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jim hardy
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some folks use transformersGuineafowl said:Another thing - is there a better way to isolate the driver ICs
some folks use transformersGuineafowl said:Another thing - is there a better way to isolate the driver ICs
I've never used any, and they are on the expensive side, but Altech offers a line of 'Z trip' circuit breakers supposedly capable of protecting semiconductor power controllers. Would one of these open quickly enough to protect a MOSFET bridge from a load short or severe overload?Guineafowl said:Another thing - is there a better way to isolate the driver ICs and other semiconductor devices from a rogue short or overvoltage condition?
Doesn't look encouraging. The safe operating area (SOA) of the IRF640 peaks around 30A and 10ms. The breaker curve shows a trip time anywhere from 10ms up to 20 seconds for a 30A load. Ouch!Asymptotic said:Would one of these open quickly enough to protect a MOSFET bridge from a load short or severe overload?
C73:Tom.G said:Doesn't look encouraging. The safe operating area (SOA) of the IRF640 peaks around 30A and 10ms. The breaker curve shows a trip time anywhere from 10ms up to 20 seconds for a 30A load. Ouch!
@Guineafowl Could you verify C73 and C74 values, both on the board and on the schematic? Also inspect them for any signs of failure or prior replacement.
They are bootstrap capacitors used to supply gate drive to the high side MOSFETs. If you have a Capacitance Meter to measure them, check both capacitance and ESR or DF (Dissipation Factor). Do so while the associated MOSFETs are out of the circuit. If they are faulty or the wrong value they could destroy their associated MOSFETs at heavy loads.
I suspect them because the overall circuit is a symmetrical H-bridge and those caps should be the same; but the schematic shows different values (schematic marked-up?).
Were all eight MOSFETs (Q34 thru Q41) the IRF640?
Wow! i never before saw a breaker faster than 10 milliseconds. There's a limit to how fast the mechanical parts can move, and it takes finite time to quench the arc.Asymptotic said:I've never used any, and they are on the expensive side, but Altech offers a line of 'Z trip' circuit breakers supposedly capable of protecting semiconductor power controllers.
Guineafowl said:As far as I can find out, this unit has multiple oscillators which, when combined in a Fourier-type way, and when filtered through a large LC, result in the near-perfect sine wave.
What an odd character! I assume there's a practical reason the system isn't used widely. I would say that if you have a sound engineering idea there's no need to concoct a website that's set out like a pyramid scheme or faith-healer's advert.jim hardy said:wow !
try a search on
magic sine waves don lancaster
old jim
Guineafowl said:Was your "wow" for the brilliance or the idiocy of my deduction?
Yes, the older link is more sober!jim hardy said:For your discovery of that inverter.
I once had a Hewlett Packard function generator that synthesized functions that way.
Been years since i looked in on Lancaster's "Magic sinewave" pages and it does look like he's gone a bit off kilter... Sorry ... he used to be imminently practical and authored a lot of "how to" books.
Here's today's version of his old introduction
http://www.tinaja.com/glib/msintro1.pdfGood luck with that inverter ! Teach us how it works ?
old jim
Ouch indeed!Tom.G said:Doesn't look encouraging. The safe operating area (SOA) of the IRF640 peaks around 30A and 10ms. The breaker curve shows a trip time anywhere from 10ms up to 20 seconds for a 30A load. Ouch!
I remember being surprised as well after finding them in the Altech catalog. Went looking for, but couldn't find an in-depth explanation how they operated, and didn't try any, but I've used plenty of form 101 Amptrap fuses protecting everything from SCR DC drive bridges to resistance heater solid-state contactors.jim hardy said:Wow! i never before saw a breaker faster than 10 milliseconds. There's a limit to how fast the mechanical parts can move, and it takes finite time to quench the arc.
That choice as you say depends on the application.Asymptotic said:Just jawing here, but my opinion of fuses versus circuit breakers for semiconductors balances on a razor edge. When a fuse blows, it takes time to get a replacement from stores, lock out the circuit, install the replacement, and re-power the circuit. During that time the semiconductor has cooled significantly, and increases it's chances of survival if the replacement fuse blows. A second fuse failure also prompts the technician to dive deeper into why, if only because there isn't an infinite number of replacements in bench stock.
Guineafowl said:My best guess is that the inverter uses that enormous inductor as part of a resonant filter to shape the boxy output into a more pleasing sinewave.
Sounds great but all i did was admire from a distance you folks's work.Guineafowl said:pints at the local pub.
Hey folks, how many are up for a group pub crawl across the pond?Guineafowl said:TomG, Jim Hardy and others, I'm obliged under British social law to take you all for several pints at the local pub.
If i can get there !Tom.G said:Hey folks, how many are up for a group pub crawl across the pond?
Holy thread revival!... etcshjacks45 said:Seriously, 500 pounds? Most retailers would be less than $99 US. I think England has Walmarts. I haven't seen a 4093 in a power supply built since 1993. Power supplies (Inverters) is the most likely to fail on tech equipment. If your Inverter is that old, it needs to be replaced as part of prudent maintenance.