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| Do you guys use an isolation transformer for your lab/workbench? |
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| AVGresponding:
--- Quote from: Electro Detective on February 03, 2023, 10:35:35 am --- --- Quote from: tautech on February 03, 2023, 01:58:10 am --- --- Quote from: timeandfrequency on February 03, 2023, 01:45:11 am ---I couldn't find any seller that only sells one glove. --- End quote --- :-DD --- End quote --- Bob has you covered: :-+ www.bobthewelder.com.au/products/xt-left-handed-welding-gloves-green-long --------------------- FWIW folks: 30ma RCDs rarely trip at 30ma Anywhere from 15 to 28ma is what usually happens, and a good unit will have about 2 to 3ma repeatability i.e. test the suckers properly before trusting your life and gear with them, better still, use two RCDs piggy backed. One of the two 'may' trip 'faster', or both will work if the trip current approaches zap city. But they won't do you much good with an electrical fault or short in the chain, so..FUSE UP, just past the DUTs current rating, and you won't need an imitation rabbits foot or garlic necklace :phew: --- End quote --- Yes, unlike fuse or circuit breaker ratings, the RCD trip current is the maximum allowable for it to meet its standards. This is a pretty good source of info on RCDs: https://www.eaton.com/content/dam/eaton/products/electrical-circuit-protection/circuit-breakers/xeffect-rccb/eaton-rcd-application-guide-br019003en-en-us.pdf |
| nightfire:
While we are getting into the topic of RCD: a) They usually trip in between 0,5*rated diff. current and 1*rated diff.current. Usually manufacturers try to adjust the ti the middle of that range when they are new, so usually those RCD trip between 20-25mA for a 30 mA standard type. b) When relying on RCD protection: Which waveforms do you expect? If it is not sine wave, the standard RCD type A would not do much... German manufacturer Doepke has very good material there, called "Allstrom Fibel", downloadable as pdf. Also some general notes on RCD and stuff. (www.doepke.de) |
| themadhippy:
Out of curiosity do the rules for GFCI in the states stipulate a disconnection time,ive had a quick google but find conflicting advice,the only thing that made sense was T = (20/I)1.43 , but this seems to give longer times than permitted in the uk,so whilst ours have a higher current before operation it appears ours must operate faster |
| nightfire:
In germany, the corresponding standards mandate a maximum of 0.3s, the low voltage regulations ((up to 1000V) mandate 0.2s above 230V- in reality a fresh RCD in mains installation is tripping faster than 30ms- older models can take a bit longer, in some cases due to old grease in them. This is also the reason why those RCD should be actuated in regular intervals, to prevent grease hardening etc. |
| wilhe_jo:
Just a thing to consider... Even at some none budget suppliers website, a differential probe is at 200.- I got my vintage Tektronix ones very well below this... Migsig ones are below 100.- Do you really want to risk touching life mains, or do you want to risk mains/Gnd short just because it always was like this? I had quite a enlightening event with a client (10B/a revenue!) some years ago. When I arrived, I was taken too seriously, because I got there with dated stuff.... Yeahh... Ok..I sell knowledge not decoration ... Then they got their measurement rig up.... Probing with two brand new Lecroy HD Scopes and 2 isolation transformers (also fresh from the egg).... Perfect. Effectively they had 2 usable channels per scope. And using the touch screen is out on the intentional use.... Yeahh. That's the way I want to work! They were frightened about frying the touch... So we had to shutdown power for every interaction with the scope.... Really, get diff-probes! 2x diff probes 1 current probe That's what you want to have for single phase! Just to be clear: my 3 phase dif-probes and my 3 phase current probes were around the price of the 2 premium iso-transformers. Apart from this, a RCD protects you from things, somebody clever hasn't thought about (or is really, really, really unlikely). Debating whether ab RCD is an appropriate safety measure to protect you from common mistakes is ... brave. Work as if you were drunk! Honestly. That's pretty much what happens in accidents due to laziness or distraction. Diff-probes keeps the RCD on your side. An Iso transformer makes the 10+A breaker your only friend! Oh, yes I work with isolation transformers... A LISN needs that... But you can reduce the pain... 73 |
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