If you derate that to 5A it's no longer fragile. But if you want to use it at 25A-30A, a workable one-time protective fuse will cost way more than the part.
Why can't we get a 100A (die rating) triac (with isolated-input maybe) in an 8A package for < $1? The cost of silicon has plummeted it would only take more area to make it really robust- like a 1000A MOSFET that is package limited to 75A.
IGBTs are available short-circuit rated. VFDs drivers can shut off before the current rises to harmful levels. Maybe it's possible to make a triac or something similar self-protecting the way a 7805 shuts down when the die temperature or current rises too much.
I guess it's too hard to compete against a 25-cent UL/CSA approved 12A relay.
--sp
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Best regards,
Spehro Pefhany
Amazon link for AoE 3rd Edition: http://tinyurl.com/ntrpwu8
Minding that IGBTs are rated for 10, maybe 20us tops -- I suspect the intent is to say "hey, these fragile IGBTs aren't as fragile as they used to be" -- IGBT reliability had been something of a concern in previous years (fragility, and latchup).
Nevermind that the MOSFET (or BJT) alternative would handle the same conditions for 100us or more -- a huge step up from the "high short-circuit withstand" that they're claiming for IGBTs!
The latter doesn't /need/ a "short circuit" rating, because the whole active operating region appears on the SOA.
For mains applications, semiconductors are usually too vulnerable. An inrush capacity of 10us is a thousand times less than needed to start an SMPS load, and a hundred thousand times shorter than needed to start a motor!
And that's with active circuitry to control the transistor, so, added cost. And then isolation...
But the nice thing about SCR/TRIACs is they're self limiting and fully protected!*
*In a sense. It doesn't work out perfectly in practice, because almost all power distribution is constant voltage. Thyristors are ideally suited to /constant current/ systems, just as MOSFETs are ideal for constant voltage inverters. Just as a MOSFET is passively safe when "off", a thyristor is passively safe when on. In both cases, this assumes the supply voltage/current is within ratings, of course. Which isn't always the case after including transients, but that's all part of the design process.
/Anything/ costing 25 cents, with UL/CSA rating, is somewhat astonishing. The cost of the materials is probably near zero cents. Which is also somewhat astonishing...
HP's first sampling scope, the HP185 (I have one! mostly tubes) used an avalanche transistor to make the sampling pulse. Boff used it to accidentally discover the step-recovery diode, which soon was used to increase the same scope's bandwidth to 1 GHz. Sampling scopes bootstrapped the evolution of fast semiconductors.
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John Larkin Highland Technology, Inc
lunatic fringe electronics
I once ran a DC gearmotor (steamship throttle) from 60 Hz AC through two phase-controlled antiparallel triacs, each with a series diode. I can't remember why I used triacs. A "cosine modified ramp" circuit, inspired by the old GE SCR manual (well, old now) linearized the phase-control transfer function.
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John Larkin Highland Technology, Inc
lunatic fringe electronics
The analog bandwidth was over 12 GHz. The actual sample rate was much lower, in the 100 KHz range.
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(Look at all those guys wearing skinny ties!)
I have one around here somewhere. A 1430 sampler, not a skinny tie. I learned high-speed electronics using flea-market Tek and HP samplers.
The effective aperature time, for 12 GHz bw, is about 30 ps. They used a step-recovery diode to enable a dual-schottky sampling gate. Tek followed up with their 6-diode traveling-wave sampler, which could be done on a PC board, without all that machining.
Mark Kahrs has a paper:
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John Larkin Highland Technology, Inc
lunatic fringe electronics
How is easy; big red switch, or yank the battery, or apply a crowbar across MT1 and MT2. I've never used a triac with DC; it's easy to turn them off only if you fiddle with moving parts to do it.
When I say 'crowbar', I have in mind a hunk of metal (maybe a screwdriver), not some flimsy semiconductor substitute.
I had to rehabilitate an olde test rig using those nasty press fit triacs .. that was maybe 25 years ago and the rig was 15 years older than that. The 'designer' commutated the triacs switching AC like SCRs. It worked (barely) with the olde triacs but not with newer ones.
Ah series diode turns it into an SCR.
It *might* work (perhaps even on AC) with an alternistor too.
--sp
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Best regards,
Spehro Pefhany
Amazon link for AoE 3rd Edition: http://tinyurl.com/ntrpwu8
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