Re: [EVGRAY] Re: Winding BiTT with C shape winding tool

Body

Hi Kone, Garry,

The reason for the correction is that the dot convention is at odd because of the different phase relationships. For a one phased transformer the dot convention tells that when the current enters a dot in a winding it exits the dot of the other windings. The windings are all wound in the same direction around the same leg (ring) and all windings have the dot at either the beginning or at the end of each winding. I.e. that's at the first (or last) layer end of each winding. For the UDT and BiTT (and the Bill Alek trafo and three legged trafos) this is true when seen from the primary. Each winding of the secondaries placed on other legs then has the current exit the dot end when entering the dot end of the primary winding. But the two secondaries are actually opposing each other when seen from their common ring (omitting the primary leg). Thus the dot convention is not correct when looking at only the secondaries alone. Current entering the dot end of one secondary (when used as a primary winding) will actually also enter the dot end of the other secondary when wound as shown in the figure.

Regards
Ole