Current sensing in an EV wall box - Page 1
Forum section: electronics / general

author: Faringdon
author_rank: Super Contributor
timestamp: August 15, 2021, 11:39:47 am
content: EV wall boxIs it true, there is a need to do the following sensing?1....Live current measurement (using CT torroid round the live)...this is AC current sesnsing2....Live/Neutral current imbalance (using CT torroid round live and neutral). This is AC current sensing3.....AC current in the CPC..using CT torroid round the CPC wire.What DC current is needed to be measured, for protection purposes?....eg a DC current level in the live line?, DC current in the CPC?......are Hall sensors used to detect the DC level?

author: Gyro
author_rank: Super Contributor
timestamp: August 15, 2021, 12:28:05 pm
content: Give it up Treez. You can't design an EV charger based on Youtube tear-downs.Your employer needs to fork out for the standards, and you need to study them!EDIT: As has already been said, the Rolec is one of the oldest chargers (or should I say, charging points) and requires external PEN fault protection, adding to material and installation costs and making it less popular with installers.

author: f4eru
author_rank: Super Contributor
timestamp: August 15, 2021, 04:48:31 pm
content: Quote from: Gyro on August 15, 2021, 12:28:05 pmmaking it less popular with installersin the UK.PEN protection is not needed in other countries, due to TT earthing (or other schemes not using PEN).

author: Faringdon
author_rank: Super Contributor
timestamp: August 15, 2021, 07:53:36 pm
content: Thanks, the thing is, that DC current in the CT primary may saturate it, and mean its not effectively there.Also, as you know, a CT cant measure DC current, so a Hall sensor must be used to sense the DC, but i dont hear details of hall sensors in these wall boxes.What is the DC level in live and neutral under which the live/neutral imbalance CT is still required to work under.?....ie, without saturating the CT?I presume that this gets addressed by just using a CT much bigger than would normally be needed?

author: Gyro
author_rank: Super Contributor
timestamp: August 15, 2021, 09:45:11 pm
content: Quote from: Faringdon on August 15, 2021, 07:53:36 pmYou don't appear to even have the knowledge or attention span to follow images and verbal commentary of the 13 minute video that you linked then! Either that or you only watched the first few minutes. If you can't follow a fairly layman description like that then there is no chance for you to safely start to develop such a product.I really cannot believe that you can't see what's right in front of your eyes (or listen to what is being said on the video). Youhaveto be trolling us. I'm sorry, but words fail me!

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: August 15, 2021, 10:45:23 pm
content: QuoteNot actually necessary, though some EVSEs measure AC current for information, apps etc. It could potentially be used to detect if the car is drawing more than it has been told is available, but this is a fairly unlikely situation, and would usually be covered by the circuit breaker feeding the unitQuoteYesQuoteNot usually as (2) handles this.QuoteNeither - DC common-mode /leakage current on L & N. The video is incorrect, or at least unclear in this aspect, but then they are only electricians...QuoteHall sensors are probably not sensitive enough. One sensor I took apart uses a fluxgate ( core saturation) type method, others might use GMR sensors.

author: NiHaoMike
author_rank: Super Contributor
timestamp: August 16, 2021, 01:54:59 am
content: Since a DC ground fault is most likely to involve the car chassis, add a sense resistor with bypass diodes in series with the ground line. Now it would be easy to detect a small DC leakage current.

author: uer166
author_rank: Super Contributor
timestamp: August 16, 2021, 04:27:57 am
content: Quote from: NiHaoMike on August 16, 2021, 01:54:59 amGod. We already went through this, please don't give advice unless you read the relevant standards. This is not how it's done and this will not be compliant. If it wasthateasy you wouldn't see everyone use some form of a overly complicated fluxgate sense. I guess who cares, it'll be interesting to see the train wreck of a product.

author: Faringdon
author_rank: Super Contributor
timestamp: August 16, 2021, 06:54:40 am
content: QuoteThanks, yes,.....it took me ages to find that video.....hours and hours of searching...the only video that gives any significant info about the standards.The problem is, it doesnt tell if its necessary to detect a DC current in the CPC?Also, it doesnt tell under what DC current level the RCD must be able to work up to ?(as you know, above a certain DC current level and the RCD wont work as it will be saturated)Also, it doesnt tell if the CPC AC current has to be detected, and what is the trip level?We payed money for the EV standards...on the web....but they took our money and ran.Also,can you get round the DC>6mA problem by just having a very large CT torroid RCD?....so it wont saturate on 6mA DC?...What DC current is it allowed to saturate at? (if you dont also have a residual dc current detector)?

author: Gyro
author_rank: Super Contributor
timestamp: August 16, 2021, 08:18:18 am
content: Quote from: uer166 on August 16, 2021, 04:27:57 amThis is all just prolonging the agony. It's 'don't try to design theproductwithout reading the relevant standards'! The train wreck stage is going to be far too late in terms of financial investment (presumably somebody is intending to spend money trying to manufacture it) and safety.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: August 16, 2021, 08:30:02 am
content: Quote from: Faringdon on August 16, 2021, 06:54:40 amWho did ?QuoteNo because you don't know what RCD protection may exist upstream - you may be sharing an RCD with other loads, so a DC leak current could prevent that RCD acting on faults in the other loads.

author: Gyro
author_rank: Super Contributor
timestamp: August 16, 2021, 08:50:24 am
content: Quote from: Faringdon on August 16, 2021, 06:54:40 amIf you think that is "significant info about the standards" then it is best that I refrain from further comment.QuoteYou mean you got ripped off by some fake bootleg site in China or Russia over some too-cheap-to-be-real bootleg copy. Or is it just another lie, like"My Rolec EV charger wall box has stopped working....."(Direct quote)?As for the rest of the stuff, it would be irresponsible for anyone who hasn't read the relevant standards to comment. It would be unprofessional to give you possibly inaccurate safety related advice.My honest advice at this point would be to go on bended knee to your customer and ask them to fund the purchase of the standards. If they expect to make any significant profit from this product, and considering the amount of money they stand to loose at the moment, they may well consider it a worthwhile investment - assuming that they are not too annoyed that you didn't do that in the first place.

author: fourtytwo42
author_rank: Super Contributor
timestamp: August 16, 2021, 12:36:55 pm
content: I agree with Gyro, IMOP it really is about time the mods got off there asses and did something about this guy. The number of inane posts is stupefying BUT here once again we have someone with little or no knowledge trying to become involved in potentially dangerous technology with a view to making a product for public use. By continuing to allow these posts this website could be construed as being complicit in some unfortunate persons death.

author: voltsandjolts
author_rank: Unknown
timestamp: August 16, 2021, 03:26:10 pm
content: I get the impression that treez' workplace is something akin to Fawlty Towers (British sitcom).That is of course, if it actually exists. These days I'm inclined to think that just like Basil Fawlty, treez is also a fictional character.I mean, all this, can't be real. Thank me if I'm right treez.

author: Faringdon
author_rank: Super Contributor
timestamp: August 16, 2021, 06:20:03 pm
content: Thanks, will get the standards.

author: fcb
author_rank: Super Contributor
timestamp: August 16, 2021, 06:26:45 pm
content: Dear Mods, please please keep Faringdon/Treez on this forum. We all need a laugh now and again.Free the Standards!!! Rock-on Faringdon

author: Simon
author_rank: Unknown
timestamp: August 16, 2021, 06:34:32 pm
content: For goodness sake Farringdon, either shut up or put up!Information abounds:https://en.wikipedia.org/wiki/SAE_J1772I could knock up a useable charger in a couple of hours given this information, granted may not be safe for the never never to occur event or be legal but I could get power into a car, or buy a chinese portable 16A or even 32A portable charging access device for little more than I can buy a plug with the cable on it and less than a Type 2 level 3 cable costs in the UK!There is a shortage of work in all sectors in the UK, maybe time to look for another job?

author: Simon
author_rank: Unknown
timestamp: August 16, 2021, 06:35:45 pm
content: Quote from: Faringdon on August 16, 2021, 06:20:03 pmIf it's a standard it's copyright! if you have to pay money for it then sharing is definitely illegal.

author: fcb
author_rank: Super Contributor
timestamp: August 16, 2021, 06:37:17 pm
content: Quote from: Faringdon on August 16, 2021, 06:20:03 pmI am trying to be humourous lest my previous comment is taken in the wrong way.Are you suggesting that you are designing EVSE for a 3rdworld country??

author: Bud
author_rank: Super Contributor
timestamp: August 16, 2021, 07:24:43 pm
content: 3rd world countries can afford having electric vehicles but can't afford buying a few pages of information ?

author: Ian.M
author_rank: Super Contributor
timestamp: August 16, 2021, 07:47:07 pm
content: Many leading third world countries *DO* make their safety standards (which are often closely based on or direct copies of UK/EU standards) publicly and freely available, so contractors have no excuse (or legal defense) for shoddy or unsafe design or workmanship. However some third world countries are not so enlightened. e.g. your typical African kleptocratic 'government' never seems to get the idea that to maximize the amount they can steal, they have to feed the 'Goose that Laid the Golden Eggs' rather than killing it!

author: Gyro
author_rank: Super Contributor
timestamp: August 16, 2021, 08:31:53 pm
content: Quote from: Faringdon on August 16, 2021, 06:20:03 pmThis tactic reminds me of a post in his rambling "Electronics products...where are they made/designed?" thread - the one in which he revealed that his friend was setting up a duplicate of his company in China to manufacture his British products(https://www.eevblog.com/forum/chat/electronics-products-where-are-they-madedesigned/msg3609021/#msg3609021)Maybe Rolec are about to get a duplicate that they don't know about!This post strikes me as having a very similar tone...QuoteOurTreezFaringdon is quite the philanthropist when under pressure or his motives are questioned.

author: f4eru
author_rank: Super Contributor
timestamp: August 16, 2021, 09:43:11 pm
content: Standards mandated by law should always be free to use.Sometimes they are!If not, feel free to copy them.

author: NiHaoMike
author_rank: Super Contributor
timestamp: August 17, 2021, 01:55:29 am
content: Quote from: uer166 on August 16, 2021, 04:27:57 amLooking at the OpenEVSE project, it looks like they detect DC ground faults by injecting a signal to the ground fault sense transformer and checking that it returns at about the expected level. Cheaper than adding a current sense to the ground wire.https://github.com/OpenEVSE/OpenEVSE_PLUSOf which, it looks like the license allows commercial use under some conditions. Not sure how to satisfy the attribution part without giving the impression that it's an official OpenEVSE product or is endorsed by the OpenEVSE team.

author: Simon
author_rank: Unknown
timestamp: August 17, 2021, 07:31:36 am
content: Quote from: f4eru on August 16, 2021, 09:43:11 pmOften standards are freely available. You have to purchase a copy of the UK wiring regs as an electrician, but it's sub £100 which is what? an hours work for an electrician and the book does need printing. Ultimately someone has to pay and the cost of a standard is the least thing you will pay for when starting on something requiring the standard.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: August 17, 2021, 08:29:05 am
content: Quote from: NiHaoMike on August 17, 2021, 01:55:29 amI think that is just for functional testing of the RCD, not DC detection.Though I do wonder if you could add DC detection to a conventional CT sensor by injecting a known waveform and detecting asymmetry, effectively turning the sense core into a fluxgate sensor

author: uer166
author_rank: Super Contributor
timestamp: August 17, 2021, 10:01:20 pm
content: Quote from: mikeselectricstuff on August 17, 2021, 08:29:05 amThere's not much fundamental difference between a fluxgate core and a CT core. The fluxgate core is optimized to have a very square BH curve with low-ish coercivity, while a CT one has high permeability for high secondary inductance to reduce phase shift. If you do this, you might as well get the correct core for the job. Other things include a massive difference in turns, you have 2000 for CT but say 10-20 for a fluxgate excited secondary. A fluxgate core can generally be much smaller since secondary inductance is not well defined and irrelevant. The trade secrets are the drive waveforms, various filtering details, and the cores themselves.

author: voltsandjolts
author_rank: Unknown
timestamp: August 18, 2021, 01:48:21 pm
content: The OP shouldn't bother designing an EV wall charger.It would be a waste of time, because the electric car revolution car never happen.That is, according to forum member opampsmoker.https://www.eevblog.com/forum/beginners/electric-vehicle-revolution-cannot-happen-its-proven-do-you-agree/...and what do users treez, ocset, zenerbjt, opampsmoker, coffeefet, Faringdon have in common?

author: coppice
author_rank: Super Contributor
timestamp: August 18, 2021, 02:15:07 pm
content: Quote from: mikeselectricstuff on August 17, 2021, 08:29:05 amFluxgate sounds like a scandal over measurement errors. Its not obvious to me why fluxgate sensors are not more widely used. There's nothing inherently costly about them, compared to the widely used sensors which have numerous limitations compared to a fluxgate - no DC measurement, saturation, etc.GMR sensors are another technology which seems to be limited more by a lack of effort than by inherent limitations.

author: nightfire
author_rank: Frequent Contributor
timestamp: August 18, 2021, 06:17:12 pm
content: Detection of a small DC leakage current is (in germany) mandatory because a RCD in the feeding network can go "blind".More specifically RCD Type A go into saturation at 6 mA DC, so if this occurs, they will not trip anymore at AC leakage currents exceeding the nominal/rated current.To overcome this a DC sensing has to be present at charging stations or charging adapters to prevent this.Alternatively one could use a RCD type B which allows for higher DC leakage currents that maybe originate from very powerful battery circuits.Attention: Because of this fact, a RCD Type B is not allowed to be put behind a RCD type A in those or similar applications.

author: uer166
author_rank: Super Contributor
timestamp: August 18, 2021, 06:55:27 pm
content: Quote from: coppice on August 18, 2021, 02:15:07 pmIt's obvious once you try to actually design and use now, they are a major pain in the ass because:They need to inject a few 100mV common mode to work for the excitation, therefore:Anything that prevents/shorts out that common mode voltage af a few kHz will prevent the fluxgate from operating, therefore:They don't work when the output is not "floating" relative to the input. E.g. you can't just put one in the output of a buck converter because there are caps at the input and output that create a "shorted turn" shunting the common mode.That same voltage injection creates massive conducted EMC problems unless you have big Y-caps at the input and you let the output (i.e. vehicle) bounce around at ~kHz at a few 100mVIf you don't want to have the above issues, you use 2 cores in series, where one is the sense, and the other is CM cancellation, now you need extremely well matched cores otherwise the physics don't workSaturation is not magically a non-issue as you alluded, you need to design the drivers/sense specifically to counter the primary current to avoid saturation. If you fluxgate is open-loop (most 6mA DC detection are), then you have the exact same problem.If you have an option to go with CT, go with CT every time!

author: Faringdon
author_rank: Super Contributor
timestamp: August 25, 2021, 07:52:33 pm
content: Thanks, can the ZCT409 CT be used as a fluxgate sensor.....?...or is it one anyway?ZCT409https://www.ctzentar.com/zero-phase-current-transformer-for-leakage-current-detection-zct409_p28.html

author: Simon
author_rank: Unknown
timestamp: August 25, 2021, 08:40:32 pm
content: Ask the manufacturer?

author: m98
author_rank: Frequent Contributor
timestamp: August 25, 2021, 09:59:00 pm
content: Quote from: Faringdon on August 16, 2021, 06:54:40 amYou can't be serious.Have fun:https://www.bsigroup.com/en-GB/standards/how-to-access-and-buy-ISO-standards/https://shop.bsigroup.com/products/electric-vehicle-conductive-charging-system-electric-vehicle-requirements-for-conductive-connection-to-an-ac-dc-supply-emc-requirements-for-off-board-electric-vehicle-charging-systems?pid=000000000030269923

author: Simon
author_rank: Unknown
timestamp: August 26, 2021, 07:32:41 am
content: Yep, there is only one source for standards. Obviously if you go somewhere dodgy that promises for a cheaper price, um, yea....

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: August 26, 2021, 08:08:48 am
content: Quote from: Simon on August 26, 2021, 07:32:41 amActually there are multiple - you can buy from each country's standards body. Apparently Estonia is the cheapest.

author: fcb
author_rank: Super Contributor
timestamp: August 26, 2021, 08:24:12 am
content: Quote from: Simon on August 26, 2021, 07:32:41 amIf the standard is in use in the EU, then each EU countries standards body (BSI in UK) can sell the standard. They can sell it for whatever price they wish.We use the Estonian standards agency as they typically 5-20% of the price of BSI.61010-1:2010 from BSI £350 (members £175, membership is £207 upwards)61010-1:2010 from EVS €31.80 incl. TAX (£27.20)www.EVS.ee

author: Faringdon
author_rank: Super Contributor
timestamp: August 26, 2021, 08:38:28 am
content: Can you use a "non fluxgate CT" for Fluxgate type sensing?.....if so, is there an associated inaccuracy?....i mean, arent the secondaries very low inductance with fluxgate sensor CTs? (as kindly mentioned here already).Also, if you need to do both 6mA DC testing, and the AC testing for 30mA imbalance aswell...then doesnt it make sense to use the "fluxgate" type approach, to kill two birds with one stone?

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: August 26, 2021, 09:03:04 am
content: Quote from: Faringdon on August 26, 2021, 08:38:28 amif it isn't specified for that usage, you have no idea of the tolerances of the coreQuoteYes it makes sense to use the same sensor for AC and DC.ISTR reading somewhere that current standards dictate that the EVSE shouldn't (maybe even must not ?) do the AC RCD function, but instructions should specify that they are connected to a type A RCD at source. Not sure how accurate this is, or where it is specified, but apparently at least one EVSE manufacturer (Anderson) has removed the AC RCD functionality from its unit.

author: Faringdon
author_rank: Super Contributor
timestamp: August 26, 2021, 02:10:31 pm
content: QuoteThanks, thats interesting. In fact, i have only recently found out that EV wall box's should not have a Type A RCD function, because it would be blinded by a DC current level at 6mA or greater.An EV wall box needs to have a type B RCD, which trips out on 30mA of AC imbalance, but doesnt get blinded by even 100mA of DC level in the mains.So an EV wall box needs a type B RCD and a DC level sensor which can sense up to greater than 200mA DC.This is quite a spec...do you know of off-the-shelf devices that can do this?Does it mean only fluxgate sensors, or Hall sensors can be used?...since any "Normal" CT would be blinded by the DC.

author: fcb
author_rank: Super Contributor
timestamp: August 26, 2021, 03:26:33 pm
content: EVSE needs (depending somewhat on market/spec) someway of measuring current draw. Monitor the current in both L & N legs with shunts, monitor the line voltage and process this with a micro to extract power, current, balance, DC, freq, etc..Even if you only use the shunt(s) to detect DC fault conditions, still pretty low-cost.Or look up how AC+DC clamp meters work (split iron core & hall effect), and build something like that.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: August 26, 2021, 04:14:40 pm
content: Quote from: Faringdon on August 26, 2021, 02:10:31 pmThat isn't the reason. a 6mA DC sensor could sense 30mA AC.QuoteNope. A type B RCD trips on DC or AC imabalance.QuoteThe Type B RCD IS the DC leakage sensor.I have no clue where you got 200mA from, but am losing the will to care.

author: nightfire
author_rank: Frequent Contributor
timestamp: August 26, 2021, 07:00:41 pm
content: Quote from: Faringdon on August 26, 2021, 02:10:31 pmJust got out of my yearly training for refreshments of knowledge here in germany regarding EVSE. Focus on the checks for electrical safety in operation here in germany and german regulations. (VDE is used here)In short: RCD type B is not always necessary. There has to be a RCD present with max 30 mA for person protection, AND there has to be some way in a 3-phase setup to detect DC currents, because above 6mA a RCD type A (which might be in the main distribution) will go "blind".In a brand wallbox we had available for testing, a standard RCM module was used for this in combination with a standard RCD type A you could get at every corner.OR one could use one of those quite new RCD type A-EV, which combine a traditional RCD type A and DC 6mA sensing.Of course, the more highend way would be to use an RCD type B, which might be better available. And depending on the testing equipment (here in germany regulations say that once a year in commercial enviroment a wallbox etc. has to be tested) a RCD type B might be easier to test because of preprogrammed values in testing equipment.In fact, many wallboxes in germany use only an inbuilt RCD type A and a DC recognition of 6mA.Word of warning: It is not allowed to mount a RCD type B behind a RCD type A- simply because the type B would tolerate much more DC current than type A can handle- and what would affect some possible other circuits that might reside on the same RCD.

author: NiHaoMike
author_rank: Super Contributor
timestamp: August 27, 2021, 02:23:12 am
content: Wouldn't it be possible to have the AC GFCI continuously self test itself by injecting a signal at a substantially different frequency from the mains frequency? If there's a DC ground fault enough to disable the GFCI, the signal won't come back.

author: Faringdon
author_rank: Super Contributor
timestamp: August 27, 2021, 05:48:38 am
content: QuoteThanks, what form would that take...a fluxgate sensor?Also..Some fluxgate sensor questions?1....Can an RCD fluxgate sensor be done with a standard CT with a single coil? eg a torroid through which the power conductor pair are meant to simply traverse the aperture.2....What makes a fluxgate sensor accurate?.....is it the feedback loop?3....If a batch of fluxgate cores have different saturation current levels, will they not give different current readings?4....If a batch of fluxgate cores have varying BH loop widths, then wont they give different current readings?5....If a batch fo fluxgate cores are pulsed with different frequencies, then wont they give different current readings?

author: Faringdon
author_rank: Super Contributor
timestamp: August 28, 2021, 02:37:40 pm
content: Hi,Supposing an electrician installs an EVSE in a household premises.then suppose it fails the RCD test.....eg it trips on <15mA of AC imbalance, or doesnt trip till Fault DC gets up to 10mA..etc etc etc...Is the electrician likely to de-install it , even though he wont be payed to do so?Or will he just check it charges the car, and whether it electrocutes him when he touches the car?...... and if it does this , then he takes th emoney and runs?.....who is ever going to find out ?

author: Simon
author_rank: Unknown
timestamp: August 28, 2021, 04:42:17 pm
content: what does it matter to you? my electrician was sweating badly when he tested mine and got dodgy figures. it reported an insane earth path resistance that we both know was wrong. He then as randomly as he got a fail got a pass and put those figures down. You tell me, was he right or wrong? I am happy, I watched him and helped him install it and knew very well that the install was fine. The meter was one side of the wall and the charging point the other side, total cable length was no more than 2m.There are rules beyond your original topic that govern the installs. So you get the design right, leave the electrician to get the install right and everyone is happy. There are people all over the place that break rules in all sorts of things. The idea is that there are sufficient checks in place to catch the persistent wrong doers.Ultimately I could have put that charging access point in myself with no obligation to show a future tenant or buyer the install paperwork, then what? That is why your job apparently is to design a device so safe that even if mis-installed would protect itself, the car and people. Mine has cut out on an RCD fault.

author: floobydust
author_rank: Super Contributor
timestamp: August 28, 2021, 05:11:39 pm
content: These kind of threads should get locked, IMHO.Faringon, don't ask us questions about subverting electrical safety with your company's EVSE product.EE's have ethics and morals in protecting the safety of the public. We cannot enable anything criminal and have a cup of tea discussion about the electrician's ethics catching it.Your test fixture is late, will not work etc. etc. and better to bite the bullet and face that fact instead of cheating and rolling out untested or fake tested product to the marketplace.In jail there will be plenty of time for reading about CT construction and design. The leakage current test exists for good reason.

author: dmills
author_rank: Super Contributor
timestamp: August 28, 2021, 05:51:39 pm
content: There used to be a guy who posted here about his inability to design small switched mode converters for street lighting that actually worked reliably, he was vaguely amusing.It is less so when someone starts doing much the same thing with power levels that are actually both dangerous and are directly exposed to the public.Seriously, the standards are not THAT expensive in the scheme of things, get them, design to reliably meet them, and get your product approved by a suitable test house as meeting them, then profit.I would expect a sparks to confirm that the feed to the equipment was correct, and it would be nice if they tested the load, but I don't particularly expect it, any more then I expect the guy running a three phase feed to my new welder to run a quick bead to check the welder under load doesn't take the RCD out.

author: floobydust
author_rank: Super Contributor
timestamp: August 28, 2021, 06:05:08 pm
content: We've already told OP to purchase the safety standards, the answer is "We payed money for the EV standards...on the web....but they took our money and ran."Any solution offered gets punted aside:"Thanks, also i am wondering about..""the thing is, the datasheets dont tell you""Yes but we cant do this""OK thanks, i can't tell you any more, but if you know..."But knowingly bypassing safety regs is a no-no and you might ask the executive for an opinion.

author: Gyro
author_rank: Super Contributor
timestamp: August 28, 2021, 06:12:36 pm
content: Quote from: Simon on August 28, 2021, 04:42:17 pmThe difference is that you bought a hopefully legit charge point, and therefore had some reasonable confidence that the install was actually safe and acceptable!

author: Faringdon
author_rank: Super Contributor
timestamp: August 28, 2021, 06:20:28 pm
content: QuoteThanks, thats interesting....the RCD is a bugbear for EVSE's.........if you buy offtheshelf you have to buy the RCD (30mA/6mA) and relay in one package, and it costs a fortune.....so people want to make them themselves...and designing a 30ma/6ma RCD needs a fluxgate and isnt a quick cheap job.Do you know if its possible to buy a type B RCD (30ma/6ma) which doesnt contain the relay/contactor?.....but rather just a signal for you to use to actuate a relay/contactor?....i am pretty sure such a thing doesnt exist on the market?................-----------------------......................Incidentally, what would you think if an EVSE tripped out on 10mA of AC imbalance (instead of 30mA)?......thats a standards fail!....even though its safer as it trips out on less current.............---------------------....................Also, is there any reason that you cant use a cheap type B RCD, with a cheap relay in it...but just use it to instigate a signal to turn off a more high quality relay/contactor?Cheap Type B RCD (£20)https://www.toolstation.com/axiom-incomer-devices/p90500?store=I6&utm_source=googleshopping&utm_medium=feed&utm_campaign=googleshoppingfeed&mkwid=s_dc&pcrid=515847200330&pkw=&pmt=&gclid=Cj0KCQjwvaeJBhCvARIsABgTDM4osmCd5dA_6O6J_ZpILg38mJGsz5GgxGBm0qkjN-WYnVQY5aEzKKoaAqE7EALw_wcB&gclsrc=aw.ds

author: Simon
author_rank: Unknown
timestamp: August 28, 2021, 07:58:20 pm
content: As most of us are not privy to the standards we can't answer what you do and don't need.Your link does not clearly explain what type the RCD is, which is part of being cheap!Get the standards, read them, understand them because they also will not tell you how to design something only what the end result must be. Note that meek words like "shall" and "should" in standards mean: "YOU MUST DO THIS OR YOUR SORRY ASS WILL WIND UP IN JAIL AND IT'S YOUR FUCKING PROBLEM TO WORK OUT HOW TO ACHIEVE THIS AND THEN DEMONSTRATE HOW IT ADHERES TO THE STANDARD, ELSE YOU GO TO THE AFFORE MENTIONED JAIL".My house earthing appears weird. It is both connected to the neutral and the conduit from the substation. My electrician has suggested I contact the distribution network to get them to confirm which it should be. My neighbours house is the same.

author: dmills
author_rank: Super Contributor
timestamp: August 28, 2021, 10:48:46 pm
content: No access to the standards, but fluxgate sensors for DC measurements like that seem to be an off the shelf Part, Kemet FG-R05-3A for one example among others.In sufficient production volumes it is probably cheaper to do your own, but certification costs make this sort of thing a better buy in at more modest volumes.I was actually not aware that fluxgate was an off the shelf technology, but it appears to have very much become a thing.Seriously, this shit is just not that hard, I found that part in distribution in < 30 seconds.In standardese "Shall" is usually mandatory to comply, "Should" and "May" are quality of implementation things, "Should" generally being stronger then "May", but there will probably be a bit at the start of the document which explains this.Thing is, there are PLENTY of standards around street furniture and lighting and I know you have played in that space so this shit should not be anything new.

author: nightfire
author_rank: Frequent Contributor
timestamp: August 29, 2021, 01:13:07 am
content: Quote from: Faringdon on August 28, 2021, 06:20:28 pmRCD Type B per Definition does NOT trip at 6mA DC, because ita) can and shall allow higher DC leakage currentsb) for this reason it is NOT allowed to put a RDC type B behind a RCD type ATripping due to imbalance:A standard RCD is allowed to trip within 50% and 100% of rated currrent, this means a 30mA RCD (AC) is allowed to trip anywhere between 15mA and 30mA. In the factory it is usually produced to get off at something between 20mA and 25mA to allow for some tolerance to both sides.To answer that question: A EVSE, where the RCD trips outside spec, is considered defective and should be returned to point of purchase. Period.A RCD Type B has different ranges on DC leakage current: Here we are talking about 15mA to 60mA DC as normative standard.For all those, that maybe want to dive deeper in RCD technologies: German company Doepke publishes the so called "Allstromfibel", which is also available in english.https://www.doepke.de/en/services/downloads/

author: Simon
author_rank: Unknown
timestamp: August 29, 2021, 07:18:41 am
content: Quote from: dmills on August 28, 2021, 10:48:46 pmI didn't know the words themselves had um, standardized meanings. But standards are not the law. This is where it's a bit of a mind screw. The beginning of the UK wiring regs standard (BS 7673:2018 - yes I bought a copy, because I felt like it, oh so not expensive at £80 quid) points out that the standard is not the law but laws may impose that these standards are followed or recommend them as best practice. Again, a meek sounding expression - best practice. But in legalese this means it's all shits and giggles about what you care to do until something goes wrong, THEN it is up to you to prove that you followed best practice. This effectively translates into, "just do it this way or else". And this is why installations are supposed to be spot checked at random.

author: Faringdon
author_rank: Super Contributor
timestamp: August 29, 2021, 01:58:05 pm
content: QuoteThanks, it would be good to know the cost of those, i beleive we have to email them?

author: themadhippy
author_rank: Super Contributor
timestamp: August 29, 2021, 02:21:29 pm
content: Quotesounds like they've converted TNS to a TNC-S at some point,what is unusual is conduit from the substation,plastic ducting yea,some type of armoured cable,yea,but never seen conduit on the suppliers side.

author: Faringdon
author_rank: Super Contributor
timestamp: August 29, 2021, 02:31:32 pm
content: QuoteThanks, that looks a great part, and for $50BTW, i am still a bit baffled why a RCD trip at 5 or 10mA would be a fail of standards...surely if the standards threshold is 15mA , and you trip at 5mA, then youre safer than the standards? I cant see how you could be jailed over this, or even fined.

author: Simon
author_rank: Unknown
timestamp: August 29, 2021, 03:11:22 pm
content: Quote from: themadhippy on August 29, 2021, 02:21:29 pmWell it is some sort of armoured cable I suspect as it's external braiding that has be twisted into a wire and bonded to the neutral. Yea it does the electricians head in.

author: Simon
author_rank: Unknown
timestamp: August 29, 2021, 03:20:08 pm
content: QuoteOh FFS get a job stacking shelves in your nearest supermarket!Who said you go to jail or get fined if it trips lower than the standard? Again unless YOU buy the standard YOU will never know, those of us here not trying our hands at designing car charger access points could not give a flying toss what a standard we do not need to buy says.If an RCD is too sensitive it will start tripping out at random due to leakage currents!!!!! That will make your customers mighty pleased now wont it? Your company will go bust due to all the returns of goods that are unusable! If the earth and neutral are ultimately connected together don't you think that the capacitance between the live and the earth will cause some permanent leakage? especially where the usual flat cable is used in the UK with the earth wire locked between the live and neutral.When I connected my parents house that we rented when I lived in italy where dodgy electrics abound to earth I actually got current passing through me, the whole of the leakage current in the house was passing through me as I held the earth wire in one hand and the water pipe that was I was about to bond it to.

author: nightfire
author_rank: Frequent Contributor
timestamp: August 29, 2021, 08:43:43 pm
content: Quote from: Faringdon on August 29, 2021, 01:58:05 pmNope. Free to download.

author: Faringdon
author_rank: Super Contributor
timestamp: August 30, 2021, 12:00:19 am
content: QuoteThnaks, this is interesting, i see your point, now an EV will be the only thing coming off that wallbox, and the leakage from the charger will be just that bit from the y caps....so were taking maybe 3mA max.........this wouldnt spuriously trip an RCD which tripped at 5mA to 30mA.

author: Faringdon
author_rank: Super Contributor
timestamp: August 30, 2021, 12:01:18 am
content: Hi,We wish to make a RCD for an EVSE single phase “wall box”. We will use a simple CT for the 30mA imbalance detection. This may get “blinded” by any DC leaking in either line or neutral.Therefore, we will also have a second CT the same as the first one, but will constantly also inject 30mA AC 50Hz through its aperture with a wire loop. As soon as this second CT does not detect the 30mA , then that means it has been “blinded” by a DC current flow in either line or neutral, so therefore we turn off the relay.(We will inject the 30mA with constantly alternating polarity.)Would this pass regulations? Why not? It surely guarantees safety, and is far cheaper than offtheshelf RCDs for 30mA/6mA which are £30 upwards.

author: nightfire
author_rank: Frequent Contributor
timestamp: August 30, 2021, 12:25:09 am
content: In a single-phase setup DC recognition is not used by many of those ICCB that are use to charge a car from an ordinary outlet.Reason: During operation, DC currents cannot happen.Depending on the stuff you want to do, it might not be necessary- here you would have to look it up in the applicable standards.Other question: If you really need a 6mA DC detection, why is a ready-made RCM module no way? They are regularly used by some big brands in their 3-phase wallboxes, which are sold in germany... In those a standard RCD Type A is used and a dedicated RCM for 6mA DC recognition is coupled via relay to a circuit breaker to switch off the box upon detection.Makes the setup modular and repairable.

author: Faringdon
author_rank: Super Contributor
timestamp: August 30, 2021, 09:34:29 am
content: Thanks, but those offtheshelf RCDs are upwards of 30 euros each.With an EVSE, i am not sure if the standards require DC detection, or just an assurance that any DC fault current wont blind the RCD.?I know the metrel EVSE testers actually do a test for DC leakage current, and if the EVSE doesnt trip at >6mA DC than thats a fail, (or at least, a fail according to the metrel tester)....whether its a standards fail i dont know.?

author: Gyro
author_rank: Super Contributor
timestamp: August 30, 2021, 10:03:54 am
content: REM Loop indefinitely (buy standards, understand standards, implement according to standards)!GOTO 10

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: August 30, 2021, 10:13:35 am
content: Quote from: Faringdon on August 28, 2021, 06:20:28 pmThat is not a type BType B's start at around £100The type is indicated by these symbols. It can be confusing, especially with RCBOs as the same letters are used for RCD type and overcurrent time characteristic, which was a really dumb decision by somebody

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: August 30, 2021, 10:24:23 am
content: Quote from: Faringdon on August 30, 2021, 09:34:29 amWhy are you not sure ? You have either read and understood the standards or you haven't. In the latter case you are just wasting yours and everyone else's time.Standards are not always the easiest things to understand, but things like this are usually pretty well specified.I only have access to BS62752, for in-cable level 2 EVSEs but I'd be surprised if the standard for fixed units is any different in this respect.This states :QuoteWhat's not to understand?

author: Faringdon
author_rank: Super Contributor
timestamp: August 30, 2021, 02:18:58 pm
content: QuoteThanks, BTW, sorry i forgot to add, that we dont need the type B RCD to contain the relay...just the signal.Also, BTW, RCD in EVSE is covered by standard EN62955 (which we cant afford yet) .....as you know, its a "30mA/6mA" RCD, and these can be made "home-brew" style very cheaply (a lot less than £100).....what is the cheapest you think a "home-brew" RCD (Type B) could be done for? (for use in EVSE)...and not inclduing the relay...just the signal

author: Zero999
author_rank: Super Contributor
timestamp: August 31, 2021, 09:50:50 am
content: Quote from: Faringdon on August 30, 2021, 09:34:29 amFor goodness sake. Don't be such a niggard. Spend the money. Failing to design this properly will result in greater costs, later on!

author: pardo-bsso
author_rank: Frequent Contributor
timestamp: September 01, 2021, 02:06:57 pm
content: Tangential to this,I'm not sure if I understand the problem properly.I assume (based on this thread and the others...) the current flows from mains, thru the charger and thru the car making a closed loop under normal conditions.A fault to earth or unsuspecting engineer will divert some of it, no matter if it happens before or after the charger and that difference will be picked up by an rcd upstream.At least here a simple test of that worked (and the quality of most of our breakers/protection devices is on par with Simons recollection of Italy)

author: fcb
author_rank: Super Contributor
timestamp: September 01, 2021, 03:02:20 pm
content: Quote from: pardo-bsso on September 01, 2021, 02:06:57 pmCorrect. But.... if there is a DC leakage current (EV battery charging electronics?) it can 'blind' a normal RCD (by magnetizing the CT). The 'Type A' RCD must not be blinded by <6mA DC - technically any more than this can blind/desensitize a 'Type A'.

author: Faringdon
author_rank: Super Contributor
timestamp: September 01, 2021, 06:25:11 pm
content: Thanks, is the DC leakage of 6mA (or more, eg 20mA DC) actually dangerous, or is it just bad because it can blind the RCD?

author: fcb
author_rank: Super Contributor
timestamp: September 01, 2021, 07:15:06 pm
content: Quote from: Faringdon on September 01, 2021, 06:25:11 pmIT'S THE FUCKING RULES!Irrelevant - it's just what the standards say.

author: Zero999
author_rank: Super Contributor
timestamp: September 01, 2021, 07:16:29 pm
content: Quote from: Faringdon on September 01, 2021, 06:25:11 pmDC is less likely to cause death, compared to the same mains frequency AC, but 6mA of leakage is still bad, whether it's AC, or DC.An RCD being blinded is only dangerous, if there's a lethal leakage current to earth. It isn't dangerous, if there's no leakage. RCDs only became widespread over the last 30 years. Before that, proper insulation, earth connections and fuses/circuit breakers provided protection against electric shock. RCDs are only one layer of shock protection.

author: pardo-bsso
author_rank: Frequent Contributor
timestamp: September 01, 2021, 08:58:09 pm
content: Quote from: fcb on September 01, 2021, 03:02:20 pmThanks! I totally missed that aspect.

author: nightfire
author_rank: Frequent Contributor
timestamp: September 01, 2021, 09:39:46 pm
content: And for this reason a RDC type B is not allowed behind a RDC type A- because the type B would allow for far greater DC leakage currents than 6 mA and therefore provide false safety.

author: Faringdon
author_rank: Super Contributor
timestamp: September 03, 2021, 08:38:08 am
content: Thanks,As you know, if there's only one item of equipment being supplied, then it doesnt matter if you use Type A and/or Type B, in any order, as long as a relay trips off the connections in the event of DC >6mA or AC imbalalance >30mA.

author: alexnoot
author_rank: Contributor
timestamp: September 03, 2021, 02:37:32 pm
content: I think your 'product' will simply not be needed.It will be badly designed, it won't adhere to any standards (as you can't afford them), and it will probably never work as you don't seem to know anything about what you're doing.What is your actual job?

author: Faringdon
author_rank: Super Contributor
timestamp: September 03, 2021, 05:52:03 pm
content: Thanks, Finance assistant at a startup in London(this is for a sensor which will detect 30mA imbalance current in 32Arms wires...and also detect 6mA DC and more.

author: Monkeh
author_rank: Super Contributor
timestamp: September 03, 2021, 05:57:19 pm
content: Quote from: alexnoot on September 03, 2021, 02:37:32 pmStacking shelves at Tesco. Or it should be.

author: Faringdon
author_rank: Super Contributor
timestamp: September 04, 2021, 11:36:11 am
content: Quote...Thanks, I am going to go into business making RCDs.They are the most over-engineered and over expensive thing in the world!

author: fcb
author_rank: Super Contributor
timestamp: September 04, 2021, 11:52:54 am
content: Quote from: Faringdon on September 04, 2021, 11:36:11 amGenuinely good luck for your venture.

author: Gyro
author_rank: Super Contributor
timestamp: September 04, 2021, 12:06:43 pm
content: Quote from: Faringdon on September 04, 2021, 11:36:11 amI'm not sure what you mean by over-engineered, I'm greatly in favour of devices that can reliably detect leakage current and safely interrupt at least 6kA, and obviously rigorously tested to meet all relevant approvals.You should also note that the IET wiring regs (which you have presumably purchased by now) stipulate that only breakers approved by a consumer unit manufacturer (basically meaning their own!) may be used in their enclosures. It's something of a closed-shop from that perspective - they will have no interest in approving your 'RCDs'. [Edit: In your case, Section 740 may have some relevance too.]Personally I think Monkeh has done you a great disservice, I think you should set your sights on Waitrose!

author: alexnoot
author_rank: Contributor
timestamp: September 04, 2021, 01:53:39 pm
content: Quote from: Faringdon on September 04, 2021, 11:36:11 amSo you've given up on your EV charger project then? Or is this just another thing?You should design your own electric car too! They are probably over-engineered and overly expensive too, a lot of corners could be cut to make one on the cheap!

author: Faringdon
author_rank: Super Contributor
timestamp: September 04, 2021, 02:02:59 pm
content: QuoteWe would just do a signal version...customer would need to put in their own contactor/relay.

author: Gyro
author_rank: Super Contributor
timestamp: September 04, 2021, 02:04:14 pm
content: Stop it, you're killing me!

author: Monkeh
author_rank: Super Contributor
timestamp: September 04, 2021, 02:07:56 pm
content: Quote from: Faringdon on September 04, 2021, 02:02:59 pm£30 RCDs are too expensive, let's make a £5 one to use with a £30 contactor!Good grief, it hurts. Please stop.

author: fcb
author_rank: Super Contributor
timestamp: September 04, 2021, 02:44:01 pm
content: Quote from: Faringdon on September 04, 2021, 02:02:59 pmI didn't see that coming. I guess time will tell if 'the people' want your idea. I'd probably do some market research before committing funds to this endeavour.

author: Monkeh
author_rank: Super Contributor
timestamp: September 04, 2021, 02:56:13 pm
content: Oh, and in this genius plan of yours, have you calculated the operating costs of the contactor coils?Your imaginary savings are just that.

author: Gyro
author_rank: Super Contributor
timestamp: September 04, 2021, 04:58:43 pm
content: You probably also want to look at pictures of the internals of an RCD - contact opening speed, spacing of open contacts, arc cooling plates, arc chute etc. and compare with a typical contactor - there's no comparison. I don't know where you could source a contactor / relay style device that would have similar construction - at any realistic price anyway.You probably have a signal level driver with absolutely nothing suitable to drive! You definitely need to start researching this stuff before you come out with it.

author: Faringdon
author_rank: Super Contributor
timestamp: September 04, 2021, 05:25:56 pm
content: QuoteThanks, but sorry if i misled.........if you buy an RCD that contains a contactor, then its a minimum of £100 that you'll be shelling out.!.....Type B RCD with contactor...£100...cheapest out there!!!https://shop.evchargersdirect.co.uk/products/type-b-rcd-rccb-40a-for-ev-charge-point-installations-2-pole-single-phase-30ma-ekl1-63?variant=31988378140768&currency=GBP&utm_medium=product_sync&utm_source=google&utm_content=sag_organic&utm_campaign=sag_organic&gclid=EAIaIQobChMI3LzRxenl8gIVrWYVCB2f5wIQEAEYASABEgIRT_D_BwESoon we will take this market!Quote...we would source from our Chinese contacts....just like everyone else already does....including the so-called "standards compliant" ones.QuoteThanks, we will indeed make some that contain both signal circuit and contactor.

author: Monkeh
author_rank: Super Contributor
timestamp: September 04, 2021, 05:29:49 pm
content: Quote from: Faringdon on September 04, 2021, 05:25:56 pmThat has nothing to do with 'containing a contactor' and everything to do with 'type B RCD with low volumes'.You're not taking any market. If you do somehow get to market there's no way I'd ever trust a product you've had a hand in anywhere on my property.

author: Faringdon
author_rank: Super Contributor
timestamp: September 04, 2021, 05:33:34 pm
content: QuoteThanks, but you cant really buy them much cheaper even if your volumes are high.....and to be honest, if you have high volumes...the lead times theyll give you are so ridiculously long

author: Gyro
author_rank: Super Contributor
timestamp: September 04, 2021, 05:41:31 pm
content: Quote from: Faringdon on September 04, 2021, 05:25:56 pmThese are presumably the same Chinese contacts (Customer?) that you haven't yet told that you have no clue what you are doing, and who are currently spending their money setting up multiple production lines!There is no 'so called' when it comes to safety standards! Not unless you personally import fake shit anyway!

author: dmills
author_rank: Super Contributor
timestamp: September 06, 2021, 12:51:47 pm
content: There actually ARE 'earth leakage relays' that control external contactors, but you will not find them in domestic or even small scale three phase installs, these go to the industrial panel builders and are typically used together with zero phase current transformers and some seriously butch shunt trip switchgear. Remember an RCD is NOT AN OVERLOAD device, it does NOT have to break the PSC, so it has a substantially easier switching role then an RCBO or MCB has.Nobody playing in this space gives a shit about a hundred quid for a safety component, in fact I get increasingly twitchy as the price of such things falls.Also, nearly nobody pays list price for this gear, you generally get at least 20% off down the wholesalers for knowing enough to ask for it.