In message <[email protected]> Richard Meyette writes:
> I measured the following phase voltages for the 3-phase power lines feeding > a breaker box: > > phase to phase (all three phases) = 240V > > phase to neutral (2 of 3 phases) = 120V > > phase to neutral (1 of 3 phases) = 208V > > Normally you would expect the phase to phase voltages to measure 208V and > the phase to neutral voltages to measure 120V for a Y-connected transformer. > > What kind of power transformer configuration would provide these phase > voltages? This is not a Y-connection, rather a delta connection with one center- tapped phase. This is a quite well known scheme in which a delta supply has a tap half way along one phase, so that single-phase loads can be supplied at half the line voltage, i.e. 120V for a 240V delta supply. There is a good explanation at http://www.franceformer.com/foreign_current/home.htm This scheme is quite common in Caribbean countries, e.g. Bahamas and Jamaica. Single-phase 120V appliances are connected between the outers of the center-tapped phase and center tap, 240V across the other two phases. The 208V connection is normally not used. Bill Lyons -- Claude Lyons Limited Brook Road, Waltham Cross, Herts EN8 7LR, UK Specialists in power and voltage control Tel: +44 (0)1992 768888 Fax: +44 (0)1992 788000 URL: http://www.claudelyons.co.uk This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: [email protected] Dave Heald: [email protected] For policy questions, send mail to: Richard Nute: [email protected] Jim Bacher: [email protected] Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
