47000 Watt Magnetizer

[citfta]

Hi Brad,

Your wire is too small.  According to the ampacity charts that size wire is only good for a maximum of 302 amps.  If I understand your system you are trying to get 1000 amps through that wire.  You are going to have to parallel some of those wires together to reduce the voltage drop.

I don't have time right now to do the research but I think 35 ms is too short of an on time to magnetize something.  Just roughly I remember our magnetizers at work taking at least a second to magnetize something and several seconds to demagnetize an object.  I'll try to look up some info on that later in the day unless someone else gets it first.

Carroll

[tinman]

Hi Brad,

Your wire is too small.  According to the ampacity charts that size wire is only good for a maximum of 302 amps.  If I understand your system you are trying to get 1000 amps through that wire.  You are going to have to parallel some of those wires together to reduce the voltage drop.

I don't have time right now to do the research but I think 35 ms is too short of an on time to magnetize something.  Just roughly I remember our magnetizers at work taking at least a second to magnetize something and several seconds to demagnetize an object.  I'll try to look up some info on that later in the day unless someone else gets it first.

Carroll

Hi Carroll

No,the wire is not to small,as it is 12mm in diameter,not 12mm square area.The cable i am using is from the machine that had this battery bank in it,and as we heard from PW not so long ago,it dosnt take to much to gain instantaneous current,which is a lot different to that of continuous current.


Brad

[tinman]

Hi Brad,

Yes, I also think the erratic start of the pulse can be caused by the arching across the solenoid contacts, looks like flyback pulses due to current interruptions.  You have surely checked and improved the contacts since then?
The voltage drop may still be caused by resistive loss as was the case initially for Luc's setup, when dealing with peak currents of several Ampers or some tens of Ampers , every milliOhm counts.

I think it would still be worth checking the voltage drop across the battery by your oscilloscope during the ON time, due to the 24 cells in series,  the inner resistances add up.
Just considering say 0.01 Ohm for a single cell,  24*0.01=0.24 Ohm and when you have a 10 Amper peak current at the switch-on moment, the drop is 2.4V. You seem to have a 23-24V drop from the start battery voltage...  as if you had a 100 Amper peak current at switch-on? (assuming the total 0.24 Ohm resistance in the circuit). I do not know the resitance of the solenoid.   
A quick test: connect a high uF capacitor across the battery bank and see whether the drop reduces.

Gyula

Hi Gyula

Yes-i believe the relay is letting me down here,and that clearly looks like arcing at the start of the power pulse. Voltage up to the relay remains at 49 volts when the relay switches on,but at the coil you can see a clear drop. The resistance of the coil i cant measure,as it only go's to the second decimal. So it seems that the relay is the cause of the current drop. The resistance across these batteries would be extremely low as they have a very large plate area. But how to switch a current load this large cleanly if not with a relay ?

I can magnetize metal objects,but only weakly. The field is very strong in the pot,as i placed a speaker magnet in there,and hit the button while holding it with my hand. It blew my hand out of the pot no problem at all--and i was holding it with a fair bit of force. I think the unclean switching is why i cannot get a good permanent magnet to form.


Brad

[picowatt]

Hi Carroll

No,the wire is not to small,as it is 12mm in diameter,not 12mm square area.The cable i am using is from the machine that had this battery bank in it,and as we heard from PW not so long ago,it dosnt take to much to gain instantaneous current,which is a lot different to that of continuous current.


Brad

What???

I have no idea what this comment is in regards to.

PW

[tinman]

What???

I have no idea what this comment is in regards to.

PW

In regards to a small wattage valued resistor being able to deliver a large amount of instantaneous current to a load in a pulsed situation. Of course in this case we are talking about 350 amp cables being able to handle say a quick 1000 amp pulse,due to the fact that the amp rating for cables is continuous.