shorted transformer winding

Yes, I did. It's the kind of fault that you find well-represented in any collection of speech error and errors of action (typos) but I'm still kicking myself.

-- Bill Sloman, Nijmegen

the

la.

True, but both refer to a dead genius.Most of us have got used to living in a world where words can have more than one meaning - lead me to the lead mine, I've got to install some LED lamps.

-- Bill Sloman, Nijmegen

Or a radio brand:

Joop

Hundreds of teslas == millions of Gauss. A fully saturated piece of good iron has a remanence of (iirc) about 8 kG. The world's record for a long-pulse magnet is about 60 T.

Hundred-tesla fields require things like copper coils compressed by high explosives.

Cheers

Phil Hobbs

Yeah I had a colleague who did that back in Japan. A single turn of copper (artfully sculptured). I think they discharged some big cap bank through it and got to 100T at the peak.. for maybe... (pure guess here) 10's of us? It was a one shot device, sample and coil were destroyed with each shot. (hard to do any averaging of the data.)

George H.

I knew that. Last week we were playing with a smallish spectrosopy magnet at UC Davis, just 7.5T, worth about $10 per gauss.

John

Not any longer. The September 2008 copy of the IEEE Spectrum had a piece on the new magnet being built at the US National High Magnetic Field Laboratory Pulsed Field Facility inside the Los Alamos National Laboratory in New Mexico.

Apparently this system is intended to produce a number of 20 millisecond pulses of 100T over a two second period, and takes an hour to recover between these bursts.

It's a two part system - the outside coil is energised to produce 40T for two seconds, and it can survive some 10,000 of these brief episode. The inner coil is driven from a 2 megajoule capacitor bank and is only good for about 100 pulses.

At the time of writing, this time last year, the set-up had got to

-- Bill Sloman, Nijmegen

Cheers

Phil Hobbs

What kind of EMF does that give the inside one?

Though I suppose it doesn't matter much if you zap the inside one at a zero crossing, where current (and B) is maxima.

Tim

Hopefully took the credit cards out of them britches before getting too close ;-)

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They've yet to get to the "hundred-Tesla fields" that you were claiming needed explosives, but that was what the system was designed to achieve, and they seem to be on track to get there soon, without explosives.

-- Bill Sloman, Nijmegen

My wife kept losing magnetic strips, until I caught her dropping her cell phone into her purse, sliding by her wallet :-( Now she uses a pocket high up in the purse.

...Jim Thompson

The Nijmegen pulsed high field magnet was going to charge its capacitor bank to 15kV, The last thing I did at the university was look at protection circuits for equipment in the vicinity - apparently the capacitors don't always discharge across the magnet coil, which can be hard on the experimenter's sample-probing electronics.

-- Bill Sloman, Nijmegen

Maybe a switcher in there where they saved half a penny by opting for an open core inductor?

My suspicion is the earphone magnetics.

...Jim Thompson

Usually you only find those on larger phones, like older cordless ones. I often take such stuff apart after its useful life has ended, mostly to learn about packaging and layout tricks. On newer devices the speaker is a piezo. It is incredible what they pump through there when switched to hands-free mode.

Most likely like my phone, that has a magnetic strap to keep the case closed with the optional protective jacket.

I also once had a phone with a magnet attached on the back so that it would fit into a mini holder case in the car for hands off where it allowed the phone to still be accessible when docked.

I left my wallet in my backpack, across the room, but it's probably not necessary. Most modern magnets are self-shielded, so the 10-gauss line is just a few feet away.

We do plan to use some small telecom-type relays in the next-gen electronics, so we'll be testing the regular and latching versions for field sensitivity. I'm guessing that the latching relays will be better.

John

What kind of switch do they use?

John