SCR Trigger for Coil Gun
fatboyslim, Fri Nov 23 2012, 09:56AMHi There
I am planning a coil gun project, however while sourcing parts the SCR has been the most difficult to find. What I am wondering is whether anyone has any experience using the SCR which are so accessible on ebay.
This is what i'm referring to: SCR Thyristor 1600v 100A
My capacitor bank is 450v @ 5000uf. Barry's coilgun calculator puts my peak amps at around 800-900 amps. What i'm wondering is if anyone has previously used these SCR's and whether they have a peak amp rating high enough.
The one i have linked have a average rating of 100A and i've seen OTHER SCR with a average rating of 70A which can handle 1200A peak, so was wondering about this one.
Messaging the seller yielded no information or datasheets :(
Help would be much appreciated
Thanks :D
Re: SCR Trigger for Coil Gun
Shrad, Fri Nov 23 2012, 11:31AM
such rated block thyristor have a pulsed current rating of at least 1000 amps, for what I know
anyway, for their price, its worth testing them
Shrad, Fri Nov 23 2012, 11:31AM
such rated block thyristor have a pulsed current rating of at least 1000 amps, for what I know
anyway, for their price, its worth testing them
Re: SCR Trigger for Coil Gun
Yandersen, Sat Nov 24 2012, 06:32AM
Don't!
At first, there are no datasheet. Second - this huge monster is obviously far more than you really need. Third - for $20 you can buy a few couples of normal thyristors so to have a backup.
Yandersen, Sat Nov 24 2012, 06:32AM
Don't!
At first, there are no datasheet. Second - this huge monster is obviously far more than you really need. Third - for $20 you can buy a few couples of normal thyristors so to have a backup.
Re: SCR Trigger for Coil Gun
fatboyslim, Sat Nov 24 2012, 12:04PM
I've increased my capacitor bank to 10000uf. Unfortunately i cannot find any Thyristors which can handle switching roughly around 1000-1100 amps. I'm limited to what I can find on Ebay as i live in New Zealand. Would it be safe to assume that since its so beefy that it should be able to handle this peak current?
fatboyslim, Sat Nov 24 2012, 12:04PM
I've increased my capacitor bank to 10000uf. Unfortunately i cannot find any Thyristors which can handle switching roughly around 1000-1100 amps. I'm limited to what I can find on Ebay as i live in New Zealand. Would it be safe to assume that since its so beefy that it should be able to handle this peak current?
Re: SCR Trigger for Coil Gun
klugesmith, Sat Nov 24 2012, 07:18PM
Are you inexperienced at searching the Internet? Google helped me to find KP100 data in less than a minute.
This one
points to a nice-looking data sheet without the spec you want.
This one points to a fuzzy scanned datasheet with the spec you want. KP100 without the A suffix, but IMHO close enough.
Note the pulse rating I_TSM of 1.8 kA @ 50 Hz, without further detail. A conservative interpretation would be that that's the peak of a single half-sine pulse 10 ms wide.
Good luck with your coilgun. Keep these things in mind:
1) SCR gate, unlike MOSFET, is low impedance & depends on current, but not too much! A fresh 9V battery could probably source enough current to damage the gate.
2) While waiting for your SCR, you could trigger the coilgun by just touching wires together. This is relatively gentle with a coil in the circuit, compared to a short circuit on the capacitor bank. Wear eye protection & mind your 450 volt insulation. If LCR network is underdamped, the metallic switch (unlike SCR) does not turn off at the reverse-voltage peak. (click the "show voltage" box in Barry's simulator.)
klugesmith, Sat Nov 24 2012, 07:18PM
Are you inexperienced at searching the Internet? Google helped me to find KP100 data in less than a minute.
This one
points to a nice-looking data sheet without the spec you want.This one
points to a fuzzy scanned datasheet with the spec you want. KP100 without the A suffix, but IMHO close enough.Note the pulse rating I_TSM of 1.8 kA @ 50 Hz, without further detail. A conservative interpretation would be that that's the peak of a single half-sine pulse 10 ms wide.
Good luck with your coilgun. Keep these things in mind:
1) SCR gate, unlike MOSFET, is low impedance & depends on current, but not too much! A fresh 9V battery could probably source enough current to damage the gate.
2) While waiting for your SCR, you could trigger the coilgun by just touching wires together. This is relatively gentle with a coil in the circuit, compared to a short circuit on the capacitor bank. Wear eye protection & mind your 450 volt insulation. If LCR network is underdamped, the metallic switch (unlike SCR) does not turn off at the reverse-voltage peak. (click the "show voltage" box in Barry's simulator.)
Re: SCR Trigger for Coil Gun
Yandersen, Sun Nov 25 2012, 09:52AM
I believe, DigiKey ships everywhere, check them out:
Here, directly to SCRs:
fatboyslim, to find thyristor which will fit your circuit you need to find out the approximate pulse length (T=Pi*sqrt(L*R)), peak current (I=U*sqrt(C/L)) and see I*I*t rating for fusing for the thyristor. Probably, your pulse length will be around 1ms, so you may just triple amperage given for 50Hz operation mode of a thyristor - it should handle the estimated current.
Yandersen, Sun Nov 25 2012, 09:52AM
I believe, DigiKey ships everywhere, check them out:
Here, directly to SCRs:
fatboyslim, to find thyristor which will fit your circuit you need to find out the approximate pulse length (T=Pi*sqrt(L*R)), peak current (I=U*sqrt(C/L)) and see I*I*t rating for fusing for the thyristor. Probably, your pulse length will be around 1ms, so you may just triple amperage given for 50Hz operation mode of a thyristor - it should handle the estimated current.
Re: SCR Trigger for Coil Gun
fatboyslim, Mon Nov 26 2012, 01:08AM
Thanks so much! Just as a back up I went out and bought SKKH57/12E Thyristor. I know its has a much higher pulse current rating than I need but it was only 15 dollars. It gives me a bit of leeway in case I up the cap bank.
This may sound dumb but do you have to wind the coil in one direction?
For example when starting from the left do you wind from (left ---- right, then start back at the left and go right) or is it ok to go (left ---- right then go back from right ---- left)
fatboyslim, Mon Nov 26 2012, 01:08AM
Thanks so much! Just as a back up I went out and bought SKKH57/12E Thyristor. I know its has a much higher pulse current rating than I need but it was only 15 dollars. It gives me a bit of leeway in case I up the cap bank.
This may sound dumb but do you have to wind the coil in one direction?
For example when starting from the left do you wind from (left ---- right, then start back at the left and go right) or is it ok to go (left ---- right then go back from right ---- left)
Re: SCR Trigger for Coil Gun
PSCG, Mon Nov 26 2012, 08:29AM
Only make sure that ALL the turns of the coil are facing the same direction while winding, i.e. clockwise or counter - clockwise (i hope it makes sense). Winding it as left-->right-->left is the same as left-->right-->back to left-->right.
PSCG, Mon Nov 26 2012, 08:29AM
Only make sure that ALL the turns of the coil are facing the same direction while winding, i.e. clockwise or counter - clockwise (i hope it makes sense). Winding it as left-->right-->left is the same as left-->right-->back to left-->right.
Re: SCR Trigger for Coil Gun
Yandersen, Mon Nov 26 2012, 09:55AM
And if projectile is symmetrical, make sure to mark one end as a front and do not insert it in different direction, otherwise efficiency will drop a little each time you mess with the direction (remagnetisation losses).
"only 15 dollars" - you are pretty rich, huh? :) Keep in mind, that no matter how much current your fancy SCR can handle, it will be fried more likely due to some shortcut somewhere. So far I fried few, but at no case it was overcurrented by the coil. BTW, double check insulations all around the coil - if shortcut will happen inside, the coil will blow like a grenade, and SCR together with it.
Yandersen, Mon Nov 26 2012, 09:55AM
And if projectile is symmetrical, make sure to mark one end as a front and do not insert it in different direction, otherwise efficiency will drop a little each time you mess with the direction (remagnetisation losses).
"only 15 dollars" - you are pretty rich, huh? :) Keep in mind, that no matter how much current your fancy SCR can handle, it will be fried more likely due to some shortcut somewhere. So far I fried few, but at no case it was overcurrented by the coil. BTW, double check insulations all around the coil - if shortcut will happen inside, the coil will blow like a grenade, and SCR together with it.
Re: SCR Trigger for Coil Gun
fatboyslim, Mon Nov 26 2012, 12:47PM
Oh Wow, thanks for the tip, i'll definitely double check my insulations. Sorry i'm just confused about the I*I*t rating. Is that a peak rating before the thyristor fuses?
My simulation right now (after some changes) peaks at over 1600 amps @ 5.4ms (91.9hz). Ascertaining from what you said, since the frequency is higher, the thyristor should be able to handle it because its for a shorter duration of time? or have i completely lost the plot here :P
fatboyslim, Mon Nov 26 2012, 12:47PM
Oh Wow, thanks for the tip, i'll definitely double check my insulations. Sorry i'm just confused about the I*I*t rating. Is that a peak rating before the thyristor fuses?
My simulation right now (after some changes) peaks at over 1600 amps @ 5.4ms (91.9hz). Ascertaining from what you said, since the frequency is higher, the thyristor should be able to handle it because its for a shorter duration of time? or have i completely lost the plot here :P
Re: SCR Trigger for Coil Gun
Steve Conner, Mon Nov 26 2012, 03:08PM
I2t works with the square of the current. So if you cut the time of current flow in half, then the magnitude of the current can be 1.4x greater.
If you're smart enough to build a coilgun successfully, you're smart enough to earn $15 quickly.
Steve Conner, Mon Nov 26 2012, 03:08PM
I2t works with the square of the current. So if you cut the time of current flow in half, then the magnitude of the current can be 1.4x greater.
If you're smart enough to build a coilgun successfully, you're smart enough to earn $15 quickly.
Re: SCR Trigger for Coil Gun
Thomas W, Mon Nov 26 2012, 04:11PM
Thomas W, Mon Nov 26 2012, 04:11PM
Steve Conner wrote ...
I2t works with the square of the current. So if you cut the time of current flow in half, then the magnitude of the current can be 1.4x greater.
If you're smart enough to build a coilgun successfully, you're smart enough to earn $15 quickly.
please let us in on this secret of yours, never been sure how to start off making money, been thinking of buying components off cirtain companys in bulk and selling them off on ebay, UCCs for exampleI2t works with the square of the current. So if you cut the time of current flow in half, then the magnitude of the current can be 1.4x greater.
If you're smart enough to build a coilgun successfully, you're smart enough to earn $15 quickly.
Re: SCR Trigger for Coil Gun
Steve Conner, Mon Nov 26 2012, 04:45PM
Well, how did your last coilgun turn out?
Steve Conner, Mon Nov 26 2012, 04:45PM
Well, how did your last coilgun turn out?
Re: SCR Trigger for Coil Gun
Yandersen, Mon Nov 26 2012, 06:41PM
Yandersen, Mon Nov 26 2012, 06:41PM
fatboyslim wrote ...
Oh Wow, thanks for the tip, i'll definitely double check my insulations.
In my case, once I didn't insulated iron washers on both sides of a coil, and wire insulation didn't sustained. In result, coil blow so hard, that I got deaf for a few seconds. Pieces of wire near shortcut evaporated, barrel cracked, being separated on two pieces, and two ferrite halves (external iron) which were covering coil from outside, which were hold together by a tape, shoot out, one of them chopped on two pieces. Thyristor fried, of course. And that was just 65 Joules of energy in the caps. Now imagine the effect you can get from yours... Be carefull, unless you making a bomb. Oh Wow, thanks for the tip, i'll definitely double check my insulations.
Re: SCR Trigger for Coil Gun
Steve Conner, Mon Nov 26 2012, 08:42PM
Yeek... How much voltage were you using when it blew up?
Steve Conner, Mon Nov 26 2012, 08:42PM
Yeek... How much voltage were you using when it blew up?
Re: SCR Trigger for Coil Gun
Yandersen, Tue Nov 27 2012, 12:06AM
780V - I use non-polar caps. :)
Yandersen, Tue Nov 27 2012, 12:06AM
780V - I use non-polar caps. :)
Re: SCR Trigger for Coil Gun
rp181, Tue Nov 27 2012, 01:29AM
Just try not to let the gate wire touch your anode, it doesn't end well for your hearing for your SCR :)
rp181, Tue Nov 27 2012, 01:29AM
Just try not to let the gate wire touch your anode, it doesn't end well for your hearing for your SCR :)
Re: SCR Trigger for Coil Gun
fatboyslim, Fri Nov 30 2012, 08:40AM
Just wondering whether i'm reading my data sheet correctly.
To trigger the gate i need 3v at 150ma, is that correct? and if so, would a 9v battery with a 47ohm resistor work?
fatboyslim, Fri Nov 30 2012, 08:40AM
Just wondering whether i'm reading my data sheet correctly.
To trigger the gate i need 3v at 150ma, is that correct? and if so, would a 9v battery with a 47ohm resistor work?
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