Gentlemen, although this may exceed the borders of this list's topics: I have been facility manager of a large research company in Germany for 36 years now, I have seen many others, talked and bargained t with many power providers and thus have a good picture of the power supply situation in Germany and, though limited, in Europe (The British sometimes refuse to belong to Europe :-) ). I want to explain some things for all to get the right idea of how we are running this country electrically:
I want to bet that there is not a single machine shop or even factory in all of Germany still running a rotary power converter, except for some antique fly wheel DC welding generators or the railway repair teams with their 16 2/3 Hz machinery. We have in Europe 500 kV to 1 MV DC European compound lines between states and countries 380 kV AC power plant and large city connections 220 kV federal state distribution lines 110 kV lines for very large customers as steel companies etc. 50 and 20 kV for city and local supply and large consumers (10 kV for low energy density regions, dieing out) 400 Volts for all others and that's it - all three phase Y, center grounded, down to the smallest village, farmstead or house. A small to medium farm hereabouts needs about 50 to 100 kW at hop harvest time, so this installation is quite necessary. Neutral is made at every 20 kV / 400 V transformer station individually by a grounded lead system, connected to the center tap of the transformer(s) and distributed as the fourth lead, though less in diameter, in the cables. From 10 sq. mm down a fifth lead is split from the neutral lead and used as protective earth (PE) in the buildings, which usually happens at the distribution box at a building's cable entrance. 230 Volts for ordinary home use is made by simply splitting off a single phase, each referenced to neutral. This is part of the basic supplying conditions set by the power providers, not to get by when erecting new appliances or buildings. And low voltage lines, i.e. 400 V, with the exception of low density regions, are all cabled underground, even in our little village. We had the roof mounted power line on our house replaced some years ago by underground cable on our own demand (it was an obstacle for the observatory) which cost about 2000 D-marks at the time, maybe $ 1000 at the time. I am sure this is the most reliable regional supply I can imagine. There is a lot to do, let's wait for it! Peter Blodow Jon Elson schrieb: > On 03/16/2011 2:00 PM, Peter Blodow wrote: > >> Jon Elson schrieb: >> >> >> >>> When using a 2-phase to 3-phase converter, the motor's center point is >>> NOT at ground potential. >>> >>> >>> >> This is highly dangerous. Never let a motor float electrically! It's >> wire insulation could be stressed with any voltage to ground, e.g., if >> the high potential DC circuit insulation fails! >> >> > Well, there are many thousands of users running shops, even fairly large > commercial shops > with rotary phase converters in this manner. Assuming most of these > motors are 240/480 > Volt motors and are being run from 240 V single-phase mains, their > insulation is not being > overstressed. Also, running a motor this way is IDENTICAL in voltage to > running from > a center-grounded open-delta system. This has one traditional > center-tapped 240 V transformer > as is used in residential service, with one additional 240 V transformer > to provide the 3rd phase > wire. There are thousands of commercial shops using this service > provided by the utilities. > This allows you to run 120 V appliances from the same service as the > 3-phase loads, which > is a major convenience in the US. The alternative is either 120/208 > 3-phase, or separate > single and 3-phase feeds, or providing your own transformer for office > loads. > > Jon > >>> This is also true when using several of the unbalanced 3-phase supply >>> systems available in the US, such as corner-grounded and center-grounded >>> open delta supplies. >>> >>> >>> >> Center grounded sounds not so bad. Corner grounded is less economical, >> but acceptable from a supplier's point of view. For measuring it's less >> favourable... >> >> I remember two rules from my electricity course at Muskegon, Mich. High >> School: Ground everything you can get a hold of and always leave one >> hand in your pocket! >> >> Peter Blodow >> >> ------------------------------------------------------------------------------ >> Colocation vs. Managed Hosting >> A question and answer guide to determining the best fit >> for your organization - today and in the future. >> http://p.sf.net/sfu/internap-sfd2d >> _______________________________________________ >> Emc-users mailing list >> Emc-users@lists.sourceforge.net >> https://lists.sourceforge.net/lists/listinfo/emc-users >> >> >> > > > ------------------------------------------------------------------------------ > Colocation vs. Managed Hosting > A question and answer guide to determining the best fit > for your organization - today and in the future. > http://p.sf.net/sfu/internap-sfd2d > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > > ------------------------------------------------------------------------------ Colocation vs. Managed Hosting A question and answer guide to determining the best fit for your organization - today and in the future. http://p.sf.net/sfu/internap-sfd2d _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
