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Registered Member #3688
Joined: Mon Feb 14 2011, 07:39PM
Location: Europe
Posts: 38
Greetings, Ladies and Gentlemen.
I am in the process of creating a 900j railgun with a solenoid (coilgun) injector. I am using a 12v LA battery, coupled to uzzor's cap charger. ( see I have assembled most of the components. Now, I just need to troubleshoot the charger to actually work :) The sequence is thus: the projectile is loaded into the coilgun stage, and the capacitor trio's charge is sent into the coil using an SCR (as per uzzor's schematic) (here (the whole bank is charged as a whole, but the three caps are isolated by dual relays) the coil resistance is 2 ohms. Coupled with the 1500 uf, 400v total capacitance i'm using that's 200 A peak. I'm using two p600m (here ) diodes as protection. My first question: are the diodes fast enough to block the reverse transient? Then, the projectile moves onto the rails, where it acts as a switch in itself. The remaining 750j (10340 uf, 390v) is discharged into the rails. My other questions are thus: what kind of peak current can I expect from the railgun arrangement? What kind of diodes do you recomend me to use, to defend the device from the subsequent reverse transients? My final question: what can I employ, to protect myself, if one of the caps shorts at full charge? some sort of device accross the caps?
EDIT: I can't seem to make the url's work, can someone help out?
Registered Member #162
Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140
The P600M diodes are 'standard' so recovery time will be around 1 to 5 us, which should 'catch' the coilgun back-emf ok.
The peak current for the railgun part will depend mainly upon - Total circuit resistance . .Capacitor bank esr, . .wiring resistance, . .'resistance' of the rails/projectile short-circuit AND - Total circuit inductance . .Capacitor bank esl . .Wiring inductance
To add a URL I just 'copy' the URL then 'paste' in my post, leaving a space at the front and back of the pasted URL like this
Registered Member #3688
Joined: Mon Feb 14 2011, 07:39PM
Location: Europe
Posts: 38
Thanks for your fast reply.
how do you measure capacitor esr? I have seen several meters that do it, but have never invested in one... But back to protection: what can i use, to protect the bank from reverse charging and shorting out?
Registered Member #3688
Joined: Mon Feb 14 2011, 07:39PM
Location: Europe
Posts: 38
Greetings. The esr seems to be 400 mohm-ish. The main question is cap bank protection from shorted caps. I can always add more reverse diodes, but I cannot sew my hand back on, if one of the caps decides to get capricious :)
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Hybrid Projectile Acclelrator: late production stages, need Advice.
