stop battery from blowing up

use a fuse in series with the coil.

"Jasen Betts" wrote in message news:h46r1c$557$ snipped-for-privacy@reversiblemaps.ath.cx...

That makes a fuse tester. A resistor would work better. Size? Not nearly enough info.

A resistor would limit the energy you are putting through the coil. The key is the resistance of the coil and the power rating. Also, the circuitry of the pulser will also limit the current. The series resistance of the coil and the pulser circuitry will be the max current. Fuse or use a quick acting circuit breaker just above that current.

How long is the pulse. The leading edge of the pulse will be at a lower current because of the inductance. If the pulse is quick enough you dump less energy than if the current reaches steady state.

Are you putting a long train of pulses into the coil, or only a couple? The power dissipation number of the coil is for steady state, which is a function of duty cycle. You need to factor in the duty cycle for steady state. If only a few pulses, the value given for the coil power dissipation is not really applicable.

Also, are you using the voltage rating of the coil, or are you dumping a lot of overvoltage into it- i.e, are you using a 12 volt battery on a 3 volt coil?

I haven't actually made the coil yet. I was going to do like 2 layers of 14 AWG coil and pulse it once with a car battery. 12V would be fine I think.

If it is home made you then have no idea of the thermal properties of it However, for a single pulse then the equilibrium thermal properties are not an issue. If it is a quick pulse, then the max current for 14 gauge wire is the issue. Look that up. Then, figure out how much wire, given the resistance of the wire per foot, is needed to limit the total resistance so that 12 volts into that resistance gives just less than the max allowable current.

Could always charge a bank of capacitors. They're somewhat better at massive current outrush than a battery would be.

I worked at an engineering company that manufactured such a machine.

It used a bank of FGCs***** charged up to 1kV, and then discharged them through a coil of about 10 turns of 1/4" copper rod. More than about

This was sufficient to coerce any material to its maximum magnetic strength in only one pulse.

You had to ensure that the material to be magnetised was securely held down, else it'd be thrown across the room.

anyone know where I can get a good set of capacitors designed to do this? Is it just anything with a large voltage like the ones listed (450V) at the end of this list?

they would be in parallel correct?