What is the vector diagram of a transformer?

What is the vector diagram of ynd11 transformer?

• Answer:

  In the vector group representation for this transformer, the letter 'y' represents a wye- or star-connection, and the letter 'd' represents a delta- or mesh-connection (I have no idea what 'n' stands for -anyone?). An upper-case letter indicates the higher voltage, while a lower-case letter represents the lower voltage. The sequence of the letters indicates the primary and the secondary windings. So the transformer in question is a wye-delta connection (presumably the 'y' should have been capitalised, meaning that this is a step-down transformer: i.e. Yd11). The number appearing after the letter group (in this case '11') is a multiplier of 30o and indicates the transformer connection's angular displacement (or phase displacement). In this case, the angular displacement is 11 x 30o = 330o. As angular displacement is defined as 'the angle by which the secondary line voltages lag the primary line voltages', this means the secondary line voltages of this particular transformer lags its corresponding primary line voltages by 330o. So, to draw the phasor (not 'vector') diagram for this particular transformer, you would start by drawing the phase voltages (VAN, VBN, and VCN) of the primary wye connection (using VAN as the phasor of reference), from which you would then construct the corresponding line voltages (VAB, VBC, and VCA). To finish the diagram, you will then draw the secondary delta phasor diagram, starting with Vab lagging VAB by 330o (or, if you prefer, leading by 30o), then drawing Vbc and Vca displaced by 120o.