the danger of higher power levels, voltage vs. current

"TimPerry" > | how about phosphorescent strips? no heat, no moving parts

Tritium. That's what the two T's in the "T SWISS T" mean at the bottom of some watch dials.

Tritium has been replaced with something else now, can't remember what ...

Reply to
Nicholas O. Lindan
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Not necessarily true. I have seen 5 VDC Power supplies for banks of memory in video equipment that have vaporized circuit boards due to the arc-flash and the large current capabilites available. The arc was literally as hot as a commercial arc-welder. All it takes is a short circuit in the wrong place (in one case, it was a technicians screwdriver).

The key is to subdivide the current branches with individual, well-designed fuses or circuit breakers. Edision understood this when he was constructing the first DC Central Station system in New York and had to be concerned about safety.

Another example...In the case of a telephone company it is very common to use large DC supplies common to hundreds or thousands of customers. In this case, individual impedences are placed in every subscriber line to limit the current in case of a direct short.

Beachcomber

Reply to
Beachcomber

I asked an electrician neighbor if he ever got to work on something big and bad like "480 volts at 4000 amps or anything like that" and he responded that he worked on 600V and 550V systems at times, so there may be some 600V systems around in Mass. (I asked further about the

550V systems, he said it was common in the old mills and factories around here. I once worked in an old mill building and there was a conduit marked 550 VOLTS running around feeding the ancient elevators. Parts were still knob-and-tube)
Reply to
Michael Moroney

not right.

common

not correct.

Delta. 230 between phases. any line to ground or grounded neutral is 115 volts. If it was a wye, you would get 115 any line to ground and 230 or whataver its wound for between phases. yer 400 volt notion does not align.

If you have a combination wye / delta (two diffferent transformers in series) with any range of taps mid phase then you can get all sorts of strange anomalies of which you are beating around the edges of.... 277 volts primarily for lighting... 115 to ground for recepticles, and some single and

3 phase 230 for motors....still 400v would not be commonly arranged,..you might get a stinker close to that range...a single line to ground...not used for anything in that case by itself.

Phil Scott

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Reply to
Phil Scott

|> |> You'd have 400 volts between phases in that, right? | | not right. | |> | |> | 230 the way the gen set was wired. |>

|> But if that was 230 volts 3 phase, and each phase was on a | common |> neutral, you have 400 volts between phases. | | not correct. | | |> Was it wires wye/star or |> delta? Or maybe 230Y/133? | | Delta. 230 between phases. any line to ground or grounded | neutral is 115 volts. If it was a wye, you would get 115 | any line to ground and 230 or whataver its wound for between | phases. yer 400 volt notion does not align.

The 400 volt was for 230 between phase and ground. The exact values are closer to 230.94 and 400, or 230 and 398.37. You must be describing a single phase Edison style system to get

115 and 230 volts.

Since you said 230 volts and 3 phase, what came to mind was the

400Y/230 system standardized in Europe (with actual voltages in various places ranging from 381Y/220 to 416Y/240).

But if you get 115 and 230 in a 3 phase delta, then it sounds like you have the kind of system where one of the delta windings is center tapped and grounded so you can get 115 volts between ground and TWO of the phases. The third (often called high leg or wild leg) phase would be 200 volts to ground. Lots of 3 phase power is delivered in the US like that, but the voltages are standardized at 240, 120, and 208.

| If you have a combination wye / delta (two diffferent | transformers in series) with any range of taps mid phase then | you can get all sorts of strange anomalies of which you are | beating around the edges of.... 277 volts primarily for | lighting... 115 to ground for recepticles, and some single and | 3 phase 230 for motors....still 400v would not be commonly | arranged,..you might get a stinker close to that range...a | single line to ground...not used for anything in that case by | itself.

I have no idea how you could wire a wye transformer in series with a delta transformer. I assume thats what you mean by "two different transformers in series".

What is the frequency of the system? 50 Hz? 60 Hz? That might be more telling about what kinds of configuration you are designing for. Since you mention 277 volts, it sounds like a 60 Hz system as I have seen that voltage only in 60 Hz systems.

What did the generators produce? Wye? Delta? From there you can transform it to other voltages and other configurations. If the transformers have delta primaries you could be running the generators in either delta or wye.

Reply to
phil-news-nospam

a

grounded

115

between

exact

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in

sounds

windings

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leg

phase

It could have been 240 .. that was 20 years ago.. I know it wasnt 400v to ground, and that we had both single phase

230, three phase, and 110 from the generators.. and yes there is stinger with that arrangement.

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look up various transformer configurations in a basic power distribution manual, there are many options... you sound like you would be fully familiar with these strategies.

might

designing

I designed and built it in 1982 aboard the Hawaiian Princess (Honollulu, 200' fisher processor)..its not a project in progress.

the 277 was mentioned in context with other systems entirely... commercial lighting on land... not on this boat at all.

you can

the

generators

We wired it delta as discussed above.

Phil Scott

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Reply to
Phil Scott

| It could have been 240 .. that was 20 years ago.. I know | it wasnt 400v to ground, and that we had both single phase | 230, three phase, and 110 from the generators.. and yes there | is stinger with that arrangement.

Then it sounds like 230 delta with one side center tapped for 115 volts, and a 200 volt wild leg.

| look up various transformer configurations in a basic | power distribution manual, there are many options... you sound | like you would be fully familiar with these strategies.

I've seen many. Probably just about anything can be done with enough creativity. But making it economical is another matter.

| the 277 was mentioned in context with other systems | entirely... commercial lighting on land... not on this boat at | all.

Ah, OK. The common 480Y/277 where industrial motors use 480 in a delta connection to the wye, and lighting circuits connected to get 277 volts to ground (common for fluorescent and HID lighting that voltage is available).

Reply to
phil-news-nospam

I priced rack mount computers versus regular AT chassis. The AT machines cost way less, and I put them on 'bakers rack' wire shelving. They are inexpensive and since they had wheels, I could pack them all into the back of the computer room, just had to roll out the shelf unit I needed when I needed physical access to them. Not quite as many systems per square foot as racked systems, but it saved me way more money than the cost of the additional square feet of computer room.

--Dale

Reply to
Dale Farmer

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