What you stated above is not the case. I donn't know what "several posts" you are referring to. There are many posts in this thread. The situation you describe won't happen if you pay attention to the operation of the circ uit and consider that the components are not chosen randomly.
Did YOU have a point? Care to explain it rather than refer to an arbitrary "several posts"?
Rick C.
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No. Because I've already covered all the failure cases I can see in excruciating detail.
I don't intend to repeat myself because you choose not to be bothered to read them.
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rary "several posts"?
We already discussed that and I explained that K3 will drop out because it is specified and selected to drop out in that situation.
You replied that it "may not" perform adequately which is not the same thin g as saying it can't be designed to work adequately. You seemed to say the relay won't provide the required 3 mm gap which you can't know if you don' t know what relay is being used. Where did you get this idea? Then you ta lked about "all" loads without explaining a problem scenario. Yes, I expec t there could be a problem if this circuit is feeding a motor with the abil ity to back feed power into the circuit. So I suppose this circuit would n ever meet code. But for the use intended it should be fine. There are man y code violations that only happen when something is misused.
Repeat yourself or not, if you don't say anything worth replying to you are n't likely to get a reply. It your point is that certain requirements must be met to make this circuit safe, fine. But saying things like "it's a ho rrible design" aren't in any way useful.
Discuss the issues or not.
Rick C.
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D you install a tandem 220 breaker OF LOWER RATING than either of the branc h circuits coming in.
Just to be clear, the scenario you describe here will *NOT* produce a dange rous situation. There will be no current backfed from the load unless the "load" is another 240 volt power source. Is that what you are talking abou t??? Don't connect any power sources where the load is expected and you wo n't have a problem. That can happen without a Y cord. Any extension cord becomes dangerous if you feed power into the load end.
Rick C.
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Right all 'helpful' individuals are informed that there is no power, the generator is running and not to go outside and energize the AC cut-off switch. It only happens once every few years, and I don't worry about it.
But people always complain when I describe what I do.
George H.
I wouldn't do that. Regardless if there is no one else around, proper safety procedures require you to use a lockout padlock. There may come a time when you are distracted, forgetful, or just plain stupid. This has happened to me many times. I would not trust myself to work on "safe" circuits that could kill me if I gave them half the chance.
Always, always follow safety procedures. Never, ever bypass them.
For example, look at the number of airplane crashes caused by pilots not followong proper procedures. They forget to lower the flaps for takeoff, forget to do the checklists, forget to lower the landing gear when needed, and all kinds of other human failures. These often result in serious damage and loss of life. These are professionals who do this for a living, and they still forget.
Don't let your next mistake be your last.
I see nothing to show that it does meet the necessary conditions - I was critiquing the design in general. As the circuit provided did not supply part numbers, I always take the most pessimistic view.
It is certainly a horrible idea because it is difficult to select parts that will make it safe and even more difficult to guard against the edge cases in which it will fail unsafely.
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It doesn't sound especially dangerous. Don't grab that male-male plug when it's hot; that might sting a bit.
We are electrical engineers!
-- John Larkin Highland Technology, Inc lunatic fringe electronics
I despair...
Current can be backfed from one of the two 120V supplies via the load's impedance and there are cases I can see where it is not wholly unfeasible that having been energised, all relays may see enough coil voltage to hold them closed even if one 120V hot goes away.
I refuse to argue with you any more.
If you want to maintain this is a safe circuit, do what you like.
To anyone else who actually cares: they can make up their own mind.
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Sure. Children OTOH sometimes find things lying around & stick them in their mouths.
NT
Good thing doctors are immune to that principle. They don't even use checklists.
Rick C.
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itrary "several posts"?
to
it is specified and selected to drop out in that situation.
thing as saying it can't be designed to work adequately. You seemed to say the relay won't provide the required 3 mm gap which you can't know if you don't know what relay is being used.
aren't likely to get a reply. It your point is that certain requirements must be met to make this circuit safe, fine. But saying things like "it's a horrible design" aren't in any way useful.
I think you are not being very constructive at all. Every home charging un it sold uses a relay to provide protection against flash on unplugging and other potential problems. They obviously can easily meet the 3 mm requirem ent. The rest of your concerns are very simple to protect against by selec ting parts that do the job correctly. All you needed to say was, "make sur e you select parts to meet all safety requirements" instead of "It is certa inly a horrible idea" which is entirely unsubstantiated.
Rick C.
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Good, because that is all you are doing... arguing. You don't provide any useful info. I have explained to you repeatedly why this won't happen and you don't discuss the facts, you just continue to make the same assertions.
Yes, they can. Thanks for providing some insight.
Rick C.
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I always get the same reaction. Some good samaritan is going to come along, open up my disconnect box, energize the line and kill someone.
I get similar responses when I tell people about floating my 'scope.
I'm not going to mention the times I hot wired electrical lines in the lab 'cause the electrical box was locked and if you put in a work order it would be a week till an electrician would show up.
George H.
If I told you there was a padlock on the disconnect box would you feel better?
It's very hard to forget that the generator is on, the new one is quieter than the old one, but still makes a racket.
George H.
We have a Tek TPS2024, with fully floating inputs and trigger. That's very handy some times.
On my bench, I have eight things that are always powered, and sometimes four or six more for some tests. And one wall outlet [1]. Power strips plugged into power strips! The loads are tiny. The most dangerous things in my office are a ladder and a box cutter.
All the bookshelves and such are bolted to the walls in case of earthquake.
[1] it's a dual, but one outlet is switched pseudo-randomly by absurdly complex motion and room light sensors that the city thinks will save energy.-- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
I recall seeing a Chinese system that used capacitors and every bus stop had a connection for a short recharge during the stop. Found an article.
Mikek
Most EV batteries are around 400V. We just need the source to be high enough to avoid the DC booster. There is not much advantage of going kV. There is also higher chance of shock with higher voltage.
480V 100A should be enough.
A problem for suburban and rural bus lines is how to provide high peak currents to the bus stops. Taking it from a local weak network would dim the lights when there is a bus at the stop. Alternatively running dedicated medium voltage lines along each bus route and using step-down transformers on each bus stop would be quite expensive.
Arranging MV feeds to the end of the line only would be easierm which of course requires a bigger battery capacity.
The DC booster might not be a bad idea.
On the mains side, you may need some PFC, so that the charger doesn't generate too much mains harmonics.
Using a DC booster also provides a nice way to have an isolated supply and in case of ground leakage or short circuit, the output voltage can be dropped in milliseconds.
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