Hi,

I've got 4 capacitors with the following specs:

CAPACITOR, 4700UF 400V;
Capacitor dielectric type: Aluminium Electrolytic;
Temperature, operating (a) max: 85°C;
Temperature, operating (a) min: -40°C;
Time, operating life: 3000h;
Current, ripple AC @ 100Hz: 14.22A;
Current, ripple AC @ 10kHz: 19.91A;
Frequency, ESR: 100Hz;
Resistance, ESR: 38mR;
Temperature, ESR: 20°C;
Temperature, operating life: 85°C;
Temperature, ripple current: 85°C;
Tolerance, +: 20%;

I plan to combine the 4 to make a large capacitor of 800V @ 9400uF (2 pairs
in parallel connected together in series). I was then hoping to use this
large capacitor in a coilgun (e.g. charge them up and discharge them through
a coil). My question is, are these capacitors suitable for such an
application? In particular, should these be discharged through a coil (they
won't blow up will they)? Im aware of the electrical dangers (touch them
and die basically) but I'm not sure about the suitability for my
application.

If you have any info or advice then I'll be glad to here it.

Thanks in advance.

Steve wrote in message
...
Hi,

I've got 4 capacitors with the following specs:

CAPACITOR, 4700UF 400V;
Capacitor dielectric type: Aluminium Electrolytic;
Temperature, operating (a) max: 85°C;
Temperature, operating (a) min: -40°C;
Time, operating life: 3000h;
Current, ripple AC @ 100Hz: 14.22A;
Current, ripple AC @ 10kHz: 19.91A;
Frequency, ESR: 100Hz;
Resistance, ESR: 38mR;
Temperature, ESR: 20°C;
Temperature, operating life: 85°C;
Temperature, ripple current: 85°C;
Tolerance, +: 20%;

I plan to combine the 4 to make a large capacitor of 800V @ 9400uF (2
pairs
in parallel connected together in series). I was then hoping to use this
large capacitor in a coilgun (e.g. charge them up and discharge them
through
a coil). My question is, are these capacitors suitable for such an
application? In particular, should these be discharged through a coil
(they
won't blow up will they)? Im aware of the electrical dangers (touch them
and die basically) but I'm not sure about the suitability for my
application.

If you have any info or advice then I'll be glad to here it.

Thanks in advance.

You might get away with it but the best capacitors to use for this
application would be electronic flash ones. They are designed for very high
discharge currents. These currents can burn out the internal connections in
capacitors not designed for the purpose.

One safety precaution you might like to consider: Bleeder resistors across
the caps so that they don't retain their charge for too long after you've
stopped using them.

Another idea: Use a ceramic tube for the barrel (no eddy currents) with a
series of coils along its length which when energised in the correct
sequence will accelerate the projectile in stages. This can be more
efficient that a single large coil.

Each coil has its own capacitor and these are discharged via high-voltage
SCRs which are in turn fired by a digital sequencer circuit.

And BTW, coil guns are still covered by the Official Secrets Act here in the
UK! So don't tell anyone I said that! )

Hi Steve,

Steve wrote: I've got 4 capacitors with the following
specs:

CAPACITOR, 4700UF 400V;

I plan to combine the 4 to make a large capacitor of 800V @ 9400uF (2
pairs in parallel connected together in series).
If you have any info or advice then I'll be glad to here it.


Two capacitors (4700UF @ 400 volts) in series and two in parallel equals
4700 UF at 800 volts not 9400 UF at 800 volts.

Two in series equals 2350 UF at 800 volts.

Two of these in parallel equals 4700 UF at 800 volts.


--
Jay
--------------------------------------------------------------------
"I'm pullin' for you; we're all in this together", Red Green
--------------------------------------------------------------------