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
