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stop battery from blowing up

K

Ken Williams

Jan 1, 1970
0
hi, I need to pulse a coil to create a permanent magnet. how can I do
this with a car battery but making sure the car battery doesn't blow the
hell up?

Its like I'm shorting it I guess. I thought about using an old UPS
(uninterpretable power supply) but not sure if thats smart either.
 
J

Jasen Betts

Jan 1, 1970
0
hi, I need to pulse a coil to create a permanent magnet. how can I do
this with a car battery but making sure the car battery doesn't blow the
hell up?

use a fuse in series with the coil.
 
L

lurch

Jan 1, 1970
0
in message
use a fuse in series with the coil.
That makes a fuse tester. A resistor
would work better.
Size? Not nearly enough info.
 
D

Don Stauffer

Jan 1, 1970
0
lurch said:
in message

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?
 
K

Ken Williams

Jan 1, 1970
0
Don said:
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.
 
D

Don Stauffer

Jan 1, 1970
0
Ken said:
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.
 
T

T

Jan 1, 1970
0
hi, I need to pulse a coil to create a permanent magnet. how can I do
this with a car battery but making sure the car battery doesn't blow the
hell up?

Its like I'm shorting it I guess. I thought about using an old UPS
(uninterpretable power supply) but not sure if thats smart either.

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

Geek

Jan 1, 1970
0
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
10 turns and the inductance was too great and restricted the current
build-up

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.




***** British industrial humour ... F***ing Great Capacitors !!!
 
K

Ken Williams

Jan 1, 1970
0
Geek said:
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
10 turns and the inductance was too great and restricted the current
build-up

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?
http://www.abra-electronics.com/pro...ge-Radial-Electrolytics-Capacitor-p-4406.html

they would be in parallel correct?
 
G

Geek

Jan 1, 1970
0
If you do not know the answer to your question then it would be
irresponsible of anyone to offer you further help.
 
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