Need some help with ratings
Tipp, Sun Feb 19 2006, 09:22PMAlright, so I've been doing CG's for a while now, and am trying to get into solid state switching (SCR's). I need help figuring out what my SCR and protection diode should be rated at. I understand this is dependant on my capacitors, so here is my current bank:
330v (only going to charge to 300 for safety)
3420uF
Coil resistance is 1 ohm, so Ohms Law dictates it will pass 300 amps.
Yeah, they're photoflashes
Whatcha expect? They're FREE! Working on getting more soon, though. Any help will be gratefully accepted. I dont want to spend a ton of $$$ on an SCR and then overcurrent it. I also dont want to spend $$$ on a protection diode and have it blow up. Thanks all! (BTW New forum is hottt)Re: Need some help with ratings
Madgyver, Sun Feb 19 2006, 09:58PM
Try this in order to calculate maximum discharge current.
300A will be the maximum, for the case that your coil has no inductivity. In reality you coil of course has some inductivity, so the current will be less.
A SCR with 300A peak rating will be fine. The Diode on the other hand has to withstand a current of the same magnitude but also possibly a larger induced voltage comming from the coil. If the protection Diode is underrated, you will possbly fry your SCR and your charger circuit too. (If you have the charger still connected of yourse.)
Madgyver, Sun Feb 19 2006, 09:58PM
Try this in order to calculate maximum discharge current.
300A will be the maximum, for the case that your coil has no inductivity. In reality you coil of course has some inductivity, so the current will be less.
A SCR with 300A peak rating will be fine. The Diode on the other hand has to withstand a current of the same magnitude but also possibly a larger induced voltage comming from the coil. If the protection Diode is underrated, you will possbly fry your SCR and your charger circuit too. (If you have the charger still connected of yourse.)
Re: Need some help with ratings
Tipp, Sun Feb 19 2006, 10:08PM
Alright, well I bought a 110 amp 600v SCR the other day (10$!! Can you beleive?!) which has a surge of roughly 1kA. I was all worried it wouldnt work
Ok, so now for the anti-parrellel diode. Approximatly what should the diode be rated at? Unfortunatly, larger diodes start to get costly. Can I use a crapload of 1N4007's wired in parrellel?
Tipp, Sun Feb 19 2006, 10:08PM
Alright, well I bought a 110 amp 600v SCR the other day (10$!! Can you beleive?!) which has a surge of roughly 1kA. I was all worried it wouldnt work
Ok, so now for the anti-parrellel diode. Approximatly what should the diode be rated at? Unfortunatly, larger diodes start to get costly. Can I use a crapload of 1N4007's wired in parrellel?
Re: Need some help with ratings
Simon, Mon Feb 20 2006, 03:01AM
One big set of 1N4007s in parallel isn't reliable for pulse work. The current generally won't go through all the diodes. It can be made to work if you use a resistor on each diode, as in the "dump and quench" circuit.
Simon, Mon Feb 20 2006, 03:01AM
One big set of 1N4007s in parallel isn't reliable for pulse work. The current generally won't go through all the diodes. It can be made to work if you use a resistor on each diode, as in the "dump and quench" circuit.
Re: Need some help with ratings
Electroholic, Mon Feb 20 2006, 06:59AM
ive been using 4 1n5408 in parallel with no problem at all
mine current system is
1050v peak charge to 950v for safety
around 1kj at 950v
scr is a semikron skkt 132/12e
1.2kv 4.7ka for 10ms surge
and 4 1n5408s in parallel for CEMF
5408s are rated for 1kv 3a cont
forgot the surge
but i blew my 1.5ka peak stud when i put the diode pack in reverse,
so they must have a surge of atleast 400a each...
oh and no equalizing resistors at all
Electroholic, Mon Feb 20 2006, 06:59AM
ive been using 4 1n5408 in parallel with no problem at all
mine current system is
1050v peak charge to 950v for safety
around 1kj at 950v
scr is a semikron skkt 132/12e
1.2kv 4.7ka for 10ms surge
and 4 1n5408s in parallel for CEMF
5408s are rated for 1kv 3a cont
forgot the surge
but i blew my 1.5ka peak stud when i put the diode pack in reverse,
so they must have a surge of atleast 400a each...
oh and no equalizing resistors at all
Re: Need some help with ratings
rupidust, Mon Feb 20 2006, 08:04AM
Diodes:
RURG8060 600V 80A rms 800A surge $5.20 to-247
20ETF10-S 1000v 20A rns 355A surge $3.30 D2pack
DSEI30-10A 1000V 30a RMS 375A surge $4.65 to-247
6A10 100v 6A rns 400A surge $0.70 radial
Since the ratings is covered, just a few some device examples. Some of the diodes are naturally larger in size hence current rating due to the case type. I use those reqularly and buy them from digikey. As for SCRs, try some to-218 or just smaller to-220 case of surge ratings about 800A to 500A. Those run about $3 - $5 and are good for small space requirements.
rupidust, Mon Feb 20 2006, 08:04AM
Diodes:
RURG8060 600V 80A rms 800A surge $5.20 to-247
20ETF10-S 1000v 20A rns 355A surge $3.30 D2pack
DSEI30-10A 1000V 30a RMS 375A surge $4.65 to-247
6A10 100v 6A rns 400A surge $0.70 radial
Since the ratings is covered, just a few some device examples. Some of the diodes are naturally larger in size hence current rating due to the case type. I use those reqularly and buy them from digikey. As for SCRs, try some to-218 or just smaller to-220 case of surge ratings about 800A to 500A. Those run about $3 - $5 and are good for small space requirements.
Re: Need some help with ratings
Tipp, Thu Feb 23 2006, 11:06PM
Alright, I've tracked down some 1N5408's, so unless something goes horribly wrong (hey, y'never know!
) I should be set. Thanks all!
Tipp, Thu Feb 23 2006, 11:06PM
Alright, I've tracked down some 1N5408's, so unless something goes horribly wrong (hey, y'never know!
) I should be set. Thanks all!Print this page