Voltages used in "neighborhood" power distribution

Hey Don,

Finally someone explains it, thanks so much Don, so the percentage is a number assigned by factory right? You can't calculate it from input parameter can you? If you can let's see if you can calculate this real data:

a.. 3 Phase a.. 60 Hertz a.. Class: OA a.. KVA Rating @ 5,000 Ft. Altitude: a.. 2,500 Continuous 55°C Self-Cooled b.. 2,800 Continuous 65°C Self-Cooled c.. 3,500 Continuous 65°C Future Forced-Air a.. Primary Voltage: 24,900Y / 14,400 Volts a.. Secondary Voltage: 4,160Y / 2,400 Volts a.. HV Winding: Copper a.. LV Winding: Copper a.. Connection: Wye/Wye a.. Impedance: ?? % @ Rated Volts @ 2.5 MVA

All that I have done is give an example of what Salmon Egg stated.

The % value is determined by actual factory test measurements of the impedance. I can't calculate it from the data given. All I can do is what Salmon Egg mentioned- in a given range, transformer impedances will all be close to a typical values .This one falls in about 6%.

Note that the winding resistance is much lower than the reactance so X/R =10 to 12 is typical in this size and resistance can be ignored in such things as short circuit studies. If the transformer was boosted to 2800KVA the actual impedance would not change significantly so the % impedance would change to about 5.4 % from 6%

The only live experience I have with 50/60Hz transformers is on smaller va units....say under 300va units. The lamination sizes were always aprox double the weight of same iron gauge. I have been told by design engineers that on larger units this still roughly applies but have actual experience with the figures. I have torn apart 33MVA transformers but have no size comparison for 50Hz, never being in the UK or other countries with the S-L-O-W-E-R frequencies.

It would surprise me the Can Oxford Dictionary would state both spellings are OK as "center" was never an acceptable spelling for the word in Canada.

However, somebody has now edited the "Billion" definition on wikipedia to state that Engilsh Canada uses the 10^9 and French (should be french) Canada uses the 10^12 definition, similar to most of Europe. I was educated to believe that a billion was always 10^12 (bi-million) and that only the USA used the 10^9 billion definition. Now I am reading that Britain converted in

1974 on a flippant remark from parliament and Canada has also, except there is no back-up reference of when, who, what or why. **SIGH**

We sit in the middle of it all between the US and the Brits, confused how to say "Z" and still make the nursery rhymes rhyme....LOL

I hope this doesn't change GigaBytes or TeraBytes! Those big quantities are changing things to be common place faster than we like sometimes.

On that note: a question???

What is the quantity "milliHelen" (see bottom of post for definiton)

As for center vs centre- (US vs UK) both are valid according to the Canadian Oxford Dictionary- so being neither a Brit or a Yank, my choice is dependent on the colour/.color of my mood.

In terms of electrical supply as with language details - what exists in different regions is a rational approach (mostly) based on historical choices (right or wrong- the conversion in the latter case becomes irrationally prohibitive).

Cheers

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"milliHelen" is a measurement of beauty! The quantity of beauty it takes to launch one ship.

Yup, we designed for 13.8kV an attempted to ship 14.2kV from ou stations.

13.8kV (again, line to line).

Charles Perry P.E.

For a given voltage, maximum flux density and turns per winding, the core cross section is increased by a factor of 1.2 so the core side length is increased by a factor of nearly 10% (square cross section). Assume a square core window (not true in general) and the same winding window area, the average core length and width increase by a factor of 1.2 leading to a volume/weight less that 1.5 times that at 60 Hz. Twice the weight is a conservative estimate and may involve factors other than frequency dependence. The core dimensions of 300VA transformers (50/60 Hz) are affected by a number of factors-of which cost and customer reaction are dominant. Hammond put out reasonably priced transformers which sacrificed core losses in order to have better voltage regulation [balance between core and copper losses for a given price]

"Josepi" wrote in message news:h30fo.103954$ snipped-for-privacy@newsfe07.iad...

Boy are you ever lost...

There isn't really any accurate math formula to compute the output winding. For instance, you guys like to wind your transformer using inner window area, I get more output power using outer core. 150V as supposed to get

100V.

After all that cunning display of accuracy and knowledge I doubt you meant to type 10^6 twice (Two times for the USanians)...LOL

My family has been in Canuckistan since the early 1700s when a ship from "jolly old" sank off the banks of Newfoundland...4 miles out. Only one survivor swam ashore. Fiance (sp?) came years later and we had offspring in rabbit succession. Funny thing is, we have a long list of swimmers in our family. One cousin was set to take gold in the Russian olympics that were boycotted years back. Son swam for the Ontario championships. Funny coincidence but I hate my webbed feet!

As to billion - In general usage in Canada, economically and in general ,the 10^6 value is what is used. Do you think that Quebec uses a different value? Does the world of economics use a different value? I recognize (recognise) that these differences exist so kilo/mega/tera make more sense. For Canada,within my memory (I am approaching 79) the 10^6 value was a billion.

Don Kelly cross out to reply

---------------- It is the interior window area that physically limits the winding net cross section (turns, conductor cross section and insulation) -either HV or LV- half the winding is inside the window. So we have a balance between conductor cross section (i.e allowable current) and number of turns( voltage) for a given rated power. Once the voltage and KVA ratings are fixed, then it is a choice of balance between of core and copper losses for a given $ input and load profile (is the average load going to be 50% of rating or 90%- it makes a difference).

Possibly you could clarify "outer core" vs "inner window" which are two different things-neither of which determine power. (100V vs 150V is not power).

Officially, I have an edge- Newfoundland wasn't part of Canada until 1949. There is also the possibility, not proven (damn, no tax benefits) that some of my ancestors were complaining about illegal immigrants.

I like the "rabbit succession" a common factor!

So you were a foreigner until Newf joined into our great country?...LOL

Officially, I have an edge- Newfoundland wasn't part of Canada until 1949. There is also the possibility, not proven (damn, no tax benefits) that some of my ancestors were complaining about illegal immigrants.

I like the "rabbit succession" a common factor!

Hey, we sent you the moose as an alternative to salt cod, in return for Newfie jokes! :>))

I like a nice rack!

"Don Kelly" wrote in message news:6shgo.102571$f snipped-for-privacy@newsfe17.iad... Hey, we sent you the moose as an alternative to salt cod, in return for Newfie jokes! :>))