POLY PHASE TRANSFORMER
poly phase transformer
For poly phase systems,
multiple single-phase transformers can be used, or all phases can be connected
to a single poly phase transformer. For a three phase transformer, the three
primary winding are connected together and the three secondary winding are
connected together. Examples
of connections are wye-delta, delta-wye, delta-delta and wye -wye. A vector
group indicates the configuration of the winding and the phase
angle difference between them. If a winding is connected to
earth (grounded), the earth connection point is usually
the center point of a wye winding. If the secondary is a delta winding, the
ground may be connected to a center tap on one winding (high leg
delta) or one phase may be grounded (corner grounded delta). A
special purpose poly phase transformer is the zigzag transformer. There are many possible
configurations that may involve more or fewer than six winding and various tap
connections.