KACO Powador XP500-XP550-HV TL - Manual (Page 9)

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Z
H
(1%)
Z
La
(5%)
Z
Lb
(5%)
Fig. 10 Equivalent series impedance Z(%) of dual stacked (four-winding) transformer
4. No neutral point is required on the low voltage side. Nevertheless, if a neutral point shows up on
the low‑voltage side, this neutral point must not be either connected or grounded.
5. dual stacked (four-winding) transformers with varying windings each on the high‑voltage side and
the low‑voltage side can be used. For example YNd11d11, YNd5d5, YNd1d1 or Dy11y11, Dy5y5,
Dy1y1 with an ungrounded neutral point on the low‑voltage side (see Fig.11).
Fig. 11 Diagram of dual stacked (four-winding) transformer