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Registered Member #1497
Joined: Thu May 22 2008, 05:24AM
Location: Toronto, Ontario, Canada
Posts: 801
Yikes, how much did you pay for a *pile* that size?
You could try getting a pair of aluminum or steel slabs, drilling and tapping holes for bolts since for pulsed application you don't really need much cooling. Finding some flat slabs on the cheap might be hard though.
Registered Member #30
Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706
A couple of 1/2" bolts will handle 700lbs of force no problem. And some place like Metal Supermarkets could probably give you two pieces of thick aluminium bar to make your clamps. The problem is actually finding an electrical insulator that can take the force, since of course the two clamps need to be insulated from each other.
If you think about it, it's very difficult for the SCR makers to bond the silicon die to the terminals over its whole surface. Pressure is probably the easiest way. If you don't apply the pressure, or apply it wrong, you get uneven contact and the device will seem to work, but fail below its rated current.
Registered Member #510
Joined: Sat Feb 10 2007, 09:28AM
Location: Hannover
Posts: 12
Professional SCR clamps usually have a "bearing" on one side, so that slight differences are tolerated, otherwise it would be possible that you crack the SCR because of uneven pressure...
Registered Member #162
Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140
If you have a 'dead' one it's interresting to open them up. (By cutting through the thin copper surround) (Quite hazardous unless you wear thick gloves) (We get plenty dead ones where I work) The two ends are thick copper slugs, plated for anti-corrosion The slugs are held in place by a thin copper corrugated sheet Often the gate lead internally is just held by 'springyness' both ends are not soldered/welded ! The high current is meant to pass through the copper slugs, not the side connection(s) (if present) For something like a launcher/coilgun/railgun the heatsinking will be unimportant at low repetition rates. The clamping force really should be applied properly however. Experimentally you could just have a single pressure point in the middle where the dimple is. There are two main clam types - The bolts need to be tightened with a torque wrench/accurately set - An internal spring washer 'snaps' once correct torque is applied.
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Hockey puck SCRs: why they need clamping force?
