At the 6 Stand Cold reduction Mill of the US Steel, Gary Works, they needed a system to control the pairs of 9000 HP motors that drove the top and bottom rollers to stretch cold steel inches thick.
Solid state electronics, and even tubes, weren't up to the task.
Earl Pace was the Westinghouse engineer to figured out how to do it. He used a set of Synchronous AC motors to take the incoming 3 Phase, and drive a set of DC generators. The technology to control the field windings on the DC generators was just within reach. So he used the biggest SCR systems of the day to drive those. Driving the field windings allowed you to zero or even reverse the output of the generator.
In effect, it was one of the largest magnetic amplifiers in history.
Those generators then drove the DC motors on 6-stand.
Some of the control circuitry used Magnetic amplifiers when they need to have multiple isolated inputs. The amazing thing is that they can pass DC signals to about 1 khz. (They had a 10 Khz drive signal)
All of this from 1964. I repaired some of the control modules back in the 1980s, which is how I learned about it all.
When I read the title, my first thought was about the cryotron: "Tantalum in superconducting state can carry large amount of current as compared to its normal state. Now when current is passed through the niobium coil (wrapped around tantalum) it produces a magnetic field, which in turn reduces (kills) the superconductivity of the tantalum wire and hence reduces the amount of the current that can flow through the tantalum wire. Hence one can control the amount of the current that can flow in the straight wire with the help of small current in the coiled wire."
I actually mentioned the Cryotron in the original draft of this article, but there wasn't room for it. Some of the other forgotten computing technologies of the 1960s are tunnel diodes, microwave oscillators (Parametron), and electroluminescent photoconductors.
As far as I can understand superconductivity, the devices are similar but opposite. Superconductors have a both a critical current (in the absence of a field), and a critical magnetic field (in the absence of a current). So, cranking the control line raises the field, which squelches current capacity to zero (and/or since there's an excess of either/both, superconductivity is lost).
> “Many engineers are under the impression that the Germans invented the magnetic amplifier; actually it is an American invention. The Germans simply took our comparatively crude device, improved the efficiency and response time, reduced weight and bulk, broadened its field of application, and handed it back to us.”
Quoting a quote: I found this quote of the 1951 US manual amusing.
Thanks! I'd long wondered exactly how radio carriers were modulated before vacuum tubes. (Technical details of that era are often skimpy in histories.)
Might want to get a head start on the receiving hardware, though. Most SDRs don't go that low, and though soundcards can go that high, their input impedance may not be well suited to whatever antenna you can cobble up. Oh, and you'll want an absolutely enormous antenna. Get a roll of cheap fence wire and string it halfway down the block...
Magnetic amplifiers have been in use long past WWII, they were never obsoleted by War's end.
For example, many stage lighting systems still use them. For example, the Sydney Opera House which opened in 1973 with the latest equipment used them for its stage lighting dimming (although they have now been replaced with solid state dimmers).
Magnetic amplifiers are wonderful devices albeit a bit slow for some applications. Moreover, unlike SCR and other solid state switching, they produce no RF switching noise.
> In the 1920s, improvements in vacuum tubes made this combination of Alexanderson alternator and magnetic amplifier obsolete. This left the magnetic amplifier to play only minor roles, such as for light dimmers in theaters.
An important transition is missed, that is that magnetic amplifiers are analog amplifiers.
It was William Steagall of Sperry-Rand who realized that the flux saturation could be used as a digital logic element. If you send a pulse in the same direction as the core is already magnetized, you get no output pulse. From this, and a multi-phase clock to supply drive power, digital computing elements were created.
A paper bag of magnetic cores disappeared while the engineers were out to lunch:
> But shortly after, the engineer called and asked if the shipment was there. This did not sound too good. With a little detective work we found a cleaning crew had worked in the office while we were gone. A little more sleuthing revealed that the bag had been accidentally knocked into a waste basket, and that load of waste had already been dumped into the plant incinerator. The incinerator ashes were spread over a concrete floor, and sure enough there were small magnetic cores, about one sixteenth of an inch in outside diameter, mixed in with the ashes. The CP-642 B had 32,768 30-bit words in its memory, meaning, with spares, there were just about one million magnetic cores in the ashes. At ten cents per core, the ashes held about one hundred thousand dollars worth of cores.
We reasoned the cores were the result of a firing process, and the heat of the incinerator probably had not hurt them. Maybe it even made them better. A quick test of some of the cores picked from the ashes revealed the cores were as good as ever. We and a contingent of Univac engineers & technicians spent a fun filled day rescuing the cores from the ashes with long needles. The cores were strung into the machine’s memory planes, and it passed all performance and environmental tests with flying colors.
That entire history is worth a read if you are interested in computer history of the military variety.
> Researchers soon constructed what was called core memory from dense grids of magnetic cores. And these technologists soon switched from using wound-metal cores to cores made from ferrite, a ceramic material containing iron oxide. By the mid-1960s, ferrite cores were stamped out by the billions as manufacturing costs dropped to a fraction of a cent per core.
> In the mid-1990s, the ATX standard for personal computers required a carefully regulated 3.3-volt power supply. It turned out that magnetic amplifiers were an inexpensive yet efficient way to control this voltage, making the mag amp a key part of most PC power supplies.
Somebody think of poor yttrium -- once the world's go-to source for electron-beam stimulated red dots of color TVs (although the red photons came, confusingly, out of europium instead) -- now languishing in relative obscurity, used mainly to make high-temperature superconductors, solid-state garnet lasers, and (with iridium and manganese) an intensely blue pigment. Or its cousins, ytterbium, terbium, and erbium, all of which were first refined out of an obscure mineral, ytterbite, and all named with a stunning deficit of creativity.
Erbium has found a use, in picogram quantities, to amplify optical signals in fibers directly from exposure to light. Terbium was once used for the green dots on TV screens, but is still used in a material that expands and contracts in response to magnetic fields. Uses for ytterbium are more obscure.
High-temperature superconductivity might be useful someday.
Curiously, the most important CURRENT application of magnetic amplifiers was not mentioned. In every excimer laser used for photolithography and thin film panel annealing, and possibly for LASIK, their is a multistage saturable inductor chain that compresses and amplifies the electrical pumping pulse generated by an IGBT or SCR switch. There are indeed few uses for this technology OTHER than the excimer laser.
> One Navy training manual of 1951 explained magnetic amplifiers in detail -- although with a defensive attitude about their history: "Many engineers are under the impression that the Germans invented the magnetic amplifier; actually it is an American invention. The Germans simply took our comparatively crude device, improved the efficiency and response time, reduced weight and bulk, broadened its field of application, and handed it back to us."
Does that sound "defensive" to everyone?
I don't know this area of engineering, so, to my ear, this could also plausibly be an almost admiring acknowledgement of someone else succeeding where you'd failed, combined (non-defensively) with confidence, because you had the strength or other superior merit to take it from them?
Not that it should matter, but considering the source (and time), the phrasing could be understood to imply a level of pride that we got there first. Although, they do seem to give the Germans credit for expanding the technology. Nevertheless, it's the reader that chooses how to interpret the text, and what lessons to learn from it.
At the height of early computing there were relays (Turing-Welchman
Bombe) competing with vacuum-tubes (Manchester Mk1 etc), and all had
MTBF times measured in hours. Constant replacement of valves and
relays was a full time job. Why didn't magamps replace them? I don't
think it was necessarily the efficiency, but the problem of doing
logic using AC signals. Any EE's have thoughts on this?
"After the war, U.S. intelligence officers scoured Germany for useful scientific and technical information. Four hundred experts sifted through billions of pages of documents and shipped 3.5 million microfilmed pages back to the United States, along with almost 200 tonnes of German industrial equipment."
[+] [-] neonate|4 years ago|reply
[+] [-] mikewarot|4 years ago|reply
Solid state electronics, and even tubes, weren't up to the task.
Earl Pace was the Westinghouse engineer to figured out how to do it. He used a set of Synchronous AC motors to take the incoming 3 Phase, and drive a set of DC generators. The technology to control the field windings on the DC generators was just within reach. So he used the biggest SCR systems of the day to drive those. Driving the field windings allowed you to zero or even reverse the output of the generator.
In effect, it was one of the largest magnetic amplifiers in history.
Those generators then drove the DC motors on 6-stand.
Some of the control circuitry used Magnetic amplifiers when they need to have multiple isolated inputs. The amazing thing is that they can pass DC signals to about 1 khz. (They had a 10 Khz drive signal)
All of this from 1964. I repaired some of the control modules back in the 1980s, which is how I learned about it all.
[+] [-] jacquesm|4 years ago|reply
[+] [-] 13of40|4 years ago|reply
https://en.wikipedia.org/wiki/Cryotron
[+] [-] kens|4 years ago|reply
[+] [-] klyrs|4 years ago|reply
[+] [-] nobodyandproud|4 years ago|reply
Quoting a quote: I found this quote of the 1951 US manual amusing.
[+] [-] noja|4 years ago|reply
[+] [-] 8bitsrule|4 years ago|reply
This chronology of AM radio is interesting: [https://web.archive.org/web/20071118155548/http://members.ao...] It mentions Fessenden's 1906 Xmas broadcast, and it looks like he'd just gotten one of Alexanderson's alternators.
Paul Mali, Magnetic Amplifiers (1960;PDF) [https://web.archive.org/web/20061114175548/http://www.pmille...]
Home-made MA's: [http://sparkbangbuzz.com/mag-amp/mag-amp.htm]
[+] [-] myself248|4 years ago|reply
https://alexander.n.se/en/the-radio-station-saq-grimeton/saq...
Might want to get a head start on the receiving hardware, though. Most SDRs don't go that low, and though soundcards can go that high, their input impedance may not be well suited to whatever antenna you can cobble up. Oh, and you'll want an absolutely enormous antenna. Get a roll of cheap fence wire and string it halfway down the block...
[+] [-] nateburke|4 years ago|reply
https://niklasriewald.com/2020/01/02/the-math-behind-gravity...
[+] [-] JKCalhoun|4 years ago|reply
Solid-state-punk.
[+] [-] hilbert42|4 years ago|reply
For example, many stage lighting systems still use them. For example, the Sydney Opera House which opened in 1973 with the latest equipment used them for its stage lighting dimming (although they have now been replaced with solid state dimmers).
Magnetic amplifiers are wonderful devices albeit a bit slow for some applications. Moreover, unlike SCR and other solid state switching, they produce no RF switching noise.
[+] [-] krallja|4 years ago|reply
[+] [-] c3534l|4 years ago|reply
[deleted]
[+] [-] mikewarot|4 years ago|reply
It was William Steagall of Sperry-Rand who realized that the flux saturation could be used as a digital logic element. If you send a pulse in the same direction as the core is already magnetized, you get no output pulse. From this, and a multi-phase clock to supply drive power, digital computing elements were created.
https://en.wikipedia.org/wiki/Magnetic_logic
[+] [-] zw123456|4 years ago|reply
[+] [-] nand4011|4 years ago|reply
https://ethw.org/First-Hand:The_Naval_Tactical_Data_System_i...
A paper bag of magnetic cores disappeared while the engineers were out to lunch:
> But shortly after, the engineer called and asked if the shipment was there. This did not sound too good. With a little detective work we found a cleaning crew had worked in the office while we were gone. A little more sleuthing revealed that the bag had been accidentally knocked into a waste basket, and that load of waste had already been dumped into the plant incinerator. The incinerator ashes were spread over a concrete floor, and sure enough there were small magnetic cores, about one sixteenth of an inch in outside diameter, mixed in with the ashes. The CP-642 B had 32,768 30-bit words in its memory, meaning, with spares, there were just about one million magnetic cores in the ashes. At ten cents per core, the ashes held about one hundred thousand dollars worth of cores.
We reasoned the cores were the result of a firing process, and the heat of the incinerator probably had not hurt them. Maybe it even made them better. A quick test of some of the cores picked from the ashes revealed the cores were as good as ever. We and a contingent of Univac engineers & technicians spent a fun filled day rescuing the cores from the ashes with long needles. The cores were strung into the machine’s memory planes, and it passed all performance and environmental tests with flying colors.
That entire history is worth a read if you are interested in computer history of the military variety.
[+] [-] krallja|4 years ago|reply
[+] [-] WalterBright|4 years ago|reply
[+] [-] myself248|4 years ago|reply
[+] [-] dr_hooo|4 years ago|reply
[+] [-] noipv4|4 years ago|reply
[+] [-] krallja|4 years ago|reply
[+] [-] erosenbe0|4 years ago|reply
[+] [-] ncmncm|4 years ago|reply
Erbium has found a use, in picogram quantities, to amplify optical signals in fibers directly from exposure to light. Terbium was once used for the green dots on TV screens, but is still used in a material that expands and contracts in response to magnetic fields. Uses for ytterbium are more obscure.
High-temperature superconductivity might be useful someday.
[+] [-] jmbwell|4 years ago|reply
[+] [-] aj7|3 years ago|reply
[+] [-] neilv|4 years ago|reply
Does that sound "defensive" to everyone?
I don't know this area of engineering, so, to my ear, this could also plausibly be an almost admiring acknowledgement of someone else succeeding where you'd failed, combined (non-defensively) with confidence, because you had the strength or other superior merit to take it from them?
[+] [-] ILMostro7|4 years ago|reply
[+] [-] unknown|4 years ago|reply
[deleted]
[+] [-] nonrandomstring|4 years ago|reply
[+] [-] skeptikal|4 years ago|reply
Subs use them, high T and rad places still use them (Im told).
[+] [-] Lammy|4 years ago|reply
Don't forget "and a bunch of actual Nazi scientists just for good measure" https://en.wikipedia.org/wiki/Operation_Paperclip#Key_recrui...