IEC 61000-4-5 Surge immunity test - Page 1
Forum section: electronics / projects

author: Mad ID
author_rank: Regular Contributor
timestamp: July 02, 2014, 09:41:34 pm
content: Hello,to obtain an EMC "Declaration of Conformity" my circuit needs to past 61000-4-5 test with 500V @ 2R internal resistance giving 8/20us 250A current pulse. During the initial testing the whole board got fried and I would like to get some advice from expertsFirst the info:- Input voltage to the board is 9-30V, goes to a DC/DC +5V buck converter. Nominal voltage is 24V.- Board is powered with 24V when 500V@2R surges with alternating polarity are applied on top of 24V. (1 minute pause between each, 10 times)- The circuit which didn't withstand this is shown in the attachment.Probably a very bad design decision, the DC/DC converter has an operating voltage range up to 32V (34V maximum rating). Nevertheless, I'm sure it's possible to design a surge protection which will give a only few hundred milivolt rise from 24V.The varistor will clamp to 70V, by which time the capacitors will already be charged to 70V and the DC/DC fried. If I put a TVS diode in parallel with the varistor it dies during the first blow because it activates at much lower voltage than the varistor. TVS diodes are much better but there are only few which can withstand >200A @ 30V.Here are my questions:0. Would you use a DC/DC converter which has much larger operating voltage, like 50V? This increases cost of course..1. Would you put a TVS instead of varistor? There are few which can take 250A but are very expensive.2. How can I increase the impedance looking into capacitors which would drop this extra voltage and decrease the leftover current charging the capacitors? 10A of current during 10us will not charge the capacitors much, but 100A will. My first thought was to put an inductor, but won't the inductor saturate and loose all of its inductance when such a large current is applied?3. Can a common mode choke help? In my understanding this is a differential surge and a common mode choke will have no effect?4. Would you put the reverse protection diode before the varistors/other protection?5. I think I also need a fuse up front, how can I be sure it will withstand the surge and not blow up?Thank you very much for your time.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: July 02, 2014, 10:13:29 pm
content: Try some resistance after the MOV (as much as you can tolerate, for acceptable losses at maximum load current).Maybe even a second MOV after that.Use bigger capacitors.Current limiting devices (e.g., automotive load dump protection).Crowbar type protection (thyristor type TVS, etc.).Series fuse -- assuming it blows fast enough to matter, of course. (Even the fastest fuses take nearly a milisecond to open, so that's probably not helpful here. A fuse of any sort would be helpful to clear the fault and protect the wiring if a latching / thyristor type TVS is chosen.)Series resistance helps by making a current divider. So, the first MOV soaks up almost all the current and clamps the voltage to a more reasonable value, then your circuit only has to deal with the ~70V or whatever. Which is still a lot more than 12V, but if you were to add another 2 ohms in series, you'd need to clamp only 30A, not 250A.Note that a 20us time constant at 2 ohms suggests the test involves a charged 5uF capacitor; 100 times more, or ~500uF, will only be charged by 1/100th as much, or ~5V. Assuming the ESR is equally low: 1/100th of 2 ohms is 20 miliohms, which might be practical using aluminum polymer type caps. If you don't mind the price.Correct, common mode doesn't matter here, and although you could filter the spike with inductance, it's not generally practical to do so. Example: suppose you want to absorb the 500V spike, rather than shunt it. It has a flux of about 5-10mWb, so for a current rise of say, 10A, that would require 500-1000uH, rated for saturation above 10A. 10A is certainly a lot more manageable, though still a lot of energy for an avalanche TVS to absorb (10A in 1mH is 50mJ, which -- maybe not too bad for an SMC size TVS, actually?). A thyristor type would be great here, given the limited dI/dt and transient filtering action resulting from the inductance. Or the dumb old MOV again.Tim

author: Precipice
author_rank: Frequent Contributor
timestamp: July 03, 2014, 09:56:13 am
content: What actually fails? The anti-reverse diode or the switcher?(I've got to admit, there's less headroom between 24V and 32V than I'd be happy with in a real product, if the power isn't completely under your control. )I might be tempted by either a cheap but hair-trigger TVS diode after the input diode, where it will be somewhat protected (especially if you can sneak a resistor into the path), or just bite the bullet and fit ahttp://uk.farnell.com/stmicroelectronics/sm30t28ay/diode-tvs-3500w-28-1v-smc/dp/2327845at the front end. (Other TVSes exist, but, for all my ranting about ST, theirs do seem to mostly work)I've pretty much abandoned anti-reverse diodes for this reason - they capture and prolong overvoltage. If it's acceptable to blow fuses, then a big single-ended TVS and a fuse protects most things. Polyswitch fuses if I need to make a pretence at recovering. Other than that, get a decent automotive rated PSU chip, and let them deal with the over/reverse voltage problems, and chop the top off big spikes with a TVS.

author: qno
author_rank: Frequent Contributor
timestamp: July 05, 2014, 08:21:54 am
content: Is the circuit Mains operated?

author: AndyC_772
author_rank: Super Contributor
timestamp: July 05, 2014, 08:35:38 am
content: I'd like to seek confirmation that this test is even applicable.Where does the 24V supply come from in normal service? Are 500V spikes representative of some real-world scenario?Even the ISO pulses for 24V vehicle systems aren't this big.

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: July 05, 2014, 08:59:01 am
content: Hi,Here is an LTspice model for the pulse generator and some ideas that you can explore to protect the DC/DC converter. You will probably need a 60V chip for this application.I have attached a zip file with the model.The Transorb models are from Littelfuse.Regards,Jay_Diddy_B

author: Neilm
author_rank: Super Contributor
timestamp: July 05, 2014, 05:14:18 pm
content: Quote from: AndyC_772 on July 05, 2014, 08:35:38 amIt could be relevant if the DC supply lines were long, or it was explicitly required by the standard to meet it. By long I mean more than 30m.

author: Gribo
author_rank: Frequent Contributor
timestamp: July 05, 2014, 06:45:56 pm
content: I have just managed to pass the same surge test with a similar circuit. I have used a varistor (clamping to 60V), reverse protection diode and a TVS (Clamping to 45V). However, I have used an automotive rated LDO (NCV4274 from Onsemi) which can tolerate 60V spikes and load dumps.

author: Mad ID
author_rank: Regular Contributor
timestamp: July 07, 2014, 09:46:48 pm
content: Hi.You have all been very helpful!Series resistance together with more capacitance should do the trick even without expensive TVS..just with varistor and fuse up front.Regarding the reverse protection, I'm not sure that the circuit would survive reverse polarity if it has to wait for a fuse to blow... probably depends of the circuit and the current the source can supply. e.q. in a lab with current limited power supply.As for my next designs, I'll definitely use a 40V+ supply. Looks like it all depends on how big series resistance can be fitted in the circuit.

author: AndyC_772
author_rank: Super Contributor
timestamp: July 08, 2014, 06:32:17 am
content: Quote from: Neilm on July 05, 2014, 05:14:18 pmI think I've found why I've not come across this requirement before; I found an app note from a PSU manufacturer which states that:"The surge immunity test is applicable to products, whichare connected to mains supplies or other networks leavingthe building."I've designed dozens of dc powered products before, but they're all powered from a local mains adapter or a battery, and never a dc supply from another building. The mains adapter gets surge tested, of course, but not the dc input to the product itself.

author: Precipice
author_rank: Frequent Contributor
timestamp: July 08, 2014, 07:04:48 am
content: Quote from: Mad ID on July 07, 2014, 09:46:48 pmThe race is between the (unidirectional, in reverse mode) TVS and the fuse. Your stuff downstream should only see a volt or so of negative, while that race is on. But yes - if the supply droops far enough to stop the fuse blowing, the fuse will have to sustain that current for longer, which might be a thermal problem...Quote from: Mad ID on July 07, 2014, 09:46:48 pmHigh voltage tolerant (particularly automotive) regulators aren't too expensive, and make a lot of these problems go away. Be warned that some LDOs protect themselves by disabling the output during high voltage events, so if you can't tolerate a power dropout / reset, don't use those! (Switchers obviously come with a burden of filtering to stop noise leaving on the DC supply lines, but switching frequencies keep getting higher, making filtering cheaper, easier and smaller...)

author: Richard Head
author_rank: Frequent Contributor
timestamp: July 08, 2014, 07:11:15 am
content: I concur with AndyC_772Trying to get a small DC-DC converter (or even a large one!) to comply with that is ridiculous.I have designed mains PSU's that have to comply with that and that's tough enough, but for a 24VDC input it's crazy.If I could show you the size of the capacitor bank that is used to generate the surge you would be shocked.My first PSU came away with plenty of loose parts inside and a burned smell. My test was 3kA 8/20us pulse.By the time the MOV's clamp the voltage is about 900V peak.

author: Mad ID
author_rank: Regular Contributor
timestamp: July 08, 2014, 09:21:11 am
content: Quote from: Precipice on July 08, 2014, 07:04:48 amOhmy faultThe circuit will survive.I will definitely consider omitting reverse polarity diode (i.e. use unidirectional TVS) for designs which are susceptible to surge events.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: July 08, 2014, 09:35:07 am
content: Quote from: Precipice on July 08, 2014, 07:04:48 amI disagree: if that power supply is backed with a nice beefy capacitor, that diode might very well end up toasted. The voltage drop might spike to 3-5V in the process, maybe even more.It cannot be stressed enough that fuses blow in themillisecondsand semiconductors in themicroseconds!Diodes at least are generally quite robust, and occasionally can be saved by suitable choice of fuse. Of course, they don't provide I^2*t for TVS diodes, so you'd have to guess at that one.Tim

author: Precipice
author_rank: Frequent Contributor
timestamp: July 08, 2014, 01:32:03 pm
content: Quote from: T3sl4co1l on July 08, 2014, 09:35:07 amPartly - but we've established that the use here has long cables feeding the power in - there's some useful resistance in there. (possibly enough resistance to stop the fuse blowing, of course, you can't win them all, but, on the upside, the fuse has resistance too...). In my experiences, at least 1.5V is transiently surviveable by most power devices. It's never guaranteed or specified, of course...1.5V gets you 100A in figure 9 ofhttp://www.farnell.com/datasheets/1716635.pdf, which should start most fuses popping.In using beefy TVSes, I've seen similar I^2t for the forward and reverse directions - it's the same die after all.OP is still definitely stuck with a hard problem - but it's a problem I'd attack with TVSes. Quite big TVSes, and not complete confidence. A 'proper' solution would have him gating the power off, but I don't know if the budget or space allows, or if his spec requires, or whether this is just a 'nice to have'.

author: HackedFridgeMagnet
author_rank: Super Contributor
timestamp: July 08, 2014, 01:49:40 pm
content: Quote from: Precipice on July 03, 2014, 09:56:13 amNice one.BTW can't you do the surge stuff separately? Whats the application that needs to satisfy this test.Would a Fuse and MOV do the job?

author: Mad ID
author_rank: Regular Contributor
timestamp: July 08, 2014, 08:00:56 pm
content: Quote from: HackedFridgeMagnet on July 08, 2014, 01:49:40 pmHere in Europe it's a standard CE mark EMC Declaration of conformity for a DC powered device.

author: Precipice
author_rank: Frequent Contributor
timestamp: July 08, 2014, 08:11:31 pm
content: Hang on - is this a product you're selling with a power adaptor, for a relatively normal indoor use?If so, I normally see them tested as a pair, with the power supply - no directly injecting surge into the DC power. Standard immunity stuff, but not this...There's not a consumer product I've ever seen that would survive what you're testing on the 5V or 12V supply.Edit: other people have asked this before me in this thread. It's the big question...

author: AndyC_772
author_rank: Super Contributor
timestamp: July 09, 2014, 06:43:21 am
content: Quote from: Mad ID on July 08, 2014, 08:00:56 pmNo, it's not. Having to cope with a 500V spike is anything but 'standard'. It's a very severe test indeed, and not one I've ever had equipment subjected to in nearly two decades of designing electronics for sale.Please, before you go any further in bullet proofing your product, go back and check exactly which standard you're testing to, and that this surge test is actually applicable and required.If the product you're making is an ordinary piece of consumer or industrial kit, and it'll be sold with a mains adapter, then I can virtually guarantee that your circuit doesn't need to meet this requirement.The mains adapter it's sold with does need to pass a surge test, but that's another story - and 99.9% of the time you'll find the adapter has already been tested by its manufacturer. If your combination of adapter + product fails surge testing (in which the surges are applied to the ac mains, not the dc side), use a different adapter.

author: Precipice
author_rank: Frequent Contributor
timestamp: July 09, 2014, 07:12:51 am
content: Also: Does your test house think you should be applying this test, or are you doing it all in-house and interpreting the standards yourself?If the latter, I'd have to recommend some reading other than the standards - I'm not sure what books are current and good, but there must be some.Suggestions, anyone?

author: AndyC_772
author_rank: Super Contributor
timestamp: July 09, 2014, 07:28:43 am
content: I'd start by going back to the lab and asking them to show which standard they're applying to the product and why they believe this specific test applies.Then, I'd go to another lab, and ask them for their opinion on which tests would be applicable. See what the correlation looks like between the two.I'm happy to swap lab recommendations - or otherwise! - by PM.

author: Mad ID
author_rank: Regular Contributor
timestamp: July 09, 2014, 10:49:50 am
content: Quote from: Precipice on July 08, 2014, 08:11:31 pmHi, sorry for not stating this clearly.The answer is no, the product is not a consumer but an industrial one which is used in 24V trucks. DC power comes from truck's 24V internal power bus. No adapter involved.

author: Mad ID
author_rank: Regular Contributor
timestamp: July 09, 2014, 10:52:52 am
content: Quote from: Precipice on July 09, 2014, 07:12:51 amHi, I'm not doing the tests.The test are being done by a testing laboratory which is certified for EMC testing here in EU.I asked multiple times, this surge is applicable in my case and they test many products with the same surge setup.

author: AndyC_772
author_rank: Super Contributor
timestamp: July 09, 2014, 11:55:12 am
content: To the best of my knowledge, the standard applicable to 24V vehicle powered equipment is ISO 7637-2.I'd still strongly recommend checking with a different lab before incurring any more costs redesigning your product.

author: Precipice
author_rank: Frequent Contributor
timestamp: July 09, 2014, 02:50:06 pm
content: If it's for an OEM, each has their own book of rules, and between you, you generate a test plan that calls for specific tests in specific ways, and you then test to that plan. I've just finished a GM product, that was hell on earthNext time, I shall campaign for having a say in the test plan...

author: lewis
author_rank: Frequent Contributor
timestamp: July 09, 2014, 03:14:31 pm
content: I agree with Andy C, ISO 7637-2 is the applicable standard for automotive conducted susceptibility in supply lines. Pulse 5 (load dump pulse) from 7637 is now referenced in ISO 16750-2. The most onerous load dump pulse is 174V, 1R, 350ms for a 24V nominal supply. That's a pain to comply with, almost all standard TVSes will die easily. More info here:http://www.radiocad.co.uk/files/1413/6921/7114/LoadDumpPaper-final.pdfBuy a copy of these standards. EN/IEC 61000-4-5 is probably only applicable to mains voltage transients, or transients on communication or signal ports, and should not be necessary for power inputs in your application. Triple check whether you really need to comply with it.

author: Mad ID
author_rank: Regular Contributor
timestamp: July 09, 2014, 03:32:07 pm
content: Quote from: lewis on July 09, 2014, 03:14:31 pmHi. At the moment we need the CE declaration. I undestand there are other tests but once again, CE mark (Declaration of conformity) is what we are after at the moment.You have all been very helpful, thank you very much!

author: AndyC_772
author_rank: Super Contributor
timestamp: July 09, 2014, 04:04:56 pm
content: Just to be clear: I (and, it would appear, we) believe that ISO 7637-2isthe applicable test which your equipment would need to pass in order to qualify for a CE mark, and not necessarily IEC 61000-4-5.Sometimes, determining which tests are applicable to a product can be as difficult as engineering the product to pass them

author: Mad ID
author_rank: Regular Contributor
timestamp: July 10, 2014, 01:47:57 pm
content: Quote from: AndyC_772 on July 09, 2014, 04:04:56 pmI will look into it.Thanks.

author: qno
author_rank: Frequent Contributor
timestamp: July 10, 2014, 04:05:47 pm
content: I have passed the test by placing a P Mosfet in front of a 7805 that switches off when input voltage is > 35V.The MOSFET has to be able to withstand 200V.You fall into the category that will reset when the puls is aplied but resumes normal operation when normal power is restored.If you define this behavior in advance you will pass.Please set your country.

author: Circuitous
author_rank: Unknown
timestamp: July 10, 2014, 04:25:08 pm
content: Quote from: qno on July 10, 2014, 04:05:47 pmqno that sounds like a neat approach, do you have an example schematic of that?

author: qno
author_rank: Frequent Contributor
timestamp: July 13, 2014, 07:37:51 pm
content: I can not give you the exact circuit but this datasheet gave me the idea.http://www.maximintegrated.com/en/app-notes/index.mvp/id/4081Here is where it is based on.

author: Circuitous
author_rank: Unknown
timestamp: July 14, 2014, 12:10:04 am
content: Perfect! That looks like just what I need for an upcoming project. Thanks!

author: AndersJ
author_rank: Frequent Contributor
timestamp: February 23, 2016, 03:05:36 am
content: 61000-4-5 says that surge transients are injected between ground and signal lines."Ground" in this case means the device chassis, protective ground."Signal lines" in my case, and for many other devices are signal ground and the signal itself,such as 5V digital inputs, 0-10V analog inputs, or an industrial 24V dc signal input, or similar outputs.Often, as in a PC, and many lab instruments,signal ground is galvanically connected to chassis/PG.In these cases,are surges applied between ground and signal ground?This implies injecting the surge on a short circuit.Is this how it is done?

author: T3sl4co1l
author_rank: Super Contributor
timestamp: February 23, 2016, 08:20:58 pm
content: I'd have to look at the precise wording of the standard, but I don't see that there would be any harm of it. The surge generator is designed for open, resistive and short loads. As is true of any other pin, it should simply not do anything. Right?Tim

author: HackedFridgeMagnet
author_rank: Super Contributor
timestamp: February 23, 2016, 10:07:34 pm
content: Your ground wire will probably come into the DUT from a different wire than the signal ground.Every wire has an inductance so what is a short circuit at dc may not be for a surge.Surges are generally modelled as a current source. eg. 50kA 10us up and 350 us down.The voltages that are generated by the surge through the inductances may cause arcing between different parts of the DUT.This is one of the things you would be testing for.Also not all signals are unbalanced with one side grounded.So put the surge across each signal wire to the ground lead of the DUT.To create the surge use something like Mikes electric stuff's destructor or whatever he calls it. He has a video where he tests the circuit breaker.A capacitor bank charged up with high voltage. Obviously very dangerous!Use an isolated (wireless?) remote to trigger a thryristor to send the surge.You can measure the surge with a current transformer that attaches to a scope.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: February 24, 2016, 09:26:33 am
content: Er, well, not just ANY bare capacitor, or random wiring, and certainly not a bank of defibrillator capacitors at full charge!!IEC 61000-4-5 defines a maximum Class 4 of 4kV (into 2 ohms, 2kA) surge. The time constant into 2 ohms is about 28us (it's not really a time constant because an RLC circuit is used), so about 14uF is needed.To get the open-circuit waveform, some series inductance and parallel resistance is needed. Resistance might be around 3 ohm, which means the 1.2us rise time (for this condition) needs around 2uH.To get the short-circuit waveform, more series inductance is needed (though not much more), a total of double I guess. The extra parallel resistance means more capacitance will be needed, maybe 24uF.In the two conditions, sqrt(L/C) is much less than the ESR of the loop thus formed, so it should have no undershoot (the standard allows for 30% phase reversal), and no need for diodes and stuff. A contactor is probably okay for switching the surge (it's over before the contacts can bounce open again), or thyristors of not too extreme ratings (but do turn them onhard!).Tim

author: jeroen74
author_rank: Frequent Contributor
timestamp: February 24, 2016, 12:21:55 pm
content: A few years ago I did this very test on a mains-fed lamp controller widget supposed to be mounted in a lantern pole, but up to 8KV. Naturally things got quite explosive once that poor MOV decided it was time to give up around the 25th pulse.The scope indicated about 1 megawatt of dissipation for a microsecond.

author: zare.zz
author_rank: Newbie
timestamp: June 15, 2021, 05:55:05 am
content: how can I find a appropriate TVs diode for pass a IEC61000-4-5 CLASS3(2KV)?

author: jonpaul
author_rank: Super Contributor
timestamp: June 15, 2021, 06:46:50 am
content: Hello: Are you sure that IEC 61000-4-5 Surge immunity test is required for your product? Normally that is for mains connected PSU, not low voltage.Which surge tester was used?Generally we avoid MOVs as they are very 'soft" and wear out. Sometimes they catch fire after an overload.Load dump protection for 28V systems were very large die Zeners like Motorola MR2525.Vishay TransZorb diode,https://www.vishay.com/diodes/protection-tvs-esd/Bon chance,Jon