KACO Powador XP500-XP550-HV TL - Manual (Page 8)

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Fig.8 Equivalent circuit with short circuited high voltage winding
2. Equivalent series impedance between both low voltage winding:
The equivalent series impedance Z(%) between both low‑voltage windings must be 10 %. The
tolerance limits of this impedance voltage of 9 % ~ 11 % must be maintained. This value can be
determined when one of the low‑voltage winding is short-circuited and the voltage on the other
low‑voltage winding is increased until the nominal current flows. At the same time the
high‑voltage windings are idle (see Fig.9).
Y
Y
V
sc
I
sc
∆
∆
Fig.9 Equivalent circuit with short circuited low voltage winding
3. Equivalent series impedance Z(%) of the dual stacked (four-winding) transformer:
To summarize of the contents in Article 1 and Article 2, the equivalent series impedance Z(%) of
the dual stacked (four-winding) transformer can be shown as followed.
Z
L
is the equivalent series impedance of low voltage winding, and Z
H
is the equivalent series
impedance of high voltage winding.