded in will also
take a little current since it is also in parallel, and this current will
make a little heat which must be minimized so that the wire doesn't warm up
and go non-superconducting. Stare at the meters and the clock for a couple
of hours until the current gets up to 20-25 A and the field up to about 2/3
of full value, then turn the voltage down to about 2.5 or 3 V to slow down
the rate of rise and stare some more. Somewhere near 32 A out of 36 A total
slow down again, and let the current get to the final value. Now gird your
loins and grab the current limit knob and tweak it slightly to bump the
current up about 0.005%, leave it for a few minutes, and then turn it back
down to 36 A. This slight overcurrent empirically was found to make the
final field much more stable. The fear is from knowing that you are already
right at the edge of the critical current density at that field and now you
are creeping a little closer. (If you weren't that close to the edge they
would rate the magnet higher and put you right back on the edge; wire is
expensive :-).) If you go too far the wire goes normal in some spot which
then gets hot which then makes the rest of the coil normal, all in about a
millisecond. Enough heat is released from the energy stored in the magnetic
field to boil off all the liquid helium and blow it into the room in about
30 seconds, and to warm the coil so somewhere near 100 K or warmer.
Stopping the current that fast through that large an inductor leads to
horrific voltage spikes, potentially thousands of volts, which in the old
days lead to arcs and destroyed coils. Remember those power resistors?
That's why they are there, to snub the voltage in case of a quench. Okay,
now the current is back down that smidge and the field is stable where you
want it, so turn off the heater on the switch and let it go superconducting
again. Now the current flows out of the coil, through the switch, and back
into the coil, around and around with no resistance. The power supply
current flows to the switch, through the switch in the opposite direction
(so the net switch current is zero but this is the best way to visualize
things), and back to the power supply. Slowly turn the voltage down to
zero, and then the current down to zero, and disconnect the supply from the
magnet. Voila! a persistent mode superconducting magnet lives. With an
Oxford magnet the total time is 2-3 hours. Single filament joints like this
can be very, very good so that the power dissipated in their residual
resistance makes the magnetic field decay maybe 50-100 parts per billion per
hour. Joints with multifilament niobium-titanium aren't as good and there
are usually more of them because you only use that wire when you need higher
field which means more turns, so those magnets can decay a part per million
per hour or so. Remember the superconducting shims? Those are windings of
various shapes to produce orthogonal field gradients to correct defects in
the field from the main coil. Some of them are shaped so that they couple
to the main coil like the secondary of a transformer. Each shim has its own
switch and heater, and some of those must be turned on and left on during
the entire charging process with a resistor across the switch to dissipate
the energy to keep from inducing too large a current in the shim. If
needed, after the main coil is persistent you then connect a separate supply
to each shim and set the currents to the appropriate values, then make those
switches superconducting as before.
Oh, no ferrous material anywhere inside the coil because it would saturate
near 2 tesla and distort and limit the field. This is the same technology
used in MRI magnets. The cost of a magnet is mostly the cost of the wire,
and the amount of wire is some function of the room temperature bore size,
the homogenous volume, and the field strength. MRI magnets tend to be much
bigger bore so people can fit into them, and to keep the cost under control
they tend to be lower field. I think early ones were 1.5-2 tesla and cost
1/2 to 1 million. Nowadays they are 3-4 tesla and cost less - the miracle
of volume production. Anyway, that's enough for now. Be glad to answer any
Iggy, that was a great price. I'm hoping for under $200 and I have some
time to be patient.
(Snip very interesting and highly thought -
provoking explanation of applied superconducting
Thank you Carl!
Your post is one of those rare gems that make
it all worthwhile.
Carl, it was a bit of a hard to read (due to its scientific nature),
but extremely fascinating writeup. I did not realize how much energy
you can store in a superconducting coil and how fragile (unstable) the
superconducting state is at the edge. I appreciate you taking time to
explain it in simple terms.
I wish I could buy liquid nitrogen somewhere.
You can, Ig. If you can buy or build a small Dewar flask (easy), you can
buy it at many medical gasses supply houses, or in a large town, and a
welding gas supply.
I get mine from a local college that does electron spin resonance
research. They have an LN2 generator on-site.
Thanks for the kind words, guys. Iggy, you can get liquid nitrogen at most
welding gas suppliers. If they fill nitrogen gas cylinders there they will
have a liquid bulk station (big tank that gets refilled by semi-trucks), and
if not they probably keep a 160 L transport dewar on hand for small sales.
Just get a stainless steel thermos bottle, like the Stanley brand, that
holds a quart or two (bigger is much better). It will probably keep liquid
nitrogen for a couple of hours, at least, maybe up to six hours. A good 2 L
glass dewar will hold LN2 for 8-12 hours. For freezing rubber to machine
it, I bet dry ice would do nearly as well and it will keep much longer in an
ice chest or thermos bottle.
Whoever suggested checking the sense wires, thank you, they show one view of
the back and you can see that they are present, sigh :-). Like I said, I
have time so I'll keep looking.
I've found it easily on the Gulf Coast (Texas). Very useful for
returning with frozen shrimp or fish. Actually, I've never looked for
it here in Michigan. I've never wanted to carry any foodstuffs the
I was in Meijer a few weeks ago and I'm pretty sure the
people ahead of me bought some at the checkout. Don't know
where they have it stashed though, other than I would look
around the regular ice cooler or just ask the cashier about
There used to a place that sells dry ice off of Grand Ave down by the Radio
Here it is.
Jefferson Ice Co.
2248 N. Natchez Avenue
Chicago, IL 60707
FAX (773) 622-7955
The web site says that the customer routes are now owned by "Home City Ice".
Who know what that means?
Paul K. Dickman
Not only that, most welding dealers have it shipped in overnight.
They normally have a large CO2 gas as well as other gases being pumped
out of air or other processes off site in a safe zone. Hydrogen and
oxygen are two more.
So if the ice company is far - call the welder -
Paul K. Dickman wrote:
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