largest value passive components in existance?

[T3sl4co1l]

What about the Large Hadron Collider, isn't it a giant electromagnet+++++.

Probably many of them.  All the important ones are superconducting though.  You can say this for sure: there's nothing that makes 10T+ fields that isn't storing a lot of energy.  And we're talking miles of beam line here...

The ITER tokamak's main field coils, I believe, are rated at something like 10H and a thousand amperes.

Tim

[VK5RC]

I am not an EE but I must imagine the problems of releasing that stored energy must be very challenging! I don't really understand what would happen to a superconducting coil when you switch off the electricity, the 'back EMF' could be terrible or perhaps the superconducting properties mitigate it to some degree.
 I friend I cycle with (a radiologist) was talking about MRI imaging machines (a few Tesla) in which they leave the main magnet ( a liquid nitrogen cooled superconductor) powered on the whole time, when they want to shut down they let it warm up first!

[SeanB]

The big problem with superconductors is turning them off when charged with current, as the energy has to be dissipated somehow. Letting it warm up till it transitions to a regular conductor has the problem that it suddenly results in massive heating inside the conductor, which stresses it. With MRI they have to sheath the superconductor with silver coated copper to allow it to dump the energy in the copper coat's resistance more or less safely, though that heats the windings very fast, and with time will crack the brittle ceramic superconductors inside, needing the coil to be replaced. Thus most MRI units will never be turned off, and will have enough backup to allow the cryocoolers to operate for a long time if the power fails.

[VK5RC]

Thanks seanB. Interesting! When I did  a quick google about the LHC, I noted the huge energy requirements and one proviso that Wikipaedia mentioned was the power contract is on an "Instant cut off" if  loads need it basis, your comments on back up for a 'simple' medical imaging MRI machine made me think as I work next door to one and the cooling fans work day and night, the 'back up' power supply and the switch off routine for the LHC must be complex.

I will tackle my Radiologist friend a little more about the switch off routine, I suspect the MRI Radiographers have more to do with that side of things, as an aside he had some photos of the room they are about to install a new MRI machine in, the copper plate lining was impressive and the single door also part of the Faraday cage. The venue is directly over a car park and once a car is parked directly below the MRI unit, for consistent field density in the machine, the car can't be moved without a 20min or so recalibration, staff carpark!!

[SeanB]

LHC did have some issues during initial testing in that a few magnets had a cooling failure and quenched, and destroyed themselves.

[T3sl4co1l]

You discharge it the same way you charge it, doi.   Suppose you charged it with a 12V car battery (this could take a while at 10H and 1000A..), once it reaches nominal current you short the terminals and everything's happy -- it sits there dissipating no power, developing no voltage, just lots and lots of electrons sliding around.  To discharge, simply hook it up to the battery backwards -- the 1000A (and less as it discharges) charges the battery.  When current reaches zero, you can safely open circuit the inductor.  Just as a capacitor, at zero volts, can be safely short-circuited for storage.  And by analogy... never open circuit a charged inductor: you'll get one hell of a lovely arc off a superconducting magnet.

I once heard a company developed a UPS based on superconducting storage -- you'd basically short out the inductor with an inverter when not needed (you will have to keep pumping a little flux into it to account for the inverter's losses), then hook it to the AC line alternately when needed.  Can't imagine the value is all that great though; efficiency under heavy use should be good, but the refrigeration power isn't so attractive, especially over long periods of inactivity.

Tim

[VK5RC]

Must be one hellofa switch, make before break or vice versa? Some pretty nasty switching issues. Leave the magnet open it will bite you, short the 'battery' similarly I would imagine.

[T3sl4co1l]

Shorting the car battery for a few microseconds would certainly be a much better alternative to opening a few kilovolts at the same current, but yes, if you're going from CV to CC sources, you'll want to make sure you keep things straight.  It's just a big slow buck converter, nothing unusual about that in power electronics.

Tim

[SeanB]

Except that if a small single bit of the superconductor decides to quench it will generate a very quick pulse of heat, and that in turn will trigger the entire area around it to stop superconducting, and then the remaining superconductor will be above it's critical current density and the whole lot will suddenly become a regular conductor. If you have pumped 1Mj of energy into the magnetic field having it all dissipated in 1ms in a small area will definitely take it from 50k to over 500k in under 1 millisecond. Expansion alone will do some severe damage, let along the sudden evaporation of a few litres of cryogenic nitrogen into gas. doubt it will diffuse out through the cooling channels fast enough to not pop things. That assumes it is a high temperature superconductor, if it is one of those that only occur at liquid helium temperatures then the entire structure will behave as if it was made from crystalline sugar, as it will be brittle.

[JulietMikeBravo]

Don't know about the world, but this is my largest value passive part:

http://www.flickr.com/photos/julietmikebravo/8554799549/#

1500 G Ohm resistor

[jeremy]

I am not an EE but I must imagine the problems of releasing that stored energy must be very challenging! I don't really understand what would happen to a superconducting coil when you switch off the electricity, the 'back EMF' could be terrible or perhaps the superconducting properties mitigate it to some degree.
 I friend I cycle with (a radiologist) was talking about MRI imaging machines (a few Tesla) in which they leave the main magnet ( a liquid nitrogen cooled superconductor) powered on the whole time, when they want to shut down they let it warm up first!

Are you sure it was liquid nitrogen? I have had a bit to do with MRIs and all of the ones I have dealt with use liquid helium? Although, the helium is usually surrounded by chamber of liquid nitrogen. To my knowledge, high temp superconductors aren't quite there yet for the medium to high field strengths (>=3T)

Quenching is a really big problem in MRI because it costs a lot of time and money to refill and re-setup the machine. Interestingly enough though, in a working MRI the main culprit for heating in the main magnet is due to eddy currents induced in the superconductor by the inner coils like the gradient coils; a lot of the shielding of the main magnet is to protect it from the gradient coils. I've not heard of any machines that broke due to quenching (the venting works remarkably well), but I suppose it is possible and I don't really deal with broken ones!

Also, I can vouch for the superconducting UPS idea; this has been done in MR before where the main magnet is initially "charged" and then only needs to be "topped up" at regular intervals.

[houdini]

I seem to recall an experimental nuclear fusion facility using some of the largest capacitors in the world for pulsed laser applications.

[Richard Crowley]

My  nomination for largest "ground rod"...

The grounding system at Celilo consists of 1,067 cast iron anodes buried in a two foot trench of petroleum coke, which behaves as an electrode, arranged in a ring of 3,255 m (2.02 mi) circumference at Rice Flats (near Rice, Oregon), which is 10.6 km (6.6 mi) SSE of Celilo. It is connected to the converter station by two aerial 644 mm2 ACSR (aluminum conductor, steel reinforced) conductors, which end at a "dead-end" tower situated at 45.497586°N 121.064620°W.
http://en.wikipedia.org/wiki/Pacific_DC_Intertie

It is the ground terminal of the 3.1 Giga-Watt Pacific DC Intertie.  At the other end (Sylmar, California) they use 'a line of 24 silicon-iron alloy electrodes submerged in the Pacific Ocean at Will Rogers State Beach."

[T3sl4co1l]

Hmm, couple links down on Google:
https://www.flickr.com/photos/llnl/3678999076/

Looks pretty well covered up, not that I'd imagine you'd want to get your fingers mixed up with what's inside!

Tim

[jahonen]

Except that if a small single bit of the superconductor decides to quench it will generate a very quick pulse of heat, and that in turn will trigger the entire area around it to stop superconducting, and then the remaining superconductor will be above it's critical current density and the whole lot will suddenly become a regular conductor.

That's why they have heaters embedded in LHC magnets, so that if a magnet quenches, then QPS (quench protection system) will fire quench heater resistors using a capacitor bank charged to several hundred volts to provoke controlled quench in entire magnet to prevent this small spot from burning, i.e. distribute the energy evenly. Quench may happen due to some stray particle dissipating its energy into the coil, so quench is a real issue in superconducting particle accelerators which tend to push the superconductors to their ultimate limits.

There is also a parallel diode to a magnet which bypasses the circuit current in case a quench happens. Remember that the main magnets are series connected so there are dozen other not quenched magnets in series with the one that quenched. That diode is a heavy one, it must take up to 13 kA of current (at ultimate current, in dipole/quadropole magnets). Furthermore, there is a dump resistor which is connected in series of the magnet circuit (in normal operation, it is bypassed by a redundant switch), to speed up the current decay (it still takes 10's of seconds!) and burn the stored energy in the dump resistor instead of the cryomagnets.

And, it was actually a bad interconnection between two magnets which failed during initial LHC sector testing in september 2008, interesting what one can do with 200 MJ of stored magnetic energy. But most of the damage was collateral caused by expanding helium.

Speaking of big magnets, LHCb dipole magnet is another interesting one. It is a normal conducting 5.8 kA dipole magnet. Conductors are made from 50x50 mm aluminum bar, with 24 mm hole for the cooling water. Inductance is about 2 H and stored energy is 32 MJ. Nominal dissipated power is 4.2 MW. It needs 730 volts applied to keep its current due to resistive losses (source: http://lhcb.web.cern.ch/lhcb/magnet/TDR/pdf/lhcb-magnet.pdf http://lhcb-public.web.cern.ch/lhcb-public/en/detector/Magnet-en.html)

Regards,
Janne

[lapm]

The planet Earth is the largest passive component by far.

Lol, i was going to suggest that. 

[VK5RC]

Apologies , it is liquid helium cooling re MRI.