IGBT protection from load arcs - Page 1
Forum section: electronics / projects

author: oilburner
author_rank: Contributor
timestamp: February 08, 2023, 04:10:46 pm
content: I read from the data sheets (gate drive modules) about IGBT protection circuits that measure the voltage drop across the collector and emitter and will prevent the device from turning on if the load is shorted. How do you protect an IGBT against damage from the load arcing while the device is already on?Thanks!g

author: jonpaul
author_rank: Super Contributor
timestamp: February 09, 2023, 11:29:45 am
content: load is inductive or resistance?line V, KVA of load?

author: oilburner
author_rank: Contributor
timestamp: February 09, 2023, 05:13:19 pm
content: Hi Jonpaul, thanks-Its resistive load, 2000V 300A (<1 mSec long)g

author: jonpaul
author_rank: Super Contributor
timestamp: February 09, 2023, 06:11:36 pm
content: arc fault circuit breakerj

author: ajb
author_rank: Super Contributor
timestamp: February 10, 2023, 02:39:01 am
content: When you say "load arcing", you mean the load is being shorted by an arc?In that case, you protect against it the same way you would any other overload condition. You turn it off as fast as you can and provide upstream overcurrent protection to limit the damage when that isn't fast enough. If you've got half a million VA in play then selecting that upstream protection will require some careful available fault current analysis.If you mean the connection to the load is interrupted by an arc, then yeah, upstream arc protection would be good.

author: WattsThat
author_rank: Frequent Contributor
timestamp: February 10, 2023, 06:24:42 am
content: Random thoughts:Where does the 1 ms spec originate?What does the igbt manufacturer say about peak current and time?Are you PWM’ing the load?How fast is your current measurement scheme?In general, using Vsat to predict what the final load will be as the igbt turns on can work but you need some really fast A to D and processing to make it work since you’re using the derivative of delta V across the device.Vsat for short circuit protection has been used/proven in high performance AC VFD’s for many years. But, the very fast silicon based current sensors are replacing the Vsat scheme in new designs.

author: oilburner
author_rank: Contributor
timestamp: February 10, 2023, 02:29:43 pm
content: Hi Jonpaul, I don't think arc fault circuit breakers are available for 2000V and 300 amps, but I will keep looking.Hi ajb, "load arcing" : the voltage and current are being delivered to the load fine for the first 100 uS, but then the load arcs and the current spikes greater than the 500A current sensor and the IGBT module leaks its guts and blows off its little square lids.As you suggest, I need to look at how to turn it off before bad stuff happens.Hi WattsThat, we have logic gates and counter timers to source the 1 ms signal. We are not PWM'ing the load, just turning it on for a millisecond, charge caps for a second, then hit the load again for a millisecond. The current sensor might be fast enough, but right now we just watch it on a 'scope. I guess the next step is to put a hardware comparator to shut off the gate for overcurrent. I will google for your hint of silicon current sensor to replace Vsat shutdown, thanks!g

author: oilburner
author_rank: Contributor
timestamp: February 10, 2023, 02:51:02 pm
content: Oh WattsThat, I am a bit confused about the specs for the IGBT: 900 A peak forward current for 1ms, Surge current is 4000A Vr = 0V, Tvj = 150 C, tp = 10 ms, half-signwave.g

author: jonpaul
author_rank: Super Contributor
timestamp: February 10, 2023, 02:57:55 pm
content: Rebonjour Cher monsieurArc détection relay depends on the RF and EMI an arc generates.You need an industrial grade device.A breaker panel may accept an "arc flash" interrupteur or breaker.Better can be a contactor and arc détection relay.Notice that breaking DC requires a DC rated breaker or contactor.ManufacturersSquare D, Cutler Hammer in USA orSchnieder Electric in FranceABB (AESA/Brown Boveri) in Sweden, SwitzerlandFinally get a thread on the Electricians forum, see also Mike Holt forums.Bon courageJon

author: ajb
author_rank: Super Contributor
timestamp: February 10, 2023, 09:42:25 pm
content: So....is the arcing an expected part of whatever process this is? Or could you replace/redesign/modify the load to prevent it in the first place?Note that circuit breakers, or functionally similar combinations of fault monitoring+contactor, are unlikely to be fast enough to protect your semiconductors from a significant and sudden overcurrent event, especially at the size you need. You'd ideally want a better idea of the fault current rise time and duration to determine what protection methods are suitable, but generally fuses/breakers are about protecting against fire secondary to an electrical fault, not protecting sensitive electrical equipment. You should still have them of course! But if you want any hope of protecting your semiconductors you will need to build that into your power stage.

author: oilburner
author_rank: Contributor
timestamp: February 10, 2023, 10:38:07 pm
content: Yes, the arcs are an expected part of the process and I agree that fuses, circuit breakers / mechanical contactors won't be fast enough. I will look closely at the current rise time and duration, thanks!g

author: jonpaul
author_rank: Super Contributor
timestamp: February 11, 2023, 01:10:00 am
content: Rebonjour ...0/ Any inductive circuit interruption must create a high voltage ring or transient to dissipate somewhere the stored energy, V= L di/dt and W (energy in Joules ) = 1/2 L I exp 2 (amps/hy/joules)Theory and calculation of transient electric phenomena and oscillations by Charles Proteus Steinmetz. 1920 (the pioneer of transient protection, chief of R&D General Electric)Electrical transients in power systems Allan Greenwood (Power T&D specific)EVERY circuit interruption a doorbell or ignition coil to house circuit breaker to 500 KV kilo amp DC transmission line breakers will create an arc. The job of the swithc/breaker is to quench the arc and dissipate the energy.1/ IGBT protection should be well covered in the mfg data sheet and app notes.2/ In general even a resistive heater load has the inductance of stray, heater coil, wiring.Thus there is stored energy at the break of EVERY circuit.3/ A transient absorbing Zener (TAZ) properly specified for standoff and clamp V an pulse energy joules will be placed across the device.4/ MOVs may be a second choice but poor clamp ratio and limited life.5/ The arc flash breakers are intendd for different service6/ With storage /digital scope and appropriate CAT III, CAT IV probes you may be able to observe the V/I durihng the arcs.7/ In 1980s, we made very simple RC snubber for high power cinema arc lamps, 1..12 kW.Recall ~ 10..100 nF 5 kV AC plastic cap in series with 10 Ohm ..100 Ohm flameproof UL rated power resistor, 100W, cheap and simpleBon ChanceJon

author: PartialDischarge
author_rank: Super Contributor
timestamp: February 11, 2023, 07:24:35 am
content: Can I ask which is the particular IGBTs?

author: coppercone2
author_rank: Super Contributor
timestamp: February 11, 2023, 07:32:15 am
content: put a arc fault interruptor (din rail) into your chassis / cabinet / shipping containerif its not too isolated, it should pick up the arcing because of malfunction and turn it off.If you are trying to protect against regular arcing that you expect every power on event, you need snubbers like above.So basically you might not get vaporized parts.Now, are you powering it from a DC 2000V rail, a high voltage rectified AC, or is it being stepped up.Becuase I think you won't get too much good advice (other then jon paul) about medium voltage high current circuits. Not that you would wanna trust advice from a forum anyway, any more then a pointer of where to look.2000V@300A = 0.6Megawatts. I think you should consult a engineering design team... all of these parts are gonna be beastly.I think you should put 0.6 Megawatts in your opening post so people have an idea of just how big this setup is, its kind of important, most engineers max out at 50A 240V

author: jonpaul
author_rank: Super Contributor
timestamp: February 11, 2023, 05:08:56 pm
content: Coppercone thx for the mention....Realizing the OP magnitude of V,I, KVA, of course best advice reference to a PE, consultant, and not the EEVBLOG forums... especially beginner!The safety, liability, hazard to life and property mean that the OP needs liability insurance, E&O.to the OP.....NOTHING MENTIONED IN MY ANSWERS IS TO BE TAKEN AS ADVISE OR RECCOMEDATION!STRONGLY SUGGEST TO CONSULT A LISCENCED ELECTRICIAN, AND PROFESSIONAL ENGINEER.bon chanceJon

author: coppercone2
author_rank: Super Contributor
timestamp: February 11, 2023, 05:15:25 pm
content: yeah you mention you worked with <20 kW systems, this is 30 times bigger, order of magnitude.. really needs special considerations.

author: jonpaul
author_rank: Super Contributor
timestamp: February 11, 2023, 06:51:47 pm
content: Coppertone..yes my consulting and work was ~ 20 kW max, but have had experiences at Del HV, LBL, and still have friends at SLAC, Google pulsed etc who do handle these large projects...See Gred LEYH's magavolt Tesla coil/HV site...LOD.ORGSo, I am somewhat aware of their precautions and equipment...ZAP!Jon

author: T3sl4co1l
author_rank: Super Contributor
timestamp: February 11, 2023, 07:15:27 pm
content: Meh, I would assume OP is employed by a company, under whose responsibility, liability, safety practices, etc. this is covered by. Or not covered, as the case may be, depending on where they live.If the concern is output arcing because of fault conditions, the usual consideration is desat protection. A good idea in development and regular operation anyway, can save many IGBTs that way.Arc detection is a currently unsolved or poorly solved problem, especially in the presence of inverter switching noise, as I understand it. If you find a solution to be adequately reliable for purposes, well, there you go. You may need a product or literature search to find some starting points.Tim

author: shakalnokturn
author_rank: Super Contributor
timestamp: February 12, 2023, 12:29:44 am
content: Do we know enough about the load or design in general to give advice anyway?The design sounds like a large ignition system (for IGBTs).We don't know if the "load arcing" is part of the intended behaviour or an unwanted effect. Assuming it is normal operation, the present IGBT design is obviously inadequate either requiring IGBT's with (much?) larger current capabilities or a fast enough current monitoring to open IGBT and hand the last step of arc forming over to another switching device (triggered GDT?)Although saying that handling 0.6MW needs serious design considerations isn't false, it makes it sound a lot more serious than handling 600W with 600J pulses.

author: coppercone2
author_rank: Super Contributor
timestamp: February 12, 2023, 05:57:29 am
content: for design reference, I wanted to find out what kind of inverter would power 1MW with 2000 volts. This got close I guess. Not that big.https://www.infineon.com/cms/en/product/power/igbt/igbt-modules/ff1800r23ie7p/

author: oilburner
author_rank: Contributor
timestamp: February 13, 2023, 04:00:46 pm
content: Similar to this Infineon IGBT FF450R33T3E3_B5The load arcing does not happen every time, and the IGBT can handle it if the energy in the capacitors are below a value.You are right Tim, this is not at home in my basement, so sorry to be vague about the exact load.The DC voltage come from a lab power supply.The application is not normal IGBT work of motor drive or inverter.g

author: oilburner
author_rank: Contributor
timestamp: February 13, 2023, 10:48:18 pm
content: Hi Jon, thanks for the hint "Finally get a thread on the Electricians forum, see also Mike Holt forums." Lots of good info on that forum and led me tohttps://brainfiller.com/arcflashforum/viewtopic.php?f=2&t=4873&p=22370It helps me understand more about the arc:OK, focussing on the phenomena of an arc itself. Once the voltage gets high enough and in this context we're talking about such a fast event that the fact that we're dealing with AC doesn't matter...this is a pure DC discussion that it exceeds the CFO (critical flashover voltage) of the system in it's current state, an arc starts. The core of the arc is a plasma which means that it is so hot that the electrons are so energized that they just float around in a cloud around the general vicinity of the nuclei. Chemical bonds don't really exist so instead of O2, N2, CO2, etc., we just have individual nuclei and a cloud of highly energized electrons. This cloud has very little electrical resistance for obvious reasons and it is also highly magnetic. It pulls in on itself so that effectively the arc diameter is almost a constant at around 1-2 mm. This is what the physicists have figured out about electric arcs. The properties of a plasma are temperature dependent. So physicists get really hung up on calculating plasma temperature.Energy radiated from this arc core is 99%+ absorbed by the surrounding air though. As air molecules get hot they dump photons to cool down and we perceive photons in the visible spectrum as light. Then once a photon is emitted from one atom if it strikes the next (electron), it passes the energy on at which point it is absorbed and then emitted again in a cascade. Obviously there are losses along the way as the surrounding air absorbs a lot of the energy (heats up) and some passes through to solid objects nearby. That's what you are seeing...you don't actually "see" an arc, you see it's effects and you feel the infrared photons as heat. However nearly all of the energy emitted by the arc core is absorbed and re-emitted around it. So even though the arc core where plasma exists at some crazy high temperature that only a physicist cares about (the "35,000 degrees" claim you see in the arc flash scare literature) that temperature is NEVER seen outside the arc core. If it was, it would vaporize anything exposed to it which is obviously not the case. That's not to say that arcs don't emit a lot of thermal radiation, just trying to be realistic here. If you are at the receiving end of the arc (a shock) then you are being directly exposed to the effects of having all the electrons blown off the nuclei and some skin will be vaporized and it is going to do a lot more damage, but that's not where we're going here.As far as the arc extinguishing at this point the resistance of the air within the plasma has essentially gone to almost zero. There is nothing to stop the current from flowing with a DC arc at all. There are really only three ways to extinguish a DC arc. First, disconnect the power so that the air cools back down (CFO goes back up) so that it can't reform. Second method is to increase the arc length to the point where the arc is unsustainable. The arc consumes a certain amount of power per unit length to sustain itself. If the arc is too long there isn't enough energy available to keep it going so it goes out.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: February 14, 2023, 03:21:34 am
content: Well, it's notquitethat hot, but suffice it to say, plasmas are by degree (ha!), not all-or-nothing. A cool plasma ranges from merely gas with some free ions in it, to glow discharges (enough to create visible glow, air movement, hissing), to full-on arc discharges. Extremely hot plasmas might not even look like plasma at all (as they aren't even interacting with visible wavelengths -- at least, that's my assumption; I've not actually seen an explanation of why tokamaks mostly glow in a halo near the reactor surface, come to think of it.)At the temperatures of most electrical arcs (such as for welding, or in arc flash conditions), atoms will be mostly singly ionized, I think, maybe a few double or triple ionized; molecules are still very much relevant, but mostly the strongest ones (like N2, which might be in excited states more often than fully dissociated -- but either way is an opportunity to produce NOx, say with plain O2, or radicals like O (dissociated) or O2 (e.g. superoxide) as well as various ions), and smaller molecules absolutely will be broken up at these temperatures.Also, ionization goes both ways; it tends to go positive (loss of electrons), but atoms/molecules with high electron affinity will tend to grab extras as well (oxygen being a prime example).You don't even need electrical ionization to get free ions in a gas: the orange of a sodium flame is indeed free sodium atoms/ions, excited by other radicals (the blue glow of a gas flame is from the CH radical; blue implies a substantial amount of energy i.e. ~3eV available, certainly more than the ~2eV of the sodium yellow emission!). Such flames are indeed conductive, and the conductivity can be modulated with grids just as electrons in a vacuum -- you can make a "flame triode". (The performance is abysmal of course, because ionic velocity is pitiful -- thousands of times slower than electrons.)The fact that ionization depends on power input, is key to the V-I characteristic of an arc: as power density rises, ionization degree rises, keeping the voltage fairly stable despite the power increasing over decades of range. Indeed the incremental resistance is often negative, i.e. voltage drops as current rises, which can lead to oscillation when connected to a reactive element: the rapid-fire sparking of EFT (electrical fast transients), the relaxation oscillator of a neon lamp and capacitor, the "singing arc" of certain (antiquated) oscillators, and the mandatory current limiting of welding power supplies (also a usability consideration, as the arc voltage varies with length)....If any of this is at all relevant, I have no idea. You still haven't said what it is you're actually doing, or after, here.Tim

author: coppercone2
author_rank: Super Contributor
timestamp: February 14, 2023, 06:04:43 am
content: flame triode sounds like technology the Ori use in SG1 Or Doom. How demonic.

author: jonpaul
author_rank: Super Contributor
timestamp: February 16, 2023, 02:24:14 am
content: Rebonjour, worked on similar problems in high powered cinéma arc lamps.The physics of an arc formation or of a a breaking circuit is same as encountered in open air carbon arc searchlights, welding, HV circuit breakers, switches and interruptions.See the many fine old texts, seminars, papers and sites on arcs, plasmas, gaseous conductors, circuit breakers and the GAT glow to arc transition, as well as for AC and DC arc quenching.Bon SoiréeJon