KACO Powador XP500-XP550-HV TL - Manual (Page 7)

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4. REQUIREMENTS FOR MEDIUM-VOLTAGE TRANSFORMERS, THAT ARE CONNECTED
TO 2 CENTRAL INVERTERS
The transformer shown in Fig.7, is a dual stacked (four-winding) transformer. Its low-voltage side is
connected to KACO central inverter of which rated output voltage is 370V, and its high voltage side is for
connection to the medium-voltage grid in Europe which is 20kV typically. However, other high voltages
are also available: 10 kV, 15 kV, 22 kV, 25 kV, 27 kV, 30 kV, 34.5kV or 35 kV etc.
Central Inverter
Central Inverter
MV Transformer
Fig. 7 KACO central inverter with dual stacked (four-winding) transformer
This transformer must comply with the following technical specifications:
1. Equivalent series impedance between low voltage and high voltage winding:
The equivalent series impedance Z(%) of the transformer must, in relation to every inverter, be 6 %
in each case. Impedance voltage tolerance limits of 5.4 % ~ 6.6 % must be maintained. This value
can be determined when the high-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 another low
voltage windings are idle (see Fig.8).