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Re: LTC1922/LTC3722 model and simulation
开云体育It would be much better for you
to upload your .ASC and all other files required to run it
(but not .RAW and .LOG) as a ZIP archive to Files => Temp
and then tell us you did that. ======================================================================================
Best wishes John Woodgate OOO-Own Opinions Only Rayleigh, Essex UK I hear, and I forget. I see, and I remember. I do, and I understand. Xunzi (340 - 245 BC) On 2023-07-14 15:55, R Clark via
groups.io wrote:
Hello , I am trying to simulate from LTspice libray LTC1922-1 and LTC3722 |
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Re: Spark gap physics.
开云体育We do not like being sent to
third-party sites in order to try to solve problems. But there
is no objection to posting (no more than a few) links purely
for information. ======================================================================================
Best wishes John Woodgate OOO-Own Opinions Only Rayleigh, Essex UK I hear, and I forget. I see, and I remember. I do, and I understand. Xunzi (340 - 245 BC) On 2023-07-14 14:43, Andrew Lohmann
wrote:
You do not need to look at my blog page I know that this group does not like outside links being posted but here it is anyway;? |
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Re: Regarding basic simulation of ACST
开云体育There are a whole lot of issues with the model library and the ACST symbol. The various subcircuits in the library have conflicting pin orders.You have called the called the model ACST310-8FP, which has a pin order of AKG, but the symbol you used has a pin order of AGK, which I guess was obtained from Autogenerating one from the ACST subcircuit. The error messages: Questionable use of curly braces in ".model dak d (is=5e-16 rs={rd})" ??? Error: undefined symbol in: "[rd]" Questionable use of curly braces in ".model doff1_t d (bv={bvn})" ??? Error: undefined symbol in: "[bvn]" Questionable use of curly braces in ".model doff2_t d (bv={bvp})" ??? Error: undefined symbol in: "[bvp]" Circuit: * D:\Simulations\LTspice\_Temp\karamchandani.jagdish\ACST_Files\ACST.asc Error on line 52 : .model doff2_t d (bv=(bvp)) ?? ?* Unrecognized parameter "bvp" -- ignored Error on line 51 : .model doff1_t d (bv=(bvn)) ?? ?* Unrecognized parameter "bvn" -- ignored Error on line 50 : .model dak d (is=5e-16 rs=(rd)) ?? ?* Unrecognized parameter "rd" -- ignored ..arise because the diode models are defined at the top level of the model file where the parameters in curly braces are not visible. Moving the diode models inside the top level subcircuit (ACST) fixes that and the circuit then runs. cut and paste those lines just above the ".ends" line of the "ACST" subcircuit. Did you notice the advisory in the model file?: *?? For a correct ACST behavior, the "Maximum step size" must be below *?? or equal 20?s. The way your schematic is configured,
the triac never actually turns on - you just get mVs across R1 -
"off" leakage. Perhaps that was your intention.
As it stands, I'm not sure it working with the correct model parameters because of the issues mentions at the top. But it does run. Maybe I'll fix the model file properly, but it will take time to verify it. The other thing I noticed was that your resistor values have "E" appended. This is ignored unless a number follows the "E", in which case it becomes an exponent of 10. "E" on it's own is not a valid range multiplier. Exceptionally, "R" can be used instead of a decimal point in resistor values, but the only accepted range multipliers are: f, p, n, u, m, k, Meg, G, and T. They are not case-sensitive, lower and upper case are just used as convention and to preserve sensibilities. --
Regards, Tony On 14/07/2023 08:11, Jagdish Karamchandani via groups.io wrote: I am trying to make overvoltage switch using ACST from STmicroelectronics but seems can't simulate its spice model. Any help will be appreciated. Please find all the files over here, |
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Re: Spark gap physics.
On Fri, Jul 14, 2023 at 09:34 AM, eewiz wrote:
All due to the failure of one little air blaster.Great story :)?? Arcs don't need 138kV btw - I had an automotive 6-layer PCB with just 12V (at about 1000A, car battery) that got wet, formed a cathodic short (took 6 hours), then struck an arc.? The arc then whizzed all round the board like a Pacman tornado - greatly helped by the power planes, until everything caught fire and a million pound prototype car was destroyed.? Why only the ONE little air blaster?? ?I know it's easy to be wise after the event, but an FMEA should have picked-up the catastrophic consequences.? It's relevant to LTSpice in that simulation is a tool of "best practise" - where good design process can eliminate future disasters, and FMEA is a similar thing.? ? |
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Re: ISL70444SEH declaration issue?
开云体育On 14/07/2023 12:17, Tony Casey wrote:changing the feedback resistor to 5p6 seemed to be about the optimum...changing the feedback *capacitor* to 5p6 seemed to be about the optimum --
Regards, Tony |
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Re: ISL70444SEH declaration issue?
开云体育On 14/07/2023 12:17, Tony Casey wrote:Next, you have defined a -2.5V supply (Vn), but used it.Next, you have defined a -2.5V supply (Vn), but *not* used it. --
Regards, Tony |
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Re: ISL70444SEH declaration issue?
This schematic does not run, as uploaded. Andy explained why (.options lines split up). The "+" character at the start of a line, tells LTspice to append this line to the previous one. When these are not within the same directive block, they will be not be associated with the intended line, and be appended to some other line that they are not supposed to be associated with.
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The .options... were put in the the original fixed schematic because of issues with the opamp model used in that schematic. They should not be used as a default in others, where it isn't necessary. You also used the "startup" option in the .TRAN directive, but there seems to be no reason why it would be needed. Only use these things where necessary and for good reason. Here, there isn't one. Next, you have defined a -2.5V supply (Vn), but used not it. Is it, by any chance, intended to be the opamp's negative supply? If so, you can't use +5V for the positive supply, because the datasheet says in the absolute maximum ratings section: Supply Voltage V+ to V– ...........................................5.5V With the opamp's V- supply pin grounded, the pulsed source the input voltage falls below the inverting input's minimum level and the ESD protection diodes are forced into conduction. I reconfigured the circuit to use ±2.5V supplies, including biassing the photodetector from -2.5V. The photodetector model is producing 5mA pulses. You feedback resistor is 1k, so potentially the output should reach 5V, which is, of course, is beyond the supply rail. Therefore, it can't. So, assuming you need the output voltage to be a linear function of the input current, we need to reduce the feedback resistor, so the opamp isn't clipping - I reduced it to 390 for a little margin. But... The LTC6268-10 opamp is only stable for closed loop gains in excess of 10x. That's what the "-10" suffix means. I would refer you to page 13 of the datasheet for some stability considerations. In summary, at high frequencies, the feedback gain is approximately Cin/Cfb. Your photodetector seems to have a junction capacitance of 2p, requiring a feedback capacitor of <200f. This is probably lower than the internal capacitance of the opamp. I don't know which PD you have in mind. I checked out some very high speed InGaAs PDs (infra-red for LIDAR etc) from Marktech of the sort of speed (2Gbps) you seem to be looking for. They seem to have a higher junction capacitance than 2p - more like 12p... Anyway, without treatment this TIA oscillates. It will take a quite a bit of tweaking to make it properly stable. With your original arrangement, it appears not to oscillate, but that is misleading because most of the time it is saturated on the rails. What exactly is your requirement? Just picking the fastest opamp you can find isn't necessarily the right approach. FYI, substituting an LTC6268 (unity gain stable version) made the TIA stable without further tweaking, but it still had some ringing - changing the feedback capacitor to 5p6 seemed to be about the optimum, but on a real circuit that might not quite be so. It isn't, of course, as fast. --
Regards, Tony On 14/07/2023 00:29, mliccione89@... wrote:
Thanks so much for the detailed explanation! |
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Spark gap physics.
开云体育Hello All Richard Andrews wrote:
The required voltage could be 2-3 times that due the compression ratio of 8.5 to 1 or higher. I worked a decade as instructor and maintenance contractor at a heavy industry that performed smelting. Lots of 138kV switch gear. At 138kV an air blaster is required to blow out the arc that ensues whenever a switch opens. Assume a 100A breaker rated for 150kV and the 138kV supply conductors have 10? resistance. At 100A the supply conductors will dissipate about 1000W over a distance of maybe several 1000's of feet. The load power at close to 100A is about 13.8MW. Now a 138kV to 13.8kV transformer supplied by that 100A breaker fails presenting a 50m? load. The current shoots up to around 13.7kA and the 10? supply conductors now drop 137kV. This leaves about 1kV to be dropped across the ensuing arc as the switch blades start to open. As the gap widens the arc current will start to decrease because the arc resistance will increase with distance. As the current decreases, less voltage will be dropped across the supply conductors, increasing the voltage across the arc. Now the arc has destroyed the blades in the switch and is starting to eat up the pinions that the blades once rotated upon. As the gap increases, the arc current decreases, and the arc voltage increases. Now the arc has eaten clear through the bottom of the switch gear and is continuing into underfloor conduits melting copper all along the path. The arc length might be 10 feet long now and the arc current has dropped to maybe 5kA and the arc voltage has risen to 88kV Ultimately the arc might extend as far as 100 feet dropping 137.5kV at a current of 50A before the ionized channel quenches. I was not able to see the actual fireworks. I was teaching a class at the time. I did get to see what was left of the switch gear later that day and it wasn't much. They had to cut the concrete pad the switch gear was mounted on (outdoor switch gear) and then back hoe a bunch of parking lot to get to good copper. It was a very expensive mess that took several weeks to fix. They lost about $3000 per hour for every hour that furnace had no power. Plus the cost to have the switch gear replaced. All due to the failure of one little air blaster. All for now |
John Woodgate
Tony Casey
Bonkers
eewiz