30,000 AMPS, WOW!

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jmayes
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30,000 AMPS, WOW!

Post by jmayes » Tue Dec 08, 2009 5:25 am

I read in the logs that the CMS magnet was ramped to 15,000 AMPS then on up to 30,000 AMPS! As an electronics engineer I see this as one huge figure. I am hoping someone in the know could tell us what the volts are on that buss so I could get a real picture of how much electricity that one magnet uses. I have also seen 600A on the tunnel magnets which I would love to know the volts on too.

THankx for the help!

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Xymox
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Re: 30,000 AMPS, WOW!

Post by Xymox » Tue Dec 08, 2009 5:40 am

yea impressive numbers..

Im a EE as well...

I don't remember right off hand.. Whats fun to do is search the documents. That always leads to more things that are interesting... Before long you look up and 3 hours has gone by :)

Try this...

Google

Put in site:cern.ch and then your search words.. Lots of fun... Im sure you will find extremely detailed answers to your questions

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chriwi
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Re: 30,000 AMPS, WOW!

Post by chriwi » Tue Dec 08, 2009 6:52 am

I did not search now, but I only want to bring back to your minds, that we are dealing with supercondukting coils here where the resitance is close to really 0 Ohm, so even for such high currents I don't expect very high voltages.

That is rather like the peltierelement in the practical work of my exam where I had to deal with only 0,5V and 2A, probably even much worth for superconductors.
bye

chriwi

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Re: 30,000 AMPS, WOW!

Post by pcatom » Tue Dec 08, 2009 12:21 pm

The Alice soleniod works at room temperature. I can't remember the exact figure, but the voltage is around 130V. This means an electrical power of 4MW. It is indeed an impressive magnet. It was built for the previous detector L3 which was installed in the LEP machine. For your information the it weighs about the same as the Eiffel tower.

The Superconducting circuits of the LHC have a high current, but need only a low Voltage. The largest power supplies are for the dipole circuits. Here they produce 12,000A at around 10V. What is impressive here is the inductance of the circuit which is around 15 Henries.
The 600A supplies to the corrector circuits also mainly have a low voltage of around 8V.

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Re: 30,000 AMPS, WOW!

Post by Harbles » Tue Dec 08, 2009 2:29 pm

I found this document on the Power converters used at the LHC;
http://cdsweb.cern.ch/record/1003726/files/p411.pdf

An interesting summary here;
" Furthermore, the LHC experiments require large converters for their magnets (dipoles,
solenoids, or toroids):
– ATLAS: [20.5 kA, 18 V] for the superconducting toroid magnet (inductance L = 7.5 H and a time
constant τ = 37 500 s) and [8 kA, 8 V] for the superconducting solenoid magnet (L = 1.4 H)
– CMS: [20 kA, ±26 V] for the superconducting solenoid (L = 14 H and τ = 140 000 s)
– ALICE: [31 kA, 170 V] for the warm solenoid (L = 0.33H, τ = 80 s); and [6.5 kA, 950 V] for the
warm dipole magnet (L = 1 H; τ = 10 s)
– LHCb: [6.5 kA, 950 V] for the warm dipole magnet (L = 1.3 H; τ = 10 s) "

I did not realize that the Alice Solenoid was not super conducting. So 31KA @ 170 V = 5.27 Megawatts! wow!

Also even the superconducting magnets have non super conducting cables connecting them to the power converters. Very big wires.

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jmayes
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Re: 30,000 AMPS, WOW!

Post by jmayes » Tue Dec 08, 2009 2:56 pm

This is great info!

I figured it was pretty low voltage, but Alice surprises me too @ 130v and warm.

Thankx again for the help,
J

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Re: 30,000 AMPS, WOW!

Post by Xymox » Tue Dec 08, 2009 8:15 pm

Its great to have vastly knowledgeable CERN people here at the forum.

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Re: 30,000 AMPS, WOW!

Post by NormReitzel » Wed Dec 09, 2009 2:41 am

Even though the magnet coils have essentially zero resistance, they have plenty of inductance, and it takes a reasonably stout voltage to ramp a solenoid from one field to another.

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Re: 30,000 AMPS, WOW!

Post by seabass » Wed Dec 09, 2009 2:45 am

thats pretty crazy..

that explains the $30M electric bill :shock:

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Re: 30,000 AMPS, WOW!

Post by Xymox » Wed Dec 09, 2009 6:14 am

A-hahahah really wow !!!..

Well inductance is might hard to deal with. Resistance is easy...

15 Henries is insane

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Re: 30,000 AMPS, WOW!

Post by Tau » Thu Jun 30, 2016 11:13 am

Xymox wrote:A-hahahah really wow !!!..

Well inductance is might hard to deal with. Resistance is easy...

15 Henries is insane
A quick calculation: energy in coil = 1/2 * inductance * current^2 so at 30 kA and 15 H we have 6750 MJ. The coil will have that much energy at its avail to make sure the current keeps flowing, so you will have to be careful.
Cutting a wire will cause trouble, that's for sure.
:-)
- Tau

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Re: 30,000 AMPS, WOW!

Post by mfb » Thu Jun 30, 2016 5:45 pm

I think you mixed the CMS solenoid magnet current with the LHC dipole magnet inductance, the dipoles have ~10 kA current.

The 2008 dipole quench incident was caused by the energy stored in the superconducting dipole magnets. In total over the ring about 11 GJ at 7 TeV, ~15% less at 6.5 TeV.

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