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For example, are there inductors with values in terms of kilo-henries or even mega-henries? 1 Henry inductors are not all that easy to find.

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    \$\begingroup\$ A quick google came up with an MRI magnet being only 6H, I'm surprised it's as small as that! This isn't really a physics question, it's an economics question. With a large coil of very fine wire, you could make a record-breaking inductance, that was totally useless through having very low SRF or high resistance, just to break a record. \$\endgroup\$ – Neil_UK May 4 '17 at 9:38
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    \$\begingroup\$ @Mr X .Would it be interesting to know what the highest Q inductor is ? \$\endgroup\$ – Autistic May 4 '17 at 11:12
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    \$\begingroup\$ I have seen some large values attained using gyrators (I cannot recall the exact values but certainly in hundreds of Henries and perhaps more). \$\endgroup\$ – Peter Smith Apr 10 '20 at 15:35
  • \$\begingroup\$ Whenever you find it, put two in series. \$\endgroup\$ – user253751 Jul 12 '20 at 19:48
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    \$\begingroup\$ I think gyrators are cheating. They are inductor simulators, not real inductors. If gyrators count, then an open circuit also has infinite inductance. \$\endgroup\$ – user253751 Jul 12 '20 at 19:48
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The largest inductor ever known to me was Fermi National Accelerator Lab's Tevatron magnet. If memory serves it was 1000 Henries running continuously at 1400 DC Amperes. Energy storage must have been right around 1 GigaJoule. They had a "quench resistor" designed to burn off the energy in case the magnet would develop an open circuit. The resistor (designed by my boss!) could be seen from space on Google Maps until not long ago.

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  • \$\begingroup\$ Thanks for the answer! That's pretty much exactly what I was looking for. \$\endgroup\$ – Mr X Apr 8 '18 at 2:42
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    \$\begingroup\$ BTW, do you have any links to the huge "quench resistor" used? \$\endgroup\$ – Mr X Feb 27 '20 at 23:22
  • \$\begingroup\$ Designing such a resistor was a question from my time as an undergraduate. \$\endgroup\$ – D Duck Apr 15 at 8:49
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What is the largest inductance value ever attained(in Henry's)?

The magnetic permeability of free space is 1.2566370614…×10−6 henries per metre and the universe is pretty big. "What" you might possibly say and I would say that radio waves (and light) are carried vast distances between far-away galaxies so this "inductance" is being used to convey energy we can see and detect therefore it exists.

Between earth and the sun (93 Million miles or 150,000,000 km) I estimate the inductance to be 188,000 henries.

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    \$\begingroup\$ Interesting. The Solar system is only 150 times more inductive than a ABB transformer? \$\endgroup\$ – Paul Uszak May 4 '17 at 12:17
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    \$\begingroup\$ @PaulUszak given that inductance is proportional to turns squared, that should not be surprising !! \$\endgroup\$ – Andy aka May 5 '17 at 15:48
  • \$\begingroup\$ I wonder what the capacitance and resonant frequency is? ?365.25 days≠ (not ;) \$\endgroup\$ – Tony Stewart EE75 May 11 '17 at 23:55
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I can't compete with the Universe (that's cheating anyway), but it's fairly easy to buy 25H inductors for power supply smoothing. The audiophile guys do this all the time for their valve amps.

Inductance is a way to transfer power from one bit of metal to another. So look at transformers. Clearly power rating is closely related to inductance. I can't find concrete evidence of anything bigger than 1200 MVA, but see this Wiki page. It lists the largest inductance at ~1300H for a 3000MW transformer. ABB do some large ones.

So we need another question: What's the biggest single transformer, and what's the power /inductance equation?

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    \$\begingroup\$ I've never heard of [large] inductors for PSU smoothing (unless it's a constant current one). Why/how would it be used instead of a large capacitor? \$\endgroup\$ – CL22 May 4 '17 at 12:47
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    \$\begingroup\$ @Jodes They're better than just large capacitors, and certainly were in the heyday of valve technology. It's a sentimental throwback but works. See angelfire.com/electronic/funwithtubes/3_Simple_Power.html , valvewizard.co.uk/smoothing.html , and ebay.co.uk/itm/… if you want to buy one. \$\endgroup\$ – Paul Uszak May 4 '17 at 13:02
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    \$\begingroup\$ Instead of CRC rectified-ripple filters, use CLC. The very oldest radios used the L to also provide the flux field for the loudspeaker instead of expensive ALNICO material. \$\endgroup\$ – analogsystemsrf May 4 '17 at 15:19
  • \$\begingroup\$ @analogsystemsrf i remember those... I wonder if anyone tried to make a 100kFarad LiPo Battery into a 100kHenry inductor with a power TIA. (transvestite amplifier) \$\endgroup\$ – Tony Stewart EE75 May 12 '17 at 0:01
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Not sure about those but I just measured the inductance of a Tesla Model S rear drive AC inductance motor and it's somewhere between 20H and 25H across one phase. I got 23H but it was a really rough measurement. This means it would be around 70H for the 3 phases.

It's not the largest admittedly, but it's interesting to me so I thought I'd add it as a real world thing.

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    \$\begingroup\$ But the three phases aren't one inductor unless they're in delta and you open the loop. You might be interested in my answer to electronics.stackexchange.com/a/487353/73158. \$\endgroup\$ – Transistor Apr 10 '20 at 15:14
  • \$\begingroup\$ Tesla Model S rear drive AC inductance motor is delta format \$\endgroup\$ – Graham Apr 10 '20 at 15:56
  • \$\begingroup\$ @Transistor how do you exactly define the motor inductance? the inductance seen across 2 connections, the coil inductance of a single phase or some way i didn't think of? \$\endgroup\$ – diegogmx Apr 10 '20 at 16:40
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    \$\begingroup\$ @diegogmx: Good question. I would only have to consider it from the point of view of power factor correction. For PFC we quote the capacitors in kVAr per phase so I imagine a motor would be specified in the same way using the P-N voltage and phase single phase current. \$\endgroup\$ – Transistor Apr 10 '20 at 17:08

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