Maybe you connected with single phase just one element? The rest two remained unconnected? (3 230 volts elements, connected wye). I'm sure it heated up faster, in 3 phase connection.
Probably.
Interesting. Around here I see control boxes on the pole-mounted ones. Maybe they have something to read. (I know some read SIEMENS in large letters on some of them, apparently the manufacturer)
Long ago, during one of the past "oil crises" (1973 or 1978 or so) they proposed cutting back the voltage delievered to one's home by 5-10% from the normal voltage, a "brownout", "to save energy". I once wondered how they may have done that, assuming any automated regulating equipment was hardwired to provide 13.8kV or whatever, and that setting couldn't easily be changed. Also, any automated regulators downstream would try to compensate for the lower supply and raise their output voltage, so all regulators would have to be adjusted. But if was done manually, for equipment not tied to a particular voltage, they could do it on a substation-by-substation basis, and ones "downstream" could have been left alone.
There should be no problem with the frequency, the local US base (In Gournes-decomissioned after the end of the Cold War) used a regular 15 kV,
50 Hz feed, from the cretan grid, which was stepped down to 4150 volts and then to 120/240. All with US switchgear and tranformers! (NB for US guys.#10 wire gauge->10 mm2 main feed of residence, #12 ->6 mm2 stove,#14->4 mm2 water heaters, #16->2.5 mm2 washing machines, dryers, #18->1.5 mm2 lighting.-approximately). I think that the personnel of the base used standard US fluorescent light fixtures and other equipment, sone of it was left as some of the buildings "inherited" by the greek state, were converted by us to 230/400 volts, with regular Schuko receptacles.
What I was talking about appear to be used to adjust for supplied voltage (they're often used right after a stepdown transformer bank) or long runs, which may produce somewhat variable voltages that need adjustment at times.
Around here, capacitors for power factor compensation are rectangular boxes with two bushings on top, on poles, in banks of 3, 6 or sometimes 9.
Like the ones Phil mentioned, the cans I talked about hum.
The Philippines uses 220V 60Hz with US-style 2 blade outlets as well.
| ? ?????? ??? ?????? | news: snipped-for-privacy@news3.newsguy.com... |> In alt.engineering.electrical Tzortzakakis Dimitrios |> wrote: |>
|> | Professional washing machines. One of my very first days 'in the field' |> was |> | to connect some of them. They have a large heating element, you can |> connect |> | it single phase, or 3 phase, it just heats up faster (of course) when |> you |> | connect it 3 phase. (they have a single phase motor, so it works also in |> | pure 230 V). |>
|> If it has 3 elements rated for 230 volts, with 3 separate connections that |> would be to three separate phase for a three phase feed, and all connected |> to the one phase for a single phase feed, then it should heat up at the |> same |> speed, while drawing three times the current (not accounting for the |> motor). |>
|> I don't know why it should heat up faster in three phase, or why you would |> say "of course" about it. I would think it would heat up faster if you |> took |> it over to London and hooked it up to a 240 volt supply. |>
| Maybe you connected with single phase just one element? The rest two | remained unconnected? (3 230 volts elements, connected wye). I'm sure it | heated up faster, in 3 phase connection.
You were the one who said "it just heats up faster (of course) when you connect it 3 phase."
I would disagree.
But the fact that you said "(of course)" seems you presume that to be the general case. Now your most recent comment at least acknowledges that if not all elements are connected, it won't heat up as fast.
In the simple case, each of 3 elements is individually wired, so you have a total of 6 leads. When connecting to three phase, one lead of each is connected to neutral, and each of the other leads is connected to separate phases. When connecting to single phase, they are all wired in parallel. Both cases always involve one of the leads from each element connected to neutral, so those 3 leads can be pre-connected together. So you could have just 4 leads. The common neutral lead needs to be rated for all the current together for it to be rated properly for single phase.
It should apply the same voltage (230V) to each element, and they should each draw the same current. How would you believe this would be slower to heat?
If the 3 elements were wired _internally_ in star without a neutral lead, it would still work fine on three phase as long as all elements were equal impedance. But on single phase, you could only activate 2 of the elements, and that would be 2 in series fed with 230 volts. You'd only get 1/6 the power that way.
Are you assuming the elements would be wired that way? That would clearly NOT be intended for single phase connection.
The 3 elements could be wired _internally_ in delta. In this case, these would have to be 400V elements. Connecting 2 leads to 230 volts would still give you only 1/6 the power (but more evenly distributed in this case).
So what is the situation that makes _you_ believe that 3 elements connected to single phase _will_ draw less power to heat the water than when connected to three phase?
--------------------------------- Actually I see added complexity without any gain. You may be doing the tap changing at a lower current and higher voltage but there will be no "lower Power" switching but there will be more losses during operation even when not changing taps. I suspect the complexity and the losses together would cost more than a conventional tap changer. There are some circuit factors involved which may be undesirable but I haven't done a proper analysis.
------------------------- Fair enough- but still overkill. For the bulk of the calculations that one does, single precision is more than adequate. Anything more, even for comparison of numbers is really fluff. I simply set my display to show the desired sig figs and let the calculator deal with the rest in its normal internal mode. I don't want to see the extra digits, or , if I do, 1 or 2 is sufficient. Ditto with the computer. Only if I am dealing with ill conditioned sets of simultaneous equations , will I really require double precision.
NameNotImportant wrote in news:CfWdnQNR9cg0wbHVnZ2dnUVZ snipped-for-privacy@earthlink.com:
pounds (mass), lbm, as opposed to pounds (force), lbf, or lb.
It is necessary to distinguish between mass and force but they are both measured in pounds in the english system.
Metric is 'much simpler' with grams(mass) and newtons(force).
The "English" system uses the "stone" as the measurement of mass. The pound ('lb') is the unit of *FORCE*.
Evidently *you* think the "English" system is too complicated. ;-)
krw wrote in news:MPG.2297621d47f3215f989c18 @news.individual.net:
However, FAILURE to convert has been known to cause problems, such as a Mars mission that crashed because the wrong units were used.
The 'Stone' is a unit of mass, not "The unit of mass"
All the engineering I ever learned in the British (Imperial) system used pounds.
No - the modern Metric system uses the kilogramme as its fundamental unit.
I always thought the British pound was a unit of currency. :)
Anthony
It is *the* unit of mass. The pound-mass is a recent abortion.
You must be a kid.
Only if you spell funny.
cleverly, we use the same word for two different things to confuse foreigners.
No - 68!!!
Even in 1961 the MKS system was the norm.
If you call the past 100 years or so, 'recent'. I myself have text-books from the '50's that use this 'recent abortion' as you call it.
Considering the separation of force and mass was first worked out *after* the original 'pound' for weight was in common use, it was necessary to separate which 'kind' of 'pound' was being talked about. The one that represents how much *force* is being applied to something, or the one that describes how much resistance to acceleration something has.
But for a long time a 'pound' of something was a certain amount of mass -or- the force applied to a surface by placing that certain amount of mass on it (such as used in 'dead-weight' testers for pressure instruments).
In a few obscure bits of engineering, you can even find the term 'kilograms of force' used. Obviously that is the force applied by placing a kilogram of mass on top of something. You can even find some pressure gauges calibrated to read 'kg/cm^2'. Proof that you can mess up things even with the metric system. ;-)
I'm not sure how old the 'stone' is, but I suspect it too was around before we knew the difference between force and mass. Stone is common in UK still, but it never caught on in the colonies, even as far back as colonial days when 'hundredweight' and 'long ton' were in common usage.
Trouble with pound-mass (lbm) and pound-force (lbf) is that to make F=MA work out, you need to keep another 'conversion factor', the dreaded g-sub-c (g-sub-c = 32.2 lbm-ft / lbf-s^2), around and figure out when to throw that into the mix.
daestrom
"daestrom" wrote in news:482e26af$0$5117$ snipped-for-privacy@roadrunner.com:
:)
Really gets to be fun when working with things like foot-pounds, as in torque, angular momentum, and the pressure due to a certain depth of water. Trying to remember when the pounds are mass and when they are force gets to be fun.
I first heard pound-mass about ten years ago. All through high school and college the English unit for mass was the stone (as in the FSF system of measurements).
Sure, but you still spell like a frog. ;-)
In the early '50's there were two other units around- the poundal (1/g pounds force) or a mass called a slug (g pounds mass). Learning mechanics with these units (don't use them together)is worse than working in the stone, furlong, fortnight set of units. The poundal was introduced in 1879 as part of the "english set of units" (Wikipedia is sometimes useful).
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