On a different note, I worked with Mass Spectrometers for a while. I
don't know the rating of those BIG electromagnets, but if it tried to
take a wrench away, you just let have it. It'd crush your hand
including bones.
Big magnets are great pranksters. There was a time when I had to service
large servomotors, specialized for low inertia. Those things have a flat
copper rotor, basically a set of printed coils and nothing else,
rotating between two sets of really big and strong magnets. The magnets
pull the housing of the motor together with great force. To open those
motors, the technique is to remove the screws, then bolt some levers to
the two end plates of the motor, and twist one motor end relative to the
other. Unlike poles attract each other A LOT, but by rotating the plates
by one magnet location, you have like poles facing each other, which
repel each other just as strongly. When twisting the plates carefully,
the motor easily comes apart as soon as the unlike poles no longer face
each other fully. But if you twist them in some crooked position, so
that the end plates jam in the housing, you can just keep twisting them
until the repelling force becomes enough to overcome the jamming force.
At that point, kaboom! You get the parts flying all through the room,
maybe all the way through the roof, and hopefully not in your face. It's
the well regarded magnetic cannon effect.
After reassembly, the magnets need to be remagnetized, because they
loose about half of their strength when the magnetic circuit is opened.
This is done with a one turn winding that twists between those magnets.
You simply apply a few thousand amperes to that wire, for a short
moment. I did that with two truck batteries in series. One time the wire
welded itself to the battery post and I couldn't rip it off quickly
enough (with pliers, of course). The wire evaporated, and the next time
that motor needed maintenance, I had to install a new magnetizing wire.
At the factory they probably have a nice pulse generator, rather than
banging the wire with pliers against a battery pole...
It's interesting to note that when the magnets are weak, the motors run
much faster than normal. It's logical to anyone knowing
electromagnetics, but looks counterintuitive for laymen.
Manfred
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