KACO Powador XP500-XP550-HV TL - Manual (Page 3)

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2. TECHNICAL PROPERTIES
Medium voltage transformer that is connected with transformerless solar inverter must comply with
following technical specifications:
1. The transformer must be suitable for PWM (Pulse Width Modulation) Inverter. The transformer
should be designed such that its magnetic flux is not saturated even if 1% of DC current flow on its
low voltage winding. Also the transformer should be designed and tested in accordance with
ANSI/IEEE, NEMA, and Department of Energy standards.
2. The transformer must be designed considering the voltages that arise during pulsed operation of
the inverter. The voltages can reach a magnitude of maximum ±1400 V reference to ground. The
rms‑value of the voltages reference to ground is maximum 700V. (See Fig.2)
Conductor voltage
regarding ground
V
0
Central Inverter
MV Transformer
Fig. 1 KACO central inverter with Double-winding Transformer
Fig. 2 Conductor voltage to ground and line-to-line voltage