Where can I get high voltage capacitors in Australia?
I need some high voltage and capacitance capacitors for a coil gun I'm building. I'd like them to be around the 400+volt and at least 1500uF. I'd prefer it if i could buy them instead of salvaging them from other used equipment. (not that i don't do like getting free stuff, (I usually create projects from scraps and only buy what i need) but i would prefer it if i could buy these).
Thanks : D
Thanks : D
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I am also in australia and I have had your problem. I made a 350V 1600 uF capacitor bank using 20 350V 80uF photo flash capacitors. It works well for my mini railgun. The only problem is you have to use a good switch as mine is almost ruined. I hope this helps.
Jun 2, 2009. 1:49 AMpyroten (author)
says:
yea thx that, i'v looked into it and the best i'v got so far is this capacitor. The only problem is their really expensive :(. So i think ill buy them in bulk (ie. 25) and it'll cost me close to 150 D: but i'd be worth it.
Jun 2, 2009. 5:31 PMvolthead
says:
I got my caps from disposable cameras which I scabbed from a
camera shop. Also have a look at http://www.powerlabs.org. Thats where I
get my info.
camera shop. Also have a look at http://www.powerlabs.org. Thats where I
get my info.
Jun 2, 2009. 8:15 PMpyroten (author)
says:
Yea, i'v taken my fair share from them as well, but the problem is, disposable camera's arn't being used that much any more. the numbers are slowly declining, and us. err high voltagers? :) will need to find a new source of caps. But thanks anyway
Aug 20, 2009. 4:26 PMpeterhadgraft
says:
Sorry, I answered the wrong question. I have seen a large bank of 400V caps used to magnetise large ferrite magnets (about 0.2Farads ie 200,000uF worth). Capacitors in the chain failed frequently. New caps are expensive (around $30 -$40), so I recommend you consider continuing with second-hand caps. Inspect them. Discard any that bulge, or the pressure relief is popped/missing or starting to pop. Buy an ESR (equivalent series resistance) meter from Jaycar, Altonics etc and test caps. Discard caps with high ESR (Sorry I don't know the typical value to expect). Do not expect a long life for the caps if you are doing heavy discharges, as I suspect is the case with a rail gun. I assume you will be charging directly from 240V AC through rectifiers. If you use a very large number of caps, include a choke in the charging circuit. A suitable size uses a core about as big as a large microwave oven transformer. Fill the window with wire about 2mm diameter. Put Is together, and Es together, and butt Es and Is together with a piece of writing paper between them. Place between the rectifiers and the caps. This choke should limit the charging current to less than 15 Amps at 240VAC, so you don't blow fuses and rectifiers. Alternatively put in series a resistor, value say 20 Ohms, 100 Watts or more, to limit the current. If a high charging current is maintained too long, the resistor will smoke. More Watts needed. Of course your charging circuit may include a regulating circuit that increases the charging voltage slowly. That would be the best solution of all. I myself prefer very simple solutions that don't fail easily.
Aug 19, 2009. 3:10 PMpeterhadgraft
says:
Microwave oven capacitors are rated at about one microFarad 2500V AC. They should be good for about 6kV to 7kV DC. Take care, as some have an inbuilt limiting resistor, which may make them unsuitable for your application. I believe you can buy capacitors with a value of about 0.15 uF at 3kV in USA, but do not know the supplier. They are more reliable than homemade capacitors. If you must make them, use HDPE (high density polyethylene) sheet plastic or polypropylene for the dielectric. Glass is unreliable, as it frequently has flaws, unless made in dust-free conditions under vacuum.
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